Sec Form 3 Filing - Nguyen AnhCo @ Atara Biotherapeutics, Inc. - 2023-06-01

FORM 3 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 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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1. Name and Address of Reporting Person Nguyen AnhCo 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) EVP, Chief Sci. & Tech Officer (Last) (First) (Middle) C/O ATARA BIOTHERAPEUTICS, INC., 2380 CONEJO SPECTRUM STREET, SUITE 200 3. Date of Earliest Transaction (MM/DD/YY) 06/01/2023 (Street) THOUSAND OAKS, CA91320 4. If Amendment, Date Original Filed (MM/DD/YY) 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 (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 301,125 ( 1 ) ( 2 ) D

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 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 Employee Stock Option (Right to Buy) $ 13.24 05/10/2023 05/09/2031 Common Stock 87,124 D Employee Stock Option (Right to Buy) $ 13.24 ( 3 ) 05/09/2031 Common Stock 87,125 D Employee Stock Option (Right to Buy) $ 10.21 06/01/2023 02/29/2032 Common Stock 35,048 D Employee Stock Option (Right to Buy) $ 10.21 ( 4 ) 02/29/2032 Common Stock 77,108 D Employee Stock Option (Right to Buy) $ 3.91 06/01/2023 02/28/2033 Common Stock 28,907 D Employee Stock Option (Right to Buy) $ 3.91 ( 4 ) 02/28/2033 Common Stock 317,988 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Nguyen AnhCo C/O ATARA BIOTHERAPEUTICS, INC. 2380 CONEJO SPECTRUM STREET, SUITE 200 THOUSAND OAKS, CA91320 EVP, Chief Sci. & Tech Officer Signatures /s/ Jeff Kiekhofer, Attorney-in-Fact for AnhCo Nguyen 06/09/2023 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Includes an aggregate 270,072 restricted stock units ("RSUs"), which are comprised of: (i) 57,724 RSUs that vest as to 1/8th of shares on August 15, 2023 and each of the next seven (7) Quarterly Vesting Dates (as defined herein); (ii) 41,020 RSUs that vest as to 1/11th of shares on August 15, 2023 and each of the next ten (10) Quarterly Vesting Dates; (iii) 30,000 RSUs that vest as to 1/2nd of shares on August 15, 2023 and 1/2nd on August 15, 2024; and (iv) 141,328 RSUs that vest as to 1/11th of shares on August 15, 2023 and each of the next ten (10) Quarterly Vesting Dates, each of which is subject to the reporting person's continuous service. ( 2 )"Quarterly Vesting Date" means March 1, May 15, August 15, and November 15 of each year, provided that if such date falls on a weekend or holiday, the "Quarterly Vesting Date" shall be the first (1st) business day after such date. ( 3 )1/24th of shares subject to the stock option vest and become exercisable on June 10, 2023, and the remaining shares vest in equal monthly installments over the following twenty-three (23) months, subject to the reporting person's continuous service. ( 4 )1/33rd of shares subject to the stock option vest and become exercisable on July 1, 2023, and the remaining shares vest in equal monthly installments over the following thirty-two (32) months, subject to the reporting person's continuous service.

Remarks: Exhibit 24 - Power of Attorney

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