Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
Soffer Gad
   2. Issuer Name and Ticker or Trading Symbol
Atara Biotherapeutics, Inc. [ATRA] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
Chief Operating Officer
(Last)
(First)
(Middle)
701 GATEWAY BOULEVARD, SUITE 200		 3. Date of Earliest Transaction (Month/Day/Year)
08/17/2015
(Street)

SOUTH SAN FRANCISCO, CA 94080		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 08/17/2015   M   9,615 A $ 0 (1) 75,403 D  
Common Stock 08/17/2015   M   4,145 A $ 0 (1) 79,548 D  
Common Stock 08/17/2015   M(2)   2,778 A $ 11 82,326 D  
Common Stock 08/17/2015   S(2)   8,778 D $ 50 73,548 D  
Common Stock 08/18/2015   S(2)   4,284 D $ 49.26 (3) 69,264 D  
Common Stock 08/18/2015   S(2)(4)   3,427 D $ 49.78 (5) 65,837 D  

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Restricted Stock Units (6) 08/17/2015   M     9,615   (7)   (8) Common Stock 9,615 $ 0 64,103 D  
Restricted Stock Units (6) 08/17/2015   M     4,145   (9)   (10) Common Stock 4,145 $ 0 40,076 D  
Employee Stock Option (Right to Buy) $ 11 08/17/2015   M(2)     2,778   (11) 10/24/2021 Common Stock 2,778 $ 0 37,222 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Soffer Gad
701 GATEWAY BOULEVARD
SUITE 200
SOUTH SAN FRANCISCO, CA 94080		       Chief Operating Officer  

Signatures

 /s/ Tina Gullotta, Attorney-in-Fact for Gad Soffer   05/19/2015
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) Shares issued upon settlement of vested restricted stock units ("RSUs").
(2) Transaction pursuant to Rule 10b5-1 Plan adopted May 14, 2015.
(3) The price in Column 4 is a weighted average sale price. The prices actually received ranged from $48.54 to $49.47. The reporting person will provide to the issuer, any security holder of the issuer, or the SEC staff, upon request, information regarding the number of shares sold at each price within the range.
(4) Shares sold to cover tax liability from settlement of RSUs.
(5) The price in Column 4 is a weighted average sale price. The prices actually received ranged from $49.58 to $50.51. The reporting person will provide to the issuer, any security holder of the issuer, or the SEC staff, upon request, information regarding the number of shares sold at each price within the range.
(6) Each restricted stock unit represents a contingent right to receive one share of the Issuer's common stock or a cash settlement.
(7) The RSUs were granted with both (a) a liquidity event-based vesting condition and (b) a service-based vesting condition, both of which conditions must be satisfied in order for the RSUs to vest. The liquidity event-based condition was satisfied upon the closing of the Issuer's initial public offering (the "IPO"). The shares that vested on the closing date of the IPO, and the shares that vested thereafter through May 15, 2015, were settled on May 15, 2015. The service-based vesting condition provides that 25% of the total number of shares on March 25, 2014 and 1/48th of the total number of shares monthly thereafter, subject to the holder's continuous service through each such date.
(8) The earlier of (i) March 13, 2020 or (ii) the recipient's termination date.
(9) The RSUs were granted with both (a) a liquidity event-based vesting condition and (b) a service-based vesting condition, both of which conditions must be satisfied in order for the RSUs to vest. The liquidity event-based condition was satisfied upon the closing of the Issuer's initial public offering (the "IPO"). The shares that vested on the closing date of the IPO, and the shares that vested thereafter through May 15, 2015, were settled on May 15, 2015. The service-based vesting condition provides that 1/48th of the total number of shares shall vest monthly from January 10, 2014, subject to the holder's continuous service through each such date.
(10) The earlier of (i) January 10, 2021 or (ii) the recipient's termination date.
(11) 1/48th of the shares subject to the stock option vest and become exercisable each month following October 15, 2014.

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