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): ~~November 12~~December 30, 2025

Atara Biotherapeutics, Inc.

(Exact name of Registrant as Specified in Its Charter)

Delaware	001-36548	46-0920988
(State or Other Jurisdiction of Incorporation)	(Commission File Number)	(IRS Employer Identification No.)
(State or Other Jurisdictionof Incorporation)	(Commission File Number)	(IRS EmployerIdentification No.)


1280 Rancho Conejo Blvd
Thousand Oaks, California		91320
(Address of Principal Executive Offices)		(Zip Code)

Registrant’s Telephone Number, Including Area Code: (805) 623-4211

(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:

☐	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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

Title of each class		~~Trading Symbol~~TradingSymbol(s)		Name of each ~~exchange~~exchangeon on which registered
Common Stock, par value $0.0001 per share		ATRA		The Nasdaq Stock Market LLC

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 2 1.0201 ~~Results~~Entry ofinto ~~Operations~~a ~~and~~Material ~~Financial~~Definitive ~~Condition~~Agreement.

On ~~November~~December 1230, 2025, Atara Biotherapeutics, Inc., (the “Company”) ~~announced~~entered ~~certain~~into ~~financial~~the ~~results~~Fourth ~~for~~Amendment (the ~~third~~“Amendment”) ~~quarter~~to ~~ended~~the ~~September~~Amended and Restated Commercialization Agreement dated October 3031, ~~2025~~2023 (the “Agreement”) with Pierre Fabre Medicament (“Pierre Fabre”). AUnder ~~copy~~the terms of the Amendment, the Company’s ~~press~~has ~~release,~~agreed ~~titled~~to ~~“Atara~~reduce ~~Biotherapeutics~~the ~~Announces~~aggregate ~~Third~~amount ~~Quarter~~of ~~Financial~~potential ~~Results~~milestone ~~and~~payments ~~Operational~~payable ~~Progress”~~by isPierre ~~furnished~~Fabre asto ~~Exhibit~~the 99Company upon achieving certain regulatory milestones relating to the approval by the FDA of a BLA for tab-cel from $40.10 million ~~hereto~~to $31.0 million for the right to receive an additional $15.0 million potential milestone payment from Pierre Fabre to the Company upon achieving a certain commercial milestone.

The ~~information~~foregoing ~~set~~summary ~~forth~~of inthe ~~this~~Amendment ~~Item~~does ~~2.02~~not ~~and~~purport into ~~the~~be ~~press~~complete ~~release~~and ~~included~~is asqualified ~~Exhibit~~in ~~99.1~~its ~~shall~~entirety ~~not~~by bereference ~~deemed~~to ~~“filed” for~~ the ~~purposes~~Amendment, ofa ~~Section 18~~copy of ~~the~~which ~~Securities~~is ~~Exchange~~filed ~~Act~~herewith ~~of 1934,~~ as ~~amended,~~Exhibit or10.1 ~~otherwise subject~~ to ~~the~~this ~~liabilities~~Current ofReport ~~Section 11~~on ~~and~~Form ~~12(a)(2)~~8-K ~~of the Securities Act of 1933, as amended,~~ and ~~shall~~is ~~not be~~ incorporated by reference into ~~any~~this ~~filing~~Item ~~with the U~~1.S01. ~~Securities and Exchange Commission, whether made before or after the date hereof, except as shall be expressly set forth by specific reference in such filing.~~

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

ExhibitNo.		Description
Exhibit No.		Description
99.1		Press Release, dated November 12, 2025
10.1		Fourth Amendment to the Amended and Restated Commercialization Agreement, by and between Atara Biotherapeutics, Inc. and Pierre Fabre Medicament, dated December 30, 2025
104		Cover Page Interactive Data File (embedded within the Inline XBRL document).

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 hereunto duly authorized.

		ATARA BIOTHERAPEUTICS, INC.
Date: November 12, 2025	By:	/s/ Yanina Grant-Huerta
Date: January 2, 2026	By:	/s/ AnhCo Thieu Nguyen
		Yanina Grant-Huerta Chief Accounting Officer (Duly Authorized Officer and Principal Financial and Accounting Officer)
		AnhCo Thieu Nguyen
		President and Chief Executive Officer
		(Duly Authorized Officer and Principal Executive Officer)

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