Annual Report for Fiscal Year Ending 12-31, 2025 (Form 10-K)

Item 7. Management's Discussion and Analysis of Financial Condition and Results of Operations

You should read the following discussion and analysis of our financial condition and results of operations together with our audited consolidated financial statements and related notes included elsewhere in this Annual Report on Form 10-K. This discussion and other parts of this Annual Report contain forward-looking statements that involve risk and uncertainties, such as statements of our plans, objectives, expectations and intentions. As a result of many factors, including those factors set forth in the "Risk Factors" section of this Annual Report, our actual results could differ materially from the results described in or implied by the forward-looking statements contained in the following discussion and analysis.

Overview

Atara Biotherapeutics is a leader in T-cell immunotherapy, leveraging its novel allogeneic Epstein-Barr virus (EBV) T-cell platform to develop transformative therapies for patients with cancer and autoimmune disease. Tab-cel (tabelecleucel) has received marketing authorization approval (MAA) under the proprietary name Ebvallo™ for commercial sale in the European Economic Area (EEA) by the European Commission (EC), for commercial sale and use in the United Kingdom (UK) by the Medicines and Healthcare products Regulatory Agency (MHRA), and for commercial sale and use in Switzerland by Swissmedic. We are partnered with Pierre Fabre Medicament (Pierre Fabre) for commercialization in Europe and potential commercialization, if approved, worldwide, including in the U.S. Tab-cel is currently in Phase 3 development in the U.S. for patients with EBV- associated post-transplant lymphoproliferative disease (EBV+ PTLD) who have failed rituximab or rituximab plus chemotherapy, as well as other EBV-driven diseases.

In March 2025, we announced our decision to pause development of our allogeneic CAR T cell programs and to discontinue development operations for our CAR T programs, including all clinical trials evaluating ATA3219 and development operations for ATA3431. We have completed nearly all wind-down activities for the CAR T programs. We have also stopped development on ATA188, an allogeneic T-cell immunotherapy targeting multiple sclerosis (MS).

Our T-cell immunotherapy platform is potentially applicable to a broad array of targets and diseases. Our off-the-shelf, allogeneic T-cell platform allows for rapid delivery of a T-cell immunotherapy product manufactured in advance of patient need and stored in inventory, with each manufactured lot of cells providing therapy for numerous potential patients. This differs from autologous treatments, in which each patient's own cells must be extracted, genetically modified outside the body and then delivered back to the patient, requiring a complex logistics network. We select the appropriate set of cells for use based on a patient's unique immune profile.

In October 2021, we entered into the Commercialization Agreement with Pierre Fabre (Pierre Fabre Commercialization Agreement), pursuant to which we granted to Pierre Fabre an exclusive, field-limited license to commercialize and distribute Ebvallo in Europe and select emerging markets in the Initial Territory following regulatory approval. As contemplated by the Pierre Fabre Commercialization Agreement, we entered into (i) a Manufacturing and Supply Agreement (ii) a Pharmacovigilance Agreement (iii) and a Quality Agreement, in each case, with Pierre Fabre to further advance our partnership with Pierre Fabre. In September 2022, we amended the Pierre Fabre Commercialization Agreement and received an additional $30 million milestone payment from Pierre Fabre following EC approval of Ebvallo for EBV+ PTLD and subsequent filing of the MAA transfer to Pierre Fabre, in exchange for, among other things, a reduction in: (i) royalties we are eligible to receive as a percentage of net sales of Ebvallo in the Initial Territory, and (ii) the supply price mark up on tab-cel purchased by Pierre Fabre. Additionally, we agreed to extend the time period for provision of certain services to Pierre Fabre under the Pierre Fabre Commercialization Agreement. In December 2022, we entered into the HCRx Agreement with HCR Molag Fund L.P. (HCRx,) a Delaware limited partnership. Pursuant to the terms of the HCRx Agreement, we received a total investment amount of $31 million in exchange for HCRx being entitled to receive a portion of the tiered, sales-based royalties for Ebvallo, in amounts ranging from the mid-single digits to significant double digits, as well as certain milestone payments, both related to the Initial Territory and otherwise payable to us by Pierre Fabre. The total royalties and milestones payable to HCRx related to the Initial Territory under the HCRx Agreement are capped between 185% and 250% of the total investment amount by HCRx, dependent upon the timing of such royalty and milestone payments to HCRx.

On October 31, 2023, we entered into an amended and restated Pierre Fabre Commercialization Agreement (A&R Commercialization Agreement), pursuant to which we expanded Pierre Fabre's exclusive rights to research, develop, manufacture, commercialize and distribute tab-cel (Ebvallo) to include all other countries in the world (Additional Territory) in addition to the Initial Territory (together, the Territory), subject to our performance of certain obligations as described below. In December 2023, upon the effective date of the A&R Commercialization Agreement, we met the contractual right to receive an additional upfront cash payment of $20.0 million for the expanded exclusive license grant, for which the cash was received in January 2024. In March 2024, we met the contractual right to receive $20.0 million in milestone payments upon achieving a regulatory milestone, for which the cash was received in April 2024. In July 2024, we met the contractual right to receive an additional $20.0 million in milestone payments upon achieving acceptance of our biologics license application (BLA) for tab-cel by the United States Food and Drug Administration

