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Genocea Biosciences, Inc. Index to Financial Statements

As filed with the Securities and Exchange Commission on February 3, 2014.

Registration No. 333-193043

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

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Amendment No. 3
to

FORM S-1
REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

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GENOCEA BIOSCIENCES, INC.
(Exact name of registrant as specified in its charter)

Cambridge Discovery Park
100 Acorn Park Drive, 5th Floor
Cambridge, MA 02140
(617) 876-8191
(Address, including zip code, and telephone number, including
area code, of registrant's principal executive offices)

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William Clark
Chief Executive Officer
100 Acorn Park Drive, 5th Floor
Cambridge, MA 02140
(617) 876-8191
(Name, address, including zip code, and telephone number, including
area code, of agent for service)

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Approximate date of commencement of proposed sale to public:
As soon as practicable after this Registration Statement is declared effective.

         If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box.    o

         If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

         If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

         If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

         Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of "large accelerated filer", "accelerated filer" and "smaller reporting company" in Rule 12b-2 of the Exchange Act.

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         The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the Registration Statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

   

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The information in this preliminary prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED FEBRUARY 3, 2014

PRELIMINARY PROSPECTUS

5,500,000 Shares

Genocea Biosciences, Inc.

Common Stock
$      per share

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        This is the initial public offering of our common stock. We are selling 5,500,000 shares of our common stock. We currently expect the initial public offering price to be between $12.00 and $14.00 per share of common stock.

        We have granted the underwriters an option to purchase up to 825,000 additional shares of common stock to cover over-allotments.

        We have applied to have our common stock listed on the NASDAQ Global Market under the symbol "GNCA".

        We are an "emerging growth company" as that term is used in the Jumpstart Our Business Startups Act of 2012 and, as such, have elected to comply with certain reduced public company reporting requirements for this prospectus and future filings.

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        Investing in our common stock involves risk. See "Risk Factors" beginning on page 11.

        Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed on the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

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        The underwriters expect to deliver the shares of common stock to investors on or about              , 2014 through the book-entry facilities of The Depositary Trust Company.

        Certain of our existing stockholders and their affiliated entities, including holders of more than 5% of our common stock, have indicated an interest in purchasing an aggregate of approximately $15.0 million in shares of our common stock in this offering at the initial public offering price. However, because indications of interest are not binding agreements or commitments to purchase, the underwriters could determine to sell more, less or no shares to any of these existing stockholders and any of these existing stockholders could determine to purchase more, less or no shares in this offering.

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Stifel

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Needham & Company

                        , 2014

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        We are responsible for the information contained in this prospectus and in any free-writing prospectus we prepare or authorize. We have not authorized anyone to provide you with different information, and we take no responsibility for any other information others may give you. We are not, and the underwriters are not, making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should not assume that the information contained in this prospectus is accurate as of any date other than the date on the cover of this prospectus.

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RISK FACTORS

        Investing in our common stock involves a high degree of risk. You should carefully consider the risks and uncertainties described below together with all of the other information contained in this prospectus, including our financial statements and the related notes appearing at the end of this prospectus, before deciding to invest in our common stock. If any of the following risks actually occurs, our business, prospectus, operating results and financial condition could suffer materially, the trading price of our common stock could decline and you could lose all or part of your investment. The risks and uncertainties described below are not the only ones we face. Additional risks and uncertainties not presently known to us or that we currently believe to be immaterial may also adversely affect our business.

Risks Related to Our Financial Position and Need for Additional Capital

We have incurred significant losses since our founding in 2006 and anticipate that we will continue to incur significant losses for the foreseeable future and may never achieve or maintain profitability.

        We are a clinical-stage biotechnology company, and we have not yet generated significant revenues. We have incurred net losses each year since our inception, including net losses of $14.7 million and $13.4 million for the years ended December 31, 2011 and 2012, respectively, and $8.7 million and $14.5 million for the nine months ended September 30, 2012 and 2013, respectively. As of September 30, 2013, we had accumulated a deficit of $73.6 million. To date, we have not commercialized any products or generated any revenues from the sale of products, and we do not expect to generate any product revenues in the foreseeable future. We do not know whether or when we will generate product revenues or become profitable.

        We have devoted most of our financial resources to research and development, including our clinical and preclinical technology development and development activities. To date, we have financed our operations primarily through the sale of equity securities and debt facilities and, to a lesser extent, through grants from governmental agencies and a private not-for-profit organization. The amount of our future net losses will depend, in part, on the rate of our future expenditures and our ability to obtain funding through equity or debt financings, strategic collaborations or additional grants. We have not completed pivotal clinical studies for any product candidate and it will be several years, if ever, before we have a product candidate ready for commercialization. Even if we obtain regulatory approval to market a product candidate, our future revenues will depend upon the size of any markets in which our product candidates have received approval, our ability to achieve sufficient market acceptance, reimbursement from third-party payors and other factors.

        We expect to continue to incur significant expenses and increasing operating losses for the foreseeable future. We anticipate that our expenses will increase significantly if and as we:

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continue our Phase 1/2a clinical trial of GEN-003, our most advanced product candidate that we are developing for the treatment of HSV-2 infections, and commence a planned Phase 2 clinical trial in the second quarter of 2014 to optimize the vaccine dose, and a planned Phase 2b clinical trial in second quarter of 2015 to optimize the dosing regimen;



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continue our Phase 1 clinical trial of GEN-004, our second most advanced product candidate that we are developing to prevent infections caused by all strains of pneumococcus, and commence a planned Phase 2a clinical trial of GEN-004 by mid-2014;



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initiate additional preclinical, clinical or other studies for our other product candidates;



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manufacture material for clinical trials and for commercial sale;



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seek regulatory approvals for our product candidates that successfully complete clinical trials;



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establish a sales, marketing and distribution infrastructure to commercialize any products for which we may obtain marketing approval;

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seek to discover and develop additional product candidates;



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acquire or in-license other product candidates and technologies;



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make royalty milestone or other payments under any in-license agreements;



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maintain, protect and expand our intellectual property portfolio;



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attract and retain skilled personnel; and



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create additional infrastructure to support our operations as a public company and our product development and planned future commercialization efforts.

        The net losses we incur may fluctuate significantly from quarter to quarter and year to year, such that a period-to-period comparison of our results of operations may not be a good indication of our future performance. In any particular quarter or quarters, our operating results could be below the expectations of securities analysts or investors, which could cause our stock price to decline.

        To become and remain profitable, we must succeed in developing and eventually commercializing products that generate significant revenue. This will require us to be successful in a range of challenging activities, including completing preclinical studies and clinical trials of our product candidates, discovering additional product candidates, obtaining regulatory approval for these product candidates and manufacturing, marketing and selling any products for which we may obtain regulatory approval. We are only in the preliminary stages of most of these activities. We may never succeed in these activities and, even if we do, may never generate revenues that are significant enough to achieve profitability.

        Because of the numerous risks and uncertainties associated with pharmaceutical product development, we are unable to accurately predict the timing or amount of increased expenses or when, or if, we will be able to achieve profitability. If we are required by the FDA or the European Medicines Agency to perform studies in addition to those currently expected, or if there are any delays in completing our clinical trials or the development of any of our product candidates, our expenses could increase.

        Even if we do achieve profitability, we may not be able to sustain or increase profitability on a quarterly or annual basis. Our failure to become and remain profitable would depress the value of our company and could impair our ability to raise capital, expand our business, maintain our research and development efforts, diversify our product offerings or even continue our operations. A decline in the value of our company could also cause you to lose all or part of your investment.

We will require substantial additional financing to achieve our goals, and a failure to obtain this necessary capital when needed would force us to delay, limit, reduce or terminate our product development or commercialization efforts.

        As of September 30, 2013, our cash and cash equivalents were $12.1 million. We believe that we will continue to expend substantial resources for the foreseeable future developing GEN-003, GEN-004 and our pre-clinical product candidates. These expenditures will include costs associated with research and development, potentially acquiring new technologies, potentially obtaining regulatory approvals and manufacturing products, as well as marketing and selling products approved for sale, if any. In addition, other unanticipated costs may arise. Because the outcome of our planned and anticipated clinical trials is highly uncertain, we cannot reasonably estimate the actual amounts necessary to successfully complete the development and commercialization of our product candidates.

        Our future capital requirements depend on many factors, including:

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the progress, results and costs of the Phase 1/2a clinical trial and our two planned Phase 2 clinical trials of GEN-003;

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the scope, progress, results and costs of preclinical development, laboratory testing and clinical trials for our other product candidates, including our Phase 1 clinical trial and our planned Phase 2a clinical trial of GEN-004;



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the number and development requirements of other product candidates that we pursue;



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the timing of, and the costs involved in, obtaining regulatory approvals for our product candidates if clinical trials are successful and the outcome of regulatory review of our product candidates;



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the cost and timing of future commercialization activities for our products, if any of our product candidates are approved for marketing, including product manufacturing, marketing, sales and distribution costs;



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the revenue, if any, received from commercial sales of our product candidates for which we receive marketing approval;



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the cost of manufacturing our product candidates for clinical trials in preparation for regulatory approval and in preparation for commercialization;



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our ability to establish and maintain strategic partnerships, licensing or other arrangements and the financial terms of such agreements;



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the costs involved in preparing, filing, prosecuting patent applications, maintaining, defending and enforcing our intellectual property rights, including litigation costs and the outcome of such litigation;



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the timing, receipt, and amount of sales of, or royalties or milestone payments on, our future products, if any; and



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the extent to which we acquire or in-license other products or technologies.

        Based on our current operating plan, we believe that the net proceeds we receive from this offering, and our existing cash and cash equivalents and available future borrowings under our credit facility will be sufficient to fund our projected operating expenses and capital expenditure requirements through at least the end of 2015. However, our operating plan may change as a result of many factors currently unknown to us, and we may need additional funds sooner than planned. In addition, we may seek additional capital due to favorable market conditions or strategic considerations even if we believe we have sufficient funds for our current or future operating plans. Additional funds may not be available when we need them on terms that are acceptable to us, or at all. If adequate funds are not available to us when needed, we would be required to delay, limit, reduce or terminate preclinical studies, clinical trials or other development activities for one or more of our product candidates or delay, limit, reduce or terminate our establishment of sales and marketing capabilities or other activities that may be necessary to commercialize our product candidates.

Raising additional capital may cause dilution to our existing stockholders, restrict our operations or require us to relinquish rights to our technologies or product candidates on unfavorable terms to us.

        Until such time, if ever, as we can generate substantial product revenues, we expect to finance our cash needs through a combination of equity offerings, debt financings and license and development agreements with strategic partnerships with third parties. To the extent that we raise additional capital through the sale of equity or convertible debt securities, your ownership interest will be diluted, and the terms may include liquidation or other preferences that adversely affect your rights as a stockholder. Debt financing, if available, may involve agreements that include covenants limiting or restricting our ability to take certain actions, such as incurring additional debt, making capital expenditures or declaring dividends. If we raise additional funds through strategic partnerships with third parties, we may have to relinquish valuable rights to our technologies or product candidates,

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future revenue streams, research programs or product candidates or grant licenses on terms that are not favorable to us. If we are unable to raise additional when needed, we would be required to delay, limit, reduce or terminate our product development or commercialization efforts for GEN-003, GEN-004 or our preclinical product candidates, or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.

Risks Related to Clinical Development, Regulatory Review and Approval of Our Product Candidates

Because our product candidates are in an early stage of development, there is a high risk of failure, and we may never succeed in developing marketable products or generating product revenue.

        Our early encouraging preclinical and clinical results for GEN-003 and our preclinical results for GEN-004 are not necessarily predictive of the final results of our ongoing or future clinical trials. We have not yet completed our first human clinical trial, a Phase 1/2a trial of GEN-003. Success in preclinical studies may not be predictive of similar results in humans during clinical trials, and successful results from early or small clinical trials of a vaccine candidate may not be replicated in later and larger clinical trials. If the results of our ongoing or future clinical trials are inconclusive with respect to the efficacy of our product candidates or if we do not meet our clinical endpoints with statistical significance or if there are safety concerns or adverse events associated with our product candidates, we may be prevented or delayed in obtaining marketing approval for our product candidates. Alternatively, even if we obtain regulatory approval, that approval may be for indications or patient populations that are not as broad as intended or desired or may require labeling that includes significant use or distribution restrictions or safety warnings. We may also be required to perform additional or unanticipated clinical trials to obtain approval or be subject to additional post-marketing testing requirements to maintain regulatory approval. In addition, regulatory authorities may withdraw their approval of the product or impose restrictions on its distribution in the form of a modified risk evaluation and mitigation strategy.

If we do not obtain regulatory approval for our current and future product candidates, our business will be adversely affected.

        Our product candidates are subject to extensive governmental regulations relating to, among other things, research, clinical trials, manufacturing, import, export and commercialization. In order to obtain regulatory approval for the commercial sale of any product candidate, we must demonstrate through extensive preclinical studies and clinical trials that the product candidate is safe and effective for use in each target indication. Clinical trials are expensive, time-consuming and uncertain as to outcome. We may gain regulatory approval for GEN-003, GEN-004 or our other preclinical product candidates in some but not all of the territories available or some but not all of the target indications, resulting in limited commercial opportunity for the approved vaccine, or we may never obtain regulatory approval for these product candidates in any jurisdiction.

We may find it difficult to enroll patients in our clinical trials, which could delay or prevent clinical trials of our product candidates.

        Identifying and qualifying patients to participate in clinical trials of our product candidates is critical to our success. The timing of our clinical trials depends on the speed at which we can recruit patients to participate in testing our product candidates. If patients are unwilling to participate in our studies because of negative publicity from adverse events in the biotechnology industries or for other reasons, including competitive clinical trials for similar patient populations, the timeline for recruiting patients, conducting studies and obtaining regulatory approval of potential products may be delayed or prevented. These delays could result in increased costs, delays in advancing our product development, delays in testing the effectiveness of our technology or termination of the clinical trials altogether.

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        Additionally, in order to identify vaccine candidates using our ATLAS platform, we need to collect and process blood samples from human cohorts exposed to a pathogen. If we are unable to collect blood from a sufficient cohort for an indication we may be unable to identify additional product candidates.

        We may not be able to identify, recruit and enroll a sufficient number of patients, or those with required or desired characteristics to achieve diversity in a study, to complete our clinical trials in a timely manner. Patient enrollment is affected by factors including:

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severity of the disease under investigation;



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design of the study protocol;



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size of the patient population;



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eligibility criteria for the trial in question;



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perceived risks and benefits of the product candidate under study;



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proximity and availability of clinical trial sites for prospective patients;



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availability of competing therapies and clinical trials;



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efforts to facilitate timely enrollment in clinical trials;



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patient referral practices of physicians; and



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ability to monitor patients adequately during and after treatment.

        We may not be able to initiate or continue clinical trials if we cannot enroll a sufficient number of eligible patients to participate in the clinical trials required by regulatory agencies. If we have difficulty enrolling a sufficient number of patients to conduct our clinical trials as planned, we may need to delay, limit or terminate on-going or planned clinical trials, any of which would have an adverse effect on our business.

We may not be able to comply with requirements of foreign jurisdictions in conducting trials outside of the United States.

        To date, we have not conducted any clinical trials outside of the United States. Our ability to successfully initiate, enroll and complete a clinical trial in any foreign country, should we attempt to do so, is subject to numerous risks unique to conducting business in foreign countries, including:

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difficulty in establishing or managing relationships with contract research organizations, or CROs, and physicians;



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different standards for the conduct of clinical trials;



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our inability to locate qualified local consultants, physicians and partners;



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the potential burden of complying with a variety of foreign laws, medical standards and regulatory requirements, including the regulation of pharmaceutical and biotechnology products and treatment; and



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the acceptability of data obtained from studies conducted outside the United States to the FDA in support of a Biologics License Application, or BLA.

        If we fail to successfully meet requirements for the conduct of clinical trials outside of the United States, we may be delayed in obtaining, or be unable to obtain, regulatory approval for our product candidates in the United States or in countries outside of the United States.

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We may encounter substantial delays in our clinical trials or we may fail to demonstrate safety and efficacy to the satisfaction of applicable regulatory authorities.

        Before obtaining marketing approval from regulatory authorities for the sale of our product candidates, we must conduct extensive clinical trials to demonstrate the safety and efficacy of the product candidates in humans. Clinical testing is expensive, time-consuming and uncertain as to outcome. We cannot guarantee that clinical trials will be conducted as planned or completed on schedule, if at all. A failure of one or more clinical trials can occur at any stage of testing. Events that may prevent successful or timely completion of clinical development include:

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delays by us in reaching a consensus with regulatory agencies on trial design;



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delays in reaching agreement on acceptable terms with prospective CROs and clinical trial sites;



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delays in obtaining required Institutional Review Board, or IRB, approval at each clinical trial site;



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imposition of a clinical hold by regulatory agencies for any reason, including safety concerns raised by other clinical trials of similar vaccines that may reflect an unacceptable risk with GEN-003 or after an inspection of clinical operations or trial sites;



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failure to perform in accordance with the FDA's good clinical practices, or GCP, or applicable regulatory guidelines in other countries;



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delays in the testing, validation, manufacturing and delivery of the product candidates to the clinical sites;



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delays caused by patients not completing participation in a trial or not returning for post- treatment follow-up;



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clinical trial sites or patients dropping out of a trial or failing to complete dosing;



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occurrence of serious adverse events in clinical trials that are associated with the product candidates that are viewed to outweigh its potential benefits; or



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changes in regulatory requirements and guidance that require amending or submitting new clinical protocols.

        Delays, including delays caused by the above factors, can be costly and could negatively affect our ability to complete a clinical trial. Our IND for GEN-003 was subject to a clinical hold from January 2012 to July 2012. In our original IND submission, we described a finding of osteonecrosis (microscopic evidence of bone and bone marrow death) in a toxicity study of GEN-003 conducted in mice. Because this finding was not present in toxicity studies conducted in other species, we reasoned that this was a mouse-specific finding and did not indicate a risk to humans in clinical trials. However, the FDA instituted a clinical hold and provided us with several options that would resolve this issue to their satisfaction. We selected the option to conduct an additional toxicity study in a highly relevant species (non-human primate) that would be more representative of a risk to humans. The study was conducted, no bone or bone marrow toxicity was observed, and the FDA subsequently lifted the clinical hold, allowing us to proceed with the first study in humans of GEN-003.

        We cannot give any assurance that we will be able to resolve any future clinical holds imposed by the FDA or other regulatory authorities outside of the United States, or any delay caused by other factors described above or any other factors, on a timely basis or at all. If we are not able to successfully initiate and complete subsequent clinical trials, we will not be able to obtain regulatory approval and will not be able to commercialize our product candidates.

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Our product candidates, including GEN-003 and GEN-004, are based on T cell activation, which is a novel approach for vaccines and medical treatments. Consequently, it may be difficult for us to predict the time and cost of product development. Unforeseen problems with the T cell approach to vaccines may prevent further development or approval of our product candidates. Because of the novelty of this approach, there may be unknown safety risks associated with the vaccines that we develop. Regulatory agencies such as the FDA may require us to conduct extensive safety testing prior to approval to demonstrate a low risk of rare and severe adverse events caused by the vaccines. If approved, the novel mechanism of action of the vaccines may adversely affect physician and patient perception and uptake of our products.

        We have concentrated our research and development efforts on T cell vaccine technology, and our future success is highly dependent on the successful development of T cell vaccines in general, and our product candidates in particular. There can be no assurance that any development problems we or others researching T cell vaccines may experience in the future will not cause significant delays or unanticipated costs, or that such development problems can be solved.

        Public perception of vaccine safety issues, including adoption of novel vaccine mechanisms of action, may adversely influence willingness of subjects to participate in clinical trials, or if approved, to prescribe and receive novel vaccines. For example, GEN-004 is being developed for prevention of Pneumococcal infections, and parental aversion to new vaccines or vaccines in general may adversely influence later stage clinical trials of this product candidate or, if approved, its commercial success.

GEN-003 includes a novel vaccine adjuvant and our other product candidates may include one or more novel adjuvants, which may make it difficult for us to predict the time and cost of product development as well as the requirements the FDA or other regulatory agencies may impose to demonstrate the safety of the product candidate.

        Novel vaccine adjuvants, included in some of our product candidates, may pose an increased safety risk to patients. Adjuvants are compounds that are added to vaccine antigens to enhance the activation and improve immune response and efficacy of vaccines. Development of vaccines with novel adjuvants requires evaluation in larger numbers of patients prior to approval than would be typical for therapeutic drugs. Guidelines for evaluation of vaccines with novel adjuvants have been established by the FDA and other regulatory bodies and expert committees. Our product candidates, including GEN-003, may include one or more novel vaccine adjuvants. The safety of any vaccine, because of the presence of an adjuvant, may have side effects considered to pose too great a risk to patients to warrant approval of the vaccine. Traditionally, regulatory authorities have required extensive study of novel adjuvants because vaccines typically get administered to healthy populations, in particular infants, children and the elderly, rather than in people with disease. Such extensive study has often included long-term monitoring of safety in large general populations that has at times exceeded 10,000 subjects. This contrasts with the few thousand subjects typically necessary for approval of novel therapeutics. Although GEN-003 is being developed as a treatment, and therefore is not expected to be administered to uninfected subjects, regulators nonetheless may require us to amass a prophylactic vaccine-like safety database. To date, the FDA and other major regulatory agencies have only approved vaccines containing five adjuvants, which makes it difficult to determine how long it will take or how much it will cost to obtain regulatory approvals for our product candidates in the United States or elsewhere.

If we fail to obtain regulatory approval in jurisdictions outside the United States, we will not be able to market our products in those jurisdictions.

        We intend to market our product candidates, if approved, in international markets. Such marketing will require separate regulatory approvals in each market and compliance with numerous and varying regulatory requirements. The approval procedures vary among countries and may involve requirements for additional testing, and the time required to obtain approval may differ from that required to obtain FDA approval. In addition, in many countries outside the United States, a vaccine must be approved

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for reimbursement before it can be approved for sale in that country. In some cases, the price that we intend to charge for our vaccine is also subject to approval. Approval by the FDA does not ensure approval by regulatory authorities in other countries or jurisdictions, and approval by one foreign regulatory authority does not ensure approval by regulatory authorities in other foreign countries or by the FDA. The foreign regulatory approval process may include all of the risks associated with obtaining FDA approval. We may not obtain foreign regulatory approvals on a timely basis, if at all. We may not be able to file for regulatory approvals and may not receive necessary approvals to commercialize our vaccines in any market.

Even if we receive regulatory approval for our product candidates, such vaccines will be subject to ongoing regulatory review, which may result in significant additional expense. Additionally, our product candidates, if approved, could be subject to labeling and other restrictions, and we may be subject to penalties if we fail to comply with regulatory requirements or experience unanticipated problems with our products.

        Any regulatory approvals that we receive for our product candidates may also be subject to limitations on the approved indicated uses for which the product may be marketed or to conditions of approval, or contain requirements for potentially costly post-marketing testing, including Phase 4 clinical trials, and surveillance to monitor the safety and efficacy of the vaccine potentially over many years. In addition, if the FDA approves any of our product candidates, the manufacturing processes, labeling, packaging, distribution, adverse event reporting, storage, advertising, promotion and recordkeeping for the product will be subject to extensive and ongoing regulatory requirements. These requirements include submissions of safety and other post-marketing information and reports, registration, as well as continued compliance with current good manufacturing practice, or cGMP, and GCP, for any clinical trials that we conduct post-approval.

        Later discovery of previously unknown problems with an approved product, including adverse events of unanticipated severity or frequency, or with manufacturing operations or processes, or failure to comply with regulatory requirements, may result in, among other things:

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restrictions on the marketing or manufacturing of the product, withdrawal of the product from the market, or voluntary or mandatory product recalls;



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fines, warning letters, or holds on clinical trials;



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refusal by the FDA to approve pending applications or supplements to approved applications filed by us, or suspension or revocation of product license approvals;



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product seizure or detention, or refusal to permit the import or export of products; and



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injunctions or the imposition of civil, criminal and/or administrative penalties, damages, monetary fines, disgorgement, exclusion from participation in Medicare, Medicaid and other federal health care programs, and curtailment or restructuring of our operations.

        The FDA's policies may change and additional government regulations may be enacted that could affect regulatory approval that we have received for our product candidates. We cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative action, either in the United States or abroad. If we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or not able to maintain regulatory compliance, we may lose any marketing approval that may have been obtained and we may not achieve or sustain profitability, which would adversely affect our business.

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Risks Related to Our Reliance on Third Parties

We rely on third parties to conduct preclinical studies and clinical trials for our product candidates, and if they do not properly and successfully perform their obligations to us, we may not be able to obtain regulatory approvals for our product candidates.

        We rely on third party CROs and other third parties to assist in managing, monitoring and otherwise carrying out our GEN-003 and GEN-004 clinical trials. We expect to continue to rely on third parties, such as CROs, clinical data management organizations, medical institutions and clinical investigators, to conduct our clinical trials. We compete with many other companies for the resources of these third parties. The third parties on whom we rely generally may terminate their engagements at any time, and having to enter into alternative arrangements would delay development and commercialization of our product candidates.

        Our reliance on these third parties for research and development activities will reduce our control over these activities but will not relieve us of our responsibilities. For example, the FDA and foreign regulatory authorities require compliance with regulations and standards, including GCP, for designing, conducting, monitoring, recording, analyzing, and reporting the results of clinical trials to assure that the data and results are credible and accurate and that the rights, integrity and confidentiality of trial participants are protected. Although we rely on third parties to conduct our clinical trials, we are responsible for ensuring that each of these clinical trials is conducted in accordance with its general investigational plan and protocol.

        Furthermore, these third parties may also have relationships with other entities, some of which may be our competitors. If these third parties do not successfully carry out their duties under their agreements, if the quality or accuracy of the data they obtain is compromised due to their failure to adhere to clinical trial protocols or to regulatory requirements, or if they otherwise fail to comply with clinical trial protocols or meet expected deadlines, the clinical trials of our product candidates may not meet regulatory requirements. If clinical trials do not meet regulatory requirements or if these third parties need to be replaced, preclinical development activities or clinical trials may be extended, delayed, suspended or terminated. If any of these events occur, we may not be able to obtain regulatory approval of our product candidates on a timely basis or at all.

        We also expect to rely on other third parties to store and distribute drug supplies for our clinical trials. Any performance failure on the part of our distributors could delay clinical development or marketing approval of our product candidates or commercialization of our products, producing additional losses and depriving us of potential product revenue.

We intend to rely on third parties to conduct some or all aspects of our product manufacturing, and these third parties may not perform satisfactorily.

        We do not have any manufacturing facilities or personnel. We do not expect to independently conduct all aspects of our product manufacturing. We currently rely, and expect to rely, on third parties with respect to manufacturing. For example, we rely on third party suppliers and manufacturers to manufacture and supply vaccines for our initial GEN-003 and GEN-004 clinical trials. This reliance on third parties increases the risk that we will not have sufficient quantities of our product candidates or products or such quantities at an acceptable cost or quality, which could delay, prevent or impair our development or commercialization efforts.

        Any of these third parties may terminate their engagement with us at any time. If we need to enter into alternative arrangements, it could delay our product development activities. Our reliance on these third parties for manufacturing activities will reduce our control over these activities but will not relieve us of our responsibility to ensure compliance with all required regulations regarding manufacturing.

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        Reliance on third party manufacturers entails risks to which we would not be subject if we manufactured the product candidates ourselves, including:

•

the inability to negotiate manufacturing agreements with third parties under commercially reasonable terms;



•

reduced control as a result of using third party manufacturers for all aspects of manufacturing activities, including regulatory compliance and quality assurance;



•

termination or nonrenewal of manufacturing agreements with third parties in a manner or at a time that is costly or damaging to us;



•

the possible misappropriation of our proprietary information, including our trade secrets and know-how or infringement of third party intellectual property rights by our contract manufacturers; and



•

disruptions to the operations of our third party manufacturers or suppliers caused by conditions unrelated to our business or operations, including the bankruptcy of the manufacturer or supplier.

        Any of these events could lead to clinical trial delays or failure to obtain regulatory approval, or affect our ability to successfully commercialize future products. Some of these events could be the basis for FDA action, including injunction, recall, seizure or total or partial suspension of production.

        Third party manufacturers may not be able to comply with cGMP regulations or similar regulatory requirements outside the United States. Our failure, or the failure of our third party manufacturers, to comply with applicable regulations could result in sanctions being imposed on us, including clinical holds, fines, injunctions, civil penalties, delays, suspension or withdrawal of approvals, license revocation, seizures or recalls of product candidates or products, operating restrictions and criminal prosecutions, any of which could significantly and adversely affect supplies of our products.

        Our product candidates and any products that we may develop may compete with other product candidates and products for access to manufacturing facilities. There are a limited number of manufacturers that operate under cGMP regulations and that might be capable of manufacturing for us.

        Any performance failure on the part of our existing or future manufacturers could delay clinical development or marketing approval. We do not currently have arrangements in place for redundant supply or a second source for bulk drug substance. If our current contract manufacturers cannot perform as agreed, we may be required to replace such manufacturers. Although we believe that there are several potential alternative manufacturers who could manufacture our product candidates, we may incur added costs and delays in identifying and qualifying any such replacement.

        Our current and anticipated future dependence upon others for the manufacture of our product candidates or products may adversely affect our future profit margins and our ability to commercialize any products that receive marketing approval on a timely and competitive basis.

If we are unable to manufacture our products in sufficient quantities, or at sufficient yields, or are unable to obtain regulatory approvals for a manufacturing facility for our products, we may experience delays in product development, clinical trials, regulatory approval and commercial distribution.

        Completion of our clinical trials and commercialization of our product candidates require access to, or development of, facilities to manufacture our product candidates at sufficient yields and at commercial-scale. We have no experience manufacturing, or managing third parties in manufacturing, any of our product candidates in the volumes that will be necessary to support large-scale clinical trials

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or commercial sales. Efforts to establish these capabilities may not meet initial expectations as to scheduling, scale-up, reproducibility, yield, purity, cost, potency or quality.

        We expect to rely on third-parties for the manufacture of clinical and, if necessary, commercial quantities of our product candidates. These third-party manufacturers must also receive FDA approval before they can produce clinical material or commercial products. Our products may be in competition with other products for access to these facilities and may be subject to delays in manufacture if third-parties give other products greater priority. We may not be able to enter into any necessary third-party manufacturing arrangements on acceptable terms, or on a timely basis. In addition, we may have to enter into technical transfer agreements and share our know-how with the third-party manufacturers, which can be time-consuming and may result in delays.

        Our reliance on contract manufacturers may adversely affect our operations or result in unforeseen delays or other problems beyond our control. Because of contractual restraints and the limited number of third-party manufacturers with the expertise, required regulatory approvals and facilities to manufacture our bulk vaccines on a commercial-scale, replacement of a manufacturer may be expensive and time-consuming and may cause interruptions in the production of our vaccine. A third-party manufacturer may also encounter difficulties in production. These problems may include:

•

difficulties with production costs, scale-up and yields;



•

unavailability of raw materials and supplies;



•

insufficient quality control and assurance;



•

shortages of qualified personnel;



•

failure to comply with strictly enforced federal, state and foreign regulations that vary in each country where product might be sold; and



•

lack of capital funding.

        As a result, any delay or interruption could have a material adverse effect on our business, financial condition, results of operations and cash flows.

We may not be successful in establishing and maintaining strategic partnerships, which could adversely affect our ability to develop and commercialize products.

        A part of our strategy is to evaluate and, as deemed appropriate, enter into partnerships in the future when strategically attractive, including potentially with major biotechnology or pharmaceutical companies. We face significant competition in seeking appropriate partners for our product candidates, and the negotiation process is time-consuming and complex. In order for us to successfully partner our product candidates, potential partners must view these product candidates as economically valuable in markets they determine to be attractive in light of the terms that we are seeking and other available products for licensing by other companies. Even if we are successful in our efforts to establish strategic partnerships, the terms that we agree upon may not be favorable to us, and we may not be able to maintain such strategic partnerships if, for example, development or approval of a product is delayed or sales of an approved product are disappointing. Any delay in entering into strategic partnership agreements related to our product candidates could delay the development and commercialization of our product candidates and reduce their competitiveness even if they reach the market.

        In addition, our strategic partners may breach their agreements with us, and we may not be able to adequately protect our rights under these agreements. Furthermore, our strategic partners will likely negotiate for certain rights to control decisions regarding the development and commercialization of our product candidates, if approved, and may not conduct those activities in the same manner as we would do so.

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        If we fail to establish and maintain strategic partnerships related to our product candidates, we will bear all of the risk and costs related to the development of any such product candidate, and we may need to seek additional financing, hire additional employees and otherwise develop expertise which we do not have and for which we have not budgeted. This could negatively affect the development of any unpartnered product candidate.

Risks Related to Our Intellectual Property

If we are unable to obtain or protect intellectual property rights related to our product candidates, we may not be able to compete effectively in our markets.

        We rely upon a combination of patents, patent applications, know how and confidentiality agreements to protect the intellectual property related to our platform technology and product candidates. The patent position of biotechnology companies is generally uncertain because it involves complex legal and factual considerations. The standards applied by the United States Patent and Trademark Office, or U.S. PTO, and foreign patent offices in granting patents are not always applied uniformly or predictably. For example, there is no uniform worldwide policy regarding patentable subject matter or the scope of claims allowable in biotechnology patents. The patent applications that we own or in-license may fail to result in issued patents with claims that cover our discovery platform or product candidates in the United States or in other countries. There is no assurance that all potentially relevant prior art relating to our patents and patent applications or those of our licensors has been found, and prior art that we have not disclosed could be used by a third party to invalidate a patent or prevent a patent from issuing from a pending patent application. Even if patents do successfully issue and even if such patents cover our discovery platform or product candidates, third parties may challenge their validity, enforceability or scope, which may result in such patents being narrowed or invalidated. Furthermore, even if they are unchallenged, our patents and patent applications, or those of our licensors, may not adequately protect our platform technology, provide exclusivity for our product candidates, prevent others from designing around our patents with similar products, or prevent others from operating in jurisdictions in which we did not pursue patent protection. Any of these outcomes could impair our ability to prevent competition from third parties, which may have an adverse impact on our business.

        If patent applications we hold or have in-licensed with respect to our platform or product candidates fail to issue, if their breadth or strength of protection is threatened, or if they fail to provide meaningful exclusivity for our product candidates or ATLAS discovery platform, it could dissuade companies from collaborating with us. We or our licensors have filed several patent applications covering aspects of our product candidates. We cannot offer any assurances about which, if any, patents will issue, the breadth of any such patents or whether any issued patents will be found invalid and unenforceable or will be challenged by third parties. Any successful opposition to these patent applications, or patents that may issue from them, or to any other patent applications or patents owned by or licensed to us, could deprive us of rights necessary for the successful commercialization of any product candidate that we may develop. Since patent applications in the United States and most other countries are confidential for a period of time after filing, and some remain so until issued, we cannot be certain that we or our licensors were the first to file a patent application relating to any particular aspect of a product candidate. Furthermore, if third parties have filed such patent applications, an interference proceeding in the United States can be initiated by such third party, or by the U.S. PTO itself, to determine who was the first to invent any of the subject matter covered by the patent claims of our applications.

        In the United States, for patent applications filed prior to March 16, 2013, assuming the other requirements for patentability are met, the first to invent is entitled to the patent, while outside the United States, the first to file a patent application is entitled to the patent. On March 16, 2013, the United States transitioned to a 'first to file' system more like that in the rest of the world in that the

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first inventor to file a patent application is entitled to the patent. Under either the prior system or current one, third parties are allowed to submit prior art prior to the issuance of a patent by the U.S. PTO, and may become involved in opposition, derivation, reexamination, inter partes review or interference proceedings challenging our patent rights or the patent rights of others. An adverse determination in any such submission, proceeding or litigation could reduce the scope of, or invalidate, our patent rights, which could adversely affect our competitive position with respect to third parties.

        In addition, patents have a limited lifespan. In most countries, including the United States, the natural expiration of a patent is 20 years from the date it is filed. Various extensions of patent term may be available in particular countries, however in all circumstances the life of a patent, and the protection it affords, has a limited term. If we encounter delays in obtaining regulatory approvals, the period of time during which we could market a product under patent protection could be reduced. We expect to seek extensions of patent terms where these are available in any countries where we are prosecuting patents. Such possible extensions include those permitted under the Drug Price Competition and Patent Term Restoration Act of 1984 in the United States, which permits a patent term extension of up to five years to cover an FDA-approved product. The actual length of the extension will depend on the amount of patent term lost while the product was in clinical trials. However, the applicable authorities, including the FDA in the United States, and any equivalent regulatory authority in other countries, may not agree with our assessment of whether such extensions are available, and may refuse to grant extensions to our patents, or may grant more limited extensions than we request. If this occurs, our competitors may be able to take advantage of our investment in development and clinical trials by referencing our clinical and preclinical data, and then may be able to launch their product earlier than might otherwise be the case.

        Any loss of, or failure to obtain, patent protection could have a material adverse impact on our business. We may be unable to prevent competitors from entering the market with a product that is similar to or the same as our products.

We may become involved in lawsuits to protect or enforce our intellectual property, which could be expensive, time consuming and unsuccessful.

        Competitors may infringe our patents or misappropriate or otherwise violate our intellectual property rights. To counter infringement or unauthorized use, litigation may be necessary to enforce or defend our intellectual property rights, to protect our trade secrets and/or to determine the validity and scope of our own intellectual property rights or the proprietary rights of others. Such litigation can be expensive and time consuming. Many of our current and potential competitors have the ability to dedicate substantially greater resources to litigate intellectual property rights than we can. Accordingly, despite our efforts, we may not be able to prevent third parties from infringing upon or misappropriating our intellectual property. Litigation could result in substantial costs and diversion of management resources, which could harm our business and financial results. In addition, in an infringement proceeding, a court may decide that a patent owned by or licensed to us is invalid or unenforceable, or may refuse to stop the other party from using the technology at issue on the grounds that our patents do not cover the technology in question. An adverse result in any litigation proceeding could put one or more of our patents at risk of being invalidated, held unenforceable or interpreted narrowly. Furthermore, because of the substantial amount of discovery required in connection with intellectual property litigation, there is a risk that some of our confidential information could be compromised by disclosure during this type of litigation.

Third-party claims of intellectual property infringement or misappropriation may prevent or delay our development and commercialization efforts.

        Our commercial success depends in part on our ability to develop, manufacture, market and sell our product candidates, and to use our or our licensors' proprietary technologies without infringing the

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patents and proprietary rights of third parties. There is a substantial amount of litigation, both within and outside the United States, involving patent and other intellectual property rights in the biotechnology and pharmaceutical industries, including patent infringement lawsuits, interferences, oppositions, reexamination, and inter partes review proceedings before the U.S. PTO and corresponding foreign patent offices. Numerous U.S. and foreign issued patents and pending patent applications owned by third parties exist in the fields in which we are developing and may develop our product candidates. As the biotechnology and pharmaceutical industries expand and more patents are issued, the risk increases that our product candidates may be subject to claims of infringement of the patent rights of third parties.

