UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): June 9, 2026

Atara Biotherapeutics, Inc.

(Exact name of Registrant as Specified in Its Charter)

Registrant’s Telephone Number, Including Area Code: (805) 632-4211

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

Securities pursuant to Section 12 (b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

On June 11, 2026, the Board of Directors (the “Board”) of Atara Biotherapeutics, Inc. (the “Company”) appointed Brian Cherry to serve as a member of the Board as a Class I director, effective June 11, 2026 (the “Effective Date”). Mr. Cherry was also appointed to the Audit Committee of the Board.

The Board has determined that Mr. Cherry is independent under the Company’s Corporate Governance Guidelines, applicable U.S. Securities Exchange Commission (“SEC”) requirements and Nasdaq listing standards.  There are no arrangements or understandings between Mr. Cherry and any other persons pursuant to which he was elected as a director of the Company. There are no family relationships between Mr. Cherry and any director or executive officer of the Company, and he has no direct or indirect material interest in any transaction required to be disclosed pursuant to Item 404(a) of Regulation S-K.

In connection with his appointment, on the Effective Date, the Board approved an initial equity award to Mr. Cherry of 24,000 restricted stock units covering shares of the Company’s Common Stock, which will vest on an annual basis over three years, subject to his continuous service as a member of the Board. Mr. Cherry will otherwise participate in the Company’s non-employee director compensation arrangements, which are generally described under the heading “2025 Non-Employee Director Compensation” in the Company’s Proxy Statement for its 2026 Annual Meeting of Stockholders as filed with the SEC on April 24, 2026 (the “Proxy Statement”), including an annual cash retainer of $55,000 starting on the Effective Date, with payment pro-rated for any partial period of service. The Company also entered into its standard form of indemnification agreement with Mr. Cherry.

Item 5.07 Submission of Matters to a Vote of Security Holders.

On June 9, 2026, the Company held its 2026 annual meeting of stockholders (the “Annual Meeting”). The following is a brief description of each matter voted upon at the Annual Meeting, as well as the number of votes cast for or against each matter and the number of abstentions and broker non-votes with respect to each matter. A more complete description of each matter is described in more detail in the Proxy Statement.

Each of the two nominees for director was elected to serve until the 2029 annual meeting of stockholders and until their respective successors are elected.

The stockholders approved, on an advisory basis, the compensation awarded to the Company’s named executive officers, as disclosed in the Proxy Statement.

The stockholders approved the amendment to the Company’s 2024 Equity Incentive Plan, as disclosed in the Proxy Statement.

The stockholders ratified the appointment of Deloitte & Touche LLP as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2026.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

Date: June 12, 2026