(FDA) and we received the cash in August 2024. In March 2025, we completed the transfer of all manufacturing responsibility to Pierre Fabre under the A&R Commercialization Agreement Amendment. Pierre Fabre is now responsible for manufacturing and supplying tabelecleucel for development and commercialization worldwide at its cost. Pursuant to the A&R Commercialization Agreement Amendment, Pierre Fabre has also agreed to assume the costs related to remediation of the third-party manufacturing facility to address the FDA's requests to support resubmission of the BLA for tab-cel. In exchange for accelerating the transfer of all manufacturing responsibility and assumption of such remediation costs by Pierre Fabre, among other things, we agreed to reduce the amount of certain potential future regulatory and commercial milestone payments under the A&R Commercialization Agreement. In July 2025, we further amended the A&R Commercialization Agreement and completed the transfer of all clinical (including sponsorship of the ALLELE and tab-cel multi-cohort studies) and development responsibility to Pierre Fabre. Pierre Fabre is, at its cost, responsible for all clinical (including sponsorship of the ALLELE and tab-cel multi-cohort studies) and development activities (other than responsibility for regulatory activities) for tabelecleucel worldwide. In October 2025, we further amended the A&R Commercialization Agreement to transfer all regulatory activities (including sponsorship of the tab-cel BLA) to Pierre Fabre. Pierre Fabre is, at its cost, responsible for all regulatory activities (including sponsorship of the tab-cel BLA) for tab-cel worldwide, and Pierre Fabre is to use commercially reasonable efforts to obtain BLA approval as soon as possible. We will, at Pierre Fabre's expense, continue to observe the regulatory activities and support Pierre Fabre in its efforts to obtain BLA approval. In December 2025, we amended the A&R Commercialization Agreement to, among other things, mitigate the impact of the cost of rebuilding commercial inventory in the United States. We agreed to reduce the milestone payment due upon BLA approval of tab-cel to $31 million in exchange for the right to receive an additional $15 million potential milestone payment upon achieving a certain commercial milestone. Under the terms of the A&R Commercialization Agreement, as amended by the A&R Commercialization Agreement Amendment, we are entitled to receive an aggregate of up to $308 million in remaining milestone payments upon achieving certain regulatory and commercial milestones relating to tab-cel in the Initial Territory, and an aggregate of up to $556 million in additional potential milestone payments upon achieving certain regulatory and commercial milestones relating to tab-cel in the Additional Territory, including up to $31.0 million in potential regulatory milestones in connection with the approval by the FDA of a BLA for tab-cel. We are also eligible to receive significant double-digit tiered royalties as a percentage of net sales of tab-cel (Ebvallo) in the Territory until the later of 12 years after the first commercial sale in each such country, the expiration of specified patent rights in each such country, or the expiration of all regulatory exclusivity for tab-cel in each such country. Royalty payments may be reduced in certain specified customary circumstances. Royalties and milestones from the commercialization of Ebvallo in the Initial Territory remain subject to the HCRx Agreement.

We entered into research collaborations with leading academic institutions such as Memorial Sloan Kettering Cancer Center (MSK) and the Council of the Queensland Institute of Medical Research (QIMR Berghofer) pursuant to which we acquired rights to novel and proprietary technologies and programs. In May 2025, we returned the rights to the ATA188 and EBV Vaccine programs to QIMR.

We and FUJIFILM Diosynth Biotechnologies California, Inc. (FDB) entered into a Master Services and Supply Agreement (Fujifilm MSA), which became effective in April 2022 and could extend for up to ten years. Pursuant to the Fujifilm MSA, FDB will supply us with specified quantities of our cell therapy products (if approved) and product candidates, manufactured in accordance with cGMP standards. The Fujifilm MSA does not obligate us to purchase products and product candidates exclusively from FDB. In March 2025, in connection with the transition of manufacturing responsibility for tab-cel to Pierre Fabre, we assigned and Pierre Fabre assumed, the Fujifilm MSA.

We had non-cancellable minimum commitments for products and services, subject to agreements with a term of greater than one year, with CROs and CMOs. In March 2025, the CMO agreements were assigned to Pierre Fabre as part of the A&R Commercialization Agreement Amendment, and we have been relieved of our obligations under the CMO agreements as of June 30, 2025. In July 2025, the CRO agreements were assigned to Pierre Fabre and we have been relieved of our obligations under the CRO agreements.

We have executed various strategic reductions in force over the past several years. In November 2023, we announced a reduction in force of approximately 30% of our workforce at that time. This workforce reduction resulted in total restructuring charges of $6.7 million, comprised primarily of severance payments and wages for the 60-day notice period in accordance with the California Worker Adjustment and Retraining Notification (WARN) Act. In most cases, the severance payments were paid as a lump sum in January 2024. As of December 31, 2025, there are no remaining payments for the November 2023 reduction in force. All of the costs were cash expenditures and represent one-time termination benefits.

In January 2024, we announced a reduction in force at that time of approximately 25%. The workforce reduction resulted in total restructuring charges of $5.1 million, comprised primarily of severance payments and wages for the 60-day notice period in accordance with the California WARN Act. In most cases, the severance payments were paid during the first half of 2024. Certain of the notified employees had employment agreements that provided for separation benefits in the form of salary continuation, which were paid from February 2024 through January 2025. As of December 31, 2025, there are no remaining payments for the January 2024 reduction in force. The majority of the associated costs were cash expenditures and primarily represented one-time termination benefits.

In January 2025, we announced another reduction in force at that time of approximately 50%. We recognized approximately $7.2 million in total severance and related benefits as a result of this reduction in force, consisting primarily of severance payments and wages for the 60-day notice period in accordance with the California WARN Act. In most cases, the severance was paid in the first half of 2025. Certain of the notified employees had employment agreements which provided for separation benefits in the form of salary continuation; these benefits will be paid by May 2026. As of December 31, 2025, approximately $0.5 million of further separation payments and benefits are required for the January 2025 reduction in force. The associated costs represent cash expenditures and primarily represent one-time termination benefits.