        Third parties may assert that we are employing their proprietary technology without authorization. There may be third-party patents or patent applications with claims for example to materials, formulations, methods of manufacture, methods of analysis, and/or methods for treatment related to the use or manufacture of our products or product candidates. In some cases, we may have failed to identify relevant such third-party patents or patent application. For example, applications filed before November 29, 2000 and certain applications filed after that date that will not be filed outside the United States remain confidential until patents issue. Except for the preceding exceptions, patent applications in the United States and elsewhere are generally published only after a waiting period of approximately 18 months after the earliest filing. Therefore, patent applications covering our platform technology or our products or product candidates could have been filed by others without our knowledge. Additionally, pending patent applications which have been published can, subject to certain limitations, be later amended in a manner that could cover our platform technologies, our products or product candidates and/or the use, analysis, and/or manufacture of our product candidates.

        If any third-party patents were held by a court of competent jurisdiction to cover aspects of our materials, formulations, methods of manufacture, methods of analysis, and/or methods for treatment, the holders of any such patents would be able to block our ability to develop and commercialize the applicable product candidate until such patent expired or unless we obtain a license. Such licenses may not be available on acceptable terms, if at all. Even if we were able to obtain a license, the rights may be nonexclusive, which could result in our competitors gaining access to the same intellectual property. Ultimately, we could be prevented from commercializing a product, or be forced to cease some aspect of our business operations, if, as a result of actual or threatened patent infringement claims, we are unable to enter into licenses on acceptable terms.

        Parties making claims against us may obtain injunctive or other equitable relief, which could effectively block our ability to further develop and commercialize one or more of our product candidates. Defending against claims of patent infringement or misappropriation of trade secrets could be costly and time consuming, regardless of the outcome. Thus, even if we were to ultimately prevail, or to settle at an early stage, such litigation could burden us with substantial unanticipated costs. In addition, litigation or threatened litigation could result in significant demands on the time and attention of our management team, distracting them from the pursuit of other company business. In the event of a successful claim of infringement against us, we may have to pay substantial damages, including treble damages and attorneys' fees for willful infringement, pay royalties, redesign our infringing products or obtain one or more licenses from third parties, which may be impossible or require substantial time and monetary expenditure.

        We may face a claim of misappropriation if a third party believes that we inappropriately obtained and used trade secrets of such third party. If we are found to have misappropriated a third party's trade secrets, we may be prevented from further using such trade secrets, limiting our ability to develop our product candidates, and we may be required to pay damages.

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        During the course of any patent or other intellectual property litigation, there could be public announcements of the results of hearings, rulings on motions, and other interim proceedings in the litigation. If securities analysts or investors regard these announcements as negative, the perceived value of our products, programs, or intellectual property could be diminished. Accordingly, the market price of our common stock may decline.

We have in-licensed a portion of our intellectual property, and, if we fail to comply with our obligations under these arrangements, we could lose such intellectual property rights or owe damages to the licensor of such intellectual property.

        We are a party to a number of license agreements that are important to our business, and we may enter into additional license agreements in the future. Our discovery platform is built, in part, around patents exclusively in-licensed from academic or research institutions. Certain of our in-licensed intellectual property also covers, or may cover, GEN-003 and other product candidates. See "Business — In-License Agreements" and "Business — Other Collaborations" for a description of our license agreements with The Regents of of the University of California, President and Fellows of Harvard College, University of Washington, Children's Medical Center Corporation, and Isconova AB.

        Our existing license agreements impose, and we expect that future license agreements will impose, various diligence, milestone payment, royalty and other obligations on us. If there is any conflict, dispute, disagreement or issue of non-performance between us and our licensing partners regarding our rights or obligations under the license agreements, including any such conflict, dispute or disagreement arising from our failure to satisfy payment obligations under any such agreement, we may owe damages, our licensor may have a right to terminate the affected license, and our ability to utilize the affected intellectual property in our drug discovery and development efforts, and our ability to enter into collaboration or marketing agreements for an affected product candidate, may be adversely affected.

Confidentiality agreements with employees and third parties may not prevent unauthorized disclosure of proprietary information.

        In addition to the protection afforded by patents, we rely on confidentiality agreements to protect proprietary know-how that may not be patentable or that we may elect not to patent, processes for which patents are difficult to enforce and any other elements of our platform technology and discovery and development processes that involve proprietary know-how, information or technology that is not covered by patents. We seek to protect our proprietary technology and processes, in part, by entering into confidentiality agreements with our employees, consultants, and outside scientific advisors, contractors and collaborators. Although we use reasonable efforts to protect our know-how, our employees, consultants, contractors, or outside scientific advisors might intentionally or inadvertently disclose our know-how information to competitors. In addition, competitors may otherwise gain access to our know-how or independently develop substantially equivalent information and techniques.

        Enforcing a claim that a third party illegally obtained and is using any of our know-how is expensive and time consuming, and the outcome is unpredictable. In addition, courts outside the United States sometimes are less willing than U.S. courts to protect know-how. Misappropriation or unauthorized disclosure of our know-how could impair our competitive position and may have a material adverse effect on our business.

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Risks Related to Commercialization of Our Product Candidates

Our future commercial success depends upon attaining significant market acceptance of our product candidates, if approved, among physicians, patients, third-party payors and others in the medical community.

        Even if we obtain marketing approval for GEN-003, GEN-004 or any other products that we may develop or acquire in the future, the product may not gain market acceptance among physicians, third-party payors, patients and others in the medical community. For example, we currently expect that GEN-003 will be required to be administered by injection initially and with boosters. Physicians or patients may not accept this product as a result of this anticipated dosing requirement. In addition, market acceptance of any approved products depends on a number of other factors, including:

•

the efficacy and safety of the product, as demonstrated in clinical trials;



•

the clinical indications for which the product is approved and the label approved by regulatory authorities for use with the product, including any warnings that may be required on the label;



•

acceptance by physicians and patients of the product as a safe and effective treatment and the willingness of the target patient population to try new therapies and of physicians to prescribe new therapies;



•

the cost, safety and efficacy of treatment in relation to alternative treatments;



•

the availability of adequate course and reimbursement by third-party payors and government authorities;



•

relative convenience and ease of administration;



•

the prevalence and severity of adverse side effects;



•

the effectiveness of our sales and marketing efforts; and



•

the restrictions on the use of our products together with other medications, if any.

        Market acceptance is critical to our ability to generate significant revenue. Any product candidate, if approved and commercialized, may be accepted in only limited capacities or not at all. If any approved products are not accepted by the market to the extent that we expect, we may not be able to generate significant revenue and our business would suffer.

If we are unable to establish sales, marketing and distribution capabilities, we may not be successful in commercializing our product candidates if and when they are approved.

        We do not have a sales or marketing infrastructure and have no experience in the sale, marketing or distribution of pharmaceutical products. To achieve commercial success for any product for which we have obtained marketing approval, we will need to establish a sales and marketing organization.

        In the future, we expect to build a focused sales and marketing infrastructure to market or co-promote some of our product candidates in the United States, if and when they are approved. There are risks involved with establishing our own sales, marketing and distribution capabilities. For example, recruiting and training a sales force is expensive and time consuming and could delay any product launch. If the commercial launch of a product candidate for which we recruit a sales force and establish marketing capabilities is delayed or does not occur for any reason, we would have prematurely or unnecessarily incurred these commercialization expenses. This may be costly, and our investment would be lost if we cannot retain or reposition our sales and marketing personnel.

        Factors that may inhibit our efforts to commercialize our products on our own include:

•

our inability to recruit, train and retain adequate numbers of effective sales and marketing personnel;

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•

the inability of sales personnel to obtain access to physicians;



•

the lack of adequate numbers of physicians to prescribe any future products;



•

the lack of complementary products to be offered by sales personnel, which may put us at a competitive disadvantage relative to companies with more extensive product lines; and



•

unforeseen costs and expenses associated with creating an independent sales and marketing organization.

        If we are unable to establish our own sales, marketing and distribution capabilities and enter into arrangements with third parties to perform these services, our product revenues and our profitability, if any, are likely to be lower than if we were to market, sell and distribute any products that we develop ourselves. In addition, we may not be successful in entering into arrangements with third parties to sell, market and distribute our product candidates or may be unable to do so on terms that are favorable to us. We likely will have little control over such third parties, and any of them may fail to devote the necessary resources and attention to sell and market our products effectively. If we do not establish sales, marketing and distribution capabilities successfully, either on our own or in collaboration with third parties, we will not be successful in commercializing our product candidates.

Coverage and reimbursement may be limited or unavailable in certain market segments for our product candidates, which could make it difficult for us to sell our products profitably.

        Market acceptance and sales of any approved products will depend significantly on the availability of adequate coverage and reimbursement from third-party payors and may be affected by existing and future health care reform measures. Third-party payors, such as government health care programs, private health insurers and health maintenance organizations, decide which drugs they will provide coverage for and establish reimbursement levels. Coverage and reimbursement decisions by a third-party payor may depend upon a number of factors, including the third-party payor's determination that use of a product is:

•

a covered benefit under its health plan;



•

safe, effective and medically necessary;



•

appropriate for the specific patient;



•

cost-effective; and



•

neither experimental nor investigational.

        Third-party payors, whether foreign or domestic, or governmental or commercial, are developing increasingly sophisticated methods of controlling health care costs. Coverage and reimbursement can vary significantly from payor to payor. As a result, obtaining coverage and reimbursement approval for a product from each government and other third-party payor will require us to provide supporting scientific, clinical and cost-effectiveness data for the use of our products to each payor separately, with no assurance that we will be able to provide data sufficient to gain acceptance with respect to coverage and reimbursement. We cannot be sure that coverage or adequate reimbursement will be available for any of our product candidates. Also, we cannot be sure that coverage determinations or reimbursement amounts will not reduce the demand for, or the price of, our products. If reimbursement is not available or is available only to limited levels, we may not be able to commercialize certain of our products. In addition, in the United States third-party payors are increasingly attempting to contain health care costs by limiting both coverage and the level of reimbursement of new drugs. As a result, significant uncertainty exists as to whether and how much third-party payors will reimburse patients for their use of newly approved drugs, which in turn will put pressure on the pricing of drugs.

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Price controls may be imposed, which may adversely affect our future profitability.

        In international markets, reimbursement and health care payment systems vary significantly by country, and many countries have instituted price ceilings on specific products and therapies. In some countries, particularly member states of the European Union, the pricing of prescription pharmaceuticals is subject to governmental control. In these countries, pricing negotiations with governmental authorities can take considerable time after receipt of marketing approval for a product. In addition, there can be considerable pressure by governments and other stakeholders on coverage, prices and reimbursement levels, including as part of cost containment measures. Political, economic and regulatory developments may further complicate pricing negotiations, and pricing negotiations may continue after coverage and reimbursement has been obtained. Reference pricing used by various European Union member states and parallel distribution, or arbitrage between low-priced and high-priced member states, can further reduce prices. In some countries, we may be required to conduct a clinical trial or other studies that compare the cost-effectiveness of our product candidates to other available vaccines in order to obtain or maintain coverage, reimbursement or pricing approval. Publication of discounts by third-party payors or authorities may lead to further pressure on the prices or reimbursement levels within the country of publication and other countries. There can be no assurance that our vaccine candidates will be considered cost-effective by third-party payors, that an adequate level of reimbursement will be available or that the third-party payors' reimbursement policies will not adversely affect our ability to sell our products profitably. If reimbursement of our products is unavailable or limited in scope or amount, or if pricing is set at unsatisfactory levels, our business could be adversely affected.

The impact of recent health care reform legislation and other changes in the health care industry and in health care spending on us is currently unknown, and may adversely affect our business model.

        In the United States, and in some foreign jurisdictions, the legislative landscape continues to evolve. Our revenue prospects could be affected by changes in health care spending and policy in the United States and abroad. We operate in a highly regulated industry and new laws or judicial decisions, or new interpretations of existing laws or decisions, related to health care availability, the method of delivery or payment for health care products and services could negatively impact our business, operations and financial condition. There is significant interest in promoting health care reform, as evidenced by the enactment in the United States of the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act in 2010. It is likely that federal and state legislatures within the United States and foreign governments will continue to consider changes to existing health care legislation. We cannot predict the reform initiatives that may be adopted in the future or whether initiatives that have been adopted will be repealed or modified. The continuing efforts of the government, insurance companies, managed care organizations and other payors of health care services to contain or reduce costs of health care may adversely affect:

•

the demand for any drug products for which we may obtain regulatory approval;



•

our ability to set a price that we believe is fair for our products;



•

our ability to obtain coverage and reimbursement approval for a product;



•

our ability to generate revenues and achieve or maintain profitability; and



•

the level of taxes that we are required to pay.

We face substantial competition, which may result in others discovering, developing or commercializing products before, or more successfully, than we do.

        The development and commercialization of new drug products is highly competitive. Our future success depends on our ability to demonstrate and maintain a competitive advantage with respect to

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the design, development and commercialization of our product candidates. Our objective is to design, develop and commercialize new products with superior efficacy, convenience, tolerability and safety. In many cases, the products that we commercialize will compete with existing, market-leading products.

        Oral antivirals, such as valacyclovir and famciclovir, are products currently approved to treat patients with HSV-2. GEN-003, our lead product candidate, will compete with these products, if approved. In addition, one or more products not currently approved for the treatment of HSV-2, including pritelivir (AiCuris) and HerpV (Agenus) and other vaccines in development by Coridon Pty, Ltd and Vical Incorporated may in the future be granted marketing approval for the treatment of HSV-2 or other conditions for which GEN-003 might be approved.

        Many of our potential competitors have significantly greater financial, manufacturing, marketing, drug development, technical and human resources than we do. Large pharmaceutical companies, in particular, have extensive experience in clinical testing, obtaining regulatory approvals, recruiting patients and in manufacturing pharmaceutical products. Large and established companies such as Merck & Co., Inc., GlaxoSmithKline plc, Novartis, Inc., Sanofi Pasteur, SA, Pfizer Inc. and MedImmune, LLC (a subsidiary of AstraZeneca PLC), among others, compete in the vaccine market. In particular, these companies have greater experience and expertise in securing government contracts and grants to support their research and development efforts, conducting testing and clinical trials, obtaining regulatory approvals to market products, manufacturing such products on a broad scale and marketing approved products. These companies also have significantly greater research and marketing capabilities than we do and may also have products that have been approved or are in late stages of development, and have collaborative arrangements in our target markets with leading companies and research institutions. Established pharmaceutical companies may also invest heavily to accelerate discovery and development of novel compounds or to in-license novel compounds that could make the product that we develop obsolete. As a result of all of these factors, our competitors may succeed in obtaining patent protection and/or FDA approval or discovering, developing and commercializing products before we do. In addition, any new product that competes with an approved product must demonstrate compelling advantages in efficacy, convenience, tolerability and safety in order to overcome price competition and to be commercially successful. If we are not able to compete effectively against potential competitors, our business will not grow and our financial condition and operations will suffer.

Our products may cause undesirable side effects or have other properties that delay or prevent their regulatory approval or limit their commercial potential.

        Undesirable side effects caused by our products or even competing products in development that utilize a common mechanism of action could cause us or regulatory authorities to interrupt, delay or halt clinical trials and could result in the denial of regulatory approval by the FDA or other regulatory authorities and potential product liability claims. We are currently conducting a Phase 1/2a clinical trial for GEN-003. Serious adverse events deemed to be caused by our product candidates could have a material adverse effect on the development of our product candidates and our business as a whole. The most common adverse events to date in the clinical trial evaluating the safety and tolerability of GEN-003 have been fatigue, myalgia (muscle pain), pain tenderness and induration (inflammatory hardening of the skin). Our understanding of the relationship between GEN-003 and these events, as well as our understanding of adverse events in future clinical trials of other product candidates, may change as we gather more information, and additional unexpected adverse events may be observed.

        If we or others identify undesirable side effects caused by our product candidates either before or after receipt of marketing approval, a number of potentially significant negative consequences could result, including:

•

our clinical trials may be put on hold;

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•

we may be unable to obtain regulatory approval for our vaccine candidates;



•

regulatory authorities may withdraw approvals of our vaccines;



•

regulatory authorities may require additional warnings on the label;



•

a medication guide outlining the risks of such side effects for distribution to patients may be required;



•

we could be sued and held liable for harm caused to patients; and



•

our reputation may suffer.

        Any of these events could prevent us from achieving or maintaining market acceptance of our products and could substantially increase commercialization costs.

Risks Related to Our Indebtedness

Our level of indebtedness and debt service obligations could adversely affect our financial condition, and may make it more difficult for us to fund our operations.

        In September 2013 we entered into a secured credit facility pursuant to a working capital term loan facility with Ares Capital Corporation providing for term loans of up to an aggregate of $10.0 million. On September 30, 2013, we drew down an initial $3.5 million under our secured credit facility and paid off our then existing secured credit facility. We drew down the remaining $6.5 million in December 2013. All obligations under our secured credit facility are secured by substantially all of our existing property and assets, excluding our intellectual property and licensed-in technology. This indebtedness may create additional financing risk for us, particularly if our business or prevailing financial market conditions are not conducive to paying off or refinancing our outstanding debt obligations at maturity. This indebtedness could also have important negative consequences, including:

•

we will need to repay our indebtedness by making payments of interest and principal, which will reduce the amount of money available to finance our operations, our research and development efforts and other general corporate activities; and



•

our failure to comply with the restrictive covenants in our secured credit facility could result in an event of default that, if not cured or waived, would accelerate our obligation to repay this indebtedness, and the lender could seek to enforce its security interest in the assets securing such indebtedness.

        To the extent additional debt is added to our current debt levels, the risks described above could increase.

We may not have cash available to us in an amount sufficient to enable us to make interest or principal payments on our indebtedness when due.

        Failure to satisfy our current and future debt obligations under our secured credit facility could result in an event of default and, as a result, our lender could accelerate all of the amounts due. In the event of an acceleration of amounts due under our secured credit facility as a result of an event of default, we may not have sufficient funds or may be unable to arrange for additional financing to repay our indebtedness. In addition, our lender could seek to enforce its security interests in the assets securing such indebtedness.

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We are subject to certain restrictive covenants which, if breached, could have a material adverse effect on our business and prospects.

        Our secured credit facility imposes operating and other restrictions on us. Such restrictions will affect, and in many respects limit or prohibit, our ability and the ability of any future subsidiary to, among other things:

•

dispose of certain assets;



•

change our lines of business;



•

engage in mergers or consolidations;



•

incur additional indebtedness;



•

create liens on assets;



•

pay dividends and make distributions or repurchase our capital stock; and



•

engage in certain transactions with affiliates.

Risks Related to Our Business and Industry

If we fail to attract and keep senior management and key scientific personnel, we may be unable to successfully develop our products, conduct our clinical trials and commercialize our product candidates.

        We are highly dependent on members of our senior management, including William Clark, our President and Chief Executive Officer, Seth Hetherington, M.D., our Chief Medical Officer, Jessica Flechtner, Ph.D., our Vice President of Research, and Paul Giannasca, Ph.D., our Vice President of Development. The loss of the services of any of these persons could impede the achievement of our research, development and commercialization objectives. We have employment agreements with each of these members of senior management and we maintain a keyman insurance policy on Mr. Clark for $2.0 million.

        Recruiting and retaining qualified scientific, clinical, manufacturing, sales and marketing personnel will also be critical to our success. The loss of the services of our executive officers or other key employees could impede the achievement of our research, development and commercialization objectives and seriously harm our ability to successfully implement our business strategy. Furthermore, replacing executive officers and key employees may be difficult and may take an extended period of time because of the limited number of individuals in our industry with the breadth of skills and experience required to successfully develop, gain regulatory approval of and commercialize products. Competition to hire from this limited pool is intense, and we may be unable to hire, train, retain or motivate these key personnel on acceptable terms given the competition among numerous pharmaceutical and biotechnology companies for similar personnel. We also experience competition for the hiring of scientific and clinical personnel from universities and research institutions. In addition, we rely on consultants and advisors, including scientific and clinical advisors, to assist us in formulating our research and development and commercialization strategy. Our consultants and advisors may be employed by employers other than us and may have commitments under consulting or advisory contracts with other entities that may limit their availability to us. If we are unable to continue to attract and retain high quality personnel, our ability to pursue our growth strategy will be limited.

Our employees, independent contractors, principal investigators, consultants, commercial partners, and vendors may engage in misconduct or other improper activities, including noncompliance with regulatory standards and requirements and insider trading.

        We are exposed to the risk of fraudulent or other illegal activity by our employees, independent contractors, principal investigators, consultants, commercial partners, and vendors. Misconduct by these

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parties could include intentional, reckless and/or negligent conduct that fails: to comply with the laws of the FDA and similar foreign regulatory bodies; provide true, complete and accurate information to the FDA and similar foreign regulatory bodies; to comply with manufacturing standards we have established; to comply with federal, state and foreign health care fraud and abuse laws and regulations; to report financial information or data accurately; or to disclose unauthorized activities to us. In particular, the promotion, sale and marketing of health care items and services, as well as certain business arrangements in the health care industry are subject to extensive laws and regulations intended to prevent misconduct, including fraud, kickbacks, self-dealing and other abusive practices. These laws and regulations may restrict or prohibit a wide range of pricing, discounting, marketing and, structuring and commission(s), certain customer incentive programs and other business arrangements. Activities subject to these laws also involve the improper use of information obtained in the course of patient recruitment for clinical trials. It is not always possible to identify and deter such misconduct, and the precautions we take to detect and prevent this activity may not be effective in controlling unknown or unmanaged risks or losses or in protecting us from governmental investigations or other actions or lawsuits stemming from a failure to be in compliance with such laws or regulations. If any such actions are instituted against us, and we are not successful in defending ourselves or asserting our rights, those actions could have a significant impact on our business, including the imposition of civil, criminal and administrative penalties, damages, monetary fines, disgorgement, possible exclusion from participation in Medicare, Medicaid and other federal health care programs, contractual damages, reputational harm, diminished profits and future earnings, and curtailment or restructuring of our operations, any of which could adversely affect our ability to operate our business and our results of operations.

Our relationships with health care professionals, institutional providers, principal investigators, consultants, customers (actual and potential) and third-party payors are, and will continue to be, subject, directly and indirectly, to federal and state health care fraud and abuse, false claims, marketing expenditure tracking and disclosure, government price reporting, and health information privacy and security laws. If we are unable to comply, or have not fully complied, with such laws, we could face penalties, including, without limitation, civil, criminal, and administrative penalties, damages, monetary fines, disgorgement, possible exclusion from participation in Medicare, Medicaid and other federal health care programs, contractual damages, reputational harm, diminished profits and future earnings, and curtailment or restructuring of our operations.

        Our business operations and activities may be directly or indirectly subject to various federal and state fraud and abuse laws, including, without limitation, the federal Anti-Kickback Statute and the federal False Claims Act. If we obtain FDA approval for any of our product candidates and begin commercializing those products in the United States, our potential exposure under such laws will increase significantly, and our costs associated with compliance with such laws are also likely to increase. These laws may impact, among other things, our current activities with principal investigators and research subjects, as well as proposed and future sales, marketing and education programs. In addition, we may be subject to patient privacy regulation by the federal government and state governments in which we conduct our business. The laws that may affect our ability to operate include, but are not limited to:

•

the federal Anti-Kickback Statute, which prohibits, among other things, knowingly and willfully soliciting, receiving, offering or paying any remuneration (including any kickback, bribe, or rebate), directly or indirectly, overtly or covertly, in cash or in kind, to induce, or in return for, either the referral of an individual, or the purchase, lease, order or recommendation of any good, facility, item or service for which payment may be made, in whole or in part, under a federal health care program, such as the Medicare and Medicaid programs;



•

federal civil and criminal false claims laws and civil monetary penalty laws, which prohibit, among other things, individuals or entities from knowingly presenting, or causing to be presented, claims for payment or approval from Medicare, Medicaid, or other third-party payors

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that are false or fraudulent or knowingly making a false statement to improperly avoid, decrease or conceal an obligation to pay money to the federal government;

•

the federal Health Insurance Portability and Accountability Act of 1996, or HIPAA, which created new federal criminal statutes that prohibit knowingly and willfully executing, or attempting to execute, a scheme to defraud any health care benefit program or obtain, by means of false or fraudulent pretenses, representations, or promises, any of the money or property owned by, or under the custody or control of, any health care benefit program, regardless of the payor (e.g., public or private) and knowingly and willfully falsifying, concealing, or covering up by any trick or device a material fact or making any materially false statements in connection with the delivery of, or payment for, health care benefits, items or services relating to health care matters;



•

HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act of 2009 and their respective implementing regulations, which impose requirements on certain covered health care providers, health plans, and health care clearinghouses as well as their respective business associates that perform services for them that involve the use, or disclosure of, individually identifiable health information, relating to the privacy, security and transmission of individually identifiable health information without appropriate authorization;



•

the federal Physician Payments Sunshine Act, created under Section 6002 of the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act of 2010, collectively, ACA, and its implementing regulations requires manufacturers of drugs, devices, biologicals and medical supplies for which payment is available under Medicare, Medicaid or the Children's Health Insurance Program (with certain exceptions) to report annually to the United States Department of Health and Human Services information related to payments or other transfers of value made to physicians (defined to include doctors, dentists, optometrists, podiatrists and chiropractors) and teaching hospitals, as well as ownership and investment interests held by physicians and their immediate family members, with data collection required beginning August 1, 2013 and reporting to the Centers for Medicare & Medicaid Services required by March 31, 2014 and by the 90^th day of each subsequent calendar year;



•

federal consumer protection and unfair competition laws, which broadly regulate marketplace activities and activities that potentially harm consumers;



•

federal government price reporting laws, changed by ACA to, among other things, increase the minimum Medicaid rebates owed by most manufacturers under the Medicaid Drug Rebate Program and offer such rebates to additional populations, that require us to calculate and report complex pricing metrics to government programs, where such reported prices may be used in the calculation of reimbursement and/or discounts on our marketed drugs (participation in these programs and compliance with the applicable requirements may subject us to potentially significant discounts on our products, increased infrastructure costs, and potentially limit our ability to offer certain marketplace discounts);



•

the Foreign Corrupt Practices Act, a United States law which regulates certain financial relationships with foreign government officials (which could include, for example, certain medical professionals); and



•

state law equivalents of each of the above federal laws, such as anti-kickback, false claims, consumer protection and unfair competition laws which may apply to our business practices, including but not limited to, research, distribution, sales and marketing arrangements as well as submitting claims involving health care items or services reimbursed by any third-party payor, including commercial insurers; state laws that require pharmaceutical companies to comply with

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the pharmaceutical industry's voluntary compliance guidelines and the relevant compliance guidance promulgated by the federal government that otherwise restricts payments that may be made to health care providers; state laws that require drug manufacturers to file reports with states regarding marketing information, such as the tracking and reporting of gifts, compensations and other remuneration and items of value provided to health care professionals and entities (compliance with such requirements may require investment in infrastructure to ensure that tracking is performed properly, and some of these laws result in the public disclosure of various types of payments and relationships, which could potentially have a negative effect on our business and/or increase enforcement scrutiny of our activities); and state laws governing the privacy and security of health information in certain circumstances, many of which differ from each other in significant ways, with differing effects.

        In addition, the regulatory approval and commercialization of any of our product candidates outside the United States will also likely subject us to foreign equivalents of the health care laws mentioned above, among other foreign laws.

        Efforts to ensure that our business arrangements will comply with applicable health care laws may involve substantial costs. It is possible that governmental and enforcement authorities will conclude that our business practices may not comply with current or future statutes, regulations or case law interpreting applicable fraud and abuse or other health care laws and regulations. If our operations are found to be in violation of any of the laws described above or any other governmental regulations that apply to us, we may be subject to penalties, including, without limitation, civil, criminal, and administrative penalties, damages, monetary fines, disgorgement, possible exclusion from participation in Medicare, Medicaid and other federal health care programs, contractual damages, reputational harm, diminished profits and future earnings, and curtailment or restructuring of our operations.

We may encounter difficulties in managing our growth and expanding our operations successfully.

        As we seek to advance our product candidates through clinical trials and commercialization, we will need to expand our development, regulatory, manufacturing, marketing and sales capabilities or contract with third parties to provide these capabilities for us. As our operations expand, we expect that we will need to manage additional relationships with various strategic partners, suppliers and other third parties. Future growth will impose significant added responsibilities on members of management. Our future financial performance and our ability to commercialize our product candidates and to compete effectively will depend, in part, on our ability to manage any future growth effectively. To that end, we must be able to manage our development efforts and clinical trials effectively and hire, train and integrate additional management, administrative and, if necessary, sales and marketing personnel. We may not be able to accomplish these tasks, and our failure to accomplish any of them could prevent us from successfully growing our company.

If product liability lawsuits are brought against us, we may incur substantial liabilities and may be required to limit commercialization of our product candidates.

        We face an inherent risk of product liability as a result of the clinical testing of our product candidates and will face an even greater risk if we commercialize any products. For example, we may be sued if any product we develop allegedly causes injury or is found to be otherwise unsuitable during product testing, manufacturing, marketing or sale. Any such product liability claims may include allegations of defects in manufacturing, defects in design, a failure to warn of dangers inherent in the product, negligence, strict liability and a breach of warranties. Claims could also be asserted under state consumer protection acts. If we cannot successfully defend ourselves against product liability claims, we may incur substantial liabilities or be required to limit commercialization of our product candidates.

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Even a successful defense would require significant financial and management resources. Regardless of the merits or eventual outcome, liability claims may result in:

•

decreased demand for any product candidates or products that we may develop;



•

injury to our reputation and significant negative media attention;



•

withdrawal of clinical trial participants;



•

significant costs to defend the related litigations;



•

a diversion of management's time and our resources;



•

substantial monetary awards to trial participants or patients;



•

product recalls, withdrawals, or labeling, marketing or promotional restrictions;



•

loss of revenue;



•

the inability to commercialize any product candidates that we may develop; and



•

a decline in our stock price.

        Failure to obtain and retain sufficient product liability insurance at an acceptable cost to protect against potential product liability claims could prevent or inhibit the commercialization of products we develop. We currently carry product liability insurance covering our clinical trials in the amount of $5.0 million in the aggregate. Although we maintain product liability insurance, any claim that may be brought against us could result in a court judgment or settlement in an amount that is not covered, in whole or in part, by our insurance or that is in excess of the limits of our insurance coverage. Our insurance policies also have various exclusions, and we may be subject to a product liability claim for which we have no coverage. We will have to pay any amounts awarded by a court or negotiated in a settlement that exceed our coverage limitations or that are not covered by our insurance, and we may not have, or be able to obtain, sufficient capital to pay such amounts.

Our auditors have identified a material weakness in our internal control over financial reporting.

        Although we are not yet subject to the certification or attestation requirements of Section 404 of the Sarbanes-Oxley Act, in the course of reviewing our financial statements in preparation for this offering, our independent registered public accounting firm has identified a deficiency that it concluded represented a material weakness in our internal control over financial reporting. The finding by our independent registered public accounting firm relates to our internal control infrastructure as of December 31, 2012. In particular, our auditors noted that our process for evaluating significant transactions and ensuring that such evaluations are properly performed and subject to an appropriate level of review was deficient. Our auditors assessed that these circumstances resulted in the failure to recognize the accretion of cumulative dividends as an adjustment to the carrying value of our Series B preferred stock. Under auditing standards established by the United States Public Company Accounting Oversight Board, a material weakness is a deficiency or combination of deficiencies in internal control over financial reporting, such that there is a reasonable possibility that a material misstatement of our annual or interim financial statements will not be prevented or detected and corrected on a timely basis. We cannot provide any assurance that there will not be other material weaknesses that our independent registered public accounting firm or we will identify. If such issues are identified or if we are unable to produce accurate and timely financial statements, our stock price may be adversely affected and we may be unable to maintain compliance with listing requirements of our stock exchange.

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We must comply with environmental laws and regulations, and failure to comply with these laws and regulations could expose us to significant liabilities.

        We use hazardous chemicals and radioactive and biological materials in certain aspects of our business and are subject to a variety of federal, state and local laws and regulations governing the use, generation, manufacture, distribution, storage, handling, treatment and disposal of these materials. We cannot eliminate the risk of accidental injury or contamination from the use, manufacture, distribution, storage, handling, treatment or disposal of hazardous materials. In the event of contamination or injury, or failure to comply with environmental, occupational health and safety and export control laws and regulations, we could be held liable for any resulting damages and any such liability could exceed our assets and resources. We are uninsured for third-party contamination injury.

We may not be able to win government, academic institution or non-profit contracts or grants.

        From time to time, we may apply for contracts or grants from government agencies, non-profit entities and academic institutions. Such grants have been our only source of revenue to date. Such contracts or grants can be highly attractive because they provide capital to fund the on-going development of our technologies and product candidates without diluting our stockholders. However, there is often significant competition for these contracts or grants. Entities offering contracts or grants may have requirements to apply for or to otherwise be eligible to receive certain contracts or grants that our competitors may be able to satisfy that we cannot. In addition, such entities may make arbitrary decisions as to whether to offer contracts or make grants, to whom the contracts or grants will be awarded and the size of the contracts or grants to each awardee. Even if we are able to satisfy the award requirements, there is no guarantee that we will be a successful awardee. Therefore, we may not be able to win any contracts or grants in a timely manner, if at all.

Risks Related to Our Common Stock and This Offering

We are eligible to be treated as an "emerging growth company" as defined in the Jumpstart Our Business Startups Act of 2012, and we cannot be certain if the reduced disclosure requirements applicable to emerging growth companies will make our common stock less attractive to investors.

        We are an "emerging growth company", as defined in the JOBS Act. For as long as we continue to be an emerging growth company, we may take advantage of exemptions from various reporting requirements that are applicable to other public companies that are not emerging growth companies. These exemptions include:

•

being permitted to provide only two years of audited financial statements, in addition to any required unaudited interim financial statements, with correspondingly reduced "Management's Discussion and Analysis of Financial Condition and Results of Operations" disclosure;



•

not being required to comply with the auditor attestation requirements in the assessment of our internal control over financial reporting;



•

not being required to comply with any requirement that may be adopted by the Public Company Accounting Oversight Board providing for supplemental auditor's reports for additional information about the audit and the financial statements;



•

reduced disclosure obligations regarding executive compensation; and



•

exemptions from the requirements of holding a nonbinding advisory vote on executive compensation and shareholder approval of any golden parachute payments not previously approved.

        We have taken advantage of reduced reporting burdens in this prospectus. In particular, in this prospectus, we have provided only two years of audited financial statements and have not included all

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of the executive compensation related information that would be required if we were not an emerging growth company. We cannot predict whether investors will find our common stock less attractive if we rely on these exemptions. If some investors find our common stock less attractive as a result, there may be a less active trading market for our common stock and our stock price may be more volatile. In addition, the JOBS Act provides that an emerging growth company can take advantage of an extended transition period for complying with new or revised accounting standards. This allows an emerging growth company to delay the adoption of these accounting standards until they would otherwise apply to private companies. We have irrevocably elected not to avail ourselves of this exemption and, therefore, we will be subject to the same new or revised accounting standards as other public companies that are not emerging growth companies.

        We could be an emerging growth company for up to five years, although circumstances could cause us to lose that status earlier, including if the market value of our common stock held by non-affiliates exceeds $700.0 million as of any June 30 before that time or if we have total annual gross revenue of $1.0 billion or more during any fiscal year before that time, in which cases we would no longer be an emerging growth company as of the following December 31 or, if we issue more than $1.0 billion in non-convertible debt during any three-year period before that time, we would cease to be an emerging growth company immediately. Even after we no longer qualify as an emerging growth company, we may still qualify as a "smaller reporting company" if the market value of our common stock held by non-affiliates is below $75.0 million as of June 30 in any given year, which would allow us to take advantage of many of the same exemptions from disclosure requirements, including not being required to comply with the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act and reduced disclosure obligations regarding executive compensation in our periodic reports and proxy statements.

We do not know whether a market will develop for our common stock or what the market price of our common stock will be and, as a result, it may be difficult for you to sell your shares of our common stock.

        Before this offering, there was no public trading market for our common stock. If a market for our common stock does not develop or is not sustained, it may be difficult for you to sell your shares of common stock at an attractive price, or at all. Further, an inactive market may also impair our ability to raise capital by selling shares of our common stock and may impair our ability to enter into strategic partnerships or acquire companies or products by using our shares of common stock as consideration. We cannot predict the prices at which our common stock will trade. It is possible that in one or more future periods our results of operations may be below the expectations of public market analysts and investors and, as a result of these and other factors, the price of our common stock may fall.

        Certain of our existing stockholders and their affiliated entities, including holders of more than 5% of our common stock, have indicated an interest in purchasing an aggregate of approximately $15.0 million in shares of our common stock in this offering at the initial public offering price. To the extent these existing stockholders are allocated and purchase shares in this offering, such purchases would reduce the available public float for our shares because these stockholders will be restricted from selling the shares by restrictions under applicable securities laws described in the "Shares Eligible for Future Sale" section of this prospectus. As a result, the liquidity of our common stock could be significantly reduced from what it would have been if these shares had not been purchased by investors that were not affiliated with us.

The market price of our common stock may be highly volatile, and you may not be able to resell your shares at or above the initial public offering price.

        The initial public offering price for our shares will be determined by negotiations between us and the representatives of the underwriters and may not be indicative of prices that will prevail in the

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trading market. The market price of shares of our common stock could be subject to wide fluctuations in response to many risk factors listed in this section, and others beyond our control, including:

•

results of clinical trials of our product candidates;



•

the timing of the release of results of our clinical trials;



•

results of clinical trials of our competitors' products;



•

regulatory actions with respect to our products or our competitors' products;



•

actual or anticipated fluctuations in our financial condition and operating results;



•

publication of research reports by securities analysts about us or our competitors or our industry;



•

our failure or the failure of our competitors to meet analysts' projections or guidance that we or our competitors may give to the market;



•

additions and departures of key personnel;



•

strategic decisions by us or our competitors, such as acquisitions, divestitures, spin-offs, joint ventures, strategic investments or changes in business strategy;



•

the passage of legislation or other regulatory developments affecting us or our industry;



•

fluctuations in the valuation of companies perceived by investors to be comparable to us;



•

sales of our common stock by us, our insiders or our other stockholders;



•

speculation in the press or investment community;



•

announcement or expectation of additional financing efforts;



•

changes in accounting principles;



•

terrorist acts, acts of war or periods of widespread civil unrest;



•

natural disasters and other calamities;



•

changes in market conditions for biopharmaceutical stocks; and



•

changes in general market and economic conditions.

        In addition, the stock market has recently experienced significant volatility, particularly with respect to pharmaceutical, biotechnology and other life sciences company stocks. The volatility of pharmaceutical, biotechnology and other life sciences company stocks often does not relate to the operating performance of the companies represented by the stock. As we operate in a single industry, we are especially vulnerable to these factors to the extent that they affect our industry or our products, or to a lesser extent our markets. In the past, securities class action litigation has often been initiated against companies following periods of volatility in their stock price. This type of litigation could result in substantial costs and divert our management's attention and resources, and could also require us to make substantial payments to satisfy judgments or to settle litigation.

Our principal stockholders and management own a significant percentage of our stock and will be able to exercise significant influence over matters subject to stockholder approval.

