Alnylam Announces Publication of Preclinical Results Based on Novel Conjugate Technology That Facilitates Delivery of Short Interfering RNA to the Central Nervous System and Other Extrahepatic Tissues

- Conjugation of 2’-O-hexadecyl (C16) to siRNA Enables Therapeutic Silencing of Target Genes Outside the Liver with Infrequent Dosing in Rodents and Non-Human Primates -

- In a Mouse Model of Alzheimer’s Disease, C16-siRNA Targeting the Amyloid Beta Precursor Protein Gene Led to Potent and Durable Knockdown in the CNS and Ameliorated Physiological and Behavioral Deficits -

- Sustained Knockdown Observed May Allow for Infrequent Dosing of C16-siRNAs in Humans and Warrants Continued Investigation in Clinical Trials, Including an Ongoing Phase 1 Study of ALN-APP in Alzheimer’s Disease, in Which Dosing Has Been Initiated -

Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), the leading RNAi therapeutics company, announced today that data from its preclinical research on delivery of lipophilic short interfering RNA (siRNA) conjugates to extra-hepatic tissues, including the central nervous system (CNS), were published online in Nature Biotechnology. The published data provide early evidence of a potential role for 2'-O-hexadecyl (C16)-conjugated siRNAs in treating diseases of the CNS, eye, and lung. The framework for designing siRNAs for extrahepatic applications leverages Alnylam’s decades long investment in the siRNA delivery platform. The full manuscript titled “Expanding RNAi therapeutics to extrahepatic tissues with lipophilic conjugates” will appear in the June issue of Nature Biotechnology.

The published data show that conjugation of C16 to metabolically stable siRNAs enables robust and long-lasting gene silencing in the CNS, eye and lung in rodents and non-human primates (NHPs) with broad cell type specificity and a favorable nonclinical safety profile. The manuscript also provides evidence demonstrating C16-siRNA-mediated gene silencing translates into efficacy in an in vivo mouse model of neurodegenerative disease.

“Diseases of the CNS are some of the most difficult to treat. Thus, we are encouraged by these preclinical findings as they suggest siRNAs may have a role in treating diseases impacting the CNS, the eye, and the lung,” said Kevin Fitzgerald, Ph.D., EVP, Chief Scientific Officer. “Our CNS delivery platform provides long durability, which is particularly advantageous in settings of intrathecal administration, where infrequent dosing is desirable. Leveraging this platform, we have initiated dosing in a Phase 1 study in patients with early-onset Alzheimer’s disease and expect to report initial human data at or around year-end 2022.”

Delivery to the CNS

Based on the published results, a single intrathecal (IT) administration of C16 conjugated siRNA targeting SOD1 in rodents resulted in a widespread uptake of the conjugate in neurons, astrocytes, and microglial cells and a dose dependent SOD1 knockdown with greater than 75 percent target knockdown at the highest dose of 0.9 mg. These results were recapitulated in NHPs treated with C16-conjugated siRNA targeting amyloid beta precursor protein (APP), with up to 70 and 80 percent reductions in the spinal cord and brain, respectively, at three months post a single IT dose of 60 mg. These reductions were sustained beyond three months based on biomarker measurements in the cerebrospinal fluid. The APP-siRNAs were well-tolerated in NHPs and there were no test item-related microscopic findings in the examined brain, spinal cord, and dorsal root ganglia sections. The published data also provide a pre-clinical proof-of-concept, whereby administration of a C16-siRNA targeting both intracellular and extracellular APP in a mouse model of Alzheimer’s disease produced a sufficiently potent and durable knockdown in the CNS to alter both the physiological deficits in the diseased mice, such as Aβ deposition and inflammation, as well as, normalizing behavioral deficits as measured by an open field test. Reduction of APP expression was correlated with reduced expression of Iba1, a marker normally upregulated in human disease, and increased levels of glutamate, a metabolite associated with improved cognition.

The safety and efficacy of ALN-APP, an investigational RNAi therapeutic conjugated to C16 and targeting APP, is currently being evaluated in a Phase 1 clinical study for the treatment of early onset Alzheimer's disease.

Delivery to the eye and lung

C16 conjugation also enables ocular delivery in NHP via intravitreal administration with greater than 95 percent target knockdown noted in the retinal pigmented epithelium at 100 μg per eye of conjugated siRNA targeting transthyretin (TTR). Similarly, intranasal administration of C16 lipophile conjugated siRNA targeting mouse SOD1 resulted in broad uptake of the conjugate to mouse lung tissue, including bronchioles and alveoli, and 57 percent SOD1 mRNA knockdown sustained for two months post a 10 mg/kg dose.

About ALN-APP

ALN-APP is an investigational, intrathecally administered RNAi therapeutic targeting amyloid precursor protein (APP) in development in collaboration with Regeneron Pharmaceuticals for the treatment of Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA). Genetic mutations that increase production of APP or alter its cleavage cause early-onset AD, early-onset CAA, or both. ALN-APP is designed to decrease APP mRNA in the central nervous system (CNS), to decrease synthesis of APP protein and all downstream intracellular and extracellular APP-derived cleavage products, including amyloid beta (Aβ). Reducing APP protein production is expected to reduce the secretion of Aβ peptides that aggregate into extracellular amyloid deposits and reduce the intraneuronal APP cleavage products that trigger the formation of neurofibrillary tangles and cause neuronal dysfunction in Alzheimer’s disease. ALN-APP is the first program utilizing Alnylam’s C16 conjugate technology, which enables enhanced delivery to cells in the CNS. The safety and efficacy of ALN-APP have not been evaluated by the FDA, EMA, or any other health authority.

