and in the press release included as Exhibit 99.1 shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of Section 11 and 12(a)(2) of the Securities Act of 1933, as amended, and shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission, whether made before or after the date hereof, except as shall be expressly set forth by specific reference in such fi…

Chief Accounting Officer — Yanina Grant-Huerta: The departure of the Chief Accounting Officer and appointment of an interim chief financial officer indicate significant changes in management.

Director — Brian Cherry: Brian Cherry was appointed as a Class I director and to the Audit Committee of Atara Biotherapeutics, Inc.

and in the press release included as Exhibit 99.1 shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of Section 11 and 12(a)(2) of the Securities Act of 1933, as amended, and shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission, whether made before or after the date hereof, except as shall be expressly set forth by specific reference in such fi…

Other Events. On May 7, 2026, Atara Biotherapeutics, Inc. (the “Company”) issued a press release titled “Atara Biotherapeutics Provides Regulatory Update on Tabelecleucel” providing an update following the Type A meeting with the U.S. Food and Drug Administration (the “FDA”) to discuss the Complete Response Letter for the EBVALLO™ Biologics License Application issued on January 9, 2026. A copy of the press release is filed herewith as Exhibit 99.1 and is incorporated by reference into this

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing. On April 30, 2026, Atara Biotherapeutics, Inc. (the “Company”) received a notice (the “Notice”) from the Listing Qualifications Department (the “Staff”) of The Nasdaq Stock Market LLC (“Nasdaq”) notifying the Company that the Company no longer meets Nasdaq’s $50 million minimum market value for listed securities (“MVLS”) requirement pursuant to Nasdaq Listing Rule 5450(b)(2)(A) (the “MVLS Requ…

and in the press release included as Exhibit 99.1 shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of Section 11 and 12(a)(2) of the Securities Act of 1933, as amended, and shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission, whether made before or after the date hereof, except as shall be expressly set forth by specific reference in such fi…

Other Events. On March 12, 2026, Atara Biotherapeutics, Inc. (the “Company”) issued a press release titled “Atara Biotherapeutics Provides Regulatory Update on Tabelecleucel” announcing that the Type A meeting with the U.S. Food and Drug Administration (the “FDA”) to discuss the Complete Response Letter for the EBVALLO™ Biologics License Application issued on January 9, 2026 has been scheduled. A copy of the press release is filed herewith as Exhibit 99.1 and is incorporated by reference into…

Other Events. On March 3, 2026, Atara Biotherapeutics, Inc. (the “Company”) issued a press release titled “Atara Biotherapeutics Provides Regulatory Update on Tabelecleucel” announcing that Pierre Fabre Pharmaceuticals, Inc. has submitted a request for a Type A meeting with the U.S. Food and Drug Administration (the “FDA”) to discuss the plan to address the issues raised by the FDA in the Complete Response Letter for the EBVALLO ™ Biologics License Application issued on January 9, 2026. A cop…

The Company issued the Warrant pursuant to the exemption from the registration requirements of the Securities Act of 1933, as amended (the “Securities Act”) available under Section 4(a)(2) of the Securities Act. Pursuant to the terms of the Warrant, the Company intends to file a registration statement relating to the resale of the Company’s Common Stock underlying the Warrant, subject to the registration rights provisions of the Warrant.

Entry into a Material Definitive Agreement. On February 20, 2026, Atara Biotherapeutics, Inc., (the “Company”) entered into an Amendment (the “Amendment”) to the Purchase and Sale Agreement dated as of December 20, 2022 (the “Agreement”) with HCR Molag Fund, L.P. (“HCR”). Under the terms of the Amendment, HCR agreed to amend the due date of the one-time of $9.0 million cash payment associated with the achievement of a certain milestone within the Amended and Restated Commercialization Agreeme…

Results of Operations and Financial Condition. In connection with the press release described in