        Upon the closing of this offering, our executive officers and directors, combined with our stockholders who owned more than 5% of our outstanding common stock before this offering will, in the aggregate, beneficially own shares representing approximately 66.1% of our capital stock. Assuming an initial offering price of $13.00 per share, if our 5% stockholders and their affiliated entities purchase all of the $15.0 million of shares they have indicated an interest in purchasing in this offering, the

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number of shares of our common stock beneficially owned by our executive officers, directors and stockholders who owned more than 5% of our outstanding common stock before this offering will, in the aggregate, increase to 72.5% of our capital stock. Accordingly, even after this offering, these stockholders will be able to exert a significant degree of influence over our management and affairs and over matters requiring stockholder approval, including the election of our board of directors and approval of significant corporate transactions. This concentration of ownership could have the effect of entrenching our management and/or the board of directors, delaying or preventing a change in our control or otherwise discouraging a potential acquirer from attempting to obtain control of us, which in turn could have a material and adverse effect on the fair market value of our common stock.

A significant portion of our total outstanding shares may be sold into the public market in the near future, which could cause the market price of our common stock to drop significantly, even if our business is doing well.

        Sales of a substantial number of shares of our common stock in the public market could occur at any time after the expiration of the lock-up agreements described in the "Underwriting" section of this prospectus. These sales, or the market perception that the holders of a large number of shares intend to sell shares, could reduce the market price of our common stock. After this offering, we will have 17,217,104 shares of common stock outstanding. This includes the 5,500,000 shares that we are selling in this offering, which may be resold in the public market immediately. The remaining 11,717,104 shares, or 68.1% of our outstanding shares after this offering, are currently restricted as a result of securities laws or lock-up agreements but will be able to be sold, subject to any applicable volume limitations under federal securities laws with respect to affiliate sales, in the near future as set forth below.

        In addition, as of November 30, 2013, there were 192,559 shares subject to outstanding warrants and 1,578,317 shares subject to outstanding options that will become eligible for sale in the public market to the extent permitted by any applicable vesting requirements, the lock-up agreements and Rules 144 and 701 under the Securities Act. Moreover, after this offering, holders of an aggregate of 11,389,725 shares of our common stock and holders of warrants to purchase 192,559 shares of our common stock will have rights, subject to some conditions, to require us to file registration statements covering their shares or to include their shares in registration statements that we may file for ourselves or other stockholders. If such holders, by exercising their registration rights, cause a large number of securities to be registered and sold into the public market, these sales could have an adverse effect on the market price for our common stock. We also intend to register all shares of common stock that we may issue under our employee benefit plans, including our 2014 Equity Incentive Plan. Once we register these shares and they are issued in accordance with the terms of the plans, they can be freely sold in the public market upon issuance, subject to the lock-up agreements and the restrictions imposed on our affiliates under Rule 144. For more information, see "Shares Eligible for Future Sale—Rule 144".

You will incur immediate and substantial dilution as a result of this offering.

        The initial public offering price of our common stock will be substantially higher than the net tangible book value per share of our common stock. Therefore, if you purchase common stock in this offering, you will pay a price per share that substantially exceeds our pro forma adjusted net tangible book value per share after giving effect to this offering. To the extent shares subsequently are issued under options or warrants, you will incur further dilution. Based on an initial public offering price of $13.00, the midpoint of the range set forth on the cover of this prospectus, you will incur immediate and substantial dilution of $8.80 per share, representing the difference between our pro forma net tangible book value per share, after giving effect to this offering, and the assumed initial public offering price. In addition, purchasers of common stock in this offering will have contributed approximately

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48.2% of the aggregate price paid by all purchasers of our stock but will own approximately 32.1% of our common stock outstanding after this offering.

We have broad discretion in the use of net proceeds from this offering and may not use them effectively.

        We currently intend to use the net proceeds from this offering to fund the continued clinical development of GEN-003 and GEN-004, and to continue to discover and develop other T cell vaccines in our pipeline, including funding the costs of operating a public company. See the section of this prospectus entitled "Use of Proceeds". Any remaining amounts will be used for working capital and general corporate purposes. Although we currently intend to use the net proceeds from this offering in such a manner, we will have broad discretion in the application of the net proceeds. Our failure to apply these funds effectively could affect our ability to continue to develop and commercialize our product candidates. Pending their use, we may invest the net proceeds from this offering in a manner that does not produce income or loses value.

We will incur increased costs as a result of being a public company and our management expects to devote substantial time to public company compliance programs.

        As a public company, we will incur significant legal, insurance, accounting and other expenses that we did not incur as a private company. In addition, our administrative staff will be required to perform additional tasks. For example, in anticipation of becoming a public company, we will need to adopt additional internal controls and disclosure controls and procedures and bear all of the internal and external costs of preparing and distributing periodic public reports in compliance with our obligations under the securities laws. We intend to invest resources to comply with evolving laws, regulations and standards, and this investment will result in increased general and administrative expenses and may divert management's time and attention from product development activities. If our efforts to comply with new laws, regulations and standards differ from the activities intended by regulatory or governing bodies due to ambiguities related to practice, regulatory authorities may initiate legal proceedings against us and our business may be harmed. In connection with this offering, we are increasing our directors' and officers' insurance coverage, which will increase our insurance cost. In the future, it will be more expensive for us to obtain director and officer liability insurance, and we may be required to accept reduced coverage or incur substantially higher costs to obtain coverage. These factors could also make it more difficult for us to attract and retain qualified members of our board of directors, particularly to serve on our audit committee and compensation committee, and qualified executive officers.

        In addition, in order to comply with the requirements of being a public company, we may need to undertake various actions, including implementing new internal controls and procedures and hiring new accounting or internal audit staff. The Sarbanes-Oxley Act requires that we maintain effective disclosure controls and procedures and internal control over financial reporting. We are continuing to develop and refine our disclosure controls and other procedures that are designed to ensure that information required to be disclosed by us in the reports that we file with the SEC is recorded, processed, summarized and reported within the time periods specified in the SEC's rules and forms, and that information required to be disclosed in reports under the Securities Exchange Act of 1934 as amended, or the Exchange Act, is accumulated and communicated to our principal executive and financial officers. Any failure to develop or maintain effective controls could adversely affect the results of periodic management evaluations. In the event that we are not able to demonstrate compliance with the Sarbanes-Oxley Act, that our internal control over financial reporting is perceived as inadequate, or that we are unable to produce timely or accurate financial statements, investors may lose confidence in our operating results and the price of our ordinary shares could decline. In addition, if we are unable to continue to meet these requirements, we may not be able to remain listed on NASDAQ.

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        We are not currently required to comply with the SEC's rules that implement Section 404 of the Sarbanes-Oxley Act, and are therefore not yet required to make a formal assessment of the effectiveness of our internal control over financial reporting for that purpose. Upon becoming a public company, we will be required to comply with certain of these rules, which will require management to certify financial and other information in our quarterly and annual reports and provide an annual management report on the effectiveness of our internal control over financial reporting commencing with our second annual report. This assessment will need to include the disclosure of any material weaknesses in our internal control over financial reporting identified by our management or our independent registered public accounting firm. To achieve compliance with Section 404 within the prescribed period, we will be engaged in a process to document and evaluate our internal control over financial reporting, which is both costly and challenging. In this regard, we will need to continue to dedicate internal resources, potentially engage outside consultants and adopt a detailed work plan to assess and document the adequacy of internal control over financial reporting, continue steps to improve control processes as appropriate, validate through testing that controls are functioning as documented and implement a continuous reporting and improvement process for internal control over financial reporting. Despite our efforts, there is a risk that we will not be able to conclude, within the prescribed timeframe or at all, that our internal control over financial reporting is effective as required by Section 404. If we identify one or more material weaknesses, it could result in an adverse reaction in the financial markets due to a loss of confidence in the reliability of our financial statement.

        Our independent registered public accounting firm will not be required to formally attest to the effectiveness of our internal control over financial reporting until the later of our second annual report or the first annual report required to be filed with the SEC following the date we are no longer an "emerging growth company" as defined in the JOBS Act. We cannot assure you that there will not be material weaknesses or significant deficiencies in our internal controls in the future.

Provisions in our charter documents and Delaware law may have anti-takeover effects that could discourage an acquisition of us by others, even if an acquisition would be beneficial to our stockholders, and may prevent attempts by our stockholders to replace or remove our current management.

        Provisions in our amended and restated certificate of incorporation and amended and restated by-laws that will become effective upon the closing of this offering contain provisions that may have the effect of discouraging, delaying or preventing a change in control of us or changes in our management. These provisions could also limit the price that investors might be willing to pay in the future for shares of our common stock, thereby depressing the market price of our common stock. In addition, because our board of directors is responsible for appointing the members of our management team, these provisions may frustrate or prevent any attempts by our stockholders to replace or remove our current management by making it more difficult for stockholders to replace members of our board of directors. Among other things, these provisions:

•

authorize "blank check" preferred stock, which could be issued by our board of directors without stockholder approval and may contain voting, liquidation, dividend and other rights superior to our common stock;



•

create a classified board of directors whose members serve staggered three-year terms;



•

specify that special meetings of our stockholders can be called only by our board of directors, the chairperson of our board of directors, our chief executive officer or our president;



•

prohibit stockholder action by written consent;



•

establish an advance notice procedure for stockholder approvals to be brought before an annual meeting of our stockholders, including proposed nominations of persons for election to our board of directors;

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•

provide that our directors may be removed only for cause;



•

provide that vacancies on our board of directors may be filled only by a majority of directors then in office, even though less than a quorum;



•

specify that no stockholder is permitted to cumulate votes at any election of directors;



•

expressly authorize our board of directors to modify, alter or repeal our amended and restated by-laws; and



•

require supermajority votes of the holders of our common stock to amend specified provisions of our amended and restated by-laws.

        These provisions, alone or together, could delay or prevent hostile takeovers and changes in control or changes in our management.

        Moreover, because we are incorporated in Delaware, we are governed by the provisions of Section 203 of the Delaware General Corporation Law, which prohibits a person who owns in excess of 15% of our outstanding voting stock from merging or combining with us for a period of three years after the date of the transaction in which the person acquired in excess of 15% of our outstanding voting stock, unless the merger or combination is approved in a prescribed manner.

        Any provision of our amended and restated certificate of incorporation, our amended and restated by-laws or Delaware law that has the effect of delaying or deterring a change in control could limit the opportunity for our stockholders to receive a premium for their shares of our common stock, and could also affect the price that some investors are willing to pay for our common stock.

Our ability to use net operating losses to offset future taxable income may be subject to certain limitations.

        In general, under Section 382 of the Internal Revenue Code of 1986, as amended, or the Code, a corporation that undergoes an "ownership change" is subject to limitations on its ability to utilize its pre-change net operating losses, or NOLs, to offset future taxable income. Our existing NOLs may be subject to substantial limitations arising from previous ownership changes, and if we undergo an ownership change in connection with or after this offering, our ability to utilize NOLs could be further limited by Section 382 of the Code. In addition, future changes in our stock ownership, many of which are outside of our control, could result in an ownership change under Section 382 of the Code. Our NOLs may also be impaired under state law. Accordingly, we may not be able to utilize a material portion of our NOLs. Furthermore, our ability to utilize our NOLs is conditioned upon our attaining profitability and generating U.S. federal taxable income. As described above under "—Risks Related to Our Financial Position and Need for Additional Capital", we have incurred net losses since our inception and anticipate that we will continue to incur significant losses for the foreseeable future; thus, we do not know whether or when we will generate the U.S. federal taxable income necessary to utilize our NOLs.

Our amended and restated certificate of incorporation designates the state or federal courts located in the State of Delaware as the sole and exclusive forum for certain types of actions and proceedings that may be initiated by our stockholders, which could limit our stockholders' ability to obtain a favorable judicial forum for disputes with us or our directors, officers or employees.

        Our amended and restated certificate of incorporation that will become effective upon the closing of this offering provides that, subject to limited exceptions, the state and federal courts located in the State of Delaware will be the sole and exclusive forum for (1) any derivative action or proceeding brought on our behalf, (2) any action asserting a claim of breach of a fiduciary duty owed by any of our directors, officers or other employees to us or our stockholders, (3) any action asserting a claim against us arising pursuant to any provision of the Delaware General Corporation Law, our amended and

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restated certificate of incorporation or our amended and restated by-laws or (4) any other action asserting a claim against us that is governed by the internal affairs doctrine. Any person or entity purchasing or otherwise acquiring any interest in shares of our capital stock shall be deemed to have notice of and to have consented to the provisions of our amended and restated certificate of incorporation described above. This choice of forum provision may limit a stockholder's ability to bring a claim in a judicial forum that it finds favorable for disputes with us or our directors, officers or other employees, which may discourage such lawsuits against us and our directors, officers and employees. Alternatively, if a court were to find these provisions of our amended and restated certificate of incorporation inapplicable to, or unenforceable in respect of, one or more of the specified types of actions or proceedings, we may incur additional costs associated with resolving such matters in other jurisdictions, which could adversely affect our business and financial condition.

Because we do not anticipate paying any cash dividends on our capital stock in the foreseeable future, capital appreciation, if any, will be your sole source of gain.

        You should not rely on an investment in our common stock to provide dividend income. We do not anticipate that we will pay any cash dividends to holders of our common stock in the foreseeable future. Instead, we plan to retain any earnings to maintain and expand our operations. In addition, our ability to pay cash dividends is currently prohibited by the terms of our debt financing arrangement, and any future debt financing arrangement may contain terms prohibiting or limiting the amount of dividends that may be declared or paid on our common stock. Accordingly, investors must rely on sales of their common stock after price appreciation, which may never occur, as the only way to realize any return on their investment. As a result, investors seeking cash dividends should not purchase our common stock.

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

        This prospectus contains forward-looking statements. Forward-looking statements are neither historical facts nor assurances of future performance. Instead, they are based on our current beliefs, expectations and assumptions regarding the future of our business, future plans and strategies, our clinical results and other future conditions. The words "anticipate", "believe", "contemplate", "continue", "could", "estimate", "expect", "forecast", "goal", "intend", "may", "plan", "potential" "predict", "project", "should", "target", "will", "would", or the negative of these terms or other similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words.

        The forward-looking statements in this prospectus include, among other things, statements about:

•

the timing of results of our ongoing and planned clinical trials;



•

our planned clinical trials for GEN-003 and GEN-004;



•

our estimates regarding the amount of funds we require to complete our two planned Phase 2 clinical trials for GEN-003 and our initiated Phase 1 trial and planned Phase 2a trial for GEN-004;



•

our estimate for when we will require additional funding;



•

our plans to commercialize GEN-003 and our other vaccine candidates;



•

the timing of, and our ability to, obtain and maintain regulatory approvals for our product candidates;



•

the rate and degree of market acceptance and clinical utility of any approved product candidate;



•

the potential benefits of strategic partnership agreements and our ability to enter into selective strategic partnership arrangements;



•

our ability to quickly and efficiently identify and develop product candidates;



•

our commercialization, marketing and manufacturing capabilities and strategy;



•

our intellectual property position; and



•

our estimates regarding expenses, future revenues, capital requirements, the sufficiency of our current and expected cash resources and our need for additional financing.

        We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. We have included important factors in the cautionary statements included in this prospectus, particularly in the "Risk Factors" section, that we believe could cause actual results or events to differ materially from the forward-looking statements that we make. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures or investments we may make or collaborations or strategic partnerships we may enter into.

        You should read this prospectus and the documents that we reference in this prospectus and have filed as exhibits to the registration statement of which this prospectus is a part completely and with the understanding that our actual future results may be materially different from what we expect. The forward-looking statements in this prospectus represent our views as of the date of this prospectus. We anticipate that subsequent events and developments will cause our views to change. However, while we may elect to update these forward-looking statements at some point in the future, we have no current intention of doing so except to the extent required by applicable law. You should, therefore, not rely on

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these forward-looking statements as representing our views as of any date subsequent to the date of this prospectus.

        This prospectus includes statistical and other industry and market data that we obtained from industry publications and research, surveys and studies conducted by third parties. Industry publications and third party research, surveys and studies generally indicate that their information has been obtained from sources believed to be reliable, although they do not guarantee the accuracy or completeness of such information. While we believe these industry publications and third party research, surveys and studies are reliable, we have not independently verified such data. With respect to the information from IMS Health, this represents MIDAS Ex-Manufacturer levels sales data. This information is an estimate derived from the use of information under license from the following IMS Health information service: MIDAS Sales Data. IMS Health expressly reserves all rights.

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USE OF PROCEEDS

        We estimate that the net proceeds of the sale of 5,500,000 shares of common stock in this offering will be approximately $63.8 million at an assumed initial public offering price of $13.00 per share, the midpoint of the price range set forth on the cover of this prospectus, after deducting underwriting discounts and commissions and estimated offering expenses payable by us. If the underwriters exercise their over-allotment option in full, we estimate that the net proceeds will be approximately $73.8 million after deducting underwriting discounts and commissions and estimated offering expenses payable by us. Each $1.00 increase or decrease in the assumed initial public offering price of $13.00 per share would increase or decrease our net proceeds by $5.1 million, assuming the number of shares offered by us, as set forth on the cover of this prospectus, remains the same and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us.

        As of September 30, 2013, we had cash and cash equivalents of $12.1 million. We intend to use the net proceeds from this offering, together with our existing cash and cash equivalents and future available borrowings under our credit facility, as follows:

•

approximately $30.0 million to fund research, manufacturing and clinical development in connection with our ongoing Phase 1/2a clinical trial and two planned Phase 2 clinical trial studies for GEN-003;



•

approximately $10.5 million to fund research and development expenses in connection our Phase 1 clinical trial and our planned Phase 2a clinical trial for GEN-004;



•

approximately $5.5 million to fund research and development and manufacturing of our prophylactic chlamydia, HSV-2 and malaria programs to finalize the vaccine candidates, advance the candidates through preclinical toxicology and file an IND; and



•

the remainder for working capital and other general corporate purposes.

        Our expected use of net proceeds from this offering represents our current intentions based upon our present plans and business condition, which could change in the future as our plans and business conditions evolve. As of the date of this prospectus, we cannot predict with certainty all of the particular uses for the net proceeds to be received upon the completion of this offering or the amounts that we will actually spend on the uses set forth above. We may also use a portion of the net proceeds to in-license, acquire or invest in complementary technologies, products or assets.

        The amount and timing of our actual expenditures will depend upon numerous factors, including the results of our research and development efforts, the timing and success of preclinical studies, our ongoing clinical trials or clinical trials we may commence in the future and the timing of regulatory submissions. As a result, our management will have broad discretion over the use of the net proceeds from this offering.

        Pending the use of the proceeds from this offering, we intend to invest the net proceeds in short-term, interest-bearing, investment-grade securities, certificates of deposit or government securities.

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DIVIDEND POLICY

        We have never declared or paid cash dividends on our common stock. We currently intend to retain all available funds and any future earnings, if any, to fund the development and expansion of our business and we do not anticipate paying any cash dividends in the foreseeable future. Any future determination to pay dividends will be made at the discretion of our board of directors. Additionally, our ability to pay dividends on our common stock is limited by restrictions under the terms of the agreements governing our secured credit facility. Payment of future cash dividends, if any, will be at the discretion of the board of directors after taking into account various factors, including our financial condition, operating results, current and anticipated cash needs, the requirements of current or then-existing debt instruments and other factors the board of directors deems relevant.

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CAPITALIZATION

        The following table sets forth our cash and cash equivalents and capitalization as of September 30, 2013:

•

on an actual basis;



•

on a pro forma basis to give effect to (i) the automatic conversion of all outstanding shares of our preferred stock into an aggregate of 11,350,870 shares of common stock upon the closing of this offering (utilizing a conversion ratio equal to 1-to-1.22, which was adjusted to 1-to-0.10 in connection with the 1-for-11.9 reverse stock split of our common stock effected on January 21, 2014, shares of common stock for each share of Series B preferred stock assuming that our initial public offering occurred as of September 30, 2013) and the filing of our amended and restated certificate of incorporation upon the closing of this offering, and (ii) the reclassification of our preferred stock warrant liability to additional paid-in-capital upon the automatic conversion of our preferred stock warrants into warrants exercisable for common stock, which will occur automatically upon the closing of this offering; and



•

on a pro forma as adjusted basis to give further effect to the sale of shares of our common stock offered in this offering, assuming an initial public offering price of $13.00 per share, the midpoint of the price range set forth on the cover page of this prospectus, after deducting underwriting discounts and commissions and estimated offering expenses payable by us.

        You should read this information together with our audited financial statements and related notes appearing elsewhere in this prospectus and the information set forth under the heading "Selected Financial Data" and "Management's Discussion and Analysis of Financial Condition and Results of Operations". Please see the section of this prospectus titled "The Offering" for a description of the rate at which our outstanding Series B preferred stock converts into shares of common stock upon the closing of this offering based on the date on which this offering closes.

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        A $1.00 increase or decrease in the assumed initial public offering price of $13.00 per share would increase or decrease each of cash and cash equivalents, additional paid-in capital, total stockholders' (deficit) equity and total capitalization on a pro forma as adjusted basis by approximately $5.1 million, assuming that the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us.

        The table above does not include:

•

1,573,626 shares of our common stock issuable upon the exercise of stock options outstanding as of September 30, 2013 at a weighted average exercise price of $2.57 per share;



•

192,559 shares of common stock issuable upon the exercise of outstanding warrants as of September 30, 2013 at a weighted-average exercise price of $7.30 per share;



•

280,597 shares of common stock reserved for issuance as of September 30, 2013 pursuant to future equity awards under our Amended and Restated 2007 Equity Incentive Plan; and



•

903,494 shares of common stock reserved for future issuance under our 2014 Equity Incentive Plan which was adopted in January 2014.

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DILUTION

        If you invest in our common stock in this offering, your ownership interest will be diluted to the extent of the difference between the initial public offering price per share of our common stock in this offering and the pro forma as adjusted net tangible book value per share of our common stock after this offering.

        We had a historical net tangible book value of $(73.6) million, or $(248.45) per share of common stock, as of September 30, 2013. The pro forma net tangible book value of our common stock as of September 30, 2013 was $8.1 million, or $0.70 per share of our common stock, after giving effect to (1) the automatic conversion of our outstanding preferred stock into common stock (utilizing a conversion ratio equal to 1-to-1.22, which was adjusted to 1-to-0.10 in connection with the 1-for-11.9 reverse stock split of our common stock effected on January 21, 2014, shares of common stock for each share of Series B preferred stock assuming that our initial public offering occurred as of September 30, 2013), and (2) the reclassification of the preferred stock warrant liability to stockholders' (deficit) equity upon the closing of this offering.

        After giving further effect to the sale of 5,500,000 shares of common stock in this offering, after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us, at an assumed initial public offering price of $13.00 per share, the midpoint of the price range set forth on the cover of this prospectus, our pro forma as adjusted net tangible book value as of September 30, 2013 would have been approximately $72.0 million, or approximately $4.20 per share of common stock. This represents an immediate increase in pro forma as adjusted net tangible book value of $3.50 per share to our existing stockholders and an immediate dilution of $8.80 per share to investors participating in this offering. Dilution per share to new investors is determined by subtracting pro forma net tangible book value per share after this offering from the initial public offering price per share paid by new investors. The following table illustrates this dilution on a per share basis:

        Each $1.00 increase (decrease) in the assumed initial public offering price of $13.00 per share would increase (decrease) our pro forma as adjusted net tangible book value by approximately $5.1 million, the pro forma as adjusted net tangible book value per share by approximately $0.30 per share and the dilution to investors purchasing shares in this offering by approximately $0.70 per share, assuming the number of shares offered by us, as set forth on the cover of this prospectus, remains the same and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us. If the underwriters exercise their option to purchase additional shares, you will experience further dilution.

        The following table summarizes, on a pro forma as adjusted basis as of September 30, 2013, the differences between the number of shares of common stock purchased from us, the total consideration and the average price per share paid by existing stockholders (giving effect to the conversion of all outstanding shares of our preferred stock into 11,350,870 shares of common stock prior to the completion of this offering) and by investors participating in this offering, after deducting underwriting discounts and commissions and estimated offering expenses, at an assumed initial public offering price

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of $13.00 per share, the midpoint of the price range set forth on the cover of this prospectus. As the table illustrates, new investors purchasing shares in this offering will pay an average price per share substantially higher than our existing stockholders paid.

        A $1.00 increase or decrease in the assumed initial public offering price of $13.00 per share would increase or decrease the total consideration paid by new investors by $5.1 million and increase or decrease the percentage of total consideration paid by new investors by approximately 1.9%, assuming that the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same.

        If the underwriters exercise their option to purchase additional shares in full, pro forma as adjusted net tangible book value as of September 30, 2013 will increase to $82.0 million, or $4.56 per share, representing an increase to existing stockholders of $0.36 per share, and there will be a decrease in the dilution to new investors of $0.36.

        The number of shares of common stock to be outstanding after this offering is based on the number of shares outstanding as of September 30, 2013 and excludes the following:

•

1,573,626 shares of common stock issuable upon the exercise of outstanding stock options having a weighted-average exercise price of $2.57 per share;



•

192,559 shares of common stock issuable upon the exercise of outstanding warrants having a weighted-average exercise price of $7.30 per share;



•

280,597 shares of common stock reserved for issuance pursuant to future equity awards under our Amended and Restated 2007 Equity Incentive Plan; and



•

903,494 shares of common stock reserved for future issuance under our 2014 Equity Incentive Plan which was adopted in January 2014.

        Furthermore, we may choose to raise additional capital through the sale of equity or convertible debt securities due to market conditions or strategic considerations even if we believe we have sufficient funds for our current or future operating plans. New investors will experience further dilution if any of our outstanding options or warrants are exercised, new options are issued and exercised under our equity incentive plans or we issue additional shares of common stock, other equity securities or convertible debt securities for lower consideration per share than in this offering in the future.

        Certain of our existing stockholders and their affiliated entities, including holders of more than 5% of our common stock, have indicated an interest in purchasing an aggregate of approximately $15.0 million in shares of our common stock in this offering at the initial public offering price. Assuming an initial public offering price of $13.00 per share, which is the midpoint of the price range set forth on the cover page of this prospectus, these entities would purchase an aggregate of up to approximately 1,153,846 of the 5,500,000 shares in this offering based on these indications of interest. However, because indications of interest are not binding agreements or commitments to purchase, the underwriters could determine to sell more, less or no shares to any of these existing stockholders and any of these existing stockholders could determine to purchase more, less or no shares in this offering. The foregoing discussion and tables do not reflect any potential purchases by these existing stockholders or their affiliated entities.

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SELECTED FINANCIAL DATA

        The selected statements of operations data for the years ended December 31, 2011 and 2012 and the balance sheet data at December 31, 2011 and 2012 have been derived from our audited financial statements included elsewhere in this prospectus. The selected statements of operations data for the nine months ended September 30, 2012 and 2013 and the balance sheet data as of September 30, 2013 have been derived from our unaudited financial statements included elsewhere in this prospectus. These unaudited financial statements have been prepared on a basis consistent with our audited financial statements and, in our opinion, contain all adjustments, consisting only of normal and recurring adjustments, necessary for a fair presentation of such financial data. Our historical results for any prior period are not necessarily indicative of results to be expected in any future period, and our interim period results are not necessarily indicative of results to be expected for a full year or any other interim period.

        The information set forth below should be read in conjunction with the "Management's Discussion and Analysis of Financial Condition and Results of Operations" section of this prospectus and with our financial statements and notes thereto included elsewhere in this prospectus. The selected financial data in this section are not intended to replace the financial statements and are qualified in their entirety by the financial statements and related notes included elsewhere in this prospectus.

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MANAGEMENT'S DISCUSSION AND ANALYSIS
OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

        You should read the following discussion and analysis of our financial condition and results of operations together with the section entitled "Selected Financial Data" and our financial statements and related notes appearing in this prospectus. Some of the information contained in this discussion and analysis or set forth elsewhere in this prospectus, including information with respect to our plans and strategy for our business and related financing, includes forward-looking statements that involve risks and uncertainties. As a result of many factors, including those factors set forth in the "Risk Factors" section of this prospectus, our actual results could differ materially from the results described in or implied by the forward-looking statements contained in the following discussion and analysis.

Overview

        We are a clinical stage biotechnology company that discovers and develops novel vaccines to address infectious diseases for which no vaccine or vaccines with limited effectiveness exist today. We use our proprietary discovery platform, ATLAS, to rapidly design vaccines that act through T cell (or cellular) immune responses, in contrast to approved vaccines, which are designed to act primarily through B cell (or antibody) immune responses. We believe that by harnessing T cells we can develop first-in-class vaccines to address infectious diseases where T cells are central to the control of the disease. In September 2013, we announced human proof-of-concept data for GEN-003, a therapeutic vaccine candidate that we are developing to treat herpes simplex virus-2, or HSV-2, infections. These data from our ongoing Phase 1/2a trial represent the first reported instance of a vaccine significantly reducing viral shedding, an indicator of disease activity in HSV-2. If GEN-003 successfully completes clinical development and is approved, we believe it would represent an important new treatment option for patients with HSV-2. We are also developing a second T cell vaccine candidate, GEN-004 for Streptococcus pneumoniae or pneumococcus, a leading cause of infectious disease mortality worldwide. We have initiated a Phase 1 trial for GEN-004, which we anticipate completing by mid-2014. This Phase 1 trial is designed to demonstrate the T cell response associated with natural protection against pneumococcus. If this trial is successful, we plan to conduct a Phase 2 clinical trial to seek to demonstrate that GEN-004 can reduce pneumococcus in humans by mid-2015.

        We commenced business operations in August 2006. To date, our operations have been limited to organizing and staffing our company, acquiring and developing our proprietary ATLAS technology, identifying potential product candidates and undertaking preclinical studies and clinical trials of our product candidates. All of our revenue to date has been grant revenue. We have not generated any product revenue and do not expect to do so for the foreseeable future. We have primarily financed our operations through the issuance of our equity securities, debt financings and amounts received through grants. At September 30, 2013, we had received an aggregate of $85.5 million in gross proceeds from the issuance of equity securities and gross proceeds from debt facilities and an aggregate of $6.7 million from grants. At September 30, 2013, our cash and cash equivalents were $12.1 million.

        Since inception, we have incurred significant operating losses. Our net losses were $14.7 million and $13.4 million for the years ended December 31, 2011 and 2012, respectively. At September 30, 2013, we had accumulated a deficit of $73.6 million. We expect to incur significant expenses and increasing operating losses for the foreseeable future. Our net losses may fluctuate significantly from quarter to quarter and year to year. We will need to generate significant revenue to achieve profitability, and we may never do so.

        We believe that the net proceeds from this offering, together with our existing cash and cash equivalents at September 30, 2013 and proceeds from our future available borrowings under our debt facility, will enable us to fund our operating expenses and capital expenditure requirements through at least the end of 2015, by which time we expect to have completed our ongoing Phase 1/2a clinical trial

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and the first of our planned Phase 2 clinical trials for GEN-003 for HSV-2 and our Phase 1 clinical trial and our planned Phase 2a clinical trial for GEN-004 for pneumococcus. However, costs related to clinical trials can be unpredictable and therefore there can be no guarantee that the net proceeds from this offering and from these other sources will be sufficient to fund these studies or our operations through this period. These funds will not be sufficient to enable us to conduct pivotal clinical trials for, seek marketing approval for or commercially launch GEN-003, GEN-004 or any other product candidate. Accordingly, to obtain marketing approval for and to commercialize these or any other product candidates, we will be required to obtain further funding through public or private equity offerings, debt financings, collaboration and licensing arrangements or other sources. Adequate additional financing may not be available to us on acceptable terms, or at all. Our failure to raise capital when needed would have a negative effect on our financial condition and our ability to pursue our business strategy.

Financial Overview

Revenue

        Grant revenue consists of revenue earned to conduct vaccine development research. We have received grants from a private not-for-profit organization and federal agencies. These grants have related to the discovery and development of several of our product candidates, including product candidates for the prevention of pneumococcus, chlamydia, and malaria. Revenue under these grants is recognized as research services are performed. Funds received in advance of research services being performed are recorded as deferred revenue. We plan to continue to pursue grant funding, but there can be no assurance we will be successful in obtaining such grants in the future.

        We have no products approved for sale. We will not receive any revenue from any product candidates that we develop until we obtain regulatory approval and commercialize such products or until we potentially enter into agreements with third parties for the development and commercialization of product candidates. If our development efforts for any of our product candidates result in regulatory approval or we enter into collaboration agreements with third parties, we may generate revenue from product sales or from such third parties.

        We expect that our revenue will be less than our expenses for the foreseeable future and that we will experience increasing losses as we continue our development of, and seek regulatory approvals for, our product candidates and begin to commercialize any approved products. Our ability to generate revenue for each product candidate for which we receive regulatory approval will depend on numerous factors, including competition, commercial manufacturing capability and market acceptance of our products.

Research and Development Expenses

        Research and development expenses consist primarily of costs incurred to advance our preclinical and clinical candidates, which include:

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personnel-related expenses, including salaries, benefits, stock-based compensation expense and travel;



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expenses incurred under agreements with contract research organizations, or CROs, contract manufacturing organizations, or CMOs, consultants and other vendors that conduct our clinical trials and preclinical activities;



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costs of acquiring, developing and manufacturing clinical trial materials and lab supplies; and



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facility costs, depreciation and other expenses, which include direct and allocated expenses for rent and maintenance of facilities, insurance and other supplies.

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        We expense internal research and development costs to operations as incurred. We expense third party costs for research and development activities, such as conducting clinical trials, based on an evaluation of the progress to completion of specific tasks such as patient enrollment, clinical site activations or information, which is provided to us by our vendors.

        The following table identifies research and development expenses on a program-specific basis for our product candidates for the years ended December 31, 2011 and 2012, the nine months ended September 30, 2012 and 2013 and the period from August 16, 2006 (inception) to September 30, 2013 (in thousands):

        At September 30, 2013, we had incurred an aggregate of $36.8 million in research and development expenses related to GEN-003 and GEN-004. We expect our research and development expenses will increase as we continue the manufacture of pre-clinical and clinical materials and manage the clinical trials of, and seek regulatory approval for, our product candidates. In the near term, we expect that our research and development expenses will increase as we conduct our ongoing phase 1/2a and planned Phase 2 clinical trials for GEN-003 and a Phase 1 and planned Phase 2a clinical trial for GEN-004. We expect that the total costs to produce material for and to conduct our two planned Phase 2 clinical trials for GEN-003 will be approximately $25.0 million. With respect to GEN-004, we have started a Phase 1 clinical trial in the fourth quarter of 2013 and plan to start a Phase 2a clinical trial in the third quarter of 2014. We expect the total costs for these two trials, including the cost to manufacture the vaccine for these trials, will be approximately $8.0 million. Due to the numerous risks and uncertainties associated with product development, we cannot determine with certainty the duration, costs and timing of these clinical trials, and, as a result, the actual costs to complete these planned clinical trials may exceed the expected costs.

General and Administrative Expenses

        General and administrative expenses consist principally of salaries and related costs for personnel, including stock-based compensation and travel expenses, in executive and other administrative functions. Other general and administrative expenses include facility-related costs, communication expenses and professional fees associated with corporate and intellectual property legal expenses, consulting and accounting services.

        We anticipate that our general and administrative expenses will increase in the future to support the continued research and development of our product candidates and to operate as a public company. These increases will likely include increased costs for insurance, costs related to the hiring of additional personnel and payments to outside consultants, lawyers and accountants, among other expenses. Additionally, if and when we believe a regulatory approval of our first product candidate

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appears likely, we anticipate that we will increase our salary and personnel costs and other expenses as a result of our preparation for commercial operations.

Interest Expense, Net

        Interest expense, net consists primarily of interest expense on our long-term debt facilities and non-cash interest related to the amortization of debt discount and issuance costs, partially offset by interest earned on our cash and cash equivalents.

Other Income (Expense)

        Other income (expense) consists of fair value adjustments on warrants to purchase preferred stock and loss on debt extinguishment.

Accretion of Preferred Stock

        Certain classes of our preferred stock are redeemable beginning in 2017 at the original issuance price plus any declared or accrued but unpaid dividends upon written election of the preferred stockholders in accordance with the terms of our articles of incorporation. Accretion of preferred stock reflects the accretion of issuance costs and, for Series B preferred stock, cumulative dividends based on their respective redemption values.

Critical Accounting Policies and Significant Judgments and Estimates

        Our management's discussion and analysis of our financial position and results of operations is based on our financial statements, which have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP. The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, we evaluate estimates, which include, but are not limited to, estimates related to clinical trial accruals, stock-based compensation expense, warrants to purchase redeemable securities, and reported amounts of revenues and expenses during the reported period. We base our estimates on historical experience and other market-specific or other relevant assumptions that we believe to be reasonable under the circumstances. Actual results may differ materially from those estimates or assumptions.

        While our significant accounting policies are described in more detail in the notes to our financial statements appearing elsewhere in this prospectus, we believe the following accounting policies to be most critical to the judgments and estimates used in the preparation of our financial statements.

Accrued Research and Development Expenses

        As part of the process of preparing our financial statements, we are required to estimate our accrued research and development expenses and other current liabilities. This process involves reviewing open contracts and purchase orders, communicating with our personnel to identify services that have been performed for us and estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of the actual cost. The majority of our service providers invoice us monthly in arrears for services performed or when contractual milestones are met. We make estimates of our accrued research and development expenses and other current liabilities as of each balance sheet date in our financial statements based on facts and circumstances known to us at that time. We periodically confirm the accuracy of our estimates with the service providers and make adjustments, if necessary. Examples of estimated accrued research and development expenses and other current liabilities include fees paid to CROs in connection with clinical trials, CMOs with respect to pre-clinical and clinical materials and intermediaries and vendors in connection with preclinical development activities.

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        We base our expenses related to clinical trials on our estimates of the services performed pursuant to contracts with clinical sites that conduct clinical trials on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. Payments under some of these contracts depend on factors such as the successful enrollment of subjects and the completion of required data submission. In accruing service fees, we estimate the time period over which services will be performed, enrollment of subjects, number of sites and services performed in each period. Additionally, we accrue 10% of the earned amounts at each clinical site, which is payable upon completion of the required data submission for the clinical trial. If our estimates of the status and timing of services performed differs from the actual status and timing of services performed we may report amounts that are too high or too low in any particular period. To date, there has been no material differences from our estimates to the amount actually incurred.

Stock-Based Compensation

        Since our inception in August 2006, we have applied the fair value recognition provisions of Financial Accounting Standards Board Accounting Standards Codification, or ASC, Topic 718, Compensation — Stock Compensation, or ASC 718, to account for stock-based compensation for employees and ASC 718 and ASC 505, Equity, or ASC 505, for non-employees. We recognize compensation costs related to stock options granted to employees based on the estimated fair value of the awards on the date of grant. Stock compensation related to non-employee awards is re-measured at each reporting period until the awards are vested. Described below is the methodology we have utilized in measuring stock-based compensation expense.