About Early-Onset Alzheimer’s Disease

Alzheimer’s disease (AD) is the most common neurodegenerative disease and the most common form of dementia, affecting over 30 million people worldwide. AD is characterized by progressive memory loss and cognitive decline, with neuropathological accumulation of amyloid plaques, neurofibrillary tangles, and neuroinflammation, ultimately resulting in significant brain atrophy. Disease progression results in progressive loss of independence, increased caregiver burden, institutionalization, and premature death. Early-onset Alzheimer’s disease (EOAD) refers to a subgroup of AD with symptom onset prior to the age of 65, representing approximately 4% to 6% of all AD. EOAD is the leading cause of dementia in younger individuals and is a significant cause of disability and early mortality. Available treatment options include symptomatic treatment and treatment to reduce amyloid deposits in the brain. There are currently no available treatments that have been shown to halt or reverse the progression of the disease.

About RNAi

RNAi (RNA interference) is a natural cellular process of gene silencing that represents one of the most promising and rapidly advancing frontiers in biology and drug development today. Its discovery has been heralded as "a major scientific breakthrough that happens once every decade or so," and was recognized with the award of the 2006 Nobel Prize for Physiology or Medicine. By harnessing the natural biological process of RNAi occurring in our cells, a new class of medicines, known as RNAi therapeutics, is now a reality. Small interfering RNA (siRNA), the molecules that mediate RNAi and comprise Alnylam's RNAi therapeutic platform, function upstream of today’s medicines by potently silencing messenger RNA (mRNA) – the genetic precursors – that encode for disease-causing or disease pathway proteins, thus preventing them from being made. This is a revolutionary approach with the potential to transform the care of patients with genetic and other diseases.

About Alnylam Pharmaceuticals

Alnylam (Nasdaq: ALNY) has led the translation of RNA interference (RNAi) into a whole new class of innovative medicines with the potential to transform the lives of people afflicted with rare and prevalent diseases with unmet need. Based on Nobel Prize-winning science, RNAi therapeutics represent a powerful, clinically validated approach yielding transformative medicines. Since its founding 20 years ago, Alnylam has led the RNAi Revolution and continues to deliver on a bold vision to turn scientific possibility into reality. Alnylam’s commercial RNAi therapeutic products are ONPATTRO® (patisiran), GIVLAARI® (givosiran), OXLUMO® (lumasiran) and Leqvio® (inclisiran) being developed and commercialized by Alnylam’s partner, Novartis. Alnylam has a deep pipeline of investigational medicines, including six product candidates that are in late-stage development. Alnylam is executing on its “Alnylam P5x25” strategy to deliver transformative medicines in both rare and common diseases benefiting patients around the world through sustainable innovation and exceptional financial performance, resulting in a leading biotech profile. Alnylam is headquartered in Cambridge, MA. For more information about our people, science and pipeline, please visit www.alnylam.com and engage with us on Twitter at @Alnylam, on LinkedIn, or on Instagram.

Alnylam Forward Looking Statements

Various statements in this release concerning Alnylam's future expectations, plans and prospects, including, without limitation, Alnylam’s views with respect to the initiation of the Phase 1 study of ALN-APP in patients with early-onset AD, the potential timing to report initial human data, its continued commitment to innovation both in pursuing new genetically validated disease targets and in advancing its platform, including C16, to target extra-hepatic tissues, Regeneron’s involvement in the research, development and commercialization of ALN-APP, Alnylam’s aspiration to become a leading biotech company, and the planned achievement of its “Alnylam P⁵x25” strategy, constitute forward-looking statements for the purposes of the safe harbor provisions under The Private Securities Litigation Reform Act of 1995. Actual results and future plans may differ materially from those indicated by these forward-looking statements as a result of various important risks, uncertainties and other factors, including, without limitation: the direct or indirect impact of the COVID-19 global pandemic or any future pandemic on Alnylam’s business, results of operations and financial condition and the effectiveness or timeliness of Alnylam’s efforts to mitigate the impact of the pandemic; the potential impact of the recent leadership transition on Alnylam’s ability to attract and retain talent and to successfully execute on its “Alnylam P5x25” strategy; Alnylam's ability to discover and develop novel drug candidates and delivery approaches, including C16, and successfully demonstrate the efficacy and safety of its product candidates, including ALN-APP; the pre-clinical and clinical results for its product candidates; actions or advice of regulatory agencies and Alnylam’s ability to obtain and maintain regulatory approval for its product candidates, as well as favorable pricing and reimbursement; successfully launching, marketing and selling its approved products globally; delays, interruptions or failures in the manufacture and supply of its product candidates or its marketed products; obtaining, maintaining and protecting intellectual property; Alnylam’s ability to successfully expand the indication for OXLUMO and ONPATTRO (and vutrisiran, if approved) in the future; Alnylam's ability to manage its growth and operating expenses through disciplined investment in operations and its ability to achieve a self-sustainable financial profile in the future without the need for future equity financing; Alnylam’s ability to maintain strategic business collaborations; Alnylam's dependence on third parties for the development and commercialization of certain products, including Novartis, Sanofi, Regeneron and Vir; the outcome of litigation; the potential impact of current and the risk of future government investigations; and unexpected expenditures; as well as those risks more fully discussed in the “Risk Factors” filed with Alnylam's most recent Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (SEC) and in its other SEC filings. In addition, any forward-looking statements represent Alnylam's views only as of today and should not be relied upon as representing its views as of any subsequent date. Alnylam explicitly disclaims any obligation, except to the extent required by law, to update any forward-looking statements.

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