In January 2025, the U.S. Food and Drug Administration (FDA) issued a Complete Response Letter (Response Letter) for the Biologics License Application (BLA) for tab-cel as monotherapy treatment for adult and pediatric patients two years of age and older with Epstein-Barr virus positive post-transplant lymphoproliferative disease (EBV+ PTLD), who have received at least one prior therapy including an anti-CD20 containing regimen. The Response Letter only cited findings that arose during a pre-license inspection of a third-party manufacturing facility for tab-cel. The Response Letter did not identify any deficiencies related to the manufacturing process, the clinical efficacy, or clinical safety data in the BLA, and the FDA did not request any new clinical trials to support a potential approval of tab-cel. Additionally, in January 2025, the FDA placed a clinical hold on Atara's active Investigational New Drug (IND) applications. These INDs include the tab-cel program as monotherapy treatment for adult and pediatric patients two years of age and older with Epstein-Barr virus positive post-transplant lymphoproliferative disease (EBV+ PTLD). The clinical hold is directly linked to inadequately addressed Good Manufacturing Practices (GMP) compliance issues referenced in the Response Letter. In May 2025, the FDA notified us that we have satisfactorily addressed all clinical hold issues and the FDA has lifted the clinical holds. In May 2025, we aligned with the FDA on a plan to address the issues raised by the FDA in the Response Letter and the path forward for resubmission of the tab-cel BLA at a Type A meeting. In July 2025, we resubmitted, and the FDA accepted, the tab-cel BLA. In January 2026, the FDA issued a second Complete Response Letter (Second Complete Response Letter) for the BLA for tab-cel as monotherapy treatment for adult and pediatric patients two years of age and older with EBV+ PTLD, who have received at least one prior therapy including an anti-CD20 containing regimen. In the Second Complete Response Letter, the FDA confirmed that the GMP compliance issues identified in the Response Letter had been satisfactorily resolved, and importantly, no safety issues were raised. However, the Second Complete Response Letter claims that ALLELE trial, previously confirmed by the FDA as adequate to support the BLA filing, is no longer considered to be an adequate and well-controlled study due to deficiencies in study design, conduct and analysis, to provide substantial evidence of effectiveness of tab-cel to treat relapsed or refractory EBV+ PTLD. In March 2026, our partner, Pierre Fabre, submitted a request for, and the FDA has granted, a Type A meeting to address the FDA's concerns in the Second Complete Response Letter. We anticipate providing a regulatory update in the second quarter of 2026.

In March 2025, we announced a further reduction in force at that time of approximately 50%. We recognized approximately $2.8 million in total severance and related benefits as a result of this reduction in force, consisting primarily of severance payments and wages for the 60-day notice period in accordance with the California WARN Act. In most cases, the severance was paid in the first half of 2025. Certain of the notified employees had employment agreements which provided for separation benefits in the form of salary continuation; these benefits will be paid by May 2026. As of December 31, 2025, approximately $0.1 million of further separation payments and benefits are required for the March 2025 reduction in force. The associated costs represent cash expenditures and primarily represent one-time termination benefits.

In May 2025, we announced a further reduction in force at that time of approximately 30%. We recognized approximately $1.4 million in total severance and related benefits as a result of this reduction in force, consisting primarily of severance payments and wages for the 60-day notice period in accordance with the California WARN Act. In most cases, the severance was paid in the second half of 2025. As of December 31, 2025, no further separation payments and benefits are required for the May 2025 reduction in force.

In October 2025, we announced a further reduction in force of approximately 30% of total workforce, retaining approximately 15 employees essential to advancing our strategic priorities. We recognized approximately $1.2 million in total severance and related benefits as a result of this reduction in force. Approximately 50% of these charges are salary continuation payments and wages for the 60-day notice period in accordance with the California WARN Act. As of December 31, 2025, approximately $0.3 million of further separation payments and benefits are required for the October 2025 reduction in force. The associated costs are cash expenditures and primarily represent one-time termination benefits.

Legislative and Regulatory Developments

On July 4, 2025, President Trump signed the tax law referred to as One Big Beautiful Bill Act ("OBBBA"). OBBBA includes a broad range of U.S. tax reform measures, including, among other provisions, the immediate expensing of U.S. research and development expenditures. In accordance with ASC 740, the Company has recognized the effects of the new tax law in the period of enactment. As the Company maintains a full valuation allowance on its U.S. deferred tax assets, the legislation does not have a material impact on its consolidated financial statements.

In March 2021, the American Rescue Plan Act of 2021 ("ARPA") was enacted. Among other provisions, ARPA expanded the scope of Internal Revenue Code Section 162(m) by increasing the number of covered employees subject to the $1 million limitation on the deductibility of compensation, effective for taxable years beginning after December 31, 2026. The Company evaluated the impact of this provision, including its potential effect on the deductibility of executive compensation and related deferred tax balances. Based on this evaluation, the Company concluded that the enactment of ARPA did not have a material impact on its income tax provision.

Review of Strategic Alternatives

Our board of directors regularly reviews our strategic plan, priorities, and opportunities as part of its commitment to act in the best interest of the Company and its stockholders. In January 2025, we announced that we had previously engaged a well-known financial advisor to support the assessment of opportunities to advance and realize value from our CAR T assets, for which we announced in March 2025 that we paused development. The advisor's scope was expanded to include a wider range of additional strategic alternatives designed to maximize value for our stockholders, which may include, but are not limited to, an acquisition, merger, reverse merger, other business combinations, sale of assets, licensing, or other strategic transactions. Through this process, we were in active discussions with several potential parties. However, there can be no assurance regarding the results or outcome of this process. It is possible that we may not pursue a strategic alternative or transaction or that any strategic alternative or transaction, if pursued, will not be completed on attractive terms, or that a strategic alternative or transaction may not ultimately be consummated. Our board of directors continues to evaluate potential strategic transactions.

Financial Overview

We have a limited operating history. Since our inception in 2012, we have devoted substantially all of our resources to identify, acquire and develop our product candidates, including conducting preclinical and clinical studies, acquiring or manufacturing materials for clinical studies, and providing general and administrative support for these operations.

Our net income (loss) was $32.7 million and $(85.4) million for the years ended December 31, 2025 and 2024, respectively. As of December 31, 2025, we had an accumulated deficit of $2.0 billion. Substantially all of our net losses have resulted from costs incurred in connection with our research and development programs and from general and administrative expenses associated with our operations. As of December 31, 2025, our cash, cash equivalents and short-term investments totaled $8.5 million, which we intend to use to fund our operations.

Revenues

We have generated commercialization revenues under the A&R Commercialization Agreement, following the December 2022 EC approval of Ebvallo. Our commercialization revenue recognized to date is derived from agreements with Pierre Fabre, primarily related to upfront license fees, milestone payments and amounts recognized from the sale of zero-cost inventories for which all performance obligations are complete, and is subject to the terms of the HCRx Agreement. We do not retain any meaningful milestone or royalty payments related to the Initial Territory under the A&R Commercialization Agreement until the applicable royalty cap under the HCRx Agreement is met, if at all, and milestone or royalty payments related to the Additional Territory under the A&R Commercialization Agreement are subject to us obtaining regulatory approval in the US or for another market within the Additional Territory.