        Determining the amount of stock-based compensation to be recorded requires us to develop estimates of the fair value of stock-based awards as of their measurement date. We recognize stock-based compensation expense over the requisite service period, which is the vesting period of the award. Calculating the fair value of stock-based awards requires that we make highly subjective assumptions. We use the Black-Scholes option pricing model to value our stock option awards. Use of this valuation methodology requires that we make assumptions as to the volatility of our common stock, the fair value of our common stock on the measurement date, the expected term of our stock options, the risk free interest rate for a period that approximates the expected term of our stock options and our expected dividend yield. Because we are a privately held company with a limited operating history, we utilize data from a representative group of publicly traded companies to estimate expected stock price volatility. We selected representative companies from the biopharmaceutical industry with characteristics similar to us. We use the simplified method as prescribed by the SEC Staff Accounting Bulletin No. 107, Share-Based Payment as we do not have sufficient historical stock option activity data to provide a reasonable basis upon which to estimate the expected term of stock options granted to employees. For non-employee grants, we use an expected term equal to the remaining contractual term of the award. We utilize a dividend yield of zero based on the fact that we have never paid cash dividends and have no current intention of paying cash dividends. The risk-free interest rate used for each grant is based on the U.S. Treasury yield curve in effect at the time of grant for instruments with a similar expected life.

        Under ASC 718, we are required to estimate the level of forfeitures expected to occur and record stock-based compensation expense only for those awards that we ultimately expect will vest. For all periods presented, our estimated annual forfeiture rate was 10.52%.

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        Stock-based compensation expense includes options granted to employees and non-employees and has been reported in our statements of operations and comprehensive loss as follows (in thousands):

        We estimated the fair value of stock options of each employee stock award at the grant date using assumptions regarding the fair value of the underlying common stock on each grant date and the following additional assumptions:

        At September 30, 2013, we had approximately $1.1 million of total unrecognized compensation expense, net of related forfeiture estimates, which we expect to recognize over a weighted-average remaining vesting period of approximately three years. While our stock-based compensation expense for stock options has not been significant to date, we expect the effect to grow in future periods due to the potential increases in the value of our common stock and increased number of stock options granted due to anticipated increases in our overall headcount.

        The following table presents the grant dates of stock options that we granted from January 1, 2012 through October 31, 2013 along with the corresponding exercise price for each option grant and our current estimate of the fair value per share of our common stock on each grant date, which we utilize to calculate stock-based compensation expense:

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        At September 30, 2013, options to purchase 1,573,626 shares of our common stock were outstanding. The aggregate intrinsic value of these options was $16.4 million, assuming an initial public offering price of $13.00 per share, the midpoint of the price range set forth on the cover page of this prospectus. The intrinsic value of all outstanding vested and unvested options as of September 30, 2013, assuming an initial public offering price of $13.00 per share, the midpoint of the price range set forth on the cover page of this prospectus, are as follows:

Determination of the Fair Value of Common Stock on Grant Dates

        Our board of directors determined the fair value of our common stock considering, in part, the work of an independent third-party valuation specialist. The board determined the estimated per share fair value of our common stock at various dates considering valuations performed in accordance with the guidance outlined in the American Institute of Certified Public Accountants Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation, also known as the Practice Aid. Following the consummation of this offering, the fair value of our common stock will be determined based on the quoted market price of our common stock. We engaged an independent third-party valuation specialist to perform contemporaneous valuations as of December 31, 2011, December 31, 2012, July 25, 2013, August 12, 2013 and October 21, 2013 and a retrospective valuation as of March 6, 2013. In conducting the valuations, the independent third-party valuation specialist considered all objective and subjective factors that it believed to be relevant for each valuation conducted in accordance with the Practice Aid, including our best estimate of our business condition, prospects and operating performance at each valuation date. Other significant factors included:

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the prices of our preferred stock sold to outside investors in arm's length transactions, and the rights, preferences and privileges of our preferred stock as compared to those of our common stock, including the liquidation preferences of our preferred stock;



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our results of operations, financial position and the status of research and development efforts;



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the composition of, and changes to, our management team and board of directors;



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the lack of liquidity of our common stock;



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our stage of development and business strategy and the material risks related to our business and industry;



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the valuation of publicly traded companies in the life sciences and biotechnology sectors, as well as recently completed mergers and acquisitions of guideline companies;



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any external market conditions affecting the life sciences and biotechnology industry sectors;



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the likelihood of achieving a liquidity event for the holders of our common stock and stock options, such as an initial public offering, or IPO, or a sale of our company, given prevailing market conditions; and



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the state of the IPO market for similarly situated privately held biotechnology companies.

        The dates of our contemporaneous valuations have not always coincided with the dates of our stock option grants. In determining the exercise prices of the stock options set forth in the table above, our board of directors considered, among other things, the most recent contemporaneous valuation of our common stock and their assessment of additional objective and subjective factors that were relevant as of the grant dates. The additional factors considered when determining whether any changes in the fair value of our common stock had occurred between the most recent contemporaneous valuation and the grant dates included our stage of research and preclinical development, our operating and financial performance and current business conditions.

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        There are significant judgments and estimates inherent in the determination of the fair value of our common stock. These judgments and estimates include assumptions regarding our future operating performance, the time to completing an IPO or other liquidity event, the related valuations associated with such events, and the determinations of the appropriate valuation methods at each valuation date. If we had made different assumptions, our stock-based compensation expense, net loss and net loss per share applicable to common stockholders could have been materially different.

        In July 2013, based on the progress of our clinical pipeline, overall capital market conditions, and the improving market for biopharmaceutical IPOs, our board of directors determined and directed management to begin preparation and submission of a confidential draft registration statement for an IPO. As a result of the updated information regarding potential future liquidity events, we performed a retrospective valuation as of March 6, 2013 because this grant date was more than two months from the most current contemporaneous valuation at December 31, 2012. From December 31, 2012 to March 6, 2013, we did not receive any significant scientific data or results or experience any other material events that would affect the fair value of our common stock.

Common Stock Valuation Methodologies

        The valuations we obtained were prepared in accordance with the guidelines in the Practice Aid, which prescribes several valuation approaches for setting the value of an enterprise, such as the cost, market and income approaches, and various methodologies for allocating the value of an enterprise to its common stock. We generally used the market approach, in particular the guideline company and precedent transaction methodologies, based on inputs from comparable public companies' equity valuations and comparable acquisition transactions, to estimate the enterprise value of our company.

Methods Used to Allocate Our Enterprise Value to Classes of Securities

        In accordance with the Practice Aid, we considered the various methods for allocating the enterprise value across our classes and series of capital stock to determine the fair value of our common stock at each valuation date. The methods considered consisted of the following:

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Probability-Weighted Expected Return Method, or PWERM.  The PWERM is a scenario-based analysis that estimates the value per share based on the probability-weighted present value of expected future investment returns, considering each of the possible outcomes available to us, as well as the economic and control rights of each share class.



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Option Pricing Method, or OPM.  Under the option pricing method, shares are valued by creating a series of call options with exercise prices based on the liquidation preferences and conversion terms of each equity class. The values of the preferred and common stock are inferred by analyzing these options.



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Hybrid Method.  The hybrid method employs the concepts of the PWERM and OPM merged into a single framework. The PWERM estimates the future equity value under a range of IPO exits and allocates the same in each scenario according to the subject company's capital structure, probability-weighting each exit and discounting the value to a present value equivalent using a risk-adjusted discount rate. The OPM consists of the scenario where we remain private, and is modeled over a weighted average term to exit using a financing round or external comparable benchmarks as the basis for fair market value determination.

        The foregoing valuation methodologies are not the only methodologies available and they will not be used to value our common stock once this offering is complete. We cannot make assurances as to any particular valuation for our common stock. Accordingly, investors are cautioned not to place undue reliance on the foregoing valuation methodologies as an indicator of future stock prices.

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Valuation of Common Stock at December 31, 2011

        We engaged a third-party valuation specialist to conduct a contemporaneous valuation of our common stock at December 31, 2011. At December 31, 2011, the most current round of equity financing was over a year earlier and therefore we did not place as much bearing on the most recent round of financing when determining the fair value of our common stock. As a result, we used the PWERM to estimate our enterprise value and to allocate this value to the various outstanding equity instruments. Under this method, the value of our common stock was based on the probability-weighted present value of expected future investment returns considering each of these possible outcomes and the rights of each class and series of our equity.

        The fair value of our common stock was estimated using a probability-weighted expected return method that afforded value to common stockholders under several future stockholder exit or liquidity event scenarios, either through (1) an IPO; (2) an acquisition or sale of our company at a premium to the cumulative liquidation preference of the preferred stockholders; or (3) an acquisition or sale of our company at a value below the cumulative liquidation preference of the preferred stockholders.

        Each individual stockholder exit or liquidity scenario considered in the analysis depended on the specific facts and circumstances, internal and external, present as of each valuation date. The future projected enterprise value used to value our common stock in the IPO scenarios and the sale scenarios were estimated by application of the market approach based on certain key assumptions, including the following:

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valuations of companies prior to the receipt of proceeds from initial public offerings completed within three years of the valuation date;



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estimated third-party sale values based on recent transactions involving biotechnology or biopharmaceutical companies; and



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expected dates for a future IPO or sale of our company.

        There were seven total scenarios considered in this valuation. Four of the scenarios assumed a stockholder exit, either through an IPO, sale of our company or sale of the technology. The remaining three scenarios assumed a downside exit event where no value is attributed to the common shareholders. For the IPO and sale scenarios, the estimated values of our common stock were estimated using assumptions as to pre-money or sale valuations determined with respect to those scenarios as described above, and dates of those scenarios, and an appropriate risk-adjusted discount rate. Finally, we calculated the present value for our common stock based on our estimate of the relative likelihood of occurrence of each scenario. A 10% weighting was assigned to the IPO scenarios split evenly between the high and low case scenarios, 30% weighting to the sale scenarios split evenly between the high and low case scenarios, and 60% weighting to the remaining scenarios.

        Finally, the estimated fair value of our common stock was reduced by a discount for lack of marketability. A discount is appropriate because our common stock is unregistered, and the holder of a minority interest in the common stock may not influence the timing of a liquidity event for our company. Our estimate of the appropriate discount for lack of marketability took into consideration put option methodologies consistent with the Practice Aid. The discount rate selected also took into account empirical studies of restricted stock issued by publicly-traded companies.

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        The following table summarizes the significant assumptions for each of the valuation scenarios used in the PWERM analysis to determine the fair value of our common stock as of December 31, 2011.

        Based on these factors, we determined that our common stock had a fair value of $1.79 per share at December 31, 2011.

Stock Options Granted from January 2012 to November 2012

        Our board of directors granted stock options to purchase 2,016, 3,360, 2,521, 46,604, and 378 shares of our common stock on January 19, 2012, February 15, 2012, May 24, 2012, July 26, 2012, and November 15, 2012, respectively, and determined the fair value of our common stock on each date of grant to be $1.79 per share.

        In addition to the factors described above, our board of directors also considered the third-party valuation as of December 31, 2011 in estimating the fair value of our common stock. From December 31, 2011 through July 26, 2012, we did not receive any significant scientific data or results, or experience any other material events that would affect the fair value of our common stock. In addition, there were no significant changes in the overall capital markets that affected the assumptions used to estimate the fair value of our common stock. Given the uncertainty around a future liquidity event and the early stages of our clinical trial for GEN-003, our board of directors considered that no significant event or other circumstances had occurred between December 31, 2011 and July 26, 2012 and determined that there was no change in the fair value of our common stock during that period.

        Subsequent to the issuance of the November 15, 2012 award, we received a valuation dated December 31, 2012, as discussed below. Since this valuation was based primarily on the issuance of Series C preferred stock in October 2012 and the related dilutive effect on the common stock, the fair value of the common stock determined in the December 31, 2012 valuation was applied retrospectively to the grant on November 15, 2012 and the fair value of our common stock was reduced from $1.79 per share to $1.31 per share for accounting purposes, which had an immaterial effect on our financial results. From November 15, 2012 through December 31, 2012, we did not receive any significant scientific data or results, or experience any other material events that would affect the fair value of our common stock. In addition, there were no significant changes in the overall capital markets that affected the fair value of our common stock.

Valuation of Common Stock at December 31, 2012

        We engaged a third-party valuation specialist to conduct a contemporaneous valuation of our common stock at December 31, 2012. In conducting this valuation, we used the OPM. We elected to switch to the OPM from the PWERM used for the December 31, 2011 valuation as the recent closing of the Series C preferred stock financing in September 2012 was considered a better indicator of value than using estimates of potential future liquidity events. Our equity value was estimated to be $71.6 million based on the recent Series C preferred stock transaction, a methodology referred to as a backsolve method according to the Practice Aid. The equity value was allocated among the outstanding shares of our preferred and common stock also using the OPM.

        The time to liquidity was estimated as two years based on then-current plans and estimates of our board of directors and management regarding a liquidity event. The risk free rate was estimated using

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the two year yield on government bonds. The annual volatility was estimated to be 64% which was based on the observed historical volatility of publicly-traded shares issued by companies which are comparable to ours.

        A discount for lack of marketability was applied to the value indicated for our common stock. The estimate of the appropriate discount for lack of marketability took into consideration put option methodologies consistent with the Practice Aid. The estimated discount for lack of marketability of 30% was applied to the value indicated for our common stock.

        Based on these factors, we determined that our common stock had a fair value of $1.31 per share as of December 31, 2012.

Stock Options Granted from January 2013 to February 2013

        Our board of directors granted options to purchase 2,394 and 31,092 shares of our common stock on January 17, 2013 and February 4, 2013, respectively, and determined the fair value of our common stock on each date of grant to be $1.31 per share. In addition to the factors described above, our board of directors also considered the valuations as of December 31, 2012 and, as discussed below, as of March 6, 2013, which concluded that the fair value of our common stock had not changed through that date, in estimating the fair value of our common stock. From January 1, 2013 through February 4, 2013, we did not obtain any significant scientific data or results, have any material corporate events such as financing events or enter into any other significant arrangements, or any other entity specific events that would affect the assumptions used to estimate the fair value of our common stock. In addition, there were no significant changes in the overall capital markets that would have affected the fair value of our common stock. As a results, the board of directors determined that the fair value of our common stock remained at $1.31 per share between January 1, 2013 and February 4, 2013.

Valuation of Common Stock at March 6, 2013

        We engaged a third-party valuation specialist to conduct a retrospective independent valuation of our common stock as of March 6, 2013. In conducting this valuation, we used the OPM. Our equity value was estimated to be $77.0 million based on the recent transaction involving our Series C preferred stock, a methodology referred to as a backsolve method according to the Practice Aid, and considered the market movement in relevant market indices between the December 31, 2012 valuation date and the March 6, 2013 valuation date. The time to liquidity was estimated to be 1.8 years based on then-current plans and estimates of our board of directors and management regarding a liquidity event. The risk free rate was estimated using the 1.8 year yield on government bonds. The annual volatility was estimated to be 61% based on the observed historical volatility of publicly-traded shares issued by companies which are comparable to ours.

        A discount for lack of marketability was applied to the value indicated for our common stock. The estimate of the appropriate discount for lack of marketability took into consideration put option methodologies consistent with the Practice Aid. The estimated discount for lack of marketability of 30% was applied to the value indicated for our common stock.

        Based on these factors, we determined that our common stock had a fair value of $1.31 per share at March 6, 2013.

Stock Options Granted from March 2013 to May 2013

        Our board of directors granted options to purchase 12,181 and 336 shares of our common stock on March 6, 2013 and May 23, 2013, respectively, and determined the fair value of our common stock on each date of grant to be $1.31 per share. Our board of directors considered the most recent independent third-party valuation at December 31, 2012.

        The fair value of our common stock at March 6, 2013 was subsequently supported by the independent third-party valuation which was dated concurrently with this grant. Subsequent to the issuance of the May 23, 2013 award, we received a valuation dated July 25, 2013, as discussed below. Since this valuation was based primarily on the changes in the capital markets and preliminary data that was received around the May 23, 2013 grant date, the fair value of the common stock determined in the July 25, 2013 valuation was applied retrospectively to the grant on May 23, 2013, and the fair value of our common stock was increased from $1.31 per share to $3.45 per share for accounting purposes, which had an immaterial effect on our financial results.

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Valuation of Common Stock at July 25, 2013

        We engaged a third-party valuation specialist to conduct a contemporaneous valuation of our common stock as of July 25, 2013. Late in the second quarter of 2013, management and our board of directors believed that a future IPO could be possible based on our preliminary GEN-003 clinical results obtained in June 2013 and the more favorable IPO market conditions in the life sciences industry than in previous periods. To estimate our enterprise value, the hybrid method was used. The hybrid method is a PWERM where the equity value in one of the scenarios is calculated using an OPM. The hybrid method considered one IPO scenario and one OPM scenario. The method to value our common stock was switched to the hybrid method from the OPM, which was used for valuing our common stock at March 6, 2013, as there was increased probability of a liquidity event through an IPO, which should be weighted in the determination of the fair value of our common stock.

        For the July 25, 2013 valuation, the estimated fair value of our common stock was determined by assigning a 75% weighting to the estimated fair value using the OPM backsolve method and a 25% weighting to the estimated fair value under the IPO scenario. The 75% weighting on the OPM backsolve method was appropriate due to the proximity of the issuance of our Series C preferred stock in September 2012 to the valuation date. The weighting for the IPO scenario was deemed appropriate because at the time of the valuation, while an IPO scenario had become more probable, there was still significant risk of completing an IPO and no decision by the board of directors to pursue a transaction had been made.

        For the OPM scenario, our estimated equity value was based on the recent transaction involving our Series C preferred stock, adjusted for the market movement observed in relevant market indices between the December 31, 2012 valuation date and the July 25, 2013 valuation date. The time to a liquidity event was estimated to be 1.4 years and an annual volatility rate of 61% was assumed based on historical trading for the guideline public companies considered.

        These methodologies were utilized to arrive at a fair value of our common stock on a marketable basis. A discount for lack of marketability was applied to the value indicated for our common stock. The estimate of the appropriate discount for lack of marketability took into consideration put option methodologies consistent with the Practice Aid. The estimated discount for lack of marketability of 20% was applied to the value indicated for our common stock.

        Based on these factors, we determined that our common stock had a fair value of $3.45 per share at July 25, 2013.

Stock Options Granted in July 2013

        Our board of directors granted options to purchase 439,865 shares of our common stock on July 25, 2013 and determined the fair value of our common stock on the date of grant to be $3.45 per share. Our board of directors considered the independent third-party valuation which was dated concurrently with the July 25, 2013 grant.

Valuation of Common Stock at August 12, 2013

        We engaged a third-party valuation specialist to conduct a contemporaneous valuation of our common stock as of August 12, 2013. To estimate our enterprise value, we used the hybrid method which is consistent with the previous valuation at July 25, 2013. The hybrid method is a PWERM where the equity value in one of the scenarios is calculated using an OPM. The hybrid method considered one IPO scenario and one OPM scenario.

        For the August 12, 2013 valuation, the estimated fair value of our common stock was determined by assigning a 75% weighting to the estimated fair value using the OPM backsolve method and a 25% weighting to the estimated fair value under the IPO scenario. These weightings remained unchanged from the July 25, 2013 valuation since there had been no significant changes in the Company's plans

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between these two dates. Specifically, there was still significant risk of completing an IPO and no decision by the board of directors to pursue a transaction had been made.

        For the OPM scenario, our estimated equity value of the Company was based on the recent transaction involving our Series C preferred stock, adjusted for the market movement observed in relevant market indices between the December 31, 2012 valuation date and the August 12, 2013 valuation date. The time to a liquidity event was estimated to be 1.4 years and an annual volatility rate of 68% was assumed based on historical trading for the guideline public companies considered.

        We used these methodologies to arrive at a fair value of our common stock on a marketable basis. A discount for lack of marketability was applied to the value indicated for our common stock. The estimate of the appropriate discount for lack of marketability took into consideration put option methodologies consistent with the Practice Aid. The estimated discount for lack of marketability of 20% was applied to the value indicated for our common stock.

        Based on these factors, we determined that our common stock had a fair value of $3.45 per share at August 12, 2013.

Stock Options Granted in August 2013

        Our board of directors granted options to purchase 35,942 shares of our common stock on August 12, 2013 and determined the fair value of our common stock on the date of grant to be $3.45 per share. Our board of directors considered the independent third-party valuation which was dated concurrently with the August 12, 2013 grant.

Valuation of Common Stock at October 21, 2013

        We engaged a third-party valuation specialist to conduct a contemporaneous valuation of our common stock as of October 21, 2013. To estimate our enterprise value, we used the hybrid method which is consistent with the previous valuations at July 25, 2013 and August 13, 2013. The hybrid method is a PWERM where the equity value in one of the scenarios is calculated using an OPM. The hybrid method considered one IPO scenario and one OPM scenario.

        For the October 21, 2013 valuation, the estimated fair value of our common stock was determined by assigning a 45% weighting to the estimated fair value using the OPM backsolve method and a 55% weighting to the estimated fair value under the IPO scenario. We increased the weighting of the IPO scenario compared to the August 12, 2013 valuation as our board of directors approved the Company to pursue an IPO and we selected investment bankers and made significant progress to file a registration statement. In addition, we have continued to make scientific progress, including filing an IND for GEN-004, which has increased the probability of successfully completing an IPO.

        For the OPM scenario, our estimated equity value of the Company was based on the recent transaction involving our Series C preferred stock, adjusted for the market movement observed in relevant market indices between the December 31, 2012 valuation date and the October 21, 2013 valuation date. The time to a liquidity event was estimated to be 1.2 years and an annual volatility rate of 75% was assumed based on historical trading for the guideline public companies considered.

        We used these methodologies to arrive at a fair value of our common stock on a marketable basis. A discount for lack of marketability was applied to the value indicated for our common stock. The estimate of the appropriate discount for lack of marketability took into consideration put option methodologies consistent with the Practice Aid. The estimated discount for lack of marketability of 20% was applied to the value indicated for our common stock.

        Based on these factors, we determined that our common stock had a fair value of $5.47 per share at October 21, 2013.

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Stock Options Granted in October 2013

        Our board of directors granted options to purchase 36,966 shares of our common stock on October 21, 2013 and determined the fair value of our common stock on the date of grant to be $5.47 per share. Our board of directors considered the independent third-party valuation which was dated concurrently with the October 21, 2013 grant.

Offering Price

        On January 17, 2014, we and our underwriters determined the estimated price range for this offering, as set forth on the cover page of this prospectus. The midpoint of the price range is $13.00 per share. In comparison, our estimate of the fair value of our common stock was $5.47 per share as of October 21, 2013. We note that, as is typical in initial public offerings, the estimated price range for this offering was not derived using a formal determination of fair value, but was determined by negotiation between us and the underwriters. Among the factors that were considered in setting this range were our prospects and the history of and prospects for our industry, the general condition of the securities markets and the recent market prices of, and the demand for, publicly-traded common stock of generally comparable companies. The difference between the fair value of our common stock as of the most recent common stock valuation date and the midpoint of the estimated price range for this offering is primarily the result of the initiation of a Phase 1 trial for GEN-004 in November 2013 and the allowance by the U.S. Patent and Trademark Office of a patent application covering HSV-2 vaccine formulations in November 2013, the issuance of a patent covering HSV-2 formulations in December 2013, the filing of a registration statement with the Securities and Exchange Commission and preparation to launch a roadshow for this offering and the anticipated conversion of all outstanding shares of our preferred stock into common stock upon completion of this offering, thus eliminating the superior rights and preferences of our preferred stock as compared to our common stock. The estimated price range was also affected by, among other things, the size of this offering and the continuing significant volatility in the financial markets. The estimated initial public offering price range reflected our discussions with the underwriters and the factors above and was not determined using the methodology used by management and the third party valuation firm to value our stock in October 2013. Because the price range was determined through discussions with the underwriters and was not determined using the methodology that management and the third party valuation firm used to value our stock in October 2013, we are not able to quantify the amount that any particular factor contributed to the determination of the estimated price range.

Results of Operations

Comparison of the Years Ended December 31, 2011 and December 31, 2012

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Grant Revenue

        Grant revenue increased by $0.2 million from the year ended December 31, 2011 to the year ended December 31, 2012. This increase was due to the additional revenue in 2012 of $0.4 million related to a grant to fund research for our pneumococcus program and additional grant revenue of $0.1 million under our chlamydia grant offset by decreased revenue related to our government grant of $0.3 million due to lower costs incurred in our malaria program.

Research and Development Expenses

        Research and development expenses decreased by $2.3 million from the year ended December 31, 2011 to the year ended December 31, 2012. This decrease was primarily due to higher costs in 2011 of $3.3 million attributable to material costs incurred in preparation for the commencement of our toxicology and Phase 1 clinical trial for GEN-003 which did not recur in 2012 and decreased purchases of lab supplies in 2012 of approximately $0.9 million. These decreases were partially offset by an increase in 2012 of $2.0 million attributable to the cost of our clinical trial for GEN-003 which began in the third quarter of 2012.

General and Administrative Expenses

        General and administrative expenses increased by $0.7 million from the year ended December 31, 2011 to the year ended December 31, 2012. This increase was primarily due to additional overhead and personnel costs in 2012 of $0.2 million to support our on-going business development activities, $0.1 million in increased facility costs and $0.2 million related to higher legal patent expenses.

Other Income

        Other income consisted of the fair value adjustment of our warrants to purchase preferred stock. The increase in other income from the year ended December 31, 2011 to the year ended December 31, 2012 of $18 thousand was due primarily to a decrease in the fair value of the underlying preferred stock.

Interest Expense, Net

        Interest expense, net increased $0.5 million from the year ended December 31, 2011 to the year ended December 31, 2012. The increase in net interest expense was primarily attributable to an increase amounts borrowed under our loan facility that we entered into in October 2011, resulting in additional borrowings of $5.0 million in March 2012.

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Comparison of the Nine Months Ended September 30, 2012 and September 30, 2013

Grant Revenue

        Grant revenue decreased by $0.7 million from the nine months ended September 30, 2012 to the nine months ended September 30, 2013. This decrease was primarily due to the completion of the grant to fund research for our pneumococcus program during 2012.

Research and Development Expenses

        Research and development expenses increased by $4.1 million from the nine months ended September 30, 2012 to the nine months ended September 30, 2013. This increase was due primarily to higher costs of $2.1 million in 2013 attributable to external manufacturing costs for preclinical and clinical supply of GEN-004 in preparation for the commencement of our toxicology and clinical trials for GEN-004, an increase of $1.1 million in 2013 attributable to the cost of our clinical trial for GEN-003 which began in the third quarter of 2012 and an increase of $0.5 million due to higher salary and salary related costs to support additional research and manufacturing efforts.

General and Administrative Expenses

        General and administrative expenses increased $0.5 million from the nine months ended September 30, 2012 to the nine months ended September 30, 2013. This increase in 2013 was due primarily to higher legal, professional and audit fees of $0.3 million and employee related costs of $0.1 million.

Other Income (Expense)

        Other income (expense) consisted of the fair value adjustment of our warrants to purchase preferred stock and loss on debt extinguishment. The decrease in other income (expense) from the nine months ended September 30, 2012 to the nine month ended September 30, 2013 of $0.4 million was due primarily to a $0.2 million increase in fair value of our warrants to purchase preferred stock as a result of an increase in the fair value of the underlying preferred stock and $0.2 million loss on debt extinguishment recorded during the nine months ended September 30, 2013 with no comparable activity in the prior year.

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Interest Expense, Net

        Interest expense, net decreased $23 thousand from the nine months ended September 30, 2012 to the nine months ended September 30, 2013. The decrease was primarily attributable to lower average principal balances outstanding during the nine months ended September 30, 2013 compared to the nine months ended September 30, 2012.

Liquidity and Capital Resources

Overview

        Since our inception and through September 30, 2013, we have received an aggregate of $85.5 million in gross proceeds from the issuance of equity securities and gross proceeds from debt facilities and an aggregate of $6.7 million from grants. At September 30, 2013, our cash and cash equivalents were $12.1 million.

Debt Financings

        In October 2011 we entered into a Loan and Security Agreement, or the Term Loan, which provided for up to $5.0 million in debt financing. The Term Loan provided for a draw-down period on the loan through March 1, 2012. In March 2012, we drew down the full $5.0 million available through the facility.

        From March 1, 2012 through May 1, 2012 we were obligated to make interest-only payments at the greater of (1) the lender's prime rate plus 5.0%, or (2) 8.0%. Thereafter, we were required to make 36 equal monthly payments of principal and accrued interest. During this 36-month period the Term Loan bore interest at the greater of (i) the lender's prime rate plus 4.75% or (ii) 8.0%. We were also obligated to pay 6.5% of the advance on the final repayment date, which was scheduled to be April 1, 2015. In connection with the Term Loan, we issued warrants to purchase 517,242 shares of Series B preferred stock at an exercise price of $0.58 per share. Upon execution of the Term Loan, the warrant to purchase 258,621 shares was immediately exercisable and the remaining warrant to purchase 258,621 shares became exercisable when we drew down the full amount of the loan on March 1, 2012. The $5.0 million term loan was collateralized by all of our corporate assets, excluding our intellectual property, and by a negative pledge on our intellectual property.

        On September 30, 2013, we entered into a new loan agreement, or the New Term Loan, which provided up to $10.0 million in debt financing. Upon the closing, we drew down $3.5 million and paid off the outstanding principal and interest on the Term Loan. Under the terms of the New Term Loan, we can draw additional advances up to the remaining $6.5 million through December 31, 2013. Each advance shall be repaid in 42 monthly installments. For the first nine months following each advance, we are obligated to make interest only payments. Thereafter, we are required to make 33 equal monthly payments of principal and interest. On the first business day of the 42^nd month, we are also obligated to make a payment equal to 2.0% of the original principal amount of the advance. We may prepay the outstanding principal amount of the New Term Loan at any time. The New Term Loan was collateralized by a blanket lien on all our corporate assets, excluding our intellectual property, and by a negative pledge on our intellectual property. In connection with the New Term Loan, we issued a warrant to purchase 689,655 shares of Series C preferred stock at an exercise price of $0.58 per share. Upon execution of the New Term Loan, the warrant was immediately exercisable to purchase 689,655 shares.

Operating Capital Requirements

        Our primary uses of capital are, and we expect will continue to be for the near future, compensation and related expenses, manufacturing costs for pre-clinical and clinical materials, third party clinical trial research and development services, laboratory and related supplies, clinical costs, legal and other regulatory expenses and general overhead costs.

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        We believe that the net proceeds of this offering, together with our existing cash and cash equivalents and future amounts available under the New Term Loan, will be sufficient to fund our operations through the end of 2015. Based on our planned use of the net proceeds of this offering and our existing cash resources, we believe that our available funds following this offering will be sufficient to enable us to obtain clinical data from our ongoing Phase 1/2a clinical trial and planned GEN-003 Phase 2 clinical trials and our Phase 1 clinical trial and planned Phase 2a clinical trial for GEN-004. We expect that these funds will not be sufficient to enable us to seek marketing approval or commercialize any of our product candidates.

        We have based our projections of operating capital requirements on assumptions that may prove to be incorrect and we may use all of our available capital resources sooner than we expect. Because of the numerous risks and uncertainties associated with research, development and commercialization of pharmaceutical products, we are unable to estimate the exact amount of our operating capital requirements. Our future funding requirements will depend on many factors, including, but not limited to:

•

the timing and costs of our ongoing Phase 1/2a clinical trial and the first of our planned Phase 2 clinical trials for GEN-003 and our Phase 1 clinical trial and planned Phase 2a clinical trial for GEN-004;



•

the progress, timing and costs of manufacturing GEN-003 and GEN-004 for current and planned clinical trials;



•

the initiation, progress, timing, costs and results of preclinical studies and clinical trials for our other product candidates and potential product candidates;



•

the outcome, timing and costs of seeking regulatory approvals;



•

the costs of commercialization activities for GEN-003, GEN-004 and other product candidates if we receive marketing approval, including the costs and timing of establishing product sales, marketing, distribution and manufacturing capabilities;



•

subject to receipt of marketing approval, revenue received from commercial sales of our product candidates;



•

the terms and timing of any future collaborations, licensing, consulting or other arrangements that we may establish;



•

the amount and timing of any payments we may be required to make, or that we may receive, in connection with the licensing, filing, prosecution, defense and enforcement of any patents or other intellectual property rights, including milestone and royalty payments and patent prosecution fees that we are obligated to pay pursuant to our license agreements;



•

the costs of preparing, filing and prosecuting patent applications, maintaining and protecting our intellectual property rights and defending against intellectual property related claims; and



•

the extent to which we in-license or acquire other products and technologies.

        We expect that we will need to obtain substantial additional funding in order to commercialize GEN-003, GEN-004 and our other product candidates in order to receive regulatory approval. To the extent that we raise additional capital through the sale of common stock, convertible securities or other equity securities, the ownership interests of our existing stockholders may be materially diluted and the terms of these securities could include liquidation or other preferences that could adversely affect the rights of our existing stockholders. In addition, debt financing, if available, would result in increased fixed payment obligations and may involve agreements that include restrictive covenants that limit our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends, that could adversely affect our ability to conduct our business. If we are unable to

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raise capital when needed or on attractive terms, we could be forced to significantly delay, scale back or discontinue the development or commercialization of GEN-003, GEN-004 or our other product candidates, seek collaborators at an earlier stage than otherwise would be desirable or on terms that are less favorable than might otherwise be available, and relinquish or license, potentially on unfavorable terms, our rights to GEN-003, GEN-004 or our other product candidates that we otherwise would seek to develop or commercialize ourselves.

Cash Flows

        The following table summarizes our sources and uses of cash (in thousands):

Operating Activities

        The decrease in net cash used in operations for the year ended December 31, 2012, as compared to the year ended December 31, 2011, was due primarily to a decrease in the net loss of approximately $1.3 million along with changes in our working capital accounts.

        Net cash used in operating activities was $13.5 million for the year ended December 31, 2011 and consisted primarily of a net loss of $14.7 million adjusted for non-cash items including depreciation expense of $0.3 million, stock-based compensation expense of $0.3 million, a decrease in the fair value of warrants of $0.1 million and a net increase in operating assets and liabilities of approximately $0.6 million.

        Net cash used in operating activities was $12.7 million for the year ended December 31, 2012 and consisted primarily of a net loss of $13.4 million adjusted for non-cash items including depreciation expense of $0.3 million, stock-based compensation expense of $0.3 million, a decrease in the fair value of warrants of $0.1 million, and a net increase in operating assets and liabilities of $0.1 million.

        The increase of $4.1 million in net cash used in operations for the nine months ended September 30, 2013 as compared to the nine months ended September 30, 2012 was due primarily to an increase in the net loss of approximately $5.8 million along with changes in our working capital accounts.

        Net cash used in operating activities was $9.4 million for the nine months ended September 30, 2012 and consisted primarily of a net loss of $8.7 million adjusted for non-cash items including depreciation expense of $0.2 million, stock-based compensation expense of $0.2 million, a decrease in the fair value of warrants of $0.1 million, and a net decrease in operating assets and liabilities of $1.1 million.

        Net cash used in operating activities was $13.5 million for the nine months ended September 30, 2013 and consisted primarily of net loss of $14.5 million adjusted for non-cash items including depreciation expense of $0.2 million, stock-based compensation expense of $0.4 million, an increase in the fair value of warrants of $0.2 million, and a net decrease in operating assets and liabilities of $0.1 million.

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Investing Activities

        During the years ended December 31, 2011 and December 31, 2012, our investing activities used net cash of $0.3 million and $0.5 million, respectively. The use of net cash in all periods primarily resulted from purchases of property and equipment to facilitate our increased research and development activities and headcount. The increase in net cash used in investing activities for the year ended December 31, 2011 as compared to the year ended December 31, 2012 was due primarily to an increase in laboratory equipment purchases in 2012.

        During the nine months ended September 30, 2012 and September 30, 2013, our investing activities used net cash of approximately $0.1 million and $0.4 million, respectively. The use of net cash in all periods primarily resulted from purchases of property and equipment to facilitate our increased research and development activities and headcount. The increase in net cash used in investing activities for the nine months ended September 30, 2012 as compared to the nine months ended September 30, 2013 was due primarily to an increase in laboratory equipment purchases in 2013.

Financing Activities

        Net cash used in financing activities was $0.2 million for the year ended December 31, 2011 compared to net cash provided by financing activities of $18.9 million for the year ended December 31, 2012. Cash used in financing activities for the year ended December 31, 2011 consisted of $0.2 million in repayment of long-term debt related to an equipment loan for the acquisition of capital equipment. Net cash provided by financing activities for the year ended December 31, 2012 consisted primarily of $15.1 million in net proceeds from the issuance of Series C preferred stock and $5.0 million in borrowings under the Term Loan offset by repayments of long-term debt of $1.2 million.

        Net cash provided by financing activities was $19.3 million for the nine months ended September 30, 2012 compared to $14.4 million for the nine months ended September 30, 2013. Cash provided by financing activities for the nine months ended September 30, 2012 primarily related to $15.1 in net proceeds from the issuance of Series C preferred stock and $4.2 million in net debt proceeds. Cash provided for the nine months ended September 30, 2013 primarily related to $15.3 million in net proceeds from the issuance of Series C preferred stock and $0.8 million of net debt payments.

Off-Balance Sheet Arrangements

        We do not have any off-balance sheet arrangements.

Net Operating Loss Carryforwards

        At December 31, 2011 and December 31, 2012, we had United States federal net operating loss carryforwards of approximately $38.9 million and $51.7 million, respectively, which may be available to offset future income tax liabilities and expire at various dates through 2032. At December 31, 2011 and December 13, 2012, we also had United States state net operating loss carryforwards of approximately $36.4 million and $49.0 million, respectively, which may be available to offset future income tax liabilities and expire at various dates through 2017.

        At December 31, 2011 and December 31, 2012, we had federal research and development tax credit carryforwards of approximately $1.2 million available to reduce future tax liabilities which expire at various dates through 2032. At December 31, 2011 and December 31, 2012, we had state research and development tax credit carryforwards of approximately $0.6 million and $0.9 million, respectively, available to reduce future tax liabilities which expire at various dates through 2027. Net operating loss and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities and may become subject to an annual limitation in the event of certain

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cumulative changes in the ownership interest of significant stockholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the United States Internal Revenue Code of 1986, as amended, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of our company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. At December 31, 2012, we recorded a 100% valuation allowance against our net operating loss and research and development tax credit carryforwards, as we believe it is more likely than not that the tax benefits will not be fully realized. In the future, if we determine that a portion or all of the tax benefits associated with our tax carryforwards will be realized, net income would increase in the period of determination.

Contractual Obligations

        The following table summarizes our outstanding contractual obligations as of payment due date by period at December 31, 2012 (in thousands):

        We also have obligations to make future payments to third party licensors that become due and payable on the achievement of certain development, regulatory and commercial milestones. We have not included these commitments on our balance sheet or in the table above because the achievement and timing of these milestones is not fixed or determinable. These additional contractual commitments include the following:

        License Agreement with The Regents of the University of California.    Under our license agreement with The Regents of the University of California, or UC, in respect of UC patent rights covering aspects of our ATLAS discovery platform, we agreed to pay UC low single digit royalties on net sales by us of vaccine products comprising antigens identified through use of the ATLAS discovery platform covered by licensed UC patent rights. If we sublicense UC patent rights, we will owe UC a percentage of sublicensing revenue, including any royalty paid to us on net sales by sublicensees.

