Atara Biotherapeutics Inc

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31,2024

OR

For the transition period from to

Commission File Number 001-36548

ATARA BIOTHERAPEUTICS, INC.

(Exact name of Registrant as specified in its Charter)

Registrant’s telephone number, including area code:(805)623-4211

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

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☐ NO ☒

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. YES ☐ No ☒

Indicate by check mark whether the Registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ NO ☐

Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the Registrant was required to submit such files). Yes ☒ NO ☐

Indicate by check mark whether the Registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See definitions of “large accelerated filer,” “accelerated filer," “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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.☐

Indicate by check mark whether the Registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report.☐

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the Registrant included in the filing reflect the correction of an error to previously issued financial statements.☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the Registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b). ☐

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). YES ☐ NO ☒

The aggregate market value of common stock held by non-affiliates of the Registrant, based on the closing sales price for such stock on June 30, 2024 as reported by The Nasdaq Stock Market, was $41,039,683. This calculation excludes 76,019 shares held by executive officers, directors and stockholders that the Registrant has concluded are affiliates of the Registrant. Exclusion of such shares should not be construed to indicate that any such person possesses the power, direct or indirect, to direct or cause the direction of the management or policies of the Registrant or that such person is controlled by or under common control with the Registrant.

The number of outstanding shares of the Registrant’s Common Stock as of March 3, 2025 was 5,858,909.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the Registrant’s definitive proxy statement relating to its 2025 Annual Meeting of Stockholders are incorporated by reference into Part III of this Report where indicated. Such proxy statement will be filed with the U.S. Securities and Exchange Commission within 120 days after the end of the fiscal year to which this report relates.

ATARA BIOTHERAPEUTICS, INC.

TABLE OF CONTENTS

FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K contains forward-looking statements within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. Such forward-looking statements, which represent our intent, belief or current expectations, involve risks and uncertainties and other factors that could cause actual results and the timing of certain events to differ materially from future results expressed or implied by such forward-looking statements. In some cases you can identify these statements by forward-looking words such as “believe,” “may,” “will,” “estimate,” “continue,” “anticipate,” “intend,” “could,” “would,” “project,” “predict,” “plan,” or “expect,” or the negative or plural of these words or similar expressions. The forward-looking statements include, but are not limited to, statements about:

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our review of strategic alternatives;

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our expectations regarding our clinical studies, client sites, and reporting results of clinical studies for our programs;

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the likelihood and timing of regulatory submissions or related approvals for our product candidates, including the expectations about the timing of approvals for a biologics license application (BLA) for tab-cel® for patients with Epstein-Barr virus with post-transplant lymphoproliferative disease (EBV+ PTLD);

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our ongoing discussions with Pierre Fabre Medicament related to the transition of all operational activities for tab-cel, except the BLA sponsorship, as early as the end of the first quarter of 2025;

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the potential indications for our product and product candidates;

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commercialization of tab-cel (Ebvallo™ in the United Kingdom (UK), the European Economic Area (EEA) and Switzerland) worldwide and our amended and restated Commercialization Agreement with Pierre Fabre Medicament, including potential milestone and royalty payments under the agreement (Ebvallo in the UK, the EEA and Switzerland subject to the Purchase and Sale Agreement with HCR Molag Fund, L.P.);

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our Purchase and Sale Agreement and related transactions with HCR Molag Fund, L.P.;

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the wind-down of our Commercial Manufacturing Services Agreement with Charles River Laboratories, Inc. (CRL);

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our Master Services and Supply Agreement and related transactions with FUJIFILM Diosynth Biotechnologies California, Inc.;

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our expectations regarding the potential commercial market opportunities, market size, and the size of the patient populations for our product and product candidates;

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estimates of our expenses, capital requirements, and need for additional financing;

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our expectation regarding the length of time that our existing capital resources will be sufficient to enable us to fund our planned operations, including our going concern assessment;

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our ability to enter into favorable commercialization arrangements with third parties to commercialize our product candidates;

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our ability to develop, acquire and advance product candidates into, and successfully complete, clinical studies;

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the initiation, timing, costs, progress, and results of clinical studies and our research and development programs;

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our ability to enter into and maintain contracts with clinical research organizations (CROs), contract manufacturing organizations (CMOs), and other vendors for clinical studies, supplies, and other services;

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the scope of protection we are able to obtain and maintain for the intellectual property rights covering our product and product candidates;

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our financial performance;

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our election to rely on reduced reporting and disclosure requirements available to smaller reporting companies;

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developments and projections relating to our competitors and our industry;

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our ability to have our product and product candidates manufactured for our clinical studies or for commercial sale, including at commercially reasonable values;

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the impact of public health emergencies to our business and operations, as well as the businesses and operations of third parties on which we rely;

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the impact of our workforce reductions on our ability to attract, retain, and motivate qualified personnel and on our business, operations, and financial condition; and

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timing and costs related to the qualification of the manufacturing facilities of our CMOs for commercial production.