We expect that any revenue we generate from the A&R Commercialization Agreement, subject to the terms of the HCRx Agreement, will fluctuate from period to period as a result of the timing of potential milestone achievement and any potential regulatory approvals.

Cost of Commercialization Revenue

Cost of commercialization revenue consists primarily of expenses associated with cell selection services performed for Pierre Fabre, in-license sales-related milestone costs, period manufacturing expenses and the lower of cost or net realizable value

adjustments to inventories. Costs incurred to produce Ebvallo prior to regulatory approval, referred to as zero cost inventories, have been recorded as research and development expense in our consolidated statement of operations and comprehensive income (loss). Cost of commercialization revenue for Ebvallo produced after receiving regulatory approval and in a qualified manufacturing facility also include direct and indirect costs related to the production of Ebvallo. Such costs are recorded into cost of commercialization revenue as the related commercialization revenue is recognized. Such costs include, but are not limited to, CMO costs, quality testing and validation, materials used in production, and an allocation of compensation, benefits and overhead costs associated with employees involved with production.

Research and Development Expenses

The largest component of our total operating expenses since inception has been our investment in research and development activities, including the preclinical and clinical development of our product candidates. Research and development expenses consist primarily of compensation and benefits for research and development and regulatory support employees, including stock-based compensation; expenses incurred under agreements with contract research organizations and investigative sites that conduct preclinical and clinical studies; the costs of acquiring and manufacturing clinical study materials and other supplies, including expenses incurred under agreements with CMOs; payments under licensing and research and development agreements; other outside services and consulting costs; and facilities, information technology and overhead expenses. Research and development costs are expensed as incurred.

Our expenditures on future preclinical and clinical development programs are subject to numerous uncertainties in timing and cost to completion. The duration, costs, and timing of clinical studies and development of our product candidates will depend on a variety of factors, including:

The process of conducting the necessary clinical research to obtain approval from the FDA and other regulators is costly and time consuming and the successful development of our product candidates is highly uncertain. The risks and uncertainties associated with our research and development projects are discussed more fully in the section of this report titled "1A. Risk Factors." As a result of these risks and uncertainties, we are unable to determine with any degree of certainty the duration and completion costs of our research and development projects, or if, when, or to what extent we will generate revenues from the commercialization and sale of any of our product candidates that obtain regulatory approval.

General and Administrative Expenses

General and administrative expenses consist primarily of compensation and benefits for legal, human resources, finance and other general and administrative employees, including stock-based compensation; professional services costs, including legal, patent, human resources, audit and accounting services; other outside services; and consulting costs; and information technology and overhead expenses.

Interest Income

Interest income consists of interest earned on our cash, cash equivalents and short-term investments.

Interest Expense

Interest expense consists primarily of interest expense recorded in connection with the HCRx Agreement.

Provision for Income Taxes

Provision for income taxes consists primarily of income taxes in U.S. states and foreign jurisdictions. Our effective tax rate was 0.1% and 0% for the years ended December 31, 2025 and 2024, respectively.

Critical Accounting Policies and Significant Estimates

Our management's discussion and analysis of our financial condition and results of operations is based on our consolidated financial statements, which have been prepared in accordance with accounting principles generally accepted in the U.S. The preparation of these financial statements requires us to make estimates and assumptions that affect the reported amounts of assets, liabilities and expenses. On an on-going basis, we evaluate our critical accounting policies and estimates. We base our estimates on historical experience and on various other assumptions that we believe to be reasonable in the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ from these estimates under different assumptions and conditions. Our significant judgments and estimates are detailed below, and our significant accounting policies are more fully described in Note 2 of the accompanying consolidated financial statements.

Revenue Recognition

Revenue from out-license agreements is recognized as we satisfy performance obligations and when a customer obtains control of the promised goods or services, in an amount that reflects the consideration which we expect to receive in exchange for those goods or services. Revenue generated from our out-license agreements is not subject to repayment and typically includes upfront fees, development, regulatory and commercial milestone payments and royalties on the licensee's future product sales.

Our out-license agreements may include the transfer of intellectual property rights in the form of licenses, promises to provide research and development services and promises to participate on certain development committees with the collaboration party. We assess whether the promises in these agreements are considered distinct performance obligations that should be accounted for separately. Judgment is required to determine whether these promises are distinct.

The transaction price in each agreement is allocated to the identified performance obligations based on the standalone selling price (SSP) of each distinct performance obligation.

Revenue associated with nonrefundable upfront license fees where the license fees and other promises cannot be accounted for as separate performance obligations is deferred and recognized as revenue over the expected period of performance using an appropriate recognition method based on the nature of the performance obligations. We utilize judgment to assess the pattern of delivery of the performance obligation. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition. A significant change in the assumptions and estimates, such as forecasted costs or the extent and timing of patient demand, and expected dates of technology transfer, could have a material impact on the timing and amount of revenue recognized in future periods or adjustments to cumulative revenue recognized in the period of change.

At the inception of each agreement that includes development, regulatory or commercial milestone payments, we evaluate whether the milestones are considered probable of being reached and estimate the amount to be included in the transaction price by using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. The transaction price is allocated to each performance obligation in the agreement based on relative SSP. We typically determine SSPs using a cost plus margin approach model. Milestone payments that are not within our or the licensee's control, such as regulatory approvals, are typically not considered probable of being achieved until those approvals are received. At the end of each reporting period, we re-evaluate the probability of achievement of each such milestone and any related constraint, and if necessary, adjust our estimates of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment.

Certain judgments affect the application of our revenue recognition policy. For example, we record short-term and long-term deferred revenue based on our best estimate of when such revenue will be recognized. Short-term deferred revenue consists of amounts that are expected to be recognized as revenue in the next 12 months, and long-term deferred revenue consists of amounts that we expect will be recognized after the next 12 months. As of December 31, 2025, this estimate is based on our forecasted regulatory

operating plan. If the duration or the scope of the tab-cel regulatory activities change in the future, we may recognize a different amount of deferred revenue over the next 12-month period.