        License Agreement with Harvard.    Under our license agreement with President and Fellows of Harvard College, or Harvard, in respect of Harvard patent rights covering certain chlamydia antigens,

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we agreed to pay Harvard royalties in the high single-digits on worldwide net sales by us or our sublicensees of vaccine products comprising such chlamydia antigens. In addition, we are required to pay Harvard specified milestone payments for development of the first such chlamydia vaccine. Under the same license agreement, in respect of patent rights covering aspects of our antigen discovery platform, we agreed to pay Harvard royalties in the low single-digits on worldwide net sales by us or our sublicensees, for a period of 10 years from first commercial sale, of vaccine products comprising antigens (other than chlamydia antigens above) identified through use of the antigen discovery platform covered by licensed Harvard patent rights. In addition, we are required to pay Harvard specified milestone payments for development of such vaccines. We estimate that it is reasonably likely that we will make milestone payments in the low six figures through 2015 under this agreement. If we sublicense Harvard patent rights, we will owe Harvard a percentage of sublicensing revenue, excluding payments we receive based on the level of sales or profits.

        License Ageement with Novavax.    Under our license agreement with Isconova AB, now Novavax, Inc., in respect of Novavax patent rights and trademarks covering adjuvant Matrix-M, we agreed to pay Novavax tranched royalties in the low single-digits on worldwide net sales by us or our sublicensees of vaccine products comprising our antigens and Matrix-M. In addition, we are required to pay Novavax specified milestone payments for development and commercialization of the first vaccine in each unique disease field. We estimate that it is reasonably likely that we will make milestone payments in the low six figures through 2015 under this agreement. If we sublicense Novavax patent rights, we will owe Novavax a percentage of the initial signing or upfront sublicensing fees we receive.

        License Agreement with Children's Medical Center Corporation.    Under our license agreement with Children's Medical Center Corporation, or Childrens, in respect of Childrens rights in jointly-owned patent rights covering certain Streptococcus antigens, we agreed to pay Childrens low single digit royalties on worldwide net sales by us or our sublicensees of vaccine products comprising such Streptococcus antigens. In addition, we are required to pay Childrens specified milestone payments for development and commercialization of such vaccines. We estimate that it is reasonably likely that we will pay milestone payments in the low six figures through 2015. If we sublicense the jointly-owned patent rights, we will owe Childrens a percentage of sublicensing revenue, excluding payments we receive based on the level of sales or profits.

        We also enter into contracts in the normal course of business with CROs for clinical trials and clinical supply manufacturing and with vendors for preclinical safety and research studies, research supplies and other services and products for operating purposes. These contracts generally provide for termination on notice and do not include any minimum purchase commitments, and therefore are cancelable contracts and not included in the table above.

Qualitative and Quantitative Disclosures About Market Risk

        Our cash equivalents consisted of money market funds at September 30, 2013. The investments in these financial instruments are made in accordance with an investment policy approved by our board of directors which specifies the categories, allocations and ratings of securities we may consider for investment. The primary objective of our investment activities is to preserve principal while at the same time maximizing the income we receive without significantly increasing risk. Some of the financial instruments in which we invest could be subject to market risk. This means that a change in prevailing interest rates may cause the value of the instruments to fluctuate. For example, if we purchase a security that was issued with a fixed interest rate and the prevailing interest rate later rises, the value of that security will probably decline. To minimize this risk, we intend to maintain a portfolio which may include cash, cash equivalents and investment securities available-for-sale in a variety of securities which may include money market funds, government and non-government debt securities and commercial paper, all with various maturity dates. Based on our current investment portfolio, we do not believe

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that our results of operations or our financial position would be materially affected by an immediate change of 10% in interest rates.

        We do not hold or issue derivatives, derivative commodity instruments or other financial instruments for speculative trading purposes. Further, we do not believe our cash equivalents and investment securities have significant risk of default or illiquidity. We made this determination based on discussions with our investment advisors and a review of our holdings. While we believe our cash equivalents and investment securities do not contain excessive risk, we cannot provide absolute assurance that in the future our investments will not be subject to adverse changes in market value. All of our investments are recorded at fair value.

JOBS Act

        In April 2012, the JOBS Act was enacted in the United States. Section 107 of the JOBS Act provides that an "emerging growth company" can take advantage of the extended transition period provided in Section 7(a)(2)(B) of the Securities Act of 1933, as amended, for complying with new or revised accounting standards. Thus, an emerging growth company can delay the adoption of certain accounting standards until those standards would otherwise apply to private companies. We have irrevocably elected not to avail ourselves of this extended transition period and, as a result, we will adopt new or revised accounting standards on the relevant dates on which adoption of such standards is required for non-emerging growth public companies.

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BUSINESS

Overview

        We are a clinical stage biotechnology company that discovers and develops novel vaccines to address infectious diseases for which no vaccine or vaccines with limited effectiveness exist today. We use our proprietary discovery platform, ATLAS, to rapidly design vaccines that act through T cell (or cellular) immune responses, in contrast to approved vaccines, which are designed to act primarily through B cell (or antibody) immune responses. We believe that by harnessing T cells we can develop first-in-class vaccines to address infectious diseases where T cells are central to the control of the disease. In September 2013, we announced human proof-of-concept data for GEN-003, an immunotherapy, or therapeutic vaccine, candidate that we are developing to treat herpes simplex virus-2, or HSV-2, infections. These data from our ongoing Phase 1/2a trial represent the first reported instance of a vaccine significantly reducing viral shedding, an indicator of disease activity in HSV-2. If GEN-003 successfully completes clinical development and is approved, we believe it would represent a first-in-class vaccine for patients with HSV-2. We are also developing a second T cell vaccine, GEN-004 to protect against Streptococcus pneumoniae, or pneumococcus, a leading cause of infectious disease mortality worldwide. We have initiated a Phase 1 trial for GEN-004, which we anticipate completing by mid-2014. This Phase 1 trial is designated to demonstrate that T cell response associated with natural protection against pneumococcus. If this trial is successful, we plan to conduct a Phase 2 clinical trial to seek to demonstrate that GEN-004 can reduce pneumococcus in humans by mid-2015.

        Vaccines represent a major healthcare success story, having eradicated or significantly reduced the global prevalence of many infectious diseases. To date, all approved vaccines have been developed primarily to elicit B cell responses. However, there remain many infections for which no effective vaccines or only partially effective vaccines exist. A major reason is that the organisms that cause these infections largely evade the antibody immune response generated by B cells, which can generally only address pathogens in the bloodstream. Such organisms may reside in host cells or mucosal surfaces of the nose and throat. To address these pathogens, vaccines targeting responses from the T cell arm of the immune system may present the solution.

        We believe T cell vaccine discovery has been particularly challenging for two reasons. First, the diversity of human T cell responses contrasts with the generally uniform B cell responses in humans. Second, the number of candidate targets for T cell responses can be exponentially greater than for B cell responses. These complexities represent fundamental barriers that traditional vaccine discovery tools, which rely largely on empirically selecting the potential targets from the proteins of a pathogen and iteratively testing them in animal models, have not been able to address.

        We have designed the ATLAS platform to overcome these T cell vaccine discovery challenges. We believe ATLAS represents the most comprehensive high throughput system for T cell vaccine discovery in the biopharmaceutical industry. ATLAS is designed to mimic one important part of the human immune system in a laboratory setting. Using ATLAS, we are able to measure T cell responses to the entire set of protein targets for a specific pathogen in blood samples from large, genetically diverse populations, allowing us to identify vaccine targets associated with protective T cell responses to disease. By comparing antigens identified in individuals who naturally control their infection with those who do not, we can select the antigens that may have the best likelihood of inducing protective T cell immune responses.

        We have generated human proof-of-concept data for our lead product candidate, GEN-003, which we designed using ATLAS. GEN-003 is a therapeutic vaccine, or immunotherapy, candidate we are developing to treat people with HSV-2 infections. In data from our ongoing Phase 1/2a trial, we have shown that GEN-003 significantly reduces HSV-2 viral shedding in patients with moderate-to-severe infections. Shedding is an important marker of the disease, indicating that the virus has been released to skin cells, leading to symptomatic outbreaks and to transmission through sexual contact. We believe

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this represents the first time a vaccine has been shown to reduce HSV-2 viral shedding in humans. We also believe it represents the first time anti-viral efficacy has been observed for a vaccine designed primarily to elicit T cell responses to address an infectious pathogen for which T cell immunity is considered central to the control of the disease. Our ongoing clinical trial of GEN-003 is fully enrolled, and we expect to complete this trial and initiate a Phase 2 trial in mid-2014 to confirm these results and optimize a vaccine dose.

        Our second program derived from ATLAS is GEN-004, a universal pneumococcal T cell vaccine that we are developing to protect against all strains of pneumococcus, the most common cause of bacterial pneumonia in the world. We have initiated a Phase 1 clinical trial of GEN-004 to evaluate its safety and immunogenicity in healthy subjects.

        We believe we are a leader in the field of T cell vaccine discovery and development. Our management and scientific teams possess considerable experience in vaccine and anti-infective research, manufacturing, clinical development and regulatory matters. We have also assembled a team of leading advisors, led by George Siber, M.D., to guide the further development of our programs. Previously, Dr. Siber was the Chief Scientific Officer of Wyeth Vaccines, where he led the development of several first-in-class vaccines including the pneumococcal vaccine, Prevnar, the top selling vaccine in the world by value. He is also an inventor of Respigam and Cytogam, the first antibodies approved to protect against respiratory syncytial virus and cytomegalovirus, respectively. Dr. Siber is one of our directors and chairs our Scientific Advisory Board.

        Since our inception and through September 30, 2013, we have received an aggregate of $85.5 million in gross proceeds from the issuance of equity securities and gross proceeds from debt facilities and an aggregate of $6.7 million in grant revenue. We estimate that we have spent approximately $40 million on research and development from 2011 through 2013.

Our Strategy

        Our objective is to be the leading T cell vaccine company. Key components of our strategy are:

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Continue to rapidly advance our lead vaccine candidate, GEN-003.  GEN-003 is a potential first-in-class therapeutic vaccine candidate we are developing to treat HSV-2 infections, for which we are currently conducting a Phase 1/2a trial. We intend to commence a Phase 2 trial in mid-2014 to optimize the vaccine dose, and a Phase 2b trial in mid-2015 to optimize the dosing regimen. We retain all rights to GEN-003 and plan to advance this program through regulatory approval and commercialize this vaccine through a focused commercial effort in the United States. Outside the United States, we intend to evaluate partnerships for GEN-003 opportunistically.



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Advance GEN-004 into human proof-of-concept clinical trials.  Our second clinical-stage product candidate is GEN-004, a vaccine candidate designed to prevent infections caused by all strains of pneumococcus. We have demonstrated proof-of-concept of GEN-004 in mice. We have initiated a clinical trial GEN-004, and we believe we can demonstrate our novel T cell-based mechanism of action by mid-2014 and we can achieve human proof-of-concept in our Phase 2a clinical trial with GEN-004 by mid-2015. We believe such trials would provide the first evidence in humans that T cells could enable a universal vaccine against all strains of pneumococcus. We retain all rights to this program, other than certain rights we have granted in developing countries, and intend to opportunistically partner this program.



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Advance our discovery stage and preclinical novel vaccine programs.  We expect similarly to advance our novel preclinical prophylactic vaccine programs against chlamydia, HSV-2 and malaria through human proof of concept. We will seek partnerships opportunistically for late-stage development and commercialization of such programs.

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Utilize ATLAS, our vaccine discovery platform, to develop additional T cell vaccine candidates.  We intend to continue to use ATLAS to discover and advance novel T cell vaccines. Since we begin our vaccine candidate discovery process by profiling human populations exposed to a pathogen, and use these subjects' own cells to comprehensively screen the entire proteome of the pathogens, we believe we have a better chance of identifying vaccines likely to protect against pathogens of interest. We intend to opportunistically expand our pipeline using ATLAS to discover T cell vaccines against pathogens for which B cell vaccines are ineffective or non-existent.

Vaccine Overview

        Vaccines represent a major healthcare success story. They have eradicated smallpox and dramatically reduced the mortality and morbidity associated with many other infectious diseases, such as diphtheria, measles, polio and tetanus. Today, there are vaccines approved to treat and protect against approximately 30 infectious diseases. Total global vaccine revenues in 2012 were $27 billion.

        Vaccines trace their roots to the smallpox vaccine, first tested in 1796 by Edward Jenner. Dr. Jenner demonstrated that he could protect subjects against smallpox by inoculating them with cow pox, a similar virus. More than 200 years later, the concept of a vaccine remains the same: training the immune system to respond to an infectious pathogen by exposing it to that pathogen, or a component of that pathogen, in a controlled way. Most vaccines are prophylactic, preventing an invading organism from causing disease. A vaccine can also be therapeutic, fighting an existing infection.

How Vaccines Work

        Vaccines rely on an ability of the human immune system called adaptive immunity to "remember" an invading organism and develop an immune response to it. When confronted with a new organism, the immune system first seeks to eliminate the pathogen through an initial response of the so-called "innate immune system" and then generates immunological memory, or adaptive immunity, in which the immune system recognizes and "remembers" the invasive pathogen in order to combat it in the future. A vaccine introduces a pathogen or a specific portion of a pathogen to the adaptive immune system in a controlled manner in order to invoke acquired immunity against the specific pathogen it is designed to address.

        The adaptive immune system consists of two main components: the B cell arm, and the T cell arm. B cells and T cells are types of white blood cells, or lymphocytes. To date, vaccines have been thought to work primarily by harnessing the B cell arm of the adaptive immune system. The main function of B cells is to produce antibodies, a special type of protein that identifies and initiates processes to kill foreign organisms. Antibodies bind to one or more structures on the pathogen surface. These structures may be proteins or complex sugars, called polysaccharides, or other molecules, which are specific to the organism. Some B cells turn into so-called memory B cells following exposure to an organism, ensuring that the immune system will recognize the same pathogen in the future.

Current Vaccine Discovery

        Vaccines available today have been developed to stimulate the production of antibodies and therefore protect against invading organisms that are primarily controlled by the B cell arm of the immune system. This type of immunity is effective against organisms that mediate disease in locations, primarily the bloodstream, that are accessible to antibodies and/or cells that kill organisms with the help of antibodies.

        Scientists have employed two alternative approaches for designing vaccines to induce antibody responses. The first approach has been to present a modified version of the whole pathogen to the immune system. In this approach, the vaccine is either an inactivated, or killed, pathogen or an

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attenuated pathogen, where the pathogen is live but rendered far less infectious. The advantage of this approach is that it enables vaccine development without knowing the specific surface structure of the pathogen that antibodies target for response and immunological memory. There are also significant disadvantages to this approach. Inactivating or attenuating pathogens in a large-scale, reproducible way is challenging, and there is a concern that attenuated pathogens could reactivate and cause the diseases they were designed to prevent. Another limitation is the potential that side effects of the vaccine may be more severe than when only part of the organism is used as the vaccine. A recent example is the pertussis, or whooping cough, vaccine that was originally developed as a whole killed vaccine, but later changed to a subunit, or purified protein, vaccine because of the rare but severe side effects of the whole cell vaccine. Due to these challenges, and the resultant regulatory hurdles, vaccines are increasingly designed using a second, and more targeted, approach.

        The second approach to design vaccines to induce an antibody response is to immunize with specific antigens, or immunogenic proteins, from the pathogen. Such antigens often are paired with either (1) an adjuvant that gives the immune system a "danger signal" to enhance the ability of the immune system to recognize the proteins as foreign substances or (2) a vector, such as a virus that is used to deliver the antigens to the immune system to enhance the response, or some combination of an adjuvant and vector are utilized. These so-called subunit, or purified protein, vaccines, while generally easier to produce than whole pathogen vaccines, pose a different challenge: selecting the optimal antigen or antigens from the pathogen to elicit the desired immune response.

        Modern vaccine antigen discovery largely consists of the search for the optimal antigens for immunological, and primarily B cell, responses. To date, this process has largely been empirical, meaning that it has required the testing of each potential antigen in animal models of disease to determine its ability to be recognized by the immune system. There is considerable time and cost associated with testing each antigen, singly and in various combinations, to determine which antigens can elicit the desired immune response. However, these hurdles have been somewhat mitigated by the fact that, for most pathogens currently addressed by vaccines, there is a small number of candidate antigens.

Limitations and Challenges of Current Vaccine Discovery

        Despite more than 200 years of vaccine history, there remain many organisms for which effective or comprehensive vaccines do not exist. These include viruses such as HSV-2, cytomegalovirus, and Epstein-Barr virus, which causes mononucleosis, and bacteria that include pneumococcus, Chlamydia trachomatis, or chlamydia, and Staphylococcus aureus, or staphylococcus, which causes a wide range of soft tissue, organ and blood infections. Parasites such as Plasmodium falciparum, which causes much of the world's malaria, also have yet to be addressed with vaccines. Collectively, these organisms are responsible for millions of deaths and morbidity for millions more people annually.

        Vaccines that elicit B cell responses generally do not work for these pathogens, in part because the organisms evade B cell-mediated immunity. Some pathogens, such as HSV-2 and chlamydia, spend most of their life cycles sequestered within host cells and are inaccessible to antibodies that primarily reside in the bloodstream. Mucosal surfaces of the nasopharynx (nose and throat), gastrointestinal tract and genitalia, are also less accessible to antibodies in the bloodstream and harbor pathogens such as pneumococcus and staphylococcus. To address these pathogens, vaccines that engage the T cell immune system may represent the optimal solution.

        T cells, like B cells, are a type of white blood cell, of the immune system. They are generally classified as CD8⁺ cytotoxic T lymphocytes, or CTL, or killer T cells, and CD4⁺, or helper T cells. Killer T cells recognize and eliminate pathogen-infected host cells. On the other hand, helper T cells produce compounds called cytokines that stimulate other immune cells to help fight infection. To initiate T cell responses to an infection, another type of specialized white blood cell, called

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antigen-presenting cells, or APCs, engulf invading pathogens. APCs process pathogen-derived protein antigens into smaller pieces, or epitopes, and place them on their surface as epitopes for recognition by killer T cells or helper T cells. Upon recognition, T cells activate to help eliminate the infection. Activated T cells can also become long-lived memory T cells that respond to infection should the host contact the infectious agent again, thus providing long-term protective immunity.

        As with B cell vaccine development, there are two potential approaches to developing vaccines that induce T cell immune responses. The first approach would be to develop an attenuated or inactivated pathogen vaccine. As discussed, such a vaccine may present significant manufacturing, safety and regulatory challenges. To date, no whole pathogen vaccine has been developed to induce T cell responses.

        The second potential approach would be to develop a subunit vaccine. However, there have been relatively few advances toward identifying target antigens that will elicit T cell responses, and, without the right antigen or antigens, a vaccine will not elicit the optimal immune response.

        Discovering T cell antigens is particularly challenging due to the human diversity of T cell response and to pathogen size. Humans can belong to one of nine different genetic supertypes that influence how epitopes are presented to T cells, and hence the set of proteins that make up a pathogen can range into the thousands. These challenges represent fundamental barriers to the development of vaccines against infectious organisms for which T cell immunity is critical for effective control.

        Challenge #1: Diversity of human T cell responses.    B cell responses to a particular antigen are generally more uniform across all humans than T cell responses. As a result, a vaccine designed to elicit a B cell response generally works across broad populations. However, the T cell arm of the immune system poses a complexity challenge. In contrast with a fairly uniform antibody response, each person has one of nine human leukocyte antigen, or HLA, supertypes that govern, among other things, the specific targets of T cell responses. A person belonging to one supertype may mount a T cell response to a different protein epitope—or an entirely different protein—than someone with a different supertype. Given these different HLA supertypes, modeling diseases in animals, which are typically bred from a single genetic lineage, cannot effectively account for or produce a vaccine candidate intended to address the human diversity in T cell responses.

        Challenge #2: Complexity of target selection due to pathogen size.    Antibodies produced by B cells typically target proteins on a pathogen's surface. For B cell vaccines targeting surface proteins, the number of potential targets has typically been limited. For example, the hepatitis B virus, addressable by two approved vaccines, consists of four proteins. Choosing the vaccine antigen from this small candidate list required testing only these four proteins, singly and in combination to find the most protective formulation. Here again, the T cell arm of the immune system works differently. It is not just surface proteins of a pathogen that can be targets for a vaccine, but rather every pathogen protein, collectively its full "proteome", can be a target of T cell responses. The number of candidate antigens, therefore, increases substantially based on the genetic complexity of the pathogen. For example, for HSV-2 the proteome comprises nearly 80 proteins, substantially increasing the complexity associated with target antigen selection, as the number of potential antigen combinations increases exponentially. The chlamydia proteome exceeds 900 proteins and the proteome for Plasmodium falciparum, a parasite that causes malaria, exceeds 5,000 proteins. In the case of such organisms, testing each protein in animals, singly and in various combinations to identify candidate antigens, could take many years. For many organisms, the complexities associated with the pathogen size have presented a fundamental barrier to discovering effective T cell vaccines.

        The combination of these two challenges renders discovery of T cell antigens by traditional empirical methods exceedingly difficult. We believe these challenges explain why no approved vaccines have been developed on the basis of T cell responses.

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The ATLAS Discovery Platform: A Novel Approach to Vaccine Discovery

        We have developed a proprietary technology platform that is designed to overcome the challenges associated with developing vaccines that stimulate T cell immunity. We have engineered this technology into a high throughput discovery platform we call ATLAS, our AnTigen Lead Acquisition System. This system mimics part of the human T cell immune system ex vivo, or outside the body. By comparing antigens identified in individuals who naturally control their infection with those who do not, we can select the antigens that may have the best likelihood of inducing protective T cell immune responses. We believe that this enables ATLAS to rapidly identify targets of T cell responses that are applicable to broad populations, over the range of HLA supertypes and represents a comprehensive throughput system designed for T cell antigen discovery in the biopharmaceutical industry.

        To use ATLAS, we collect T cells and APCs from hundreds of human donors who were naturally exposed to the disease-causing pathogen of interest. We segregate these donors into cohorts based on their clinical status. At one end of the spectrum are those exposed subjects who remained uninfected despite contact. At the other end of the spectrum, we include subjects who were unable to clear their infection or control their disease without significant intervention. If applicable, we also include subject cohorts between these ends of the spectrum, such as those with mild infections.

        We also create a library of every protein in the proteome of the pathogen of interest. We express each individual protein in bacterial hosts, which are cultured with APCs from each human donor. As each donor's APCs ingest the complete proteomic library, they present peptide epitopes from each protein on their surface. These epitopes can be recognized by T cells derived from the same donor. If the T cell recognizes the epitope on the surface of the APC, which it will do if has seen the epitope before and is a memory T cell for that particular epitope, it will be activated. The level of activation can be quantified by the amount of interferon gamma, or IFN-g, a cytokine produced by the T cell. We use the pattern of responses for each subject to infer which pathogen proteins are associated with productive, non-productive or even deleterious immune responses. The diagram below illustrates the process by which we use ATLAS to identify pathogens to elicit a T cell response.

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        We use ATLAS as a high throughput engine to comprehensively and rapidly screen human T cells to identify potentially relevant T cell vaccine antigens. Furthermore, ATLAS allows us to screen large proteomes in an efficient manner to identify antigens likely to best stimulate the T cell immune system, a process that is otherwise slow and labor intensive. By comparing antigens identified in individuals who control their infection with those who do not, we can select the antigens that may have the best likelihood of inducing protective immune responses. Since we discover the target antigens from human responses rather than animal responses, we believe we can use the targets to produce vaccine candidates that have a high probability of generating protective immunity in humans. To date, we have applied this platform to identify human T cell antigens from several viral and microbial proteomes, with sizes ranging from several dozen, as with HSV-2, to a few thousand expressed proteins, as with pneumococcus and chlamydia.

        In summary, we believe that ATLAS offers all of the following important advantages over other approaches to vaccine design and discovery:

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Enables vaccine discovery for pathogens that are generally inaccessible to antibodies.  For pathogens that reside in human cells or otherwise generally evade antibody responses, and which, as a result have not successfully been addressed by B cell vaccines, ATLAS represents a means to identify targets of effective T cell responses. This pathogen list includes dozens of bacteria, viruses and parasites that collectively account for millions of deaths and morbidity for millions more annually.



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Decreases the risk of vaccine discovery failure by identifying targets of T cell responses in humans.  By comprehensively screening the T cell responses of persons who have mounted effective immune responses to infectious disease pathogens, and comparing these responses to those who have not, ATLAS identifies antigens that associate with protection in humans. By identifying the targets of human T cell responses ex vivo from human samples, rather than in animal models, we both account for diversity of human T cell responses and avoid being misled by discovery in animals.



•

Selects targets relevant to broad populations.  We believe ATLAS is highly efficient and can analyze T cells from a large number of individuals. Traditional analog vaccine antigen discovery necessarily focuses on the identification of epitopes that are able to be presented by APCs for only a minority of the target population. In contrast, we can process blood samples from hundreds of ethnically diverse subjects and therefore can ensure, from analyzing across the range of HLA supertypes, that our antigens are broadly relevant. As a result, we anticipate that both GEN-003 and GEN-004 will stimulate T cell responses across broad HLA types.



•

Reduces the time and cost of vaccine discovery.  As we have demonstrated in both our HSV-2 and pneumococcus programs, after we collect blood samples from human cohorts exposed to a pathogen, we believe we can identify vaccine candidates in less than one year and for a few million dollars, compared to the industry norms of up to 10 years and $100 million to discover B cell vaccines, according to GlaxoSmithKline.

        We believe that our discovery platform can enable vaccine discovery for a wide range of infectious disease pathogens, in addition to our clinical stage vaccines. We have identified antigens that appear to associate with protective human responses in our prophylactic HSV-2 and chlamydia programs and demonstrated subsequently that these antigens can protect against disease in accepted animal models. We have also embarked upon a program to discover protective T cell antigens from Plasmodium falciparum, a causative agent of malaria under a program funded in part by an investment from the Bill & Melinda Gates Foundation, or the Gates Foundation. Many other pathogens evade antibody responses and therefore may be tractable to ATLAS, including those that cause tuberculosis, gonorrhea, and dengue fever.

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        We also believe ATLAS may offer utility in the discovery of new treatments for cancer. In recent years, new cancer immunotherapies such as Yervoy (ipilimumab; Bristol-Myers Squibb) have successfully delivered improved outcomes against cancers such as melanoma by reversing the inhibitive effect that cancer cells can have on T cell immune responses. Recruiting T cells to drive the containment of cancerous cells holds promise as a new approach to cancer treatment.

        Knowing the target or targets of the T cell responses may enable the development of next-generation immunotherapies with greater specificity that, in theory, could offer further protection against cancer.

Antigen Discovery Using ATLAS—A Vignette from the Discovery of GEN-003 to Treat HSV-2

        Strong evidence for the role of T cells in controlling an HSV-2 infection emerged when a researcher at the University of Washington, Christine Posavad, Ph.D., identified a previously unknown and relevant patient population. These people were each in a sexual relationship with someone that had an HSV-2 infection, but had no evidence of infection by culture of, or measurable antibody response to, HSV-2. However, these individuals had evidence of T cell memory against HSV-2, indicating previous contact with HSV-2. In these patients, Dr. Posavad concluded that T cells are the driver of the protective response, but she could not comprehensively screen for the specificity of T cells that drove this response.

        Based in part on Dr. Posavad's observations and other emerging evidence of the role of T cells in controlling HSV-2 infection, we decided to use ATLAS to identify T cell stimulating antigens for HSV-2. We started by collecting blood from 195 people exposed to, or infected with, HSV-2. For each person, we documented the infection severity based on clinical records and assigned the subjects to a cohort according to this. Crucially, we included 43 subjects of the type identified by Dr. Posavad. We chose our sample size to enable statistical comparisons within and across cohorts. We also recruited genetically and ethnically diverse individuals to ensure broad HLA supertype coverage. The table below provides further details on the patients:

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        We also built two copies of a library consisting of each protein in the HSV-2 proteome. Since both killer and helper T cells are thought likely to play a role in controlling an HSV-2 infection, we believed that measuring both T cell responses would be necessary to optimize the design of a candidate vaccine. Research has shown that one cytokine T cells use to defend against HSV-2 is IFN-g. Therefore, for each subject in the study, we separately measured the IFN-g responses of helper T cell and killer T cells to each HSV-2 protein. An example of the output from our assay measuring killer T cells for one subject is below. We generate similar assays for all subjects for both killer and helper T cells.

        ATLAS enables the generation of the above outputs. In this particular subject, the responses to many proteins hovered at a low level, while several proteins elicited relatively strong T cell responses.

        Analyzing the experimental results of the 195 ethnically diverse subjects has enabled us to associate T cell responses to individual proteins with better control or improved outcomes of HSV-2 infection. Using statistical analyses to identify commonalities and differences within the clinical cohorts and across them, we identified a small group of candidate antigens associated with protective T cell responses to HSV-2 in humans. We further produced and tested the selected antigens in animal models to arrive at the two proteins to be included in GEN-003. We believe that because we collected samples from ethnically diverse subjects, GEN-003 should work across patients regardless of HLA supertype. The entire process, including devising clinical cohorts, collecting the blood from 195 subjects, building two copies of the protein library, running proteins through ATLAS and determining priority candidate antigens took 15 months.

Our Product Candidate Pipeline

        The following table describes our current development programs:

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GEN-003 Market Opportunity

Herpes Simplex Virus—2 (HSV-2)

        We are developing our lead product candidate, GEN-003, to treat patients with HSV-2 infections. GEN-003 consists of two protein antigens. The first antigen is ICP4.2, a large fragment of the protein ICP4 that we discovered in ATLAS screens to be a T cell antigen associated with protection from infection or with less severe infection. The second antigen is glycoprotein D2, or gD2, a B cell antigen that is the target of antibodies that provide anti-viral activity during the time in the life cycle of HSV-2 where the pathogen is susceptible to inactivation by antibodies. gD2 was also a target of T cells in our ATLAS screens and was selected based on such ATLAS screens as ATLAS prioritized gD2 as the B cell antigen most associated with T cell responses. We pair the antigens with Matrix-M2, a novel adjuvant that we have licensed exclusively for this indication from Novavax, Inc., or Novavax. See "—Other Collaborations—Isconova AB".

        HSV-2 is a sexually transmitted disease. HSV-2 infections have become an epidemic, spreading to approximately 16% of the United States population between the ages of 14 and 49, and more than 500 million people worldwide, according to the Centers for Disease Control and Prevention, or CDC, and the World Health Organization, or WHO.

        For infected individuals, the disease can manifest in a number of ways, with so-called viral shedding as the common element. For some of the virus' life cycle, it lies dormant within nerve cells near the spine. Although there may be no visible sign of infection, the virus lives within these nerve cells. Periodically, the virus reactivates and virus travels to skin cells of the genitalia where they are released. The release of the virus is called viral shedding and can be detected by swabbing the genital area and testing the swab for the presence of viral DNA. For reasons not completely understood, reactivation of the virus within the nerve cells may occur, resulting in a large amount of virus shedding from skin and mucus membranes. If the replication is maintained for a long enough period of time and at a high enough level, the virus destroys the cells it inhabits and causes ulcers to form on the skin. Patients experiencing such visible ulcers are considered symptomatic patients. It is generally believed that the immune system responds to episodes of HSV-2 outbreaks by activating T cells that reduce viral replication and destroy infected cells, allowing healing and resolution of genital ulcers, usually after a few days, although for many patients ulcers return at variable intervals. Patients may also experience periodic, low-frequency viral shedding. Because the shedding at these times does not lead to the development of ulcers, these episodes are called asymptomatic shedding. These asymptomatic patients continue to pose a disease transmission risk through sexual contact while shedding virus.

        Some people, approximately 60% of those infected, are asymptomatic or fail to recognize or seek medical attention for an initial mild outbreak of ulcers. According to the New England Journal of Medicine, roughly 40% of persons infected with HSV-2 experience visible symptoms. It has been reported in the Annals of Internal Medicine that approximately 70% of the people with visible symptoms experience three or more outbreaks per year, which we consider to be moderate-to-severe disease. Patients with HSV-2 experience significant distress because of the potential negative impact on their ability to form and maintain sexual relationships. Infection with HSV-2 can involve substantial risks in addition to the infection itself. For example, persons with HSV-2 infection have a threefold increased risk for human immunodeficiency virus, or HIV, acquisition. Additionally, pregnant women can transmit HSV-2 to infants in childbirth, which can result in severe brain damage or death.

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*

Note: Each bar represents 1 swab; 2 swabs collected per day; the absence of a bar means no shedding was detected on the swab on a particular day.

        The total number of days during a month that HSV-2 virus can be detected in the genital area with or without visible ulcers is called the shedding frequency. A pattern of shedding and outbreak for one person is illustrated in the graph above. Viral shedding is measured by collecting swabs of the genital area, following a protocol that has been used in decades of studies of HSV-2 viral shedding. In the example shown above, the subject collected swabs twice daily for 28 days. HSV-2 DNA was detectable in approximately 66% of the collected swabs, meaning the patient's shedding frequency is 66% for the period measured. Some swabs had no detectable viral DNA, meaning the subject did not shed virus at the time of sample collection (exemplified by the blank areas of the above graph). The magnitude of viral shedding varied widely from day to day and only sometimes resulted in clinical symptoms such as visible genital ulcers. Ulcers generally appear after several days of asymptomatic shedding and at times when the magnitude of shedding is highest. The extent, frequency, and duration of shedding vary from person to person, but the pattern is relatively consistent for each person.

Limitations of Current HSV-2 Treatment Options

        There is no known cure for HSV-2. For patients infected with HSV-2, oral antiviral drugs are the only treatment option. The most commonly prescribed treatment is valacyclovir including Valtrex, marketed by GlaxoSmithKline. Other medications available are acyclovir (Zovirax, marketed by GlaxoSmithKline) and famciclovir (Famvir, marketed by Novartis). These drugs all work by limiting the ability of the virus to replicate when it emerges from latency. Sales for these oral antivirals totaled $1.6 billion globally in 2012, including nearly $700 million in the United States, according to IMS Health.

        Some patients treat their disease episodically. At the onset of outbreaks, or in the case of some patients, at the onset of prodrome, a tingling sensation that may precede an outbreak, patients take antiviral medication to reduce the duration and severity of the outbreak. According to the approved Valtrex prescribing information, episodic treatment only reduces the duration of outbreaks by up to 50% when compared to placebo. Patients treating their symptoms episodically are not protected against asymptomatic viral shedding and, therefore, have no reduced risk of transmission of infection to an uninfected sexual partner while asymptomatic.

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        Some patients treat their infection with daily antiviral medication. This approach is called chronic suppressive therapy, and has been shown to reduce—but not eliminate—viral shedding, the frequency of symptomatic outbreaks of genital ulcers, and the risk of transmission of the infection to an uninfected sexual partner. Even on chronic suppressive therapy, based on the valacyclovir prescribing information, 35% of patients taking chronic suppressive therapy suffer outbreaks within six months after initiation of treatment and 46% of patients suffer outbreaks within 12 months. Patients taking chronic suppressive therapy reduce their disease transmission risk only by as much as 52%.

        Due to the limited effectiveness of oral antiviral therapy, there remains a significant unmet medical need, against both the symptoms of HSV-2 and disease transmission risk from viral shedding.

GEN-003: A Therapeutic Vaccine Candidate for HSV-2

        GEN-003 is being studied in an ongoing Phase 1/2a trial. In a planned analysis of our data from this ongoing trial, we showed that GEN-003 is the first vaccine known to have demonstrated a statistically significant reduction in viral shedding. The data were presented in a late-breaker presentation at the Interscience Conference on Antimicrobial Agents and Chemotherapy in September 2013. The reduction in shedding appears to be durable, lasting for the six month period for which we have data. We believe that these initial clinical results demonstrate that GEN-003 has the potential to be a first-in-class vaccine to treat HSV-2.

        We believe that, if approved for the treatment of HSV-2 infections, GEN-003 could address the unmet needs of patients in several ways. For patients taking episodic therapy, GEN-003 could offer reduced symptomatic and asymptomatic viral shedding, potentially reducing disease transmission risk. Since episodic therapy offers no protection against disease transmission during asymptomatic shedding, these patients and their sexual partners are unprotected when the infected partner is not taking anti-viral medication.

        For patients on chronic suppressive therapy, we believe GEN-003 may provide both improved outcomes and increased convenience. For some patients, we anticipate that physicians will prescribe GEN-003 as baseline therapy. Such patients may still take oral antivirals in case of an outbreak to further control symptoms. Replacing daily therapy may offer convenience to these patients. For other patients, we anticipate that physicians may prescribe GEN-003 alongside chronic suppressive therapy. This combination therapy approach mirrors the treatment practice of other chronic viral infections such as HIV and hepatitis C virus. We anticipate that, since the mechanisms of action for GEN-003 and oral antiviral medication should complement each other, the control against symptoms and disease transmission risk offered by the combination would exceed that of either therapy alone. In a market research survey conducted on our behalf with more than 400 patients with HSV-2 infections in the United States, the United Kingdom, France and Germany, 56% of patients on chronic suppressive therapy indicated an intent to use GEN-003 in combination with other therapies and 37% of such patients indicated an intent to use GEN-003 on its own, if it were approved; 30% of patients on episodic therapy indicated an intent to use GEN-003 in combination with other therapies and 60% of such patients indicated an intent to use GEN-003 on its own, if it were approved; and 15% of patients not taking any HSV-2 therapy indicated an intent to use GEN-003 in combination with other therapies and 65% of such patients indicated an intent to use GEN-003 on its own, if it were approved. This was a limited survey and may or may not be representative of how patients might ultimately use GEN-003, if at all, if GEN-003 successfully completes clinical development and is approved by regulatory authorities.

Preclinical Evaluation of Our GEN-003 Product Candidate

        We tested GEN-003 in the guinea pig therapy model, the standard animal model of recurrent disease. Guinea pigs are used because the course of infection in the animal closely mirrors that of

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humans, with an initial outbreak that resolves, followed by frequent and periodic recurrences that last a few days. GEN-003 decreased ulcers over time by up to 55% versus placebo, measured over 63 days after initial immunization. This is the standard interval across which to measure impact on ulcers in the guinea pig model. Additionally, the vaccine reduced viral shedding significantly. In the period after completing immunization, from days 37-63, GEN-003 almost completely eliminated viral shedding. We are unaware of any other vaccine demonstrating similar impact either on clinical symptoms or on viral shedding in this model.

Clinical Development

GEN-003-001—Our Phase 1/2a Clinical Trial

        We are conducting a Phase 1/2a trial, testing the safety, T and B cell immunogenicity and impact on viral shedding of GEN-003 in subjects with documented recurrent HSV-2 infection. We are conducting the trial at seven sites in the United States, including some of the leading institutions for scientific and clinical research of HSV-2. The trial is double-blind, placebo-controlled and dose-escalating. We enrolled subjects between 18 and 50 years of age. An independent Data Safety Monitoring Board continues to monitor the safety of subjects enrolled in the clinical trial as well as the subject outcomes.

