Sec Form 3 Filing - Redmile Group, LLC @ Atara Biotherapeutics, Inc. - 2025-05-16

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 Redmile Group, LLC 2. Issuer Name and Ticker or Trading Symbol Atara Biotherapeutics, Inc. [ ATRA] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) ONE LETTERMAN DRIVE, BUILDING D, SUITE D3-300 3. Date of Earliest Transaction (MM/DD/YY) 05/16/2025 (Street) SAN FRANCISCO, CA94129 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ 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, par value $0.0001 per share 441,701 I See Footnote ( 2 )

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 Pre-Funded Warrants to Purchase Common Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 3,412,843 ( 1 ) I See Footnote ( 2 ) Cash-settled Swaps $ 809.858 ( 6 ) ( 3 )( 4 )( 5 ) ( 4 ) Common Stock 4,103 I See Footnote ( 2 ) Cash-settled Swaps $ 9.315 ( 6 ) ( 3 )( 4 )( 5 ) ( 4 ) Common Stock 4,872 I See Footnote ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Redmile Group, LLC ONE LETTERMAN DRIVE, BUILDING D SUITE D3-300 SAN FRANCISCO, CA94129 X Green Jeremy C/O REDMILE GROUP, LLC (NY OFFICE) 45 W. 27TH STREET, FLOOR 11 NEW YORK, NY10001 X Signatures By: /s/ Jeremy Green, Managing Member of Redmile Group, LLC 05/23/2025 Signature of Reporting Person Date /s/ Jeremy Green 05/23/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The Warrants are exercisable at any time on or after the original issuance date until fully exercised, at an exercise price equal to $0.0001 per share, subject to a 9.99% beneficial ownership blocker. The Warrants have no expiration date. ( 2 )The reported securities are directly owned by certain private funds managed by Redmile Group, LLC (collectively, the "Funds") and may be deemed beneficially owned by Redmile Group, LLC ('Redmile") as investment manager of the Funds. The reported securities may also be deemed beneficially owned by Jeremy Green as the principal of Redmile. Each of Redmile and Mr. Green (the "Reporting Persons") disclaims beneficial ownership of the reported securities except to the extent of their pecuniary interest therein, if any. This report shall not be deemed an admission that such Reporting Persons are the beneficial owners of the securities for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, or for any other purpose. ( 3 )Certain Funds are parties to swap agreements with counterparties. Each notional share subject to each swap agreement represents the economic equivalent of one share of the Issuer's common stock. These agreements do not give the Reporting Persons direct or indirect voting, investment or dispositive control over any securities of the Issuer and do not require the counterparties thereto to acquire, hold, vote or dispose of any securities of the Issuer. Accordingly, the Reporting Persons disclaim any beneficial ownership in securities that may be referenced in such swap agreements or that may be held from time to time by any counterparties to the agreements. ( 4 )The Reporting Persons have the right to terminate and close out each swap at any time. ( 5 )Upon settlement of the various swap agreements, either (i) the counterparty will pay to the Reporting Persons in cash an amount determined in part by reference to any increase between the reference price and the market value of the notional number of shares of Common Stock subject to the swap agreement or (ii) the Reporting Persons will pay to the counterparty in cash an amount determined in part by reference to any decrease between the reference price and the market value of the notional number of shares of Common Stock subject to the swap agreement. ( 6 )Represents the reference price associated with the swap agreements.

Remarks: Mr. Nachi Subramanian, a member of the board of directors of the Issuer and a managing director of Redmile, was elected to the board of the Issuer as a representative of Redmile and its affiliates. As a result, the Reporting Persons are directors by deputization for purposes of Section 16 of the Securities Exchange Act of 1934, as amended.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* 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).

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