Entry into a Material Definitive Agreement. On December 30, 2025, Atara Biotherapeutics, Inc., (the “Company”) entered into the Fourth Amendment (the “Amendment”) to the Amended and Restated Commercialization Agreement dated October 31, 2023 (the “Agreement”) with Pierre Fabre Medicament (“Pierre Fabre”). Under the terms of the Amendment, the Company has agreed to reduce the aggregate amount of potential milestone payments payable by Pierre Fabre to the Company upon achieving certain regulato…

and in the press release included as Exhibit 99.1 shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of Section 11 and 12(a)(2) of the Securities Act of 1933, as amended, and shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission, whether made before or after the date hereof, except as shall be expressly set forth by specific reference in such fi…

Costs Associated with Exit or Disposal Activities. On October 6, 2025, Atara Biotherapeutics, Inc. (the “Company”) announced a reduction in its workforce that will impact approximately 29% of its current employees, retaining approximately 15 employees essential to executing on the Company’s strategic priorities. The Company expects to complete the workforce reduction by January 2026. The Company expects to recognize approximately $1.3 million for severance and related benefits for employees l…

Director — Ameet Mallik, Pascal Touchon, Maria Grazia Roncarolo, M.D.: Three directors voluntarily resigned from the Board due to a reduction in its size.

and in the press release included as Exhibit 99.1 shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of Section 11 and 12(a)(2) of the Securities Act of 1933, as amended, and shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission, whether made before or after the date hereof, except as shall be expressly set forth by specific reference in such fi…

Results of Operations and Financial Condition. In connection with the press release described in

Other Events. On May 14, 2024, the Company entered into an underwriting agreement (the “Underwriting Agreement”) with TD Securities (USA) LLC, as representative (the “Representative”) of the underwriters (the “Underwriters”) named therein, pursuant to which the Company agreed to issue and sell to the Underwriters in an underwritten registered direct offering (the “Offering”) an aggregate of (i) 834,237 shares (the “Shares”) of the Company’s common stock, par value $0.0001 per share (the “Comm…

Director — James Huang, Nachi Subramanian: Appointment of new directors in connection with a registered direct offering.

and in the press release included as Exhibit 99.1 of this current report on Form 8-K shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of Section 11 and 12(a)(2) of the Securities Act of 1933, as amended, and shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission (the “SEC”), whether made before or after the date hereof, except as shall be expre…

Costs Associated with Exit or Disposal Activities. On May 12, 2025, Atara Biotherapeutics, Inc. (the “Company”) announced a reduction in its workforce that will impact approximately 30% of its current employees, retaining approximately 23 employees essential to executing on the Company’s strategic priorities. The Company expects to complete the workforce reduction by August 2025. The Company expects to recognize approximately $1.4 million for severance and related benefits for employees laid…

Other Events. On May 5, 2025, Atara Biotherapeutics, Inc. (the “Company”) issued a press release titled “Atara Biotherapeutics Provides Regulatory Updates on EBVALLO ™ (tabelecleucel)” announcing that the U.S. Food and Drug Administration (“FDA”) lifted the clinical hold on the Company’s active Investigational New Drug applications for the EBVALLO ™ (tabelecleucel) program that was placed in January 2025. The press release also announced that the FDA granted the Company a Type A meeting to di…

Entry into a Material Definitive Agreement. On March 31, 2025, Atara Biotherapeutics, Inc., (the “Company”) entered into an Amendment (the “Amendment”) to the Amended and Restated Commercialization Agreement dated October 31, 2023 (the “Agreement”) with Pierre Fabre Medicament (“Pierre Fabre”). Under the terms of the Amendment, as of March 31, 2025, the Company has completed the transfer of all manufacturing responsibility to Pierre Fabre and Pierre Fabre will be, at its cost, responsible for…

Chief Financial Officer and Chief Operating Officer — Eric Hyllengren: Eric Hyllengren's employment as CFO and COO ended, with no immediate successor named for the CFO role.