        This trial is fully enrolled with 143 otherwise healthy subjects with moderate-to-severe HSV-2 infections, defined as experiencing between three and nine symptomatic outbreaks per year when not on suppressive therapy. Subjects were randomized into one of three dose cohorts. Within each cohort, subjects were randomized in a 3:1:1 ratio, whereby for every three subjects receiving GEN-003, one would receive placebo and one would receive the ICP4.2 and gD2 proteins without the Matrix-M2 adjuvant. We included this last cohort to demonstrate that Matrix-M2 was necessary to biological responses. There were three vaccine dose groups, based on the amount of protein. The lowest dose group subjects received 10 µg of each protein combined with 50 µg of Matrix-M2. In the middle dose group, the protein doses increased to 30 µg. In the high dose group, subjects received 100 µg of each protein. Subjects received three vaccinations, on days zero, 21 and 42. The diagram below illustrates the dosing and swabbing regimen in the trial.

        The primary objective of this trial is to monitor the safety profile of the proposed vaccine. Additionally, we are measuring the vaccine-induced T cell and B cell immune responses. We structured and statistically powered the trial to measure the proposed vaccine's impact on viral shedding, an

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important marker of virus activity. We selected this endpoint because of the direct connection between shedding, symptomatic outbreaks, and risk of transmission of virus by sexual contact. Without shedding, a patient will not experience symptomatic ulcers. Hence, a vaccine that reduces viral shedding would be expected to reduce symptoms as well. Every subject in the study swabbed their genitalia twice per day for 28 days before receiving the first assigned treatment injection, and after treatment, using the standard protocol that has been used for many clinical trials of HSV-2 shedding.

        When we measured the viral DNA present in swabs from subjects over the 28-day measurement period after completing the three-dose regimen, subjects in the two highest GEN-003 dose cohorts showed a statistically significant reduction in viral shedding frequency from their own baseline shedding frequency, established over the 28-day measurement period preceding dosing, by an average of 50% (p<0.001) in the 30 µg dose cohort. GEN-003 reduced the magnitude of viral shedding by an average of 54% (p=0.01) in that same dose cohort. We are unaware of any other vaccine that has demonstrated such an impact on HSV-2 viral shedding in humans. The following chart summarizes the data demonstrating the statistically significant reduction in frequency of viral shedding following administration of GEN-003 vaccine.

        We believe the reduction in viral shedding afforded by GEN-003 will translate into a reduction in clinical symptoms because the link between viral shedding is well established. It has been shown that asymptomatic patients shed half as frequently as symptomatic patients. Oral anti-viral drugs, which reduce viral shedding frequency, also reduce the number of symptomatic outbreaks and the risk of transmission. And in populations where oral anti-viral drugs provide lower efficacy, the viral shedding rates are higher than in those populations where oral anti-viral drugs provide work well.

        This Phase 1/2a clinical trial was not designed to measure the impact of GEN-003 on clinical symptoms. We believe that in a larger adequately powered, well controlled clinical trial GEN-003 may demonstrate clinical benefit, such as a reduction in frequency of HSV-2 outbreaks, could be shown to reach even more stringent statistical significance.

        In this Phase 1/2a trial, we are also measuring and evaluating the durability of response to the vaccine. Durability of response is measured by having subjects conduct an additional 28-day, twice daily genital swab collection to measure viral shedding frequencies six months after vaccination. For the 30 µg dose cohort as shown in the graph below, reduction in viral shedding remains statistically significant relative to the subject's own baseline viral shedding rate. In comparison, there was no reduction in viral shedding for placebo patients either immediately after vaccination or six months later. While we have not yet tested any booster regimen, based on the durability of response to date, we anticipate booster doses, if necessary, would be administered at intervals greater than six months.

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        Our data have also demonstrated that GEN-003 induced a broad immune response in vaccinated subjects at all dose levels. T cell responses increased from baseline 21-fold to ICP4.2 and 10-fold to gD2. Subjects also experienced strong increases in antibody response to ICP4.2 and gD2, as measured by immunoglobulin G, or IgG, a standard measure of antibody response. The antibodies generated in response to the vaccine are able to prevent the virus from infecting new cells, as measured by a standard assay for evaluating the ability of the virus to infect cells in vitro. The chart below shows the T cell immune response aggregated across all dose levels.

Fold Increase in T Cell Response from Baseline by Treatment Group

        Overall, GEN-003 has been well tolerated. During the seven days following each injection, side effects have generally been those considered typically associated with vaccines, such as fatigue, site injection pain, tenderness and swelling. Among all vaccine dose groups, the frequency of adverse events, or AEs, appeared greater among those subjects given the 10 µg dose. In the 30 µg and 100 µg dose cohorts, the doses we intend to study in subsequent clinical trials, the AE rate was lower than that of the 10 µg cohort. In addition, the frequency of AEs appeared to diminish with subsequent doses.

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Beyond the week following vaccination with GEN-003 vaccine, the AE types and frequencies appeared similar to those following vaccination with placebo. The AEs have been transient, resolved over a few days and have resulted in only two subjects discontinuing further vaccinations: one for a combination of symptoms (myalgia and fatigue; and pain and tenderness at the injection site) and one for injection site pain.

        In an interim analysis in our current Phase 1/2a trial of GEN-003 in an exploratory analysis of the impact on clinical symptoms of HSV-2 as measured by ulcer days, or the number of days of self-reported observation of ulcers over a four-week period by subjects, GEN-003 showed a statistically significant (p <0.001) reduction at the 30 µg dose (n=29 subjects) immediately after three doses and at six months after the third dose of GEN-003. The reduction for the 30 µg dose at six months post treatment was 72%. The table below shows the number of ulcer days reported prior to treatment, immediately post treatment with three doses and at six months after the third dose for each of the doses measured in the trial, on a weighted-average basis for each dose cohort:

Self-Reported Days With Ulcers Over a Four-Week Period

        While these are interim data from an early stage clinical trial in a limited number of subjects, we believe this endpoint or one that similarly measures impact on disease will be the endpoint for demonstrating efficacy in pivotal studies of GEN-003.

Next Steps: Phase 2 Dose Ranging and Dose Regimen Trials for GEN-003

        We plan to initiate a Phase 2 dose ranging trial of GEN-003 in mid-2014 and anticipate efficacy data by mid-2015. The primary trial objective is to optimize the vaccine dose. We expect to compare two protein levels, including the 30 µg dose, each combined with 25 µg, 50 µg or 75 µg of Matrix-M2, for a total of six dose cohorts. We anticipate the trial to enroll approximately 300 patients in total with similar or identical enrollment criteria and endpoints as the Phase 1/2a trial. Following completion of this Phase 2 dose ranging trial, we intend to complete a Phase 2b trial where we will seek to optimize our dosing regimen, or the number of doses and the interval between doses. We anticipate that clinical trial enrollment criteria and endpoints for both of these trials will be similar or identical to those of the preceding trials.

Potential for GEN-003 to Treat HSV-1 Infection

        We anticipate that GEN-003 may also help a patient's immune system fight herpes simplex virus type-1, or HSV-1. HSV-1 is most commonly identified with cold sores and has infected approximately 60% of Americans, according to the CDC. Increasingly, HSV-1 has been associated with outbreaks of genital ulcers, though the frequency and severity of such outbreaks generally is less than those associated with HSV-2. HSV-1 and HSV-2 are related viruses and the proteins in GEN-003 are present in, and nearly identical to, those found in HSV-1. Consequently, we believe that GEN-003 will be active against HSV-1 and thus intend to study the potential for GEN-003 to combat HSV-1.

The Opportunity to Prevent HSV-2 Infections

        In addition to treating HSV-2 infection with GEN-003, we believe that ATLAS may help to develop a vaccine that can prevent HSV-2 from infecting healthy persons. We believe that a vaccine that has therapeutic effect may be the foundation for a preventative vaccine. Since there will not likely

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be pre-existing immune responses to build upon in uninfected subjects, the preventative vaccine may include additional or different antigens than those in GEN-003 to be fully protective. Using data from the same ATLAS screening effort with which we designed GEN-003, we identified eight additional candidate antigens that could be added to GEN-003 or included in another vaccine for prophylaxis of HSV-2 infections. We have already demonstrated that several of the eight candidate antigens can provide some protection against infection in initial studies in mice. A prophylactic vaccine may be an important step in halting the epidemic, and could be used to treat uninfected partners of HSV-2 infected subjects to prevent them from acquiring the disease. The vaccine could also be used more broadly as a preventative measure. We intend to pursue development of a prophylactic HSV-2 vaccine and anticipate that we would partner this program at the appropriate point of clinical development.

GEN-004 Market Opportunity

Pneumococcal Disease

        We are developing GEN-004 to prevent infections caused by pneumococcus. The Gates Foundation has noted that pneumococcus kills more children under age five globally than any other organism. GEN-004 consists of three whole Pneumococcal T cell protein antigens, SP0148, SP1912 and SP2108, combined with the adjuvant Alhydrogel, a form of alum that is available in several approved vaccines.

        There are more than 90 serotypes, or strains, of pneumococcus known to exist. Each strain differs slightly in the composition of the polysaccharide capsule, a sugar-based component that covers the bacterial cell. These differences have likely arisen as the organism has evolved to evade human antibody responses. Pneumococcus is a bacterium that often resides harmlessly in the nose and throat but can cause otitis media, or middle ear infection, as well as pneumonia, an infection in the lungs. Such consequences of infection are considered non-invasive Pneumococcal disease, or NIPD.

        Invasive Pneumococcal Disease, or IPD, arises when pneumococcus enters the bloodstream and potentially spreads to other organs. The consequences of IPD can be severe and, according to the CDC, 10% of patients with IPD die. IPD is classified into three categories. Bacteremic pneumonia is an infection in one or both lungs with pneumococcus also in the bloodstream. It is generally a more severe infection than pneumonia that is not invasive. Other examples of IPD include sepsis, the presence of bacterial infection in the blood along with symptoms such as fever, elevated heart rate and respiratory rate, and high or low white blood cell count, and meningitis, an inflammation of the brain and spinal column.

Limitations of Current Pneumococcal Vaccines

        Global revenue exceeded $5 billion in 2012, of which more than 70% came from Prevnar-13, marketed by Pfizer, which is named for the 13 capsular polysaccharides types, derived from 13 strains of pneumococcus, included in the vaccine. Other Pneumococcal vaccines include Synflorix, marketed by GlaxoSmithKline, and Pneumovax-23, marketed by Merck. These vaccines have dramatically reduced IPD caused by the serotypes addressed by the vaccines.

        The predecessor vaccine to Prevnar-13, Prevnar-7, led to the dramatic reduction of IPD caused by the seven vaccine serotypes of pneumococcus that are addressed by the vaccine. According to the CDC, the hospitalization rates due to IPD infection from these strains fell after the introduction of Prevnar-7, from 80 cases per 100,000 children in 2000 to less than 1 per 100,000 by 2007. In pre-approval randomized trials, Prevnar-7 was demonstrated to be safe and highly efficacious against IPD, moderately efficacious against pneumonia, and somewhat effective in reducing middle ear infection episodes and related office visits. The expectation is that Prevnar-13, introduced in 2010, will result in similar benefit against the seven serotypes covered by Prevnar-7 plus the additional six serotypes included in that vaccine.

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        Nevertheless, significant limitations exist with this and other pneumococcal vaccines. As noted previously, there are more than 90 known serotypes of pneumococcus. Prevnar-13 covers only 13 of these serotypes. Incidence of invasive disease caused by the 75+ serotypes not included in that vaccine are rapidly increasing. As a consequence, Pfizer is believed to be working on a third generation Prevnar vaccine. Already a complex vaccine, each of the polysaccharide shells included in Prevnar-13, representing 13 of the most common disease-causing serotypes of pneumococcus, is conjugated, or chemically linked, to a protein carrier. It is believed that there are limits to how many polysaccharides that physically can be included in the vaccine. Moreover, the protective capacity per serotype appears to diminish as new polysaccharides are added to the vaccine. Still, other large companies, including GlaxoSmithKline, Merck, and Sanofi Pasteur, are also believed to be working on new vaccines against pneumococcus. To our knowledge, all of these companies' product candidates are being developed to elicit a B cell response.

GEN-004: A Prophylactic Vaccine Candidate for Pneumococcus

        We have designed GEN-004 to fight more than 90 serotypes of pneumococcus, and to do so through a T cell-based mechanism of action that complements existing vaccines. Since 2009, we have collaborated with Rick Malley, M.D., of Boston Children's Hospital, a leading researcher on host immunity to pneumococcus. He was the first person to demonstrate that Pneumococci are rapidly cleared from the nose, before they can get into the lungs and bloodstream, by a type of helper T cell called T_H17 cells. This is important because before pneumococci can cause IPD, they need to take up residence inside the nose, known as colonization. If the immune system could be taught to make T_H17 cells against pneumococci in sufficient quantities, then the bacteria will not have the ability to colonize, thus reducing or eliminating IPD occurrence. The majority of healthy adults are not colonized with pneumococcus, presumably due to T_H17 responses that they have generated through natural exposure. We believe a vaccine that stimulates T_H17 cells to reduce or prevent colonization of the nasopharynx by pneumococcus could be highly effective against all forms of pneumococcal disease including IPD and NIPD infections.

        Guided by this insight, we used ATLAS to design a novel pneumococcal vaccine, GEN-004. Since adults are generally "protected" against colonization by pneumococcus, we screened the blood of 50 healthy, ethnically diverse adults using ATLAS. We collected their APCs and T cells and screened the entire pneumococcus proteome, which consists of more than 2,200 proteins, to identify proteins associated with a strong T_H17 T cell response, as measured by their induction of the cytokine IL-17A, the predominant cytokine secreted by T_H17 cells. Based on these studies, we identified three protein antigens that associate highly with a protective T cell response against pneumococcus in humans. Moreover, as these proteins are conserved in all sequenced strains of Pneumococci, we believe GEN-004 may be able to help protect against invasive Pneumococcal disease caused by any Pneumococcal serotype, including those covered by the Prevnar franchise.

        We have demonstrated proof-of-concept of GEN-004 in a mouse model of nasal colonization, as demonstrated below. In this model, mice are immunized with the antigens adsorbed to ahydrogel and then challenged intranasally with live pneumococci. After 10 days, the nasal cavity is washed with saline, and the numbers of pneumococcal bacteria that colonized the nose are counted. We and others

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have shown that the prevention of colonization in this model is due to IL-17A secretion from helper T cells.

Clinical Development of GEN-004

        We have filed an IND and initiated a Phase 1 clinical trial in the United States to evaluate the safety of, and immune response to, GEN-004. Immune responses will be measured by an increase in helper T cells that produce IL-17A in response to the antigens included in the vaccine. We expect to enroll as many as 90 healthy adults in this trial, and follow them for one year. This trial will help us to determine the ideal vaccine dose to test in subsequent Phase 2 trials. We expect the initial results will be available in the second quarter of 2014. If the vaccine induces a T_H17 response, we believe this will be the first time a vaccine directed against pneumococcus in humans has done so.

        In the third quarter of 2014, we intend to initiate a Phase 2a trial for GEN-004 in adults if the Phase 1 clinical trial is successful. We anticipate data from our Phase 2a trial in mid-2015. Subjects in the clinical trial will receive either GEN-004 or placebo, and then be "challenged" intranasally with live pneumococcus, much like in the mouse colonization model. This means that pneumococcus will be introduced to the nasal cavity. We expect to enroll as many as 75 healthy adults in this trial. We will monitor AEs, immune responses as determined by IL-17A, and incidence of post-challenge colonization. We will follow these patients for a year and expect the initial results will be available in the second quarter of 2015. If successful, we believe this has the potential to be the first time a protein subunit vaccine will have directly demonstrated a reduction in nasopharyngeal colonization in humans.

Our Chlamydia Program

        Chlamydia is the most commonly reported bacterial sexually transmitted disease in the United States. According to the CDC, an estimated 2.9 million infections occur annually in the United States. Despite the widespread availability of antibiotics that are effective against Chlamydia trachomatis, the pathogen that causes chlamydia infections, incidence has increased at greater than 5% per year over

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the past decade, according to the CDC. A key reason for this is that chlamydia is often an asymptomatic infection, so infected individuals do not seek treatment, which can result in severe consequences, particularly in women, such as pelvic inflammatory disease, infertility and serious neonatal infections.

        Despite the need, vaccine development to combat chlamydia has been virtually non-existent. There has not been a chlamydia vaccine clinical trial since the 1960s, in which an attenuated pathogen vaccine demonstrated no lasting protection and showed hints of disease exacerbation. Antibodies appear to be unlikely to protect against infection as the pathogen is intracellular for much of its life cycle. Additionally, as a large genome pathogen, Chlamydia trachomatis represents a large T cell antigen discovery challenge. For these reasons, we believe that chlamydia is a particularly attractive pathogen for use of ATLAS to identify a vaccine candidate.

        We have achieved promising preclinical results from candidates generated using ATLAS. We collected blood from 144 subjects spanning multiple clinical cohorts, ranging from subjects whose infections spontaneously cleared, representing a putative natural protection cohort, to subjects with infertility caused by chlamydia infection. From the more than 900 proteins in the Chlamydia trachomatis proteome, we identified 22 novel proteins associated with a protective response. From these we have demonstrated that three proteins, when given in an animal model of infection and when paired with the Matrix-M2 adjuvant can significantly reduce infection risk.

        If the program were to reach the clinic, we believe it would be the first vaccine against chlamydia to be in clinical trials in more than 50 years. If it can successfully prevent chlamydia infections, we believe it would address a major unmet clinical need. As resources permit, we intend to opportunistically pursue development of this program.

Our Malaria Program

        Malaria is one of the deadliest infectious diseases in the world. Approximately 600 thousand to one million people died in 2010 due to malaria, primarily in the developing world. There is no vaccine to prevent malaria, an infection caused by the plasmodium parasites transmitted by mosquitoes. We previously collaborated with the Naval Medical Research Center, or NMRC, and recently initiated a second collaboration with the Gates Foundation for which malaria is a priority infectious disease. When the parasite is injected into the blood through the bite of an infected mosquito, it rapidly travels to the liver where it replicates exponentially, is released into the bloodstream, and causes sickness. T cells in the liver could potentially be used to kill the cells in which the parasite is hiding, before the parasite is able to replicate itself, and could therefore protect against blood infection. Both the Gates Foundation and NMRC have sponsored several studies investigating killed or attenuated whole organism vaccines, which induce immunity, but are impractical to manufacture due to the fact that the vaccines are based on irradiated parasites grown within the salivary glands of mosquitoes.

        We are in the process of collecting blood samples from subjects immunized with the killed organism and who were either protected or not protected after live parasite challenge to use ATLAS to identify the protein antigens that are associated with protective T cell responses. The identification of the protein targets of the T cell responses can enable the generation of a protein plus adjuvant vaccine designed to induce liver T cell responses and prevent malaria disease in a safe, scalable and affordable way.

Competition

        The biotechnology and pharmaceutical industries are characterized by intense and rapidly changing competition to develop new technologies and proprietary products. While we believe that our proprietary patent portfolio and T cell vaccine expertise provide us with competitive advantages, we face potential competition from many different sources, including larger and better-funded

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pharmaceutical companies. Not only must we compete with other vaccine companies but any products that we may commercialize will have to compete with existing therapies and new therapies that may become available in the future.

        There are other organizations working to improve existing therapies or to develop new vaccines or therapies for our initially selected indications. Depending on how successful these efforts are, it is possible they may increase the barriers to adoption and success of our GEN-003 and GEN-004 product candidates, if approved. These efforts include the following:

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HSV-2:  The current standard of care for the treatment of HSV-2 is valacyclovir, an oral antiviral medicine. Other currently approved oral antiviral medications include acyclovir and famciclovir. AiCuris, a private company based in Germany, is developing a new oral antiviral, pritelivir, and has advanced the compound into Phase 2 testing. We understand the company will pursue once-weekly dosing with this drug. We believe that GEN-003 may offer advantages in terms of improved symptom control, reduced disease transmission risk and improved compliance when compared to oral antivirals.

There are also several companies attempting to develop new therapeutic vaccines against HSV-2, including Agenus Inc., Coridon Pty Ltd, Sanofi Pasteur and Vical Incorporated. We believe GEN-003 has advantages against each of the vaccines being developed by these companies based on the screens of human protection that we have conducted using ATLAS that include these competitors' antigens, published reports of preclinical vaccine efficacy, announced clinical results in the case of Agenus, Inc. and our own clinical results to date. However, there can be no assurance that one or more of these companies or other companies will not achieve similar or superior clinical results in the future as compared to GEN-003 or that our future clinical trials will be successful.

•

Pneumococcus:  The current standard of care for the prevention of pneumococcus is Prevnar-7/Prevenar-13, marketed by Pfizer. In select countries, Synflorix, marketed by GlaxoSmithKline, is also widely accepted. Additionally, Pneumovax-23, marketed by Merck, is labeled by use for persons over 65. We believe that each of these companies is seeking to develop improvements to their product. We believe these represent incremental improvements, adding a few additional strains to their coverage. In addition, we are aware of a pneumococcus vaccine that Sanofi Pasteur has taken into Phase 1 trials. This is a protein subunit vaccine designed to cover all strains of pneumococcus, but was designed to induce B cell responses. For many pneumococcal strains with dense sugars on their surface, the protein targets of the antibodies induced by the vaccine will be blocked by sugars that cover them. We believe that by covering all known pneumococcus serotypes, with a T cell-based mechanism of action that complements existing vaccines, GEN-004 may offer broader protection than existing vaccines. However, there can be no assurance that one or more of these companies or other companies will not achieve similar or superior clinical results in the future as compared to GEN-004 or that our ongoing and future clinical trials of GEN-004 will be successful.

        Many of our competitors, such as Merck, GlaxoSmithKline, and Sanofi Pasteur, either alone or with their strategic partners, have substantially greater financial, technical and human resources than we do and significantly greater experience in the discovery and development of product candidates, obtaining FDA and other regulatory approvals of vaccines and the commercialization of those vaccines. Accordingly, our competitors may be more successful than us in obtaining approval for vaccines and achieving widespread market acceptance. Our competitors' vaccines may be more effective, or more effectively marketed and sold, than any vaccine we may commercialize and may render our vaccines obsolete or non-competitive.

        Mergers and acquisitions in the biotechnology and pharmaceutical industries may result in even more resources being concentrated among a smaller number of our competitors. These competitors

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also compete with us in recruiting and retaining qualified scientific and management personnel and establishing clinical trial sites and patient registration for clinical trials, as well as in acquiring technologies complementary to, or necessary for, our programs. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies.

        We anticipate that we will face intense and increasing competition as new drugs enter the market and advanced technologies become available. We expect any vaccines that we develop and commercialize to compete on the basis of, among other things, efficacy, safety, convenience of administration and delivery, price, the level of generic competition and the availability of reimbursement from government and other third-party payors.

        Our commercial opportunity could be reduced or eliminated if our competitors develop and commercialize products that are safer, more effective, have fewer or less severe side effects, are more convenient or are less expensive than any products that we may develop. Our competitors also may obtain FDA or other regulatory approval for their products more rapidly than we may obtain approval for our products, which could result in our competitors establishing a strong market position before we are able to enter the market. In addition, our ability to compete may be affected in many cases by insurers or other third-party payors seeking to encourage the use of generic products.

Intellectual Property

        We strive to protect and enhance the proprietary technology, inventions and improvements that are commercially important to our business, including seeking, maintaining, and defending patent rights, whether developed internally or licensed from third parties. We also rely on trade secrets relating to our proprietary technology platform and on know-how, continuing technological innovation and in-licensing opportunities to develop, strengthen and maintain our proprietary position in the vaccine field. We additionally rely on regulatory protection afforded through data exclusivity, market exclusivity and patent term extensions where available. Still further, we utilize trademark protection for our company name, and expect to do so for products and/or services as they are marketed.

        Our commercial success may depend in part on our ability to obtain and maintain patent and other proprietary protection for commercially important technology, inventions and know-how related to our business; defend and enforce our patents; preserve the confidentiality of our trade secrets; and operate without infringing the valid enforceable patents and proprietary rights of third parties. Our ability to stop third parties from making, using, selling, offering to sell or importing our products may depend on the extent to which we have rights under valid and enforceable patents or trade secrets that cover these activities. With respect to both licensed and company-owned intellectual property, we cannot be sure that patents will be granted with respect to any of our pending patent applications or with respect to any patent applications filed by us in the future, nor can we be sure that any of our existing patents or any patents that may be granted to us in the future will be commercially useful in protecting our commercial products and methods of manufacturing the same.

        We have developed or in-licensed numerous patents and patent applications and possess substantial know-how and trade secrets relating to the development and commercialization of vaccine products. As of the date of this prospectus, our patent portfolio includes the following:

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ATLAS

        Our discovery platform patent portfolio includes three patent families, currently comprising four issued U.S. patents and two pending U.S. applications. We hold an exclusive license from The Regents of the University of California to the first patent family, including U.S. Patent 6,004,815 and the related U.S. Patents 6,287,556 and 6,599,502. This first family includes claims to fundamental aspects of the ATLAS platform, developed by our scientific founder, Darren Higgins, Ph.D. while he was employed at the University of California, Berkeley. Patents in this family have a patent term until August 2018. We hold a further exclusive license from President and Fellows of Harvard College to the second patent family, which covers methods related to the ATLAS discovery platform. This second patent family includes a pending U.S. application and corresponding applications in Europe, Canada and Australia. Patents issuing from these applications are expected to expire in 2027. We wholly own the third patent family, which is specifically directed to the ATLAS platform as utilized by us. This third patent family includes U.S. Patent 8,313,894, a pending U.S. patent application, and corresponding pending applications in Europe, Canada and Australia. Patents issuing from applications in this family are expected to have a patent term until at least July 2029; issued U.S. Patent 8,313,894 has a term that includes Patent Term Adjustment and extends until at least June 2030.

GEN-003 (HSV-2)

        We wholly own a portfolio of patent applications directed to HSV-2 vaccines, including GEN-003. This portfolio includes two patent families covering HSV-2 vaccine compositions and methods for inhibiting or treating HSV-2 infections. The first patent family includes U.S. Patent 8,617,564. A U.S. application and applications in Europe, Canada, Australia, Japan, Brazil, Russia, India, China and nine additional foreign jurisdictions are pending in the first patent family. A U.S. application and applications in Europe, Australia and Japan are pending in the second family. Patents that issue from applications in these families are expected to expire in 2030 and 2031; issued U.S. Patent 8,617,564 has a term that includes Patent Term Adjustment and extends until at least January 2031. We own a further patent family covering follow-on HSV-2 vaccine compositions.

        We hold a license from the University of Washington to a patent family that includes U.S. Patent 8,197,824 and European Patent No. 2263686 covering compositions of certain HSV-2 proteins and methods for treating HSV infections. This family includes pending applications in the United States, Europe and Canada. This patent family has a patent term until at least July 2023.

        We hold a license from Isconova AB (now Novavax) to two patent families covering Matrix-M2, the adjuvant used in GEN-003. Both patent families include issued patents in Europe; the first patent family also includes an issued patent in Japan. Applications in the United States, Canada, Australia, Japan (for the second family) and three additional foreign jurisdictions. These patent families have patent terms until at least July 2023 and July 2024.

GEN-004 (Pneumococcus)

        We co-own with Children's Medical Center Corporation, or Childrens, a patent portfolio of patent applications directed to pneumococcus vaccines, including GEN-004. This patent portfolio includes two patent families covering pneumococcal vaccine compositions and methods for inhibiting or treating pneumococcal infections. A U.S. application and applications in Europe, Canada, Australia, Japan, Brazil, Russia, India, China and nine additional foreign jurisdictions are pending in the first patent family. A U.S. application and applications in Europe, Australia, Japan, Brazil, Russia, India, China and nine additional foreign jurisdictions are pending in the second patent family. Patents that issue from applications in these patent families are expected to have patent terms until at least 2030 and 2032, respectively. We hold an exclusive license to Childrens' interest in these patent rights. We co-own

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with Childrens two further patent families covering follow-on pneumococcal vaccine compositions, and Childrens' interest in these patents is also exclusively licensed to us.

GEN-001 (Chlamydia)

        Our chlamydia patent portfolio includes four patent families (one of which overlaps with the ATLAS portfolio). We hold an exclusive license from President and Fellows of Harvard College to three of these four patent families. We wholly own the fourth patent family. The patent families cover chlamydia vaccine and immunogenic compositions and methods for inhibiting or treating chlamydia infections. A European Patent is issued in the first patent family; a U.S. application and applications in Canada and Australia are pending. A U.S. application and applications Europe, Canada, Australia and Japan are pending in the second and third patent families. A U.S. application and applications in Europe, Australia and Japan are pending in the fourth patent family. Patents issuing from applications in these four patent families are expected to expire between 2027 and 2031.

        In addition to the above, we have established expertise and development capabilities focused in the areas of preclinical research and development, manufacturing and manufacturing process scale-up, quality control, quality assurance, regulatory affairs and clinical trial design and implementation. We believe that our focus and expertise will help us develop products based on our proprietary intellectual property.

        The term of individual patents depends upon the legal term of the patents in the countries in which they are obtained. In most countries in which we file, the patent term is 20 years from the date of filing the non-provisional application. In the United States, a patent's term may be lengthened by patent term adjustment, which compensates a patentee for administrative delays by the United States Patent and Trademark Office in granting a patent, or may be shortened if a patent is terminally disclaimed over an earlier-filed patent.

        The term of a patent that covers an FDA-approved drug may also be eligible for patent term extension, which permits patent term restoration of a United States patent as compensation for the patent term lost during the FDA regulatory review process. The Hatch-Waxman Act permits a patent term extension of up to five years beyond the expiration of the patent. The length of the patent term extension is related to the length of time the drug is under regulatory review. A patent term extension cannot extend the remaining term of a patent beyond a total of 14 years from the date of product approval and only one patent applicable to an approved drug may be extended. Moreover, a patent can only be extended once, and thus, if a single patent is applicable to multiple products, it can only be extended based on one product. Similar provisions are available in Europe and other foreign jurisdictions to extend the term of a patent that covers an approved drug. When possible, depending upon the length of clinical trials and other factors involved in the filing of a new drug application, or NDA, we expect to apply for patent term extensions for patents covering our product candidates and their methods of use.

In-License Agreements

University of California

        In August 2006, we entered into an exclusive license agreement with The Regents of the University of California, or UC, granting us an exclusive, royalty-bearing sublicensable license to a patent family that includes claims to fundamental aspects of the ATLAS platform, to make, use, offer for sale, import and sell licensed products and services, and to practice licensed methods in all fields of use in the United States. This patent family consists entirely of issued United States patents with a patent term until August 2018. UC retains the right to practice and to allow other educational and non-profit institutions to practice, the licensed intellectual property licensed under the agreement for educational and research purposes.

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        Until first commercial sale of a licensed product or service, we are obligated to pay UC an annual license maintenance fee in the low five figures. Upon commercialization of our products and services covered by the licensed patents, we are obligated to pay UC royalties in the low single digits, subject to a minimum annual royalty in the low five figures, on the net sales of such products and services sold by us or our affiliates for the life of any licensed patents covering the products or services. The royalties payable to UC are subject to reduction for any third party payments required to be made, with a minimum floor in the low single digits. In addition, we agreed to pay UC a flat royalty in the low single digits on net sales of products sold by us or our affiliates which include a polypeptide, nucleotide sequence, biological organism or chemical entity identified in the practice of a licensed method or service, but not otherwise covered, by the licensed patent for the life of the licensed patents. If we receive any revenue (cash or non-cash) from any sublicensees, we must pay UC a percentage of such revenue, excluding certain categories of payments but including royalties on net sales by sublicensees, varying in the low-double digits for any sublicense depending on the scope of the license. Under the terms of the agreement, we are obligated to pay UC a specified development milestone payment and a specified commercial milestone payment up to $500 thousand in the aggregate for the first licensed product covered by the licensed patents, plus up to an additional $250 thousand if specified development and commercial milestones are met for each subsequent licensed product covered by the licensed patents. As of December 31, 2013, we have not made any milestone payments.

        We are required to diligently develop and market licensed products, services and methods. If we are unable to meet our diligence obligations, even after any extension thereof, UC has the right, depending on the number of years the agreement has been effective, to either terminate the agreement or convert our exclusive license to a non-exclusive license.

        Unless earlier terminated, the agreement with UC will remain in effect until the expiration of the last-to-expire patent under the licensed patent rights. We may terminate the agreement at any time by giving UC advance written notice. The agreement may also be terminated by UC in the event of a material breach by us that remains uncured after a specified period of time.

Harvard University

        In November 2007, we entered into an exclusive license agreement with President and Fellows of Harvard College, or Harvard, granting us an exclusive, worldwide, royalty-bearing, sublicensable license to three patent families, to develop, make, have made, use, market, offer for sale, sell, have sold and import licensed products and to perform licensed services. This agreement was amended and restated in November 2012. The Harvard intellectual property covers methods related to the ATLAS discovery platform, as well as certain chlamydia immunogenic compositions and methods for inhibiting or treating chlamydia infections. Any patents within this portfolio that have issued or may be issued will expire normally in 2027 and 2028. Harvard retains the right to make and use, and to grant licenses to other not-for-profit research organizations to make and use, the licensed intellectual property for internal research, teaching and other educational purposes.

        We are obligated to pay Harvard an annual license maintenance fee ranging from the low five figures to the mid five figures depending on the type of product and the number of years after the effective date of the agreement. For products covered by the licensed patent rights, we are obligated to pay Harvard milestone payments up to $1.8 million in the aggregate upon the achievement of certain development and regulatory milestones. For products discovered using the licensed methods, we are obligated to pay Harvard milestone payments up to $600 thousand in the aggregate for each of the first three products and up to $300 thousand in the aggregate for each additional product under the agreement upon the achievement of certain development and regulatory milestones. As of December 31, 2013, we have paid $66 thousand in aggregate milestone payments. Upon commercialization of our products covered by the licensed patent rights or discovered using the licensed methods, we are obligated to pay Harvard royalties on the net sales of such products and

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services sold by us, our affiliates and our sublicensees. This royalty varies depending on the type of product or service but is in the low single digits. The royalty based on sales by our sublicensees is the greater of the applicable royalty rate or a percentage in the high single digits or the low double digits of the royalties we receive from such sublicensee depending on the type of product. Depending on the type of commercialized product or service, royalties are payable until the expiration of the last-to-expire valid claim under the licensed patent rights or for a period of 10 years from first commercial sale of such product or service. The royalties payable to Harvard are subject to reduction, capped at a specified percentage, for any third party payments required to be made. In addition to the royalty payments, if we receive any additional revenue (cash or non-cash) under any sublicense, we must pay Harvard a percentage of such revenue, excluding certain categories of payments, varying from the low single digits to up to the low double digits depending on the scope of the license that includes the sublicense.

        We are required to use commercially reasonable efforts to develop licensed products, introduce them into the commercial market and market them, in compliance with an agreed upon development plan. We are also obligated to achieve specified development milestones. If we are unable to meet our development milestones for any type of product or service, absent any reasonable proposed extension or amendment thereof, Harvard has the right, depending on the type of product or service, to terminate this agreement with respect to such products or to convert the license to a non-exclusive, non-sublicensable license with respect to such products and services.

        Our agreement with Harvard will expire on a product-by-product or service-by-service and country-by-country basis until the expiration of the last-to-expire valid claim under the licensed patent rights. We may terminate the agreement at any time by giving Harvard advance written notice. Harvard may also terminate the agreement in the event of a material breach by us that remains uncured; in the event of our insolvency, bankruptcy, or similar circumstances; or if we challenge the validity of any patents licensed to us.

University of Washington

        In January 2010, we entered into a patent license agreement with the University of Washington, or UW, which was subsequently amended and partially terminated with respect to specified patent rights in July 2012 and was further amended in September 2012 and November 2013. The agreement grants a worldwide, sublicensable, co-exclusive license to certain patent rights, and an exclusive license to certain other patent rights, to manufacture, have manufactured on our behalf, use, offer to sell or sell, offer to lease or lease, import, or otherwise offer to dispose or dispose of licensed products to prevent or treat HSV-2. Patents within the remaining licensed patent rights include claims to compositions of certain HSV-2 proteins and methods for treating HSV infections, with a patent term until at least July 2023. UW retains the right for itself and the Fred Hutchinson Cancer Research Center to make and use products and processes covered by the licensed patent rights for academic research, teaching and any other academic purpose.

        Until the first commercial sale of a licensed product, we are obligated to pay UW an annual license maintenance fee in the low five figures. For each product covered by the licensed patent rights, we are obligated to pay UW milestone payments up to $750 thousand in the aggregate upon the achievement of certain development and commercial milestones. As of December 31, 2013, we have paid $25 thousand in milestone payments. Upon commercialization of our licensed products covered by the licensed patent rights, we are obligated to pay UW royalties in the low single digits on the net sales of such products sold by us, our affiliates and our sublicensees, subject to a minimum annual royalty payment in the low five figures following the first commercial sale of a licensed product. Royalties are payable on a country-by-country and licensed product-by-licensed product basis until the earlier of the termination of this agreement, or the date on which the manufacture, importation, use or sale of the licensed product is no longer covered by a valid claim of a licensed patent in such country. The

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royalties payable to UW are subject to reduction, capped at a specified percentage, for any third-party payments required to be made. In addition to the royalty payments, if we receive any additional revenue (cash or non-cash) under any sublicense, we must pay UW a percentage of such revenue, excluding certain categories of payments and payments made in consideration of additional intellectual property rights that are necessary or useful for commercialization of the licensed product, varying from the mid-single digits to the low double digit range depending on whether certain clinical study milestones have been achieved at the time the sublicense was granted.

        We are required to use commercially reasonable efforts to commercialize the inventions covered by the licensed patents and to make and sell the licensed products within a reasonable period of time. We are also obligated to achieve specified development and regulatory performance milestones.

        Our agreement with UW will expire on the date on which no valid claim in a licensed patent is pending or subsisting in any country worldwide. We may terminate the agreement on a licensed product-by-licensed product basis or in its entirety at any time by giving UW advance written notice. UW may also terminate the agreement in the event of a material breach by us that remains uncured within a specified timeframe; in the event of our insolvency, bankruptcy, or similar circumstances; or if we challenge the validity of the licensed patents.

Other Collaborations

Children's Medical Center Corporation

        In September 2008, we entered into a collaborative research agreement with Childrens that was funded by PATH Vaccine Solutions, or PATH. The collaborative research project led to the identification of certain highly conserved pneumococcal antigens that are able to protect against colonization. The intellectual property covering these antigens is co-owned by us and Childrens and covers pneumococcal vaccine compositions and methods for inhibiting or treating pneumococcus infections. In February 2010, we entered into an exclusive license agreement with Childrens, which was amended and restated in March 2012. This agreement grants us an exclusive, worldwide, sublicensable license under Childrens' rights to the jointly-owned intellectual property to make, have made, use, sell, offer for sale, import and export licensed products and to practice licensed processes for the prevention and treatment of Streptococcus pneumoniae. Childrens retains the right to practice and use, and to allow academic non-profit research organizations to practice and use, the licensed intellectual property for research, educational, clinical and charitable purposes. Under the terms of the agreement, our license from Childrens is subject to PATH's separate non-exclusive, royalty-free license from Childrens to develop pneumococcal T cell-based protein vaccines worldwide and to market and sell such vaccines in developing countries.