Accrued Research and Development Expenses

As part of the process of preparing our financial statements, we are required to estimate and accrue expenses, the largest of which is related to research and development expenses, including those related to clinical studies and clinical product candidate manufacturing. This process involves reviewing contracts and purchase orders, identifying and evaluating the services that have been performed on our behalf, and estimating the associated cost incurred for the services which we have not yet been invoiced or otherwise notified of the actual costs incurred.

Costs for preclinical studies, clinical studies and product candidate manufacturing activities are recognized based on an evaluation of our vendors' progress towards completion of specific tasks, using data such as patient enrollment, clinical site activations or information provided to us by our vendors regarding their actual costs incurred. Payments for these activities are based on the terms of individual contracts and payment timing may differ significantly from the period in which the services were performed. We determine accrual estimates through reports from, and discussions with, applicable personnel and outside service providers as to the progress or state of completion of studies, or the goods and services delivered. Our estimates of accrued expenses as of each balance sheet date are based on the facts and circumstances known at the time. Costs that are paid in advance of performance are deferred as a prepaid asset and recognized as expense as the services are provided.

For the years ended December 31, 2025 and 2024, there were no material changes from our estimates of accrued research and development expenses. We do not believe there is a reasonable likelihood that there will be a material change in the future estimates of accrued research and development expenses. However, if actual results are not consistent with our estimates, we may be exposed to changes in accrued research and development expenses that could be material or the accrued research and development expenses reported in our financial statements may not be representative of the actual economic cost of accrued research and development.

Stock-based Compensation

We have stock-based compensation programs, which include an employee incentive plan, an inducement plan and an employee stock purchase plan. See Note 2 - "Summary of Significant Accounting Policies" and Note 10 - "Stockholders' Equity" in the Notes to Consolidated Financial Statements, included in Item 8. Financial Statements and Supplementary Data of this report for a complete discussion of our stock-based compensation programs. We account for stock-based compensation expense, including the expense for grants of restricted stock units (RSUs) and stock options that may be settled in shares of our common stock, based on the fair values of the equity instruments issued. The fair value is determined on the measurement date, which is generally the date of grant. The fair value of our RSUs is measured at the market price of our common stock on the measurement date. The fair value for our stock option awards is determined at the grant date using the Black-Scholes valuation model.

Assumptions for the Black-Scholes valuation model used for employee stock awards include:

The fair value of our common stock is measured at the market price on the measurement date. For awards with performance-based vesting criteria, we assess the probability of the achievement of the performance conditions at the end of each reporting period and begin to recognize the share-based compensation costs when it becomes probable that the performance conditions will be met. For awards that are subject to both service and performance conditions, no expense is recognized until it is probable that performance conditions will be met. We do not believe there is a reasonable likelihood that there will be a material change in the future estimates or assumptions we use to determine stock-based compensation expense. However, if actual results are not consistent with our estimates or assumptions, we may be exposed to changes in stock-based compensation expense that could be material or the stock-based compensation expense reported in our financial statements may not be representative of the actual economic cost of the stock-based compensation.

Accounting for Income Taxes

See Note 11 - "Income Taxes" in the Notes to Consolidated Financial Statements, included in Item 8. Financial Statements and Supplementary Data of this report for a complete discussion of the components of our income tax expense, if any, as well as the temporary differences that exist as of December 31, 2025.

Our consolidated effective income tax rate is influenced by tax planning opportunities available to us in the various jurisdictions in which we conduct business. Significant judgment is required in evaluating our tax positions, including those that may be uncertain. We are also required to exercise judgment with respect to the realization of our net deferred tax assets. We evaluate all positive and negative evidence and exercise judgment regarding past and future events to determine if it is more likely than not that all or some portion of the deferred tax assets may not be realized. If appropriate, a valuation allowance is recorded against deferred tax assets to offset future tax benefits that may not be realized.

We do not believe that there is a reasonable likelihood that there will be a material change in our liability for uncertain income tax positions or our effective income tax rate. However, if actual results are not consistent with our estimates or assumptions, we may be exposed to losses that could be material. We recorded a valuation allowance of approximately $355.0 million as of December 31, 2025 related primarily to net operating loss carryforwards, and capitalized research expenses.

Liability related to the sale of future revenues

To the extent we account for the sale of future revenues as debt in accordance with ASC 470, we amortize the liability and recognize interest expense related to the sale of future revenues using the effective interest rate method over the estimated life of the underlying agreement. The liability and related interest expense are based on our current estimate of expected future payments over the life of the arrangement. We re-assess the amount and timing of expected payments each reporting period using a combination of internal projections and forecasts from external resources and record interest expense on the carrying value of the liability using the imputed effective interest rate. To the extent our estimates of future payments are greater or less than previous estimates or the estimated timing of such payments is materially different than previous estimates, this could impact the amount of interest expense we record each period as well as the amount and classification of the liability. We will account for any such changes by adjusting the effective interest rate on a prospective basis. The assumptions used in determining the expected repayment term of the liability and amortization period requires that we make estimates that could impact the effective interest rate, short-term and long-term classification of the liability and the period over which the liability will be amortized.

Results of Operations

Comparison of the Years Ended December 31, 2025 and 2024

Revenues

Revenue consisted of the following in the periods presented:

Commercialization revenues were $120.8 million in 2025 as compared to $128.9 million in 2024. The decrease in 2025 was primarily due to a year-over-year reduction in revenue from transition activities after tab-cel manufacturing and clinical activities transitioned to Pierre Fabre in March and July 2025 respectively; the decrease was partially offset by an increase in revenue from the

sale of inventory to Pierre Fabre and higher deferred revenue recognized in 2025 following the transition of manufacturing activities to Pierre Fabre in March 2025.

Cost of commercialization revenue

Cost of commercialization revenue consisted of the following in the periods presented:

Costs of commercialization revenues were $21.2 million in 2025 compared to $21.0 million in 2024. The 2025 cost reflects the cost of the inventory sold to Pierre Fabre on March 31, 2025, according to the A&R Commercialization Agreement, as amended, while the 2024 costs primarily includes expenses recognized associated with adjustments to reflect inventory at net realizable value.