These statements are only current predictions and are subject to known and unknown risks and uncertainties, including, without limitation, risks and uncertainties associated with the costly and time-consuming pharmaceutical product development process and the uncertainty of clinical success; the sufficiency of our cash resources and need for additional capital; and other factors that may cause our or our industry’s actual results, levels of activity, performance or achievements to be materially different from those anticipated by the forward-looking statements. We discuss many of these risks in this report in greater detail under the heading “1A. Risk Factors” and elsewhere in this report. You should not rely upon forward-looking statements as predictions of future events. New risk factors and uncertainties may emerge from time to time, and it is not possible for management to predict all risks and uncertainties.

In this Annual Report on Form 10-K, unless the context requires otherwise, “Atara,” “Atara Biotherapeutics,” “Company,” “we,” “our,” and “us” means Atara Biotherapeutics, Inc. and, where appropriate, its subsidiaries.

Summary Risk Factors

Our business is subject to numerous risks and uncertainties that may have a material adverse effect on our business, financial condition, or results of operations. These risks are more fully described under the heading “1A. Risk Factors” and elsewhere in this report and include, among others:

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our activities to review and pursue strategic alternatives may not result in a strategic transaction, and even if we do consummate a strategic transaction, there is no assurance that it will deliver the benefits we expect or enhance stockholder value;

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our board of directors may determine to pursue a liquidation and dissolution or other wind down of our business, and in such event, the amount of cash available for distribution to our stockholders, if any, will depend heavily on the timing of such liquidation as well as the amount of cash that will need to be reserved for commitments and contingent liabilities;

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we have incurred substantial losses since our inception and anticipate that we will continue to incur substantial losses for the foreseeable future;

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we have earned limited commercialization revenues to date, and we may never achieve profitability;

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we will require substantial near-term financing to continue operations, and a failure to obtain this necessary capital when needed could force us to delay, limit, reduce, or terminate our product development or manufacturing efforts, or impair our exploration of strategic alternatives, or require us to pursue a liquidation and dissolution or other wind down of our business;

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we have one approved product, Ebvallo, in the EEA, the UK, and Switzerland. In March 2025, we announced our decision to pause the development of our allogeneic CAR-T cell programs and to discontinue all CAR-T operations. If we or our collaborators are unable to successfully develop, manufacture, and commercialize our product or product candidates, or experience significant delays in doing so, our business may be materially harmed;

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our T-cell immunotherapy product and product candidates represent new therapeutic approaches that could result in heightened regulatory scrutiny, delays in clinical development or our inability to achieve regulatory approval, commercialization or payor coverage of our product candidates;

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the results of preclinical studies or earlier clinical studies are not necessarily predictive of future results, and our existing product candidates may not receive regulatory approval;

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clinical drug development involves a lengthy and expensive process with an uncertain outcome;

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there can be no assurance that we will achieve all of the anticipated benefits of the Fujifilm Transaction and we could face unanticipated challenges;

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the market opportunities for our product and product candidates may be limited to those patients who are ineligible for or have failed prior treatments and may be small;

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we may not be able to obtain or maintain orphan drug exclusivity for our product candidates;

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the proposed revision of the European legislation on pharmaceuticals, changes in governmental administration, or changes in leadership at relevant regulatory agencies could lead to uncertainties over the regulatory framework that will be applicable to medicinal products in the EU and US, including orphan medicinal products;

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if we are unable to obtain and maintain sufficient intellectual property protection for our product candidates, or if the scope of the intellectual property protection is not sufficiently broad, our ability to commercialize our product candidates successfully and to compete effectively may be adversely affected;

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our principal stockholders own a significant percentage of our stock and will be able to exert control or significant influence over matters subject to stockholder approval;

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we qualify as a “smaller reporting company” and a “non-accelerated filer,” and any decision on our part to comply only with certain reduced reporting and disclosure requirements applicable to such companies could make our stock less attractive to investors;

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our future success depends on our ability to retain our executive officers and to attract, retain, and motivate qualified personnel;

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our workforce reductions may not result in anticipated savings, could result in total costs and expenses that are greater than expected, and could disrupt our business; and

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maintaining clinical and commercial timelines is dependent on our end-to-end supply chain network to support manufacturing; if we experience problems with our third party suppliers or CMOs, development and/or commercialization of our product and product candidates may be adversely affected.