        For products covered by the licensed patent rights, we are obligated to pay Childrens milestone payments up to $390 thousand in the aggregate upon the achievement of certain development and commercial milestones. As of December 31, 2013, we have not made any milestone payments. Upon commercialization of our products, we are obligated to pay Childrens royalties in the low single digits on the net sales of licensed products sold by us, our affiliates and our sublicensees. The royalties payable to Childrens are subject to reduction for any third-party payments required to be made, with a minimum floor in the low single digits. Royalties are payable for the term of the license agreement, which is 15 years from the effective date of the amended and restated agreement or until expiration of the last-to-expire patent under the licensed patent rights, whichever period is longer. If we receive any additional revenue (cash or non-cash) under any sublicense, we must pay Childrens a percentage of such income varying from the mid-single digits to low double digits depending on the clinical stage of development of the product, provided that such percentage may increase to match our financial obligations to third parties.

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        We are required to use commercially reasonable efforts to bring at least one licensed product to market as soon as reasonably practical, consistent with sound and legal business practices and judgment and to accomplish the objectives set forth in an agreed upon development plan. If we are unable to meet our diligence obligations, even after any extensions thereof, Childrens has the right to terminate in this agreement in whole or in part.

        Unless earlier terminated, the agreement with Childrens will remain in effect until the later of 15 years from the effective date of the amended and restated agreement or the expiration of the last to expire patent under the licensed patent rights. We may terminate the agreement in its entirety or on a country-by-country and licensed product-by-licensed product basis, at any time by giving Childrens advance written notice. Childrens may terminate the agreement in the event of our bankruptcy, insolvency or similar circumstances; if we use confidential information to formally challenge Childrens' joint ownership of the licensed patent rights; or if we materially breach the agreement and do not cure such breach within a specified time period.

Isconova AB

        In August 2009, we entered into an exclusive license and collaboration agreement with Isconova AB, now Novavax. The agreement grants us a worldwide, sublicensable, exclusive license to two patent families, to import, make, have made, use, sell, offer for sale and otherwise exploit licensed vaccine products containing an adjuvant which incorporates or is developed from Matrix-A, Matrix-C and/or Matrix-M technology, in the fields of HSV and chlamydia, and the time-limited exclusive fields of Neisseria gonorrhoeae, cytomegalovirus, or CMV, and Mycobacterium tuberculosis. After a specified period of time, the license grant to us in the time-limited exclusive fields will convert to a non-exclusive license with respect to all licensed intellectual property rights that were not jointly invented by us and Novavax under the collaboration. Under the terms of this agreement, Novavax also grants us a worldwide, sublicensable, non-exclusive license under such licensed intellectual property rights to import, make, have made, use, sell, offer for sale and otherwise exploit licensed products in the field of Streptococcus pneumoniae. Our rights in the field of Streptococcus pneumoniae are exclusive with respect to all intellectual property rights jointly invented by us and Novavax under the collaboration. The agreement further grants us certain limited rights to use Novavax trademarks.

        For licensed products in each unique disease field under the agreement, we are obligated to pay Novavax milestone payments up to approximately $3 million in the aggregate upon the achievement of certain development and commercial milestones. As of December 31, 2013, we have paid $100 thousand in aggregate milestone payments. Upon commercialization of our products, we are obligated to pay Novavax royalties on the net sales of licensed products sold by us, our affiliates and our sublicensees. The royalties payable to Novavax are in the low single digits and vary on a country-by-country and licensed product-by-licensed product basis based on the amount of net sales and the nature and timing of the licensed product's development. The royalties payable to Novavax are subject to reduction if the licensed product is not covered by one or more valid claims of the licensed patent rights, or if we are required to make any third-party payments. Royalties are payable for 10 years from first commercial sale in any particular country or until the date on which offer for sale of a licensed product is no longer covered by a valid claim of the licensed patent rights in such country, whichever period is longer. In addition to the royalty payments, if we receive any additional revenue (cash or non-cash) under any sublicenses, we must pay Novavax a percentage of such revenue, up to the low double digits.

        We are required to use commercially reasonable efforts to perform specified research activities in accordance with an agreed-upon research plan. We are also obligated to use commercially reasonable efforts consistent with prudent business judgment and business and market conditions to research, develop and carry out the commercialization of licensed products in HSV and chlamydia.

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        Our agreement with Novavax will expire on a country-by-country and licensed product-by-licensed product basis on the date of the expiration of the royalty term with respect to such licensed product in such country. We may terminate the agreement on a country-by-country and licensed product-by-licensed product basis or in its entirety at any time by giving Novavax advance written notice. Both parties may also terminate the agreement in the event of a material breach by the other party that remains uncured or for bankruptcy, insolvency or similar circumstances. Novavax may terminate this agreement if we challenge the validity of any patents licensed to us.

Trade Secrets

        We may rely, in some circumstances, on trade secrets to protect our technology. However, trade secrets can be difficult to protect. We seek to protect our proprietary technology and processes, in part, by entering into confidentiality agreements with our employees, consultants, scientific advisors and contractors. We also seek to preserve the integrity and confidentiality of our data and trade secrets by maintaining physical security of our premises and physical and electronic security of our information technology systems. While we have confidence in these individuals, organizations and systems, agreements or security measures may be breached, and we may not have adequate remedies for any breach. In addition, our trade secrets may otherwise become known or be independently discovered by competitors. To the extent that our consultants, contractors or collaborators use intellectual property owned by others in their work for us, disputes may arise as to the rights in related or resulting know-how and inventions.

United States Government Regulation

        Biological products such as vaccines are subject to regulation under the Federal Food, Drug, and Cosmetic Act, or FD&C Act, and the Public Health Service Act, or PHS Act, and other federal, state, local and foreign statutes and regulations. Both the FD&C Act and the PHS Act and their corresponding regulations govern, among other things, the testing, manufacturing, safety, efficacy, labeling, packaging, storage, record keeping, distribution, reporting, advertising and other promotional practices involving biological products. FDA approval must be obtained before clinical testing of biological products. FDA approval also must be obtained before marketing of biological products. The process of obtaining regulatory approvals and the subsequent compliance with appropriate federal, state, local and foreign statutes and regulations require the expenditure of substantial time and financial resources and we may not be able to obtain the required regulatory approvals.

United States Biological Products Development Process

        The process required by the FDA before a biological product may be marketed in the United States generally involves the following:

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completion of nonclinical laboratory tests and animal studies according to good laboratory practices, or GLPs, and applicable requirements for the humane use of laboratory animals or other applicable regulations;



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submission to the FDA of an application for an IND, which must become effective before human clinical trials may begin;



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performance of adequate and well-controlled human clinical trials according to the FDA's regulations commonly referred to as good clinical practices, or GCPs, and any additional requirements for the protection of human research subjects and their health information, to establish the safety and efficacy of the proposed biological product for its intended use;

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submission to the FDA of a Biologics License Application, or BLA, for marketing approval that includes substantive evidence of safety, purity, and potency from results of nonclinical testing and clinical trials;



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satisfactory completion of an FDA inspection of the manufacturing facility or facilities where the biological product is produced to assess compliance with GMP, to assure that the facilities, methods and controls are adequate to preserve the biological product's identity, strength, quality and purity and, if applicable, the FDA's current good tissue practices, or GTPs, for the use of human cellular and tissue products;



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potential FDA audit of the nonclinical and clinical trial sites that generated the data in support of the BLA; and



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FDA review and approval, or licensure, of the BLA.

        Before testing any biological product candidate in humans, the product candidate enters the preclinical study stage. Preclinical studies, also referred to as nonclinical studies, include laboratory evaluations of product chemistry, toxicity and formulation, as well as animal studies to assess the potential safety and activity of the product candidate. The conduct of the preclinical studies must comply with federal regulations and requirements including GLPs.

        The clinical trial sponsor must submit the results of the preclinical tests, together with manufacturing information, analytical data, any available clinical data or literature and a proposed clinical protocol, to the FDA as part of the IND. Some preclinical studies may continue even after the IND is submitted. The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA places the clinical trial on a clinical hold within that 30-day time period. In such a case, the IND sponsor and the FDA must resolve any outstanding concerns before the clinical trial can begin. The FDA may also impose clinical holds on a biological product candidate at any time before or during clinical trials due to safety concerns or non-compliance. If the FDA imposes a clinical hold, studies may not recommence without FDA authorization and then only under terms authorized by the FDA. Accordingly, we cannot be sure that submission of an IND will result in the FDA allowing clinical trials to begin, or that, once begun, issues will not arise that suspend or terminate such studies.

        Clinical trials involve the administration of the biological product candidate to healthy volunteers or patients under the supervision of qualified investigators, generally physicians not employed by or under the trial sponsor's control. Clinical trials are conducted under protocols detailing, among other things, the objectives of the clinical trial, dosing procedures, subject selection and exclusion criteria, and the parameters to be used to monitor subject safety, including stopping rules that assure a clinical trial will be stopped if certain AEs should occur. Each protocol and any amendments to the protocol must be submitted to the FDA as part of the IND. Clinical trials must be conducted and monitored in accordance with the FDA's regulations comprising the GCP requirements, including the requirement that all research subjects provide informed consent. Further, each clinical trial must be reviewed and approved by an IRB at or servicing each institution at which the clinical trial will be conducted. An IRB is charged with protecting the welfare and rights of trial participants and considers such items as whether the risks to individuals participating in the clinical studies are minimized and are reasonable in relation to anticipated benefits. The IRB also approves the form and content of the informed consent that must be signed by each clinical trial subject or his or her legal representative and must monitor the clinical trial until completed.

        Human clinical trials are typically conducted in three sequential phases that may overlap or be combined:

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Phase 1.  The biological product is initially introduced into healthy human subjects and tested for safety. In the case of some products for severe or life-threatening diseases, especially when the

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product may be too inherently toxic to ethically administer to healthy volunteers, the initial human testing is often conducted in patients.

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Phase 2.  The biological product is evaluated in a limited patient population to identify possible adverse effects and safety risks, to preliminarily evaluate the efficacy of the product for specific targeted diseases and to determine dosage tolerance, optimal dosage and dosing schedule.



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Phase 3.  Clinical studies are undertaken to further evaluate dosage, clinical efficacy, potency, and safety in an expanded patient population at geographically dispersed clinical trial sites. These clinical studies are intended to establish the overall risk/benefit ratio of the product and provide an adequate basis for product labeling.

        Post-approval clinical studies, sometimes referred to as Phase 4 clinical studies, may be conducted after initial marketing approval. These clinical studies are used to gain additional experience from the treatment of patients in the intended therapeutic indication, particularly for long-term safety follow-up.

        During all phases of clinical development, regulatory agencies require extensive monitoring and auditing of all clinical activities, clinical data and clinical trial investigators. Annual progress reports detailing the results of the clinical studies must be submitted to the FDA. Written IND safety reports must be promptly submitted to the FDA, the NIH and the investigators for serious and unexpected AEs, any findings from other studies, tests in laboratory animals or in vitro testing that suggest a significant risk for human subjects, or any clinically important increase in the rate of a serious suspected adverse reaction over that listed in the protocol or investigator brochure. The sponsor must submit an IND safety report within 15 calendar days after the sponsor determines that the information qualifies for reporting. The sponsor also must notify the FDA of any unexpected fatal or life-threatening suspected adverse reaction within seven calendar days after the sponsor's initial receipt of the information. Phase 1, Phase 2 and Phase 3 clinical studies may not be completed successfully within any specified period, if at all. The FDA or the sponsor or its data safety monitoring board may suspend a clinical trial at any time on various grounds, including a finding that the research subjects or patients are being exposed to an unacceptable health risk. Similarly, an IRB can suspend or terminate approval of a clinical trial at its institution if the clinical trial is not being conducted in accordance with the IRB's requirements or if the biological product has been associated with unexpected serious harm to patients.

        Concurrent with clinical studies, companies usually complete additional animal studies and must also develop additional information about the physical characteristics of the biological product as well as finalize a process for manufacturing the product in commercial quantities in accordance with GMP requirements. To help reduce the risk of the introduction of adventitious agents with use of biological products, the PHS Act emphasizes the importance of manufacturing control for products whose attributes cannot be precisely defined. The manufacturing process must be capable of consistently producing quality batches of the product candidate and, among other things, the sponsor must develop methods for testing the identity, strength, quality, potency and purity of the final biological product. Additionally, appropriate packaging must be selected and tested and stability studies must be conducted to demonstrate that the biological product candidate does not undergo unacceptable deterioration over its shelf life.

United States Review and Approval Processes

        After the completion of clinical trials of a biological product, FDA approval of a BLA must be obtained before commercial marketing of the biological product. The BLA must include results of product development, laboratory and animal studies, human studies, information on the manufacture and composition of the product, proposed labeling and other relevant information. In addition, under the Pediatric Research Equity Act, or PREA, a BLA or supplement to a BLA must contain data to assess the safety and effectiveness of the biological product for the claimed indications in all relevant

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pediatric subpopulations and to support dosing and administration for each pediatric subpopulation for which the product is safe and effective. The FDA may grant deferrals for submission of data or full or partial waivers. The testing and approval processes require substantial time and effort and there can be no assurance that the FDA will accept the BLA for filing and, even if filed, that any approval will be granted on a timely basis, if at all.

        Under the Prescription Drug User Fee Act, or PDUFA, as amended, each BLA must be accompanied by a significant user fee. PDFUA also imposes an annual product fee for biologics and an annual establishment fee on facilities used to manufacture prescription biologics. Fee waivers or reductions are available in certain circumstances, including a waiver of the application fee for the first application filed by a small business.

        Within 60 days following submission of the application, the FDA reviews the BLA to determine if it is substantially complete before the agency accepts it for filing. The FDA may refuse to file any BLA that it deems incomplete or not properly reviewable at the time of submission and may request additional information. In this event, the BLA must be resubmitted with the additional information. The resubmitted application also is subject to review before the FDA accepts it for filing. Once the submission is accepted for filing, the FDA begins an in-depth substantive review of the BLA. The FDA reviews the BLA to determine, among other things, whether the proposed product is safe and potent, or effective, for its intended use, and has an acceptable purity profile, and whether the product is being manufactured in accordance with GMP to assure and preserve the product's identity, safety, strength, quality, potency and purity. The FDA may refer applications for novel biological products or biological products that present difficult questions of safety or efficacy to an advisory committee, typically a panel that includes clinicians and other experts, for review, evaluation and a recommendation as to whether the application should be approved and under what conditions. The FDA is not bound by the recommendations of an advisory committee, but it considers such recommendations carefully when making decisions. During the biological product approval process, the FDA also will determine whether a Risk Evaluation and Mitigation Strategy, or REMS, is necessary to assure the safe use of the biological product. If the FDA concludes a REMS is needed, the sponsor of the BLA must submit a proposed REMS; the FDA will not approve the BLA without a REMS, if required.

        Before approving a BLA, the FDA will inspect the facilities at which the product is manufactured. The FDA will not approve the product unless it determines that the manufacturing processes and facilities are in compliance with GMP requirements and adequate to assure consistent production of the product within required specifications. Additionally, before approving a BLA, the FDA will typically inspect one or more clinical sites to assure that the clinical trials were conducted in compliance with IND study requirements and GCP requirements. To assure GMP, GTP and GCP compliance, an applicant must incur significant expenditure of time, money and effort in the areas of training, record keeping, production, and quality control.

        Notwithstanding the submission of relevant data and information, the FDA may ultimately decide that the BLA does not satisfy its regulatory criteria for approval and deny approval. Data obtained from clinical trials are not always conclusive and the FDA may interpret data differently than we interpret the same data. If the agency decides not to approve the BLA in its present form, the FDA will issue a complete response letter that usually describes all of the specific deficiencies in the BLA identified by the FDA. The deficiencies identified may be minor, for example, requiring labeling changes, or major, for example, requiring additional clinical trials. Additionally, the complete response letter may include recommended actions that the applicant might take to place the application in a condition for approval. If a complete response letter is issued, the applicant may either resubmit the BLA, addressing all of the deficiencies identified in the letter, or withdraw the application.

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        If a product receives regulatory approval, the approval may be significantly limited to specific diseases and dosages or the indications for use may otherwise be limited, which could restrict the commercial value of the product. Further, the FDA may require that certain contraindications, warnings or precautions be included in the product labeling. The FDA may impose restrictions and conditions on product distribution, prescribing, or dispensing in the form of a risk management plan, or otherwise limit the scope of any approval. In addition, the FDA may require post marketing clinical trials, sometimes referred to as Phase 4 clinical trials, designed to further assess a biological product's safety and effectiveness, and testing and surveillance programs to monitor the safety of approved products that have been commercialized.

        One of the performance goals agreed to by the FDA under the PDUFA is to review 90% of standard BLAs in 10 months from filing and 90% of priority BLAs in six months from filing, whereupon a review decision is to be made. The FDA does not always meet its PDUFA goal dates for standard and priority BLAs and its review goals are subject to change from time to time. The review process and the PDUFA goal date may be extended by three months if the FDA requests or the BLA sponsor otherwise provides additional information or clarification regarding information already provided in the submission within the last three months before the PDUFA goal date.

Federal and State Fraud and Abuse, Transparency and Privacy Laws

        In the United States, our business activities are subject to numerous other laws by federal and state authorities, in addition to the FDA, including but not limited to, the United States Federal Communications Commission, the United States Department of Health and Human Services, or HHS, and its various divisions, including but not limited to, the Centers for Medicare & Medicaid Services, or CMS. These laws are enforced by various federal and state enforcement authorities, including but not limited to, the United States Department of Justice, and individual United States Attorney offices within the Department of Justice, HHS' various enforcement divisions, including but not limited to, the Office of Inspector General, or OIG, the Office for Human Research Protections, or OHRP, and the Office of Research Integrity, or ORI, and other state and local government agencies.

        The federal Anti-Kickback Statute prohibits, among other things, knowingly and willfully offering, paying, soliciting, or receiving any remuneration (including any kickback, bribe or rebate), directly or indirectly, overtly or covertly, in cash or in kind, to induce, or in return for, purchasing, leasing, ordering, or arranging for or recommending, the purchase lease, or order of any good, facility, service or item for which payment is made, in whole or in part, under a federal health care program, such as Medicare. The federal Anti-Kickback Statute has been interpreted to apply to arrangements between manufacturers on one hand and prescribers, purchasers and formulary managers on the other. There are a number of statutory exceptions and regulatory safe harbors protecting certain common activities from prosecution. Failure to meet all of the requirements of a particular applicable statutory exception or regulatory safe harbor does not make the conduct per se illegal under the federal Anti-Kickback Statute. Instead, the legality of the arrangement will be evaluated on a case-by-case basis based on a cumulative review of all of its facts and circumstances.

        The federal civil False Claims Act prohibits, among other things, any person or entity from knowingly presenting, or causing to be presented, a false or fraudulent claim for payment to, or approval by, the federal government, or knowingly making, using, or causing to be made or used, a false record or statement material to a false or fraudulent claim to the federal government. Recently, the civil False Claims Act has been used to assert liability on the basis of kickbacks and improper referrals, improperly reported government pricing metrics such as Medicaid Best Price or Average Manufacturer Price, improper use of supplier or provider Medicare numbers when detailing a provider of services, improper promotion of drugs or off-label uses not expressly approved by the FDA in a drug's label, and misrepresentations with respect to the services rendered or items provided.

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        Additionally, the civil monetary penalties statute, among other things, imposes fines against any person who is determined to have presented, or caused to be presented, claims to a federal health care program that the person knows, or should know, is for an item or service that was not provided as claimed or is false or fraudulent.

        The federal Health Insurance Portability and Accountability Act of 1996, or HIPAA, created new federal criminal statutes that prohibit knowingly and willfully executing, or attempting to execute, a scheme to defraud or to obtain, by means of false or fraudulent pretenses, representations or promises, any of the money or property owned by, or under the custody or control of, any health care benefit program and knowingly and willfully falsifying, concealing or covering up by trick, scheme or device a material fact or making any materially false, fictitious or fraudulent statement in connection with the delivery of, or payment for, health care benefits, items or services relating to health care matters.

        Many states have similar fraud and abuse statutes and regulations that apply to items and services reimbursed under Medicaid and other state programs, or, in several states, private payors.

        Additionally, the federal Physician Payments Sunshine Act within the Health Care and Education Reconciliation Act, or Health Care Reform Law, and its implementing regulations, require that certain manufacturers of drugs, devices, biological and medical supplies for which payment is available under Medicare, Medicaid or the Children's Health Insurance Program (with certain exceptions) to report to CMS, information related to certain payments or other transfers of value made or distributed to physicians and teaching hospitals, or to entities or individuals at the request of, or designated on behalf of, the physicians and teaching hospitals and to report annually to CMS certain ownership and investment interests held by physicians and their immediate family members.

        In addition, we may be subject to, or our marketing activities may be limited by, data privacy and security regulation by both the federal government and the states in which we conduct our business.

        If our operations are found to be in violation of any of the health regulatory laws described above, or any other laws that apply to us, we may be subject to penalties, including, without limitation, civil, criminal, and administrative penalties, damages, monetary fines, disgorgement, possible exclusion from participation in Medicare, Medicaid and other federal health care programs, contractual damages, reputational harm, diminished profits and future earnings, and curtailment or restructuring of our operations.

Reimbursement

        In both domestic and foreign markets, the commercial success of any approved products will depend, in part, on the availability of coverage and adequate reimbursement of such products from third-party payors, such as government health care programs, commercial insurance and managed care organizations. Patients who are provided vaccinations, and providers providing vaccinations, generally rely on third-party payors to reimburse all or part of the associated health care costs. Sales of any approved vaccines will therefore depend substantially, both domestically and abroad, on the extent to which the costs of our approved vaccines will be paid by third-party payors. These third-party payors are increasingly challenging the prices charged for medical products and services and imposing controls to manage costs. The containment of health care costs has become a priority of federal and state governments and the prices of drugs have been a focus in this effort. Governments have shown significant interest in implementing cost-containment programs, including price controls, restrictions on reimbursement and requirements for substitution of generic products. Adoption of price controls and cost-containment measures, and adoption of more restrictive policies in jurisdictions with existing controls and measures, could further limit our net revenue and results. Third-party payors may limit coverage to specific products on an approved list, or formulary, which might not include all of the FDA-approved products for a particular indication. In addition, there is significant uncertainty regarding the reimbursement status of newly approved health care products. Third-party payors are

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increasingly examining the medical necessity and cost-effectiveness of medical products and services, in addition to their safety and efficacy. We may need to conduct expensive pharmacoeconomic studies in order to demonstrate the cost-effectiveness of our products. If third-party payors do not consider our products to be cost-effective compared to other therapies, the payors may not cover our products after approved as a benefit under their plans or, if they do, the level of payment may not be sufficient to allow us to sell our products on a profitable basis.

        Within the United States, if we obtain appropriate approval in the future to market any of our current product candidates, we may seek approval and coverage for those products under Medicaid, Medicare and the Public Health Service, or PHS, pharmaceutical pricing program and also seek to sell the products to federal agencies.

        Medicaid is a joint federal and state program that is administered by the states for low income and disabled beneficiaries. Under the Medicaid Drug Rebate Program, manufacturers are required to pay a rebate for each unit of product reimbursed by the state Medicaid programs. The amount of the rebate for each product is set by law and may be subject to an additional discount if certain pricing increases more than inflation.

        Medicare is a federal program administered by the federal government that covers individuals age 65 and over as well as those with certain disabilities. Medicare Part D provides coverage to enrolled Medicare patients for self-administered drugs (i.e., drugs that do not need to be administered by a physician). Medicare Part D is administered by private prescription drug plans approved by CMS and each drug plan establishes its own Medicare Part D formulary for prescription drug coverage and pricing, which the drug plan may modify from time-to-time.

        Medicare Part B covers most injectable drugs given in an in-patient setting, and some drugs administered by a licensed medical provider in hospital outpatient departments and doctors' offices. Medicare Part B is administered by Medicare Administrative Contractors, which generally have the responsibility of making coverage decisions. Subject to certain payment adjustments and limits, Medicare generally pays for Part B covered drugs based on a percentage of manufacturer-reported average sales prices.

        Drug products are subject to discounted pricing when purchased by federal agencies via the Federal Supply Schedule, or FSS. FFS participation is required for a drug product to be covered and paid for by certain federal agencies and for coverage under Medicaid, Medicare Part B and the PHS pharmaceutical pricing program. FSS pricing is negotiated periodically with the Department of Veterans Affairs. FSS pricing is intended to not exceed the price that a manufacturer charges its most-favored non-federal customer for its product. In addition, prices for drugs purchased by the Veterans Administration, Department of Defense (including drugs purchased by military personnel and dependents through the TRICARE retail pharmacy program), Coast Guard, and PHS are subject to a cap on pricing (known as the "federal ceiling price") and may be subject to an additional discount if pricing increases more than inflation.

        To maintain coverage of drugs under the Medicaid Drug Rebate Program, manufacturers are required to extend discounts to certain purchasers under the PHS pharmaceutical pricing program. Purchasers eligible for discounts include hospitals that serve a disproportionate share of financially needy patients, community health clinics and other entities that receive health services grants from the PHS.

        The American Recovery and Reinvestment Act of 2009 provides funding for the federal government to compare the effectiveness of different treatments for the same illness. A plan for the research will be developed by the HHS, the Agency for Healthcare Research and Quality and the National Institutes for Health, and periodic reports on the status of the research and related expenditures will be made to Congress. Although the results of the comparative effectiveness studies

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are not intended to mandate coverage policies for public or private payors, it is not clear what effect, if any, the research will have on the sales of any product, if any such product or the condition that it is intended to treat is the subject of a trial. It is also possible that comparative effectiveness research demonstrating benefits in a competitor's product could adversely affect the sales of any of our approved products. If third-party payors do not consider our products to be cost-effective compared to other available therapies, they may not cover our products as a benefit under their plans or, if they do, the level of payment may not be sufficient to allow us to sell our products on a profitable basis.

        The United States and state governments continue to propose and pass legislation designed to reduce the cost of health care. In March 2010, the United States Congress enacted the Health Care Reform Law which has the potential to change health care financing by both governmental and private payors. In the future, there may continue to be additional proposals relating to the reform of the United States health care system, some of which could further limit the prices we are able to charge, or the amounts of reimbursement available for our vaccine candidates once they are approved.

        Outside the United States, ensuring adequate coverage and payment for our products will face challenges. In international markets, reimbursement and health care payment systems vary significantly by country, and many countries have instituted price ceilings on specific products and therapies. Pricing of prescription pharmaceuticals is subject to governmental control in many countries. Pricing negotiations with governmental authorities can extend well beyond the receipt of regulatory marketing approval for a product and may require us to conduct a clinical trial that compares the cost effectiveness of our product candidates or products to other available therapies. The conduct of such a clinical trial could be expensive and result in delays in our commercialization efforts. Third-party payors are challenging the prices charged for medical products and services, and many third-party payors limit reimbursement for newly-approved health care products. Recent budgetary pressures in many European Union countries are also causing governments to consider or implement various cost-containment measures, such as price freezes, increased price cuts and rebates. If budget pressures continue, governments may implement additional cost-containment measures. Cost-control initiatives could decrease the price we might establish for products that we may develop or sell, which would result in lower product revenues or royalties payable to us. There can be no assurance that any country that has price controls or reimbursement limitations for pharmaceutical products will allow favorable reimbursement and pricing arrangements for any of our products.

Foreign Regulation

        In addition to regulations in the United States, we will be subject to a variety of foreign regulations governing clinical trials and commercial sales and distribution of our product candidates. Whether or not we obtain FDA approval for a product candidate, we must obtain approval from the comparable regulatory authorities of foreign countries or economic areas, such as the European Union, before we may commence clinical trials or market products in those countries or areas. The approval process and requirements governing the conduct of clinical trials, product licensing, pricing and reimbursement vary greatly from place to place, and the time may be longer or shorter than that required for FDA approval.

        Certain countries outside of the United States have a process that requires the submission of a clinical trial application much like an IND prior to the commencement of human clinical trials. In Europe, for example, a clinical trial application, or CTA, must be submitted to the competent national health authority and to independent ethics committees in each country in which a company intends to conduct clinical trials. Once the CTA is approved in accordance with a country's requirements, clinical trial development may proceed in that country. In all cases, the clinical trials must be conducted in accordance with good clinical practices, or GCPs and other applicable regulatory requirements.

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        Under European Union regulatory systems, a company may submit marketing authorization applications either under a centralized or decentralized procedure. The centralized procedure is compulsory for medicinal products produced by biotechnology or those medicinal products containing new active substances for specific indications such as the treatment of AIDS, cancer, neurodegenerative disorders, diabetes, viral diseases and designated orphan medicines, and optional for other medicines which are highly innovative. Under the centralized procedure, a marketing application is submitted to the European Medicines Agency where it will be evaluated by the Committee for Medicinal Products for Human Use and a favorable opinion typically results in the grant by the European Commission of a single marketing authorization that is valid for all European Union member states within 67 days of receipt of the opinion. The initial marketing authorization is valid for five years, but once renewed is usually valid for an unlimited period. The decentralized procedure provides for approval by one or more "concerned" member states based on an assessment of an application performed by one member state, known as the "reference" member state. Under the decentralized approval procedure, an applicant submits an application, or dossier, and related materials to the reference member state and concerned member states. The reference member state prepares a draft assessment and drafts of the related materials within 120 days after receipt of a valid application. Within 90 days of receiving the reference member state's assessment report, each concerned member state must decide whether to approve the assessment report and related materials. If a member state does not recognize the marketing authorization, the disputed points are eventually referred to the European Commission, whose decision is binding on all member states.

Manufacturing

        We do not have any manufacturing facilities. We currently rely, and expect to continue to rely, on third parties for the manufacture of our product candidates for preclinical studies and clinical trials, as well as for commercial manufacture if our product candidates receive marketing approval. To date, we have obtained materials for GEN-003 and GEN-004 from third-party manufacturers who are sole source suppliers to us. For both product candidates, we intend to identify and qualify contract manufacturers to provide the protein process development, protein production and adjuvant production and fill-and-finish services prior to submission of an NDA to the FDA.

Employees

        As of November 30, 2013, we had 39 full time employees. Of these 39 employees, 34 employees are engaged in research and development and five employees are engaged in finance, human resources, facilities and business and general management. We have no collective bargaining agreements with our employees and we have not experienced any work stoppages. We consider our relations with our employees to be good.

Facilities

        Our principal executive offices are located at 100 Acorn Park Drive, Cambridge, Massachusetts 02140, where we occupy approximately 23,666 square feet of laboratory and office space. Our lease term expires on February 28, 2017. We believe that our existing facilities are sufficient for our present and future operations, and we currently have no plans to lease additional space.

Legal Proceedings

        From time to time, we are subject to various legal proceedings and claims that arise in the ordinary course of our business activities. Although the results of litigation and claims cannot be predicted with certainty, as of the date of this prospectus, we do not believe we are party to any claim or litigation, the outcome of which, if determined adversely to us, would individually or in the aggregate be reasonably expected to have a material adverse effect on our business. Regardless of the outcome, litigation can have an adverse impact on us because of defense and settlement costs, diversion of management resources and other factors.

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MANAGEMENT

Executive Officers, Significant Employees and Directors

        Below is a list of the names, ages as of November 30, 2013 and positions, and a brief account of the business experience of the individuals who serve as our executive officers and directors as of the date of this prospectus.

        William Clark has served as our President and Chief Executive Officer since February 2011. Previously he served as our Chief Business Officer from August 2010 to February 2011. Mr. Clark has served on our board of directors since February 2011. Prior to joining our Company, he served as Chief Business Officer at Vanda Pharmaceuticals, Inc., or Vanda, a biopharmaceutical company he co-founded in 2004. While at Vanda, he lead the company's strategic and business development activities, and played a central role in raising more than $220 million in multiple public and private financings. Prior to Vanda, Mr. Clark was a principal at Care Capital, LLC, a venture capital firm investing in biopharmaceutical companies, after serving in a variety of commercial and strategic roles at SmithKline Beecham (now GlaxoSmithKline). Mr. Clark holds a B.A. from Harvard University and an M.B.A. from The Wharton School at the University of Pennsylvania. We believe that Mr. Clark's operation and historical experience with our Company gained from serving as our Chief Executive Officer, President and member of our board of directors, combined with his prior experience at Vanda and in the venture capital industry focusing on biopharmaceutical companies qualify him to serve as a member of our board of directors.

        Seth Hetherington, M.D. has served as our Chief Medical Officer since joining our Company in January 2011. Prior to joining our Company, Dr. Hetherington served as Senior Vice President of Clinical and Regulatory Affairs at Icagen, Inc., or Icagen, from May 2006 through December 2010. Prior to Icagen, Dr. Hetherington served as Vice President, Clinical Development and Chief Medical Officer at Inhibitex Inc. from June 2002 through April 2005 and held various positions of increasing responsibility in clinical drug development at GlaxoSmithKline from 1995 through June 2002. Dr. Hetherington has also served as a faculty member at the University of North Carolina School of Medicine and held appointments at several leading academic medical centers, including the University of Tennessee, St. Jude Children's Research Hospital in Memphis and Albany Medical College. Dr. Hetherington earned his B.S. at Yale University and his M.D. at the University of North Carolina, Chapel Hill. He completed his postgraduate training in pediatrics and pediatric infectious diseases at the University of North Carolina and the University of Minnesota, respectively. Dr. Hetherington has published extensively in medical and scientific literature, and is board certified in both pediatrics and pediatric infectious diseases. He also served as the industry representative to the Vaccines and Related Blood Products Advisory Committee of the FDA. He currently serves as the industry representative on the National Vaccine Advisory Committee of the U.S. Department of Health and Human Services.

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        Robert E. Farrell Jr., CPA has served as our Vice President of Finance and Administration since joining our Company in May 2009. Prior to joining our Company, he served as Senior Director of Finance at Magen Biosciences, Inc., or Magen, from September 2008 to May 2009. In that position, he was responsible for all finance and administrative functions and he played a key role in the acquisition of Magen by PPD, Inc. Prior to Magen, Mr. Farrell held senior level financial positions at Oscient Pharmaceuticals Corp. and NeoGenesis Pharmaceuticals, Inc. where he built and directed all financial reporting efforts and helped guide the company through an initial public offering. Mr. Farrell is a licensed certified public accountant and holds a B.S. degree in Accounting from Bentley University.

        Jessica Baker Fletchtner, Ph.D. has held multiple scientific roles since joining our Company in March 2007 and has served as our Vice President of Research since 2010. Prior to joining our Company, Dr. Flechtner was an Immunology Consultant at BioVest International, Inc. from June 2006 to March 2007, where she guided the development of assays to evaluate the success of the company's autologous Follicular (Non-Hodgkin's) Lymphoma vaccine in patients. As a researcher at Mojave Therapeutics, Inc., or Mojave, and Antigenics Inc. (now Agenus), which acquired Mojave's intellectual property, from 2001 to 2005, Dr. Flechtner developed protein and peptide-based vaccines and immunotherapies for cancer, infectious disease, autoimmunity and allergy. She is an inventor on nine pending or issued patents and has multiple peer-reviewed scientific publications. Dr. Flechtner performed her post-doctoral work in the laboratory of Dr. Harvey Cantor at the Dana Farber Cancer Institute and Harvard Medical School and holds a Ph.D. in Cellular Immunology and B.S. in Animal Science from Cornell University. She is a member of the American Association of Immunologists and the American Society for Microbiology.

        Paul Giannasca, Ph.D. has served as our Vice President of Development since joining our Company in January 2010. Prior to joining our Company, Dr. Giannasca served as Vice President, Development at Acambis (now Sanofi Pasteur) from 2004 to 2010. Prior to Acambis, he was a senior scientist at OraVax from 1995 to 1999, where he contributed to the company's research initiatives for several vaccines, focusing on evaluating vaccine adjuvants and elucidating mechanisms of vaccine-induced protection. Dr. Giannasca holds multiple patents covering active and passive immunization against Clostridium difficile disease and has published more than 25 papers in the areas of infectious diseases, vaccine-induced protection and vaccine development. Dr. Giannasca received his B.S. in Biology from Fairleigh Dickinson University and his Ph.D. in Molecular and Cellular Biology from the University of Massachusetts-Amherst. He completed his post-doctoral training at Harvard Medical School/Children's Hospital Boston.

        Ravi Venkataramani, Ph.D. has served as our Vice President of Business Development since joining our Company in July 2011. Prior to joining our Company, Dr. Venkataramani served as director of business development at MedImmune Inc., or MedImmune, from 2004 to 2010. While at MedImmune, he led several key strategic, product and technology deals. In addition, he shared responsibilities for building and managing the respiratory, immunology and autoimmunity drug portfolio of the company. Prior to joining MedImmune, he advised senior management of Fortune-100 clients on all aspects of corporate strategy and execution at Booz, Allen & Hamilton (now Booz & Co). He holds a B.S. from the University of Wisconsin at Superior and a Ph.D. in biochemistry and molecular biophysics from the University of Pennsylvania.

        George Siber, M.D. has served as a member of our board of directors since 2007. From 1996 to 2007, Dr. Siber served as Executive Vice President and Chief Scientific Officer of Wyeth Vaccines, or Wyeth. While at Wyeth, Dr. Siber oversaw the development and approval of multiple widely-used childhood vaccines, including Prevnar, a pneumococcal vaccine which has achieved multibillion dollar revenues; Acel-Imune, an acellular pertussis vaccine; and Meningitec, a meningococcal meningitis vaccine. Prior to Wyeth, Dr. Siber was Director of the Massachusetts Public Health Biologic Laboratories and a Harvard Medical School Associate Professor of Medicine at Dana Farber Cancer

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Institute. During this time, Dr. Siber led the research and manufacturing of multiple vaccines and immune globulins including Respigam, a human immune globulin against respiratory syncytial virus. Dr. Siber holds an MD degree from McGill University in Canada, received post-doctoral training in Internal Medicine at Rush-Presbyterian Hospital in Chicago and Beth Israel Hospital in Boston and Infectious Disease and vaccinology training at Children's Hospital and Beth Israel Hospital, Harvard Medical School Boston. We believe that Dr. Siber's experience in life sciences and vaccine industries and his experience overseeing the development of multiple vaccines qualifies him to serve as a member of our board of directors.

        Kevin Bitterman, Ph.D. has served as a member of our board of directors since August 2006. Since 2004, Dr. Bitterman has served as principal at Polaris Partners, or Polaris, and focuses on investments in life sciences companies. Prior to joining Polaris, Dr. Bitterman completed his Ph.D. in genetics at Harvard Medical School. His doctoral research focused on the molecular regulation of caloric restriction and on modulation of a novel class of protein deacetylases. Dr. Bitterman is a cofounder of Sirtris Pharmaceuticals, Inc. acquired by GlaxoSmithKline and was the founding CEO at Visterra Inc. In additional to representing Polaris as a director of our Company, he currently represents Polaris as a director of InSeal Medical, Kala Pharmaceuticals, Neuronetics, Inc., Visterra, Inc., TARIS Biomedical, and Vets First Choice. Additionally, Dr. Bitterman is a board observer to Arsenal Medical and 480 Biomedical. He received a Ph.D. in Genetics from Harvard Medical School and a Bachelor's in Biology from Rutgers College. We believe that Dr. Bitterman's extensive experience investing in, guiding and leading start-up and early phase companies, as well as his experience as a director of other companies, qualifies him to serve as a member of our board of directors.