Research and development expenses

Research and development expenses consisted of the following costs, by function, in the periods presented (certain items have been reclassified in prior periods for consistency in presentation):

Technical operations and quality expenses were $21.9 million in 2025 as compared to $92.5 million in 2024. The decrease in 2025 was primarily due to the transition of tab-cel manufacturing activities to Pierre Fabre as of March 31, 2025, reduced headcount following the January, March and May 2025 reductions in force and pause of research and development of the CAR T programs as of March 2025.

Medical and safety expenses were $9.8 million in 2025 as compared to $44.1 million in 2024. The decrease in 2025 was primarily due to reduced headcount following the January, March and May 2025 reductions in force, the transition of tab-cel development activities to Pierre Fabre as of July 14, 2025 and termination of the ATA3219 phase 1 trials in NHL and lupus after the decision to pause research and development for CAR T assets in March 2025.

Regulatory and quality expense were $5.8 million in 2025 as compared to $14.8 million in 2024. The decrease in 2025 was primarily due to reduced headcount following the January, March and May 2025 reductions in force.

General and administrative expenses

General and administrative expenses for the periods indicated were as follows:

General and administrative expenses were $26.3 million in 2025 as compared to $39.9 million in 2024. The decrease in 2025 was primarily due to reduced headcount following the January, March and May 2025 reductions in force.

Other income (expense), net

Interest income was $0.7 million in 2025, as compared to $2.1 million in 2024. The decrease in 2025 was primarily driven by lower balances of cash, cash equivalents and available-for-sale securities.

Interest expense was $3.8 million in 2025 and $4.6 million in 2024. The decrease in 2025 was primarily due to decreased interest expense recognized on the liability related to the sale of future revenues under the HCRx Agreement.

Liquidity and Capital Resources

Sources of Liquidity

Since our inception in 2012, we have funded our operations primarily through the issuance of common and preferred stock, issuance of pre-funded warrants to purchase common stock, upfront fees and milestone payments from the Bayer License Agreement and the A&R Commercialization Agreement and the sale of our ATOM Facility to FDB in 2022.

In the past four years, we have entered into two separate sales agreements with Cowen and Company, LLC (Cowen): in November 2021 (2021 ATM Facility) and in November 2023 (2023 ATM Facility). Each ATM facility provides or provided for the sale, in our sole discretion, of shares of our common stock having an aggregate offering price of up to $100.0 million, through Cowen, as our sales agent. We filed a registration statement on Form S-3 registering the offer and sale of these shares under the Securities Act (2023 Registration Statement). Upon the effectiveness of the 2023 Registration Statement, the 2021 ATM Facility was terminated, and no further sales can be made under the 2021 ATM Facility. The issuance and sale of these shares by us pursuant to the ATM facilities are deemed "at the market" offerings defined in Rule 415 under the Securities Act of 1933, as amended (Securities Act), and were registered under the Securities Act. Commissions of up to 3.0% are due on the gross sales proceeds of the common stock sold under each ATM facility.

In January 2024, we completed a registered direct offering of pre-funded warrants to purchase 1,090,907 shares of common stock at a price of $13.7475 per warrant. We received aggregate net proceeds of $14.8 million after deducting offering expenses payable by us.

In September 2024, we completed a registered direct offering of 758,900 shares of common stock at an offering price of $8.25 per share and pre-funded warrants to purchase 3,604,780 shares of common stock at an offering price of $8.2499 per warrant. We received aggregate net proceeds of $35.8 million after deducting offering expenses payable by us.

In May 2025, we issued and sold 834,237 shares of common stock at an offering price of $6.61 per share and pre-funded warrants to purchase 1,587,108 shares of common stock at an offering price of $6.6099 per warrant in an underwritten registered direct offering pursuant to a shelf registration on Form S-3. The gross proceeds from this sale were $16.0 million, resulting in net proceeds of $14.8 million after deducting underwriting discounts and commissions and offering expenses payable by us.

During the year ended December 31, 2025, we sold an aggregate of 124,434 shares of common stock under the 2023 ATM Facility, at an average price of $12.21 per share, for net proceeds of $1.5 million, after deducting commission expenses payable by us.

As of December 31, 2025, we had $87.2 million of common stock remaining and available to be sold under the 2023 ATM Facility, which, following the filing of this Form 10-K, will be subject to the limitations under General Instruction I.B.6 to Form S-3 discussed below. Subsequent to December 31, 2025, we sold an aggregate of 493,117 shares of our common stock under the 2023 ATM Facility, at an average price of $6.08 per share, for net proceeds of $3.0 million, after deducting commission expenses payable by us.

In March 2025, we completed the transfer of all manufacturing responsibility to Pierre Fabre and Pierre Fabre is, at its cost, responsible for manufacturing and supplying tabelecleucel for development and commercialization worldwide under an amendment to the A&R Commercialization Agreement (A&R Commercialization Agreement Amendment). Pursuant to the A&R

Commercialization Agreement Amendment, Pierre Fabre has also agreed to assume the costs related to remediation of the third-party manufacturing facility to address the FDA's requests to support resubmission of the BLA for tab-cel. In exchange for accelerating the transfer of all manufacturing responsibility and assumption of such remediation costs by Pierre Fabre, among other things, we agreed to reduce the amount of certain potential future regulatory and commercial milestone payments under the A&R Commercialization Agreement.

