| FORM 4 | 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 or Section 30(h) of the Investment Company Act of 1940 |
| |||||||||||||||
| Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). | |||||||||||||||||
| Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10. | |||||||||||||||||
1. Name and Address of Reporting Person*
(Street)
(Country) | 2. Issuer Name and Ticker or Trading Symbol
Atara Biotherapeutics, Inc. [ ATRA ] | 5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
| |||||||||||||||||||||||||
| 2a. Foreign Trading Symbol
| |||||||||||||||||||||||||||
| 3. Date of Earliest Transaction
(Month/Day/Year) 06/09/2026 | 6. Individual or Joint/Group Filing (Check Applicable Line)
| ||||||||||||||||||||||||||
| 4. If Amendment, Date of Original Filed
(Month/Day/Year) |
| 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 | 06/09/2026 | A | 12,000(1) | A | $0 | 12,000 | D | |||
| Common Stock | 1,209,395 | 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 (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 Securities Underlying Derivative Security (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: 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 | ||||||||
| Explanation of Responses: |
| 1. These restricted stock units shall vest on the earlier of June 9, 2027 or the date of the next annual meeting of stockholders, subject to the Reporting Person's continuous service. |
| 2. The securities reported on this row are directly held by Adiumentum Capital Fund I LP, a limited partnership organized under the laws of Delaware ("Adiumentum"). Adiumentum Capital Fund I GP LLC, a limited liability company organized under the laws of Delaware ("Adiumentum GP"), is the general partner of Adiumentum. Gregory A. Ciongoli is the managing partner of Adiumentum and the managing member of Adiumentum GP. Each of Adiumentum, Adiumentum GP, and Mr. Ciongoli may be deemed to have the shared power to vote or direct the vote (and the shared power to dispose or direct the disposition of) the securities that are directly held by Adiumentum. Each of Adiumentum, Adiumentum GP, and Mr. Ciongoli may be deemed to have a pecuniary interest in the securities that are directly held by Adiumentum, but disclaims any beneficial ownership of such securities, except to the extent of any pecuniary interest therein. |
| Remarks: |
| Exhibit List: Exhibit 24 - Power of Attorney. Mr. Ciongoli serves as a director on the Board of Directors of the Issuer and, as a result, Adiumentum and Adiumentum GP are directors by deputization for purposes of Section 16 of the Securities Exchange Act of 1934, as amended. Neither Adiumentum nor Adiumentum GP have a pecuniary interest in the restricted stock units awarded to Mr. Ciongoli as reported in this Form 4, and therefore Adiumentum and Adiumentum GP have been excluded as reporting persons from this Form 4. |
| /s/ John Chao, Attorney-in-Fact for Gregory A. Ciongoli | 06/11/2026 | |
| ** Signature of Reporting Person | Date | |
| 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). | ||
| Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure. | ||
| Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number. | ||
| * Form 4: SEC 1474 (03-26) | ||