        Katrine Bosley has served as a member of our board of directors since March 2013 and as our chairperson since August 2013. Ms. Bosley is currently the Entrepreneur-in-Residence at The Broad Institute. She served as Chief Executive Officer of Avila Therapeutics Inc., or Avila, from May 2009 to March, 2012, when Avila was acquired by Celgene Corporation. Before Avila, she was Vice President, Strategic Operations at Adnexus, a Bristol-Myers Squibb Company and was Vice President, Business Development at Adnexus Therapeutics Inc., or Adnexus, before that. She joined Adnexus from Biogen Idec where she held roles in business development, commercial operations, and portfolio strategy in the United States and Europe and led the in-licensing of Tysabri (natalizumab) among a number of other transactions. Earlier, she was part of the healthcare team at the venture firm Highland Capital Partners from 1993 to 1995. In addition to serving as a director of our Company, Ms. Bosley currently serves as a director of Galapagos NV and Coco Therapeutics Ltd. Ms. Bosley graduated from Cornell University with a Bachelor of Arts degree in biology. We believe that Ms. Bosley's experience as a chief executive officer of a biotechnology company and her breadth of experience in creating strategic and business development value qualifies her to serve as a member of our board of directors.

        Simeon J. George, M.D. has served as a member of our board of directors since February 2009. Since 2007, Dr. George has served as partner of S.R. One, Limited, or S.R. One, and leads S.R. One's west coast investment activities. Prior to joining S.R. One, Dr. George was a consultant at Bain & Company from October 2006 to August 2007. In addition to serving as a director of our Company, Dr. George currently serves as a director of Anaphore, Auxogyn, Inc., HTG Molecular and Principia Biosciences. He received his BA in Neuroscience from the Johns Hopkins University, where he graduated Phi Beta Kappa, and received his MD from the University of Pennsylvania School of Medicine and his MBA (Mayer Scholar) from the Wharton School of the University of Pennsylvania. We believe that Dr. George's experience in the venture capital industry, particularly with biotechnology and pharmaceutical companies, as well as his experience as a director of other companies, qualifies him to serve as a member of our board of directors.

        Stephen J. Hoffman, M.D., Ph.D. has served as a member of our board of directors since December 2010. Dr. Hoffman has served as a managing director at Skyline Ventures, a venture capital

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firm, since May 2007. From January 2003 to March 2007, Dr. Hoffman was a general partner at TVM Capital, a venture capital firm. Prior to that, he served as President, Chief Executive Officer and a director of Allos Therapeutics, Inc., or Allos, a biopharmaceutical company, from 1994 to 2002, and as Chairman of the Board until 2012. From 1990 to 1994, Dr. Hoffman completed a fellowship in clinical oncology and a residency/fellowship in dermatology, both at the University of Colorado. Dr. Hoffman was the scientific founder of Somatogen Inc., a biotechnology company that was acquired by Baxter International, Inc., a global medical products and services company, in 1998, where he held the position of Vice President of Science and Technology from 1987 until 1990. In addition to serving as a director of our Company, he currently serves as a director of several biopharmaceutical companies, including AcelRx, Inc., Concert Pharmaceuticals, Inc., Collegium Pharmaceuticals, Inc., Dicerna Pharmaceuticals, Inc. and Proteon Therapeutics, Inc. Previously, Dr. Hoffman served on the board of directors of Sirtris Pharmaceuticals, Inc., a pharmaceutical company that was acquired by GlaxoSmithKline, in 2008. Dr. Hoffman holds a Ph.D. in bio-organic chemistry from Northwestern University and an M.D. from the University of Colorado School of Medicine. We believe that Dr. Hoffman's scientific, financial and business expertise, including his diversified background as an executive officer and investor in public pharmaceutical companies as well as a director of a public pharmaceutical company, qualifies him to serve as a member of our board of directors.

Board Composition and Election of Directors

Board Composition

        Our board of directors is currently comprised of six members. Our board of directors has determined that each of Dr. Bitterman, Ms. Bosley, Dr. George and Dr. Hoffman is independent for NASDAQ purposes. The members of our board of directors were elected in compliance with the provisions of the voting agreement among us and our major stockholders. The voting agreement will terminate upon the closing of this offering and we will have no further contractual obligations regarding the election of our directors. See "Certain Relationships and Related Party Transactions". Our directors hold office until their successors have been elected and qualified or until their earlier death, resignation or removal. There are no family relationships among any of our directors or executive officers.

        Our amended and restated certificate of incorporation and amended and restated bylaws that will become effective upon the closing of this offering provide that the authorized number of directors may be changed only by resolution of our board of directors. Our amended and restated certificate of incorporation and amended and restated bylaws also provide that our directors may be removed only for cause by the affirmative vote of the holders of at least 75% of the votes that all our stockholders would be entitled to cast in an annual election of directors, and that any vacancy on our board of directors, including a vacancy resulting from an enlargement of our board of directors, may be filled only by vote of a majority of our directors then in office.

        In accordance with the terms of our certificate of incorporation and bylaws that will become effective upon the closing of this offering, our board of directors will be divided into three classes, class I, class II and class III, with members of each class serving staggered three-year terms. Upon the closing of this offering, the members of the classes will be divided as follows:

•

the class I directors will be Dr. Bitterman and Dr. George;



•

the class II directors will be Ms. Bosley and Dr. Hoffman; and



•

the class III directors will be Mr. Clark and Dr. Siber.

        Upon the expiration of the term of a class of directors, directors in that class will be eligible to be elected for a new three-year term at the annual meeting of stockholders in the year in which their term expires.

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        We have no formal policy regarding board diversity. Our priority in selection of board members is identification of members who will further the interests of our stockholders through his or her established record of professional accomplishment, the ability to contribute positively to the collaborative culture among board members, knowledge of our business and understanding of the competitive landscape.

Director Independence

        Applicable NASDAQ rules require a majority of a listed company's board of directors to be comprised of independent directors within one year of listing. In addition, the NASDAQ rules require that, subject to specified exceptions, each member of a listed company's audit, compensation and nominating and corporate governance committees be independent and that audit committee members also satisfy independence criteria set forth in Rule 10A-3 under the Securities Exchange Act of 1934, as amended, or the Exchange Act. Under applicable NASDAQ rules, a director will only qualify as an "independent director" if, in the opinion of the listed company's board of directors, that person does not have a relationship that would interfere with the exercise of independent judgment in carrying out the responsibilities of a director. In order to be considered independent for purposes of Rule 10A-3, a member of an audit committee of a listed company may not, other than in his or her capacity as a member of the audit committee, the board of directors, or any other board committee, accept, directly or indirectly, any consulting, advisory, or other compensatory fee from the listed company or any of its subsidiaries or otherwise be an affiliated person of the listed company or any of its subsidiaries.

        In November 2013, our board of directors undertook a review of the composition of our board of directors and its committees and the independence of each director. Based upon information requested from and provided by each director concerning his or her background, employment and affiliations, including family relationships, our board of directors has determined that Dr. Bitterman, Ms. Bosley, Dr. George and Dr. Hoffman are "independent directors" as defined under applicable NASDAQ rules. In making such determination, our board of directors considered the relationships that each such non-employee director has with our company and all other facts and circumstances that our board of directors deemed relevant in determining his or her independence, including the beneficial ownership of our capital stock by each non-employee director. Mr. Clark is not an independent director under these rules because he is our Chief Executive Officer and Dr. Siber is not an independent director under these rules because of his consulting relationship with us. Please see the section of this prospectus titled "Certain Relationships and Related Party Transactions".

        There are no family relationships among any of our directors or executive officers.

Board Committees

        Our board of directors has three standing committees: the audit committee, the compensation committee and the nominating and corporate governance committee.

Audit Committee

        Our audit committee is composed of Ms. Bosley, Dr. George and Dr. Hoffman, with Dr. Hoffman serving as chairman of the committee. Our board of directors has determined that each member of the audit committee meets the independence requirements of Rule 10A-3 under the Exchange Act and the applicable listing standards of NASDAQ. Our board of directors has determined that Ms. Bosley and Dr. Hoffman are "audit committee financial expert" within the meaning of the SEC regulations and applicable listing standards of NASDAQ. The audit committee's responsibilities include:

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appointing, approving the compensation of, and assessing the qualifications, performance and independence of our independent registered public accounting firm;

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pre-approving audit and permissible non-audit services, and the terms of such services, to be provided by our independent registered public accounting firm;



•

reviewing the internal audit plan with the independent registered public accounting firm and members of management responsible for preparing our financial statements;



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reviewing and discussing with management and the independent registered public accounting firm our annual and quarterly financial statements and related disclosures as well as critical accounting policies and practices used by us;



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reviewing the adequacy of our internal control over financial reporting;



•

establishing policies and procedures for the receipt and retention of accounting-related complaints and concerns;



•

recommending, based upon the audit committee's review and discussions with management and the independent registered public accounting firm, whether our audited financial statements shall be included in our Annual Report on Form 10-K;



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monitoring our compliance with legal and regulatory requirements as they relate to our financial statements and accounting matters;



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preparing the audit committee report required by the rules of the SEC to be included in our annual proxy statement;



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viewing all related party transactions for potential conflict of interest situations and approving all such transactions; and



•

reviewing and discussing with management and our independent registered public accounting firm our earnings releases and scripts.

Compensation Committee

        Our compensation committee is composed of Dr. Bitterman and Dr. George, with Dr. Bitterman serving as chairman of the committee. Our board of directors has determined that each member of the compensation committee is "independent" as defined under the applicable listing standards of NASDAQ. The compensation committee's responsibilities include:

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annually reviewing and approving corporate goals and objectives relevant to the compensation of our chief executive officer;



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evaluating the performance of our chief executive officer in light of such corporate goals and objectives and determining and approving the compensation of our chief executive officer;



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reviewing and approving the compensation of our other executive officers;



•

appointing, compensating and overseeing the work of any compensation consultant, legal counsel or other advisor retained by the compensation committee;



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conducting the independence assessment outlined in NASDAQ rules with respect to any compensation consultant, legal counsel or other advisor retained by the compensation committee;



•

annually reviewing and reassessing the adequacy of the committee charter in its compliance with the listing requirements of NASDAQ;



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reviewing and establishing our overall management compensation, philosophy and policy;



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overseeing and administering our equity compensation and other compensatory plans;

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•

reviewing and approving our equity and incentive policies and procedures for the grant of equity-based awards and approving the grant of such equity-based awards;



•

reviewing and making recommendations to the board of directors with respect to director compensation; and



•

reviewing and discussing with management the compensation discussion and analysis to be included in our annual proxy statement or Annual Report on Form 10-K.

Nominating and Corporate Governance Committee

        Our nominating and corporate governance committee is composed of Dr. Bitterman, Ms. Bosley and Dr. Hoffman, with Ms. Bosley serving as chairman of the committee. Our board of directors has determined that each member of the nominating and corporate governance committee is "independent" as defined under the applicable listing standards of NASDAQ. The nominating and corporate governance committee's responsibilities include:

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developing and recommending to the board of directors criteria for board and committee membership;



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establishing procedures for identifying and evaluating board of director candidates, including nominees recommended by stockholders;



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identifying individuals qualified to become members of the board of directors;



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recommending to the board of directors the persons to be nominated for election as directors and to each of the board's committees;



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developing and recommending to the board of directors a set of corporate governance principles;



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articulating to each director what is expected, including reference to the corporate governance principles and directors' duties and responsibilities;



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reviewing and recommending to the board of directors practices and policies with respect to directors;



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reviewing and recommending to the board of directors the functions, duties and compositions of the committees of the board of directors;



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reviewing and assessing the adequacy of the committee charter and submitting any changes to the board of directors for approval;



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consider and report to the board of directors any questions of possible conflicts of interest of board of directors members;



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provide for new director orientation and continuing education for existing directors on a periodic basis;



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performing an evaluation of the performance of the committee;



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overseeing the evaluation of the board of directors and management; and



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our board of directors may establish other committees from time to time.

Compensation Committee Interlocks and Insider Participation

        None of our executive officers serves as a member of the board of directors or compensation committee, or other committee serving an equivalent function, of any other entity that has one or more of its executive officers serving as a member of our board of directors or compensation committee.

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None of the members of our compensation committee has ever been employed by us. For a description of transactions between us and members of our compensation committee and affiliates of such members, please see the section of this prospectus titled "Certain Relationships and Related Party Transactions".

Code of Business Conduct and Ethics

        We have adopted a code of business conduct and ethics that applies to all of our employees, officers and directors, including those officers responsible for financial reporting. Upon the closing of this offering, our code of business conduct and ethics will be available on our website. We intend to disclose any amendments to the code, or any waivers of its requirements, on our website.

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EXECUTIVE AND DIRECTOR COMPENSATION

Overview

        The following discussion relates to the compensation of our President and Chief Executive Officer, William Clark, and our two most highly compensated executive officers (other than our Chief Executive Officer), Seth Hetherington, M.D., our Chief Medical Officer, and Jessica Flechtner, Ph.D., our Vice President of Research. These three executives are collectively referred to in this prospectus as our named executive officers. Each year, the compensation committee of our board of directors and our board of directors review and determine the compensation of our named executive officers.

Elements of Executive Compensation

        The compensation of our named executive officers consists of base salary, annual cash bonuses and equity awards as well as employee benefits that are made available to substantially all salaried employees. Our named executive officers are also entitled to certain compensation and benefits upon certain terminations of employment and change of control transactions pursuant to employment letter agreements.

        Base Salaries.    Base salaries for our named executive officers are reviewed annually by our compensation committee and are set by our board of directors. When making its base salary recommendations to our board of directors, our compensation committee takes factors into account such as each executive's experience and individual performance, the company's performance as a whole, data from surveys of compensation paid by comparable companies, cost of living increases and general industry conditions, but does not assign any specific weighting to any factor. Our board of directors determines each named executive officer's base salary after reviewing the compensation committee's recommendation. In fiscal 2013, on the recommendation of our compensation committee, our board of directors approved a base salary of $335 thousand for Mr. Clark, $333 thousand for Dr. Hetherington and $242 thousand for Dr. Flechtner, representing an increase of 2.0%, 2.0% and 10.0%, respectively, from the base salary for each such executive in 2012.

        Annual Cash Bonuses.    Our annual cash bonus program promotes and rewards the achievement of key strategic business goals and individual performance goals. For fiscal 2013, the target annual bonus as a percentage of base salary for each of Mr. Clark, Dr. Hetherington and Dr. Flechtner was 40%, 30% and 25%, respectively. In the case of Mr. Clark, 100% of his annual bonus was based on the achievement of pre-established corporate performance goals and, in the case of Drs. Hetherington and Flechtner, 50% of the executive's respective annual bonus was based on the achievement of pre-established corporate performance goals and 50% was based on a quantitative and qualitative assessment of pre-established individual performance goals.

        At the beginning of fiscal 2013, our compensation committee established the corporate performance goals for 2013, each having a designated weighting. These corporate performance goals included key strategic and financial goals related to business development and grant funding, maintenance of a certain level of cash reserves, the development and commencement of certain clinical and commercial programs, the completion of research reports, and other strategic objectives related to our clinical pipeline. Also at the beginning of fiscal 2013, our chief executive officer, working with each of Dr. Hetherington and Dr. Flechtner, established each executive's individual performance goals and their weightings. These goals included objectives related to oversight of clinical activities for compliance with laws, developing and conducting clinical programs and studies, research and development, managing studies according to schedule and within budgets, business and corporate development and demonstrating leadership with respect to direct reports.

        As of the date of this filing, our compensation committee has not met to determine the level of performance achieved for purposes of determining the annual cash bonuses to be paid to each of our

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named executive officers for performance in fiscal 2013. Annual bonus amounts will be disclosed in a Form 8-K once determined.

        Equity Awards.    Our named executive officers participate in the Genocea Biosciences, Inc. Amended and Restated 2007 Equity Incentive Plan, which we refer to as the "2007 Equity Plan". See "Equity and Incentive Plans—2007 Equity Plan" below for additional details about this plan. Initial awards of stock options granted to our named executive officers generally vest as to 25% of the shares subject to the stock option on the vesting commencement date and thereafter continue to vest in monthly installments over the following 36 months, generally subject to the executive's continued employment. Other time-vesting stock option awards generally vest in equal monthly installments over 48 months, generally subject to the executive's continued employment.

        Each of our named executive officers received an award of time-vesting stock options in July 2013 to purchase 133,602, in the case of Mr. Clark, 57,017, in the case of Dr. Hetherington, and 56,378, in the case of Dr. Flechtner, shares of our common stock. These stock option awards vested as to 1/8^th of the shares subject to the stock option on the date of grant and continue to vest in equal monthly installments over 42 months, generally subject to the executive's continued employment. Mr. Clark also received a performance-vesting stock option to purchase 81,670 shares of our common stock that is expected to vest in full upon the completion of this offering based on the proceeds expected to be received. Stock option awards serve to align the interests of our named executive officers with our shareholders because no value is created unless the value of our common stock appreciates after grant. Stock option awards also encourage retention through the use of time-based vesting and the achievement of key strategic goals through the use of performance-based vesting. Pursuant to agreements with our named executive officers, all of each executive's stock option awards will vest automatically upon certain terminations of employment following a change of control of our company. See "—Employment Letter Agreements" below for additional details about these agreements.

        Benefits.    We provide modest benefits to our named executive officers, which are limited to participation in our 401(k) plan and basic health and welfare benefit coverage. These benefits are available to substantially all of our salaried employees.

        Employment Letter Agreements.    We have entered into an amended and restated employment letter agreement with each of our named executive officers that, in each case, includes severance and change of control protections. Our named executive officers are also subject to restrictive covenants, covering noncompetition, nonsolicitation and confidentiality.

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Summary Compensation Table

        The following table sets forth information about certain compensation awarded or paid to our named executive officers for fiscal years 2012, in the case of Mr. Clark and Dr. Hetherington, and 2013, in the case of all of our named executive officers.

Outstanding Equity Awards at Fiscal Year-End

        The following table sets forth information regarding equity awards held by our named executive officers as of December 31, 2013. Our named executive officers do not hold any equity awards other than stock options.

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OPTION AWARDS

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Retirement Benefits

        We do not maintain any qualified or non-qualified defined benefit plans or supplemental executive retirement plans that cover our named executive officers. We offer a tax-qualified retirement plan, which we refer to as our 401(k) plan, to eligible employees, including our named executive officers. Our 401(k) plan permits eligible employees to defer their annual eligible compensation subject to the limitations imposed by the Internal Revenue Service. We may, but are not required to, make discretionary profit-sharing contributions on behalf of eligible employees under this plan. We did not make any contributions on behalf of eligible employees in fiscal year 2013.

Employment Letter Agreements

        On January 16, 2014, we entered into an amended and restated employment letter agreement with each of Mr. Clark, Dr. Hetherington and Dr. Flechtner effective prior to the completion of this offering. Each employment letter agreement provides for an initial base salary of $399,433, in the case of Mr. Clark, $369,458 in the case of Dr. Hetherington, and $287,012 in the case of Dr. Flechtner, as well as a discretionary performance-based bonus, with a target, as a percentage of base salary, of 50%, 35% and 30% for each of Mr. Clark, Dr. Hetherington and Dr. Flechtner, respectively. Each agreement also provides for certain payments and benefits upon a qualifying termination of the executive's employment following a change of control of our company as described below.

        Termination of Employment without Cause or for Good Reason Following a Change of Control.    If, within 12 months after a change of control (as defined in the executive's employment letter agreement), the executive's employment is terminated by us without cause or the executive terminates his or her employment for good reason (as such terms are defined in the executive's employment letter agreement), all stock options or other equity awards then held by the executive will fully vest. In addition, the executive will be entitled to receive base salary and payment of COBRA premiums for 18 months, in the case of Mr. Clark, 15 months, in the case of Dr. Hetherington, and 12 months, in the case of Dr. Flechtner, following such termination of employment.

        Termination of Employment without Cause or for Good Reason.    If the executive's employment is terminated by us without cause or the executive terminates his or her employment for good reason (as such terms are defined in the executive's employment letter agreement) other than following a change of control as described above, the executive will be entitled to receive base salary and payment of COBRA premiums for 12 months, in the case of Mr. Clark, nine months, in the case of

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Dr. Hetherington, and six months, in the case of Dr. Flechtner, following such termination of employment.

        Termination of Employment Due to Death or Disability.    If the executive's employment is terminated by us due to the executive's disability or is terminated due to the executive's death, we will pay the executive a portion of the executive's target annual cash bonus for the year in which such termination of employment occurs, prorated based on the number of days the executive was employed during such year until the date of such termination.

        Severance Subject to Release of Claims.    Our obligation to provide the executive with any severance payments or other benefits under the executive's employment letter agreement is conditioned on the executive signing and not revoking an effective release of claims in our favor.

        Other Termination of Employment.    If the executive's employment is terminated for any reason other than by us without cause, by the executive for good reason, or due to the executive's death or disability, the executive will only be entitled to receive earned but unpaid base salary and any accrued but not used vacation as of the termination date.

        280G Better-of Provision.    In the event of a change in ownership or control of our company under Section 280G of the Internal Revenue Code of 1986, as amended, or the Code, and the regulations thereunder, if any portion of the payments made pursuant to the executive's employment letter agreement (or otherwise) constitutes an "excess parachute payment" within the meaning of Section 280G of the Code, the executive will be entitled to receive an amount of such payments reduced so that no portion of the payments would constitute an excess parachute payment, or the amount otherwise payable to the executive under the employment letter agreement (or otherwise) reduced by all applicable taxes, including the excise tax, whichever amount results in the greater amount payable to the executive.

        Employment Conditioned on Restrictive Covenants.    As a condition to the executive's employment with us, the executive was required to sign and must comply with the terms of an At-Will Employment, Confidential Information, Invention Assignment and Non-Competition Agreement, pursuant to which the executive has agreed not to compete with us for a period of 12 months following the termination of his or her employment and not to solicit our employees or independent contractors for a period of 36 months following the termination of his or her employment. Each executive has also agreed to covenants relating to the use and disclosure of confidential information and the assignment of inventions.

2013 Director Compensation

        The following table sets forth information concerning the compensation earned by our directors during 2013. In 2013, Dr. Siber and Ms. Bosley were the only directors who were compensated for service on our board of directors. Mr. Clark receives no additional compensation for his service as a director, and, consequently, is not included in this table. The compensation received by Mr. Clark as our chief executive officer during 2013 is included in the "Summary Compensation Table" above.

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Director Compensation

        As of December 31, 2013, our directors held the following aggregate number of options to purchase shares of our common stock: Dr. Siber held options to purchase 133,672 shares of our common stock, Ms. Bosley held options to purchase 36,966 shares of our common stock and Dr. Bitterman, Dr. George and Dr. Hoffman held no options to purchase shares of our common stock. As of December 31, 2013, Ms. Bosley held 24,615 restricted shares, which she received upon the exercise of the option granted to her on February 4, 2013.

Non-Employee Director Compensation Policy

        Our board of directors has adopted a non-employee director compensation policy, effective as of the completion of this offering, that is designed to enable us to attract and retain, on a long-term basis,

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highly qualified non-employee directors. Under the policy, all non-employee directors will be paid cash compensation from and after the completion of this offering, as set forth below:

        Under our non-employee director compensation policy, each individual who is not an employee who is initially appointed or elected to our board of directors will be eligible to receive a grant of stock options to purchase 10,084 shares of our common stock under our 2014 Equity Incentive Plan at the time of his or her initial appointment or election to our board of directors, which will vest annually in equal installments over a three-year period. In addition, each continuing non-employee director will be eligible to receive, on the first business day following January 1^st of each calendar year, an annual stock option grant to purchase 5,042 shares of our common stock, which will vest in full on the first anniversary of the grant date. The stock options will be granted with an exercise price equal to the fair market value of a share of our common stock on the date of grant and have a 10-year term.

Director Agreements

Dr. Siber

        We have entered into a consulting agreement with Dr. Siber dated May 16, 2007, as amended on June 30, 2009, December 16, 2010, June 15, 2011 and June 5, 2013, providing for a consulting fee of $10 thousand per month, for consulting services performed by Dr. Siber related to strategic scientific and business development as well as for his service as the chairman of our board of directors. Dr. Siber was also entitled to receive grants of restricted stock and stock options in connection with his service to us. All stock options granted to Dr. Siber pursuant to the consulting agreement will fully vest if, within 12 months following a change of control, either we (or our successor) terminate the consulting agreement without cause (as such term is described in the consulting agreement), subject to Dr. Siber's continued service to the company, or we (or our successor) do not offer to extend the term of the agreement. As of September 19, 2013, Dr. Siber ceased being the chairman of our board of directors and assumed the role of executive director and chairman of our scientific advisory board.

        Dr. Siber has agreed not to solicit our employees, contractors, and customers for a period of 12 months following the termination of the consulting agreement and is subject to covenants relating to the use and disclosure of confidential information and the assignment of inventions. Unless extended or earlier terminated, the term of the consulting agreement will expire on June 17, 2015.

        In 2013, performance-vesting and time-vesting stock options were granted to Dr. Siber. The performance-vesting stock option generally vests upon the company's achievement of certain financial goals, and is expected to vest in full upon the completion of this offering based on the proceeds expected to be received. The time-vesting stock option generally vests in equal monthly installments over 48 months and vests in full upon a change of control of our company, generally subject to Dr. Siber's continued service to our company.

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Ms. Bosley

        We entered into a letter agreement with Ms. Bosley, the chair of our board of directors, dated as of February 4, 2013, the date she was appointed to serve on our board of directors. Pursuant to the letter agreement, Ms. Bosley is entitled to an annual fee for board meeting attendance of $30,000 per year (which annual fee was subsequently increased to $50,000 per year) and, on February 4, 2013, we granted Ms. Bosley an initial stock option award that vests ratably over 48 months, subject to Ms. Bosley's continued service on our board of directors on the applicable vesting date, and vests as to all of the shares subject to the stock option immediately prior to the occurrence of a covered transaction (as defined in the 2007 Equity Plan). Ms. Bosley subsequently exercised this stock option and, with respect to the portion of the stock option that was not vested on the date it was exercised, received shares of restricted stock that vest on the same schedule as the stock option. Under the letter agreement, Ms. Bosley is also subject to covenants relating to the use and disclosure of confidential information. Unless earlier terminated, the letter agreement remains in effect so long as Ms. Bosley is a member of our board of directors and automatically terminates in the event of Ms. Bosley's removal or resignation from our board of directors or death. Effective as of the completion of this offering, this letter agreement will terminate and Ms. Bosley will be eligible to participate in our non-employee director compensation policy described above on the same terms as other directors.

        On September 19, 2013, Ms. Bosley assumed the role of chair of our board of directors. In connection with such appointment, on October 21, 2013 she was granted a stock option award that vests as to 25% of the shares subject to the stock option on the vesting commencement date and thereafter continues to vest in monthly installments over the following 36 months, subject to Ms. Bosley's continued service on our board of directors. All of the shares subject to the stock option will vest immediately prior to the occurrence of a covered transaction (as defined in the 2007 Equity Plan).

Equity and Incentive Plans

2007 Equity Plan

        The 2007 Equity Plan provides for the grant of stock and stock-based awards to key employees and directors of, and consultants and advisors to, us and our affiliates who, in the opinion of the compensation committee, are in a position to make a significant contribution to our success and the success of our affiliates. The following summary of the 2007 Equity Plan is not a complete description of all provisions of the 2007 Equity Plan and is qualified in its entirety by reference to the 2007 Equity Plan, which is filed as an exhibit to the registration statement of which this prospectus is a part.

        Plan Administration.    The 2007 Equity Plan is administered by our compensation committee, which has authority to determine eligibility for and grant awards and to determine the terms and conditions of awards, including the time or times at which awards vest or become exercisable and remain exercisable, and otherwise do all things necessary to carry out the purposes of the 2007 Equity Plan.

        Authorized Shares.    Subject to adjustment, as of November 30, 2013 the maximum number of shares of our common stock that may be delivered in satisfaction of awards under the 2007 Equity Plan is 1,859,425 shares. Shares of our common stock to be issued under the 2007 Equity Plan may be authorized but unissued shares of our common stock or previously issued shares acquired by the company.

        Types of Awards.    The 2007 Equity Plan provides for grants of stock options, stock appreciation rights, restricted and unrestricted stock, stock units (including restricted stock units), performance awards and other awards convertible into or otherwise based on shares of our common stock. Dividend equivalents may also be provided in connection with an award under the 2007 Equity Plan.

        Vesting.    Our compensation committee has the authority to determine the vesting schedule applicable to each award, and to accelerate the vesting or exercisability of any award.

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        Termination of Employment.    Our compensation committee will determine the effect of termination of employment or service on an award. Unless otherwise provided by our compensation committee, upon a termination of a participant's employment or service, all unvested stock options then held by the participant and other awards requiring exercise will terminate, all other unvested awards will be forfeited, and all vested stock options and stock appreciation rights then held by the participant will remain outstanding for three months following such termination, or one year in the case of a participant's death, or, in each case, until the applicable expiration date, if earlier. All stock options and stock appreciation rights held by a participant immediately prior to the participant's termination of employment or service will immediately terminate upon termination of employment or service if our compensation committee determines the termination of employment or service resulted for reasons that cast such discredit on the participant as to justify immediate termination of the award.

        Covered Transactions.    In the event of a covered transaction, our compensation committee may, among other things, provide for the continuation or assumption of outstanding awards, for new grants in substitution of outstanding awards, for a cash-out of outstanding awards, for the accelerated vesting or delivery of shares under awards or for the termination of awards upon the occurrence of the covered transaction, in each case on such terms and with such restrictions as it deems appropriate. Except as our compensation committee may otherwise determine, each award generally will terminate upon the occurrence of the covered transaction. Under the 2007 Equity Plan, a covered transaction generally includes a consolidation, merger or similar transaction, including a sale or other disposition of stock in which the company is not the surviving entity or which results in the acquisition of all or substantially all of our outstanding stock, a sale or transfer of all or substantially all of our assets or a dissolution or liquidation of our company.

        Amendment and Termination.    Our compensation committee may amend the 2007 Equity Plan and any awards granted under it and may terminate the 2007 Equity Plan as to future awards, except that it may not alter the terms of an award so as to affect materially and adversely a participant's rights under the award without the participant's consent, unless it reserved the right to do so at the time the award was granted.

        Following this offering, all equity-based awards will be granted under the 2014 Equity Plan described below.

2014 Equity Plan

        In connection with this offering, our board of directors has adopted the Genocea Biosciences, Inc. 2014 Equity Incentive Plan, or the 2014 Equity Plan, and, following this offering, all equity-based awards will be granted under the 2014 Equity Plan. The following summary describes the material terms of the 2014 Equity Plan. This summary of the 2014 Equity Plan is not a complete description of all provisions of the 2014 Equity Plan and is qualified in its entirety by reference to the 2014 Equity Plan, which is filed as an exhibit to the registration statement of which this prospectus is a part. On the day immediately prior to the date this Registration Statement becomes effective, our board of directors expects to approve stock option awards to certain of our employees covering 25,048 shares of our common stock, including an award to Dr. Flechtner of a stock option to purchase 11,402 shares of our common stock.

        Administration.    The 2014 Equity Plan is administered by our compensation committee. Our compensation committee has the authority to, among other things, interpret the 2014 Equity Plan, determine eligibility for, grant and determine the terms of awards under the 2014 Equity Plan, determine the form of settlement of awards (whether in cash, shares of our common stock or other property), and do all things necessary or appropriate to carry out the purposes of the 2014 Equity Plan. Our compensation committee's determinations under the 2014 Equity Plan are conclusive and binding.

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        Eligibility.    Our key employees, directors, consultants and advisors are eligible to participate in the 2014 Equity Plan.

        Authorized Shares.    Subject to adjustment, as described below, the maximum number of shares of our common stock that may be delivered in satisfaction of awards under the 2014 Equity Plan is 903,494 shares, plus 219,765 shares that were available for grant under the 2007 Equity Plan on the date the 2014 Equity Plan was adopted. The number of shares of our common stock available for issuance under the 2014 Equity Plan will be automatically increased annually on each January 1st, from January 1, 2015 through January 1, 2024, in an amount equal to the lesser of 4% of outstanding shares of our common stock as of the close of business on the immediately preceding December 31^st or the number of shares determined by our board of directors. Subject to adjustment, as described below, no more than 9,000,000 shares of our common stock may be delivered in satisfaction of incentive stock options, or ISOs, awarded under the 2014 Equity Plan.

        The shares of our common stock to be issued under the 2014 Equity Plan may be authorized but unissued shares of our common stock or previously issued shares of our common stock acquired by us. Any shares of our common stock underlying awards that are settled in cash, expire or become unexercisable without having been exercised or that are forfeited or repurchased by us will again be available for issuance under the 2014 Equity Plan. In addition, the number of shares of our common stock delivered in satisfaction of awards will be determined net of shares of our common stock withheld by us in payment of the exercise price of an award or in satisfaction of tax withholding requirements with respect to an award.

        Individual Limits.    The maximum number of shares of our common stock subject to stock options and the maximum number of shares of our common stock subject to stock appreciation rights, or SARs, that may be granted to any participant in the 2014 Equity Plan in any calendar year is each 1,000,000 shares. The maximum number of shares of our common stock subject to other awards that may be granted to any participant in the 2014 Equity Plan in any calendar year is 500,000 shares. A participant who is a non-employee director on our board of directors, in any calendar year, may not receive awards with respect to the greater of an aggregate of 250,000 shares of our common stock or $1,000,000 in aggregate grant date fair value.

        Types of Awards.    The 2014 Equity Plan provides for awards of stock options, SARs, restricted stock, unrestricted stock, stock units, performance awards and other awards convertible into or otherwise based on shares of our common stock. Eligibility for stock options intended to be ISOs is limited to our employees. Dividend equivalents may also be provided in connection with an award under the 2014 Equity Plan.

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Stock options and SARs.  The exercise price of a stock option, and the base price against which a SAR is to be measured, may not be less than the fair market value (or, in the case of an ISO granted to a ten percent shareholder, 110% of the fair market value) of shares of our common stock on the date of grant. Our compensation committee will determine the time or times at which stock options or SARs become exercisable and the terms on which such awards remain exercisable.



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Restricted and unrestricted stock.  A restricted stock award is an award of shares of our common stock subject to forfeiture restrictions, while an unrestricted stock award is not subject to such restrictions.



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Stock units.  A stock unit award is an award denominated in shares of our common stock that entitles the participant to receive shares of our common stock or cash measured by the value of the shares of our common stock in the future. The delivery of shares of our common stock or cash under a stock unit may be subject to the satisfaction of performance conditions or other vesting conditions.

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Performance awards.  A performance award is an award the vesting, settlement or exercisability of which is subject to specified performance criteria.



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Other awards.  Other awards are awards that are convertible into or otherwise based on shares of our common stock.

        Performance Awards.    The 2014 Equity Plan provides for the grant of performance awards that are made based upon, and subject to achieving, performance objectives. Performance objectives with respect to those awards that are intended to qualify as "performance-based compensation" for purposes of Section 162(m) of the Code, or Section 162(m), to the extent applicable, are limited to an objectively determinable measure or measures of performance relating to any or any combination of the following (measured either absolutely or by reference to an index or indices and determined either on a consolidated basis or, as the context permits, on a divisional, subsidiary, line of business, project or geographical basis or in combinations thereof): sales; revenues; assets; expenses; earnings before or after deduction for all or any portion of interest, taxes, depreciation, amortization or equity expense, whether or not on a continuing operations or an aggregate or per share basis; return on equity, investment, capital, capital employed or assets; one or more operating ratios; operating income or profit, including on an after-tax basis; net income; borrowing levels, leverage ratios or credit rating; market share; capital expenditures; cash flow; stock price; stockholder return; sales of particular products or services; customer acquisition or retention; acquisitions and divestitures (in whole or in part); joint ventures, strategic alliances, licenses or collaborations; spin-offs, split-ups and the like; reorganizations; recapitalizations, restructurings, financings (issuance of debt or equity) or refinancings; manufacturing or process development; or achievement of clinical trial or research objectives, regulatory or other filings or approvals or other product development milestones.

        To the extent consistent with the requirements for satisfying the performance-based compensation exception under Section 162(m), to the extent applicable, our compensation committee may provide in the case of any award intended to qualify for such exception that one or more of the performance objectives applicable to an award will be adjusted in an objectively determinable manner to reflect events (for example, the impact of charges for restructurings, discontinued operations, mergers, acquisitions, extraordinary items, and other unusual or non-recurring items, and the cumulative effects of tax or accounting changes, each as defined by U.S. generally accepted accounting principles) occurring during the performance period that affect the applicable performance objectives.

        Vesting; Termination of Employment or Service.    Our compensation committee has the authority to determine the vesting schedule applicable to each award, and to accelerate the vesting or exercisability of any award. Our compensation committee will determine the effect of termination of employment or service on an award. Unless otherwise provided by our compensation committee, upon a termination of a participant's employment or service, all unvested stock options and SARs then held by the participant will terminate and all other unvested awards will be forfeited and all vested stock options and SARs then held by the participant will remain outstanding for three months following such termination, or one year in the case of death, or, in each case, until the applicable expiration date, if earlier. All stock options and SARs held by a participant immediately prior to the participant's termination of employment or service will immediately terminate if such termination is for cause, as defined in the 2014 Equity Plan, or occurs in circumstances that would have constituted grounds for the participant's employment or service to be terminated for cause, in the determination of the compensation committee.

        Non-Transferability of Awards.    Awards under the 2014 Equity Plan may not be transferred other than by the laws of descent and distribution, unless, for awards other than ISOs, otherwise provided by our compensation committee.

        Recovery of Compensation.    Our compensation committee may cancel, rescind, withhold or otherwise limit or restrict any award at any time under the 2014 Equity Plan if the participant is not in

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compliance with the provisions of the 2014 Equity Plan or any award thereunder or if the participant breaches any agreement with our company with respect to non-competition, non-solicitation or confidentiality. Our compensation committee also may recover any award or payments or gain in respect of any award under the 2014 Equity Plan in accordance with any applicable company recoupment policy or as otherwise required by applicable law or applicable stock exchange listing standards.

        Certain Transactions; Certain Adjustments.    In the event of a consolidation, merger or similar transaction or series of related transactions, including a sale or other disposition of shares of our common stock, in which our company is not the surviving corporation or that results in the acquisition of all or substantially all of our then outstanding shares of common stock by a single person or entity or by a group of persons and/or entities acting in concert, a sale of all or substantially all of our assets or our dissolution or liquidation, our compensation committee may, among other things, provide for the continuation or assumption of outstanding awards, for new grants in substitution of outstanding awards, for the accelerated vesting or delivery of shares under awards or for a cash-out of outstanding awards, in each case on such terms and with such restrictions as it deems appropriate. Except as our compensation committee may otherwise determine, awards not assumed in connection with such a transaction will terminate automatically and, in the case of outstanding restricted stock, will be forfeited automatically upon the consummation of such covered transaction.

        In the event of a stock dividend, stock split or combination of shares, including a reverse stock split, recapitalization or other change in our capital structure that constitutes an equity restructuring within the meaning of FASB ASC 718, our compensation committee will make appropriate adjustments to the maximum number of shares of our common stock that may be delivered under, and the ISO and individual share limits included in, the 2014 Equity Plan, and will also make appropriate adjustments to the number and kind of shares or securities subject to awards, the exercise prices of such awards or any other terms of awards affected by such chan