We have incurred losses and negative cash flows from operations in each year since inception and have generated limited commercialization revenues from the A&R Commercialization Agreement, following the December 2022 EU regulatory approval of Ebvallo, which is subject to the terms of the HCRx Agreement. We do not maintain any meaningful milestone or royalty payments from Pierre Fabre relative to the Initial Territory until the applicable royalty cap under the HCRx Agreement is met, if at all. We continue to incur significant research and development and other expenses related to our ongoing operations and expect to incur losses for the foreseeable future. As a result, we will need additional capital to fund our operations, which we may raise through a combination of equity offerings, debt financings, other third-party funding and other collaborations, strategic alliances and partnering arrangements. We may borrow funds on terms that may include restrictive covenants, including covenants that restrict the operation of our business, liens on assets, high effective interest rates and repayment provisions that reduce cash resources and limit future access to capital markets. In addition, we expect to continue to opportunistically seek access to additional funds through additional public or private equity offerings or debt financings including by utilizing the 2023 ATM Facility, through potential collaboration, partnering or other strategic arrangements, or a combination of the foregoing. To the extent that we raise additional capital by issuing equity securities, our stockholders may experience substantial dilution. To the extent that we raise additional funds through collaboration or partnering arrangements, we may be required to relinquish some of our rights to our technologies or rights to market and sell our products in certain geographies or grant licenses or other rights on terms that are not favorable to us.

As of the date of this Form 10-K, our public float was less than $75 million. As a result, we are subject to the limitations of General Instruction I.B.6 to Form S-3 until such time as our public float exceeds $75 million, which means we only have the capacity to sell shares up to one-third of our public float under shelf registration statements in any twelve-month period. We will remain constrained by the limitations of General Instruction I.B.6 to Form S-3 until such time as our public float exceeds $75 million, at which time the number of securities we may sell under a Form S-3 registration statement will no longer be limited by limitations of General Instruction I.B.6 to Form S-3.

Cash in excess of immediate requirements is invested in accordance with our investment policy, primarily with a view to liquidity and capital preservation. Currently, our cash, cash equivalents and short-term investments are held in bank and custodial accounts and consist of money market funds, U.S. Treasury, and corporate debt obligations.

Our cash, cash equivalents and short-term investments balances as of the dates indicated were as follows:

Contractual Obligations and Commitments

In November 2018, we entered into a lease agreement for office space in Thousand Oaks, California, that expires in February 2026 and for which we have the option to extend the lease for an additional period of five years after the initial term. In February 2025, we vacated this office space prior to the termination of the lease, resulting in the right-of-use asset to be abandoned. When a lease right-of-use asset has been abandoned, the estimated useful life of the asset is updated to reflect the cease use date, and the remaining carrying value of the asset is amortized ratably over the period between the commitment date and the cease use date. In February 2025, with the abandonment of the lease, we recognized an acceleration of amortization expense on the abandoned right-of-use asset in the amount of $1.0 million within general and administrative expenses on the accompanying consolidated statements of operations and comprehensive income (loss) for the year ended December 31, 2025. The lease liability for the Thousand Oaks office remains on our balance sheet.

In March 2021, we entered into a lease agreement for the 33,659 square feet of office, lab and warehouse space at the Atara Research Center (ARC). During the third quarter of 2021, the initial 10.5-year lease term commenced, upon substantial completion of the landlord's work as defined under the agreement. Base rent is subject to annual increases of 3% with each annual anniversary of the rent commencement date. In March 2025, we announced a pause on our CAR T research and development activities and initiated the

wind-down of the ARC facility. We considered this to be a triggering event and performed an impairment analysis on the right-of-use asset. In April 2025, we recorded a non-cash impairment of the right-of-use asset of $4.1 million, representing the amount by which the carrying value of the right-of-use asset exceeded its estimated fair value. We recorded the impairment loss within research and development expenses on the accompanying consolidated statements of operations and comprehensive income (loss). In August 2025, we executed an amendment to the ARC lease that reduced our leased premises to 12,750 square feet and terminated our option to extend the lease. We determined that this amendment constituted a triggering event resulting in a partial lease termination modification. For the year ended December 31, 2025, we recorded a non-cash reduction of $3.4 million to the right-of-use asset to reflect the decrease in the asset's value following the lease modification. The modification also reduced the related lease liability, generating a $6.0 million gain. Overall, these changes resulted in a net gain of $2.6 million within research and development expenses on the accompanying consolidated statements of operations and comprehensive income (loss). The remaining right-of-use asset and lease liability associated with the ARC facility continue to be reflected on our balance sheet.

In February 2017, we entered into a lease agreement (the ATOM Lease) for approximately 90,580 square feet of office, lab and cellular therapy manufacturing space in Thousand Oaks, California (the ATOM Facility). The initial 15-year term of the headlease commenced on February 15, 2018, upon the substantial completion of landlord's work as defined under the agreement. In April 2022, we assigned the ATOM Lease to FDB in connection with the closing of the sale of the ATOM Facility to FDB. Under ASC 842, we are considered to be the sub-lessor of the ATOM Lease. We have not received novation from the landlord and therefore have not been relieved of our primary obligations under the headlease. Therefore, the right-of-use asset and lease liability for the ATOM Facility remain on our balance sheet. Given the continued use of the ATOM lease by another party, we did not consider there to be a trigger for valuation considerations following our restructuring activities. See Note 7 - "Leases" in the Notes to Consolidated Financial Statements, included in Item 8. Financial Statements and Supplementary Data of this report for further information on our lease obligations.

We evaluated our vendor contracts to identify embedded leases and determined that the Master Services and Supply Agreement (Fujifilm MSA) we entered into with FUJIFILM Diosynth Biotechnologies California, Inc. (FDB) contained items that constituted a lease under ASC 842, Leases, as Atara has the right to substantially all of the economic benefits from the use of the asset and can direct the use of the asset. We concluded that the Fujifilm MSA contains an embedded operating lease for certain dedicated processing rooms for the manufacturing of Atara product and an embedded finance lease for certain freezers dedicated for our use. The Fujifilm MSA includes contractual obligations in the form of payments for the processing rooms and the freezers, each over a term of five years. As a result, we added right-of-use assets and lease liabilities for the processing rooms and freezers for the initial term of the lease in the amounts of $50.8 million and $4.8 million, respectively. In November 2023, we agreed to forego the use of one processing room for approximately one year in return for a reduction in contractual obligations under the Fujifilm MSA, and in November 2024, we exercised the option to release the processing room to FDB for the remainder of the initial term. The Fujifilm MSA was novated to Pierre Fabre in March 2025 as part of the A&R Commercialization Agreement Amendment. As of June 30, 2025, we were relieved of our primary obligations under the Fujifilm MSA. Therefore, the right-of-use assets and lease liabilities for the processing rooms and the freezers have been removed from our consolidated balance sheet as of June 30, 2025.

Additionally, in 2021, we entered into an amended lease agreement (Aurora Lease) for our office and lab space in Aurora, Colorado, to add additional lab space and in November 2023, we further amended the Aurora Lease to extend the term to April 2025. The lease agreement expired on April 30, 2025, and the right-of-use asset and lease liability for the Aurora Lease are no longer on our balance sheet.

We originally leased office space in South San Francisco, California under a non-cancellable lease agreement. In December 2021, we entered into a second amendment with the landlord to extend the lease term through May 2025. The amended lease agreement does not include an option to extend the lease term. In connection with the amended lease, we were required to maintain a letter of credit in the amount of $0.1 million to the landlord. In October 2022, we entered into a sub-lease agreement with a third party for this office space. The sub-lease term commenced in November 2022 and expired in May 2025. At the expiration of the lease in May 2025 our right-of-use asset and lease liability for the South San Francisco office were removed from our balance sheet and the requirement to maintain a letter of credit was released.

We enter into contracts in the normal course of business with clinical research organizations for clinical studies, with CMOs for clinical and commercial materials, and with other vendors for preclinical studies and supplies and other services and products for operating purposes. These contracts generally provide for termination for convenience following a notice period. We have non-cancellable minimum commitments for products and services, subject to agreements with a term of greater than one year with clinical research organizations and CMOs. See Note 9 - "Commitments and Contingencies" in the Notes to Consolidated Financial Statements, included in Item 8. Financial Statements and Supplementary Data of this report for further information on our contractual obligations and commitments.

Cash Flows

Comparison of the Years Ended December 31, 2025 and 2024

The following table details the primary sources and uses of cash for each of the periods set forth below:

Operating activities

Net cash used in operating activities was $50.9 million in 2025 as compared to $68.7 million in 2024. The decrease of $17.8 million was primarily due to lower cash operating expenses in 2025 as compared to 2024, primarily due to lower compensation-related costs resulting from lower headcount driven by January, March and May 2025 reductions in force, as well as transition of tab-cel manufacturing activities to Pierre Fabre in March 2025.

Investing activities

Net cash provided by investing activities in 2025 consisted of $25.1 million received from maturities and sales of available-for-sale securities and $0.9 million in sales of property and equipment, partially offset by $7.9 million used to purchase available-for-sale securities.

Net cash provided by investing activities in 2024 consisted primarily of $28.5 million received from maturities and sales of available-for-sale securities, partially offset by $19.7 million used to purchase available-for-sale securities and $0.2 million in purchases of property and equipment.

Financing activities

Net cash provided by financing activities in 2025 consisted primarily of $14.8 million of net proceeds from sale of common stock and pre-funded warrants in underwritten registered direct offering, and $1.5 million of net proceeds from 2023 ATM facility.

Net cash provided by financing activities in 2024 consisted primarily of $50.6 million from sale of common stock and pre-funded warrants in registered direct offerings and $9.3 million of net proceeds from ATM facilities.

Operating Capital Requirements and Plan of Operations

We do not know when, or if, we will generate sufficient revenue from commercialization to offset our operating expenses. We anticipate that we will continue to generate losses for the foreseeable future, and we expect the accumulated losses to increase as we continue the development of, and seek regulatory approvals for, our product candidate. We are subject to all of the risks inherent in the development of new products, and we may encounter unforeseen expenses, difficulties, complications, delays and other unknown factors that may adversely affect our business. We anticipate that we will need to raise substantial additional funding in the near term to finance our planned operations.

Our operating plan may change as a result of many factors currently unknown to us, and we may need additional funds sooner than planned. We do not have any committed external source of funds other than milestone and royalty payments that we may receive under the A&R Commercialization Agreement, subject to the terms of the HCRx Agreement. We do not retain any meaningful milestone or royalty payments related to the Initial Territory from Pierre Fabre until the applicable royalty cap under the HCRx Agreement is met, if at all.

Our existing cash, cash equivalents and short-term investments as of December 31, 2025 will not be sufficient to fund our planned operations for at least the next 12 months after the date of issuance of these financial statements. These conditions raise substantial doubt about our ability to continue as a going concern for at least 12 months after the issuance of the accompanying consolidated financial statements.

In order to complete the process of obtaining regulatory approval for tab-cel in the US, we may require substantial additional funding. We expect to continue to seek access to additional funds through additional public or private equity offerings or debt financings, through potential collaboration, partnering or other strategic arrangements, or a combination of the foregoing. If we are unable to obtain sufficient funding on acceptable terms, we could be forced to further delay, limit, reduce or terminate clinical studies or other development activities.

We have based our projections of operating capital requirements on assumptions that may prove to be incorrect, and we may use all of our available capital resources sooner than we expect. Because of the numerous risks and uncertainties associated with research, development and commercialization of pharmaceutical products, we are unable to estimate the exact amount of our operating capital requirements. Our future funding requirements will depend on many factors, including, but not limited to:

Until we are able to generate a sufficient amount of net cash inflows from operations, which we may never do, meeting our long-term capital requirements is in large part reliant on access to public and private equity and debt capital markets, augmented by cash generated from operations and interest income earned on the investment of our cash balances. We expect to continue to seek access to the equity and debt capital markets to support our development efforts and operations. To the extent that we raise additional capital by issuing equity securities, our stockholders may experience substantial dilution. To the extent that we raise additional funds through commercialization, collaboration or partnering arrangements, we may be required to relinquish some of our rights to our technologies or rights to market and sell our products in certain geographies, grant licenses or other rights on terms that are not favorable to us, or issue equity that may be substantially dilutive to our stockholders.

As a result of economic conditions, general global economic uncertainty, political change and other factors, we do not know whether additional capital will be available when needed, or that, if available, we will be able to obtain additional capital on reasonable terms. If we are unable to raise additional capital due to the volatile global financial markets, general economic uncertainty or other factors, we will be forced to delay, limit, reduce or terminate preclinical studies, clinical studies or other development activities for one or more of our product candidates.