DEF 14A

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a)

of the Securities Exchange Act of 1934

(Amendment No.__)


Filed by the Registrant		☒
Filed by a Party other than the Registrant		☐

Check the appropriate box:


☐		Preliminary Proxy Statement
☐		Confidential, for Use of the Commission only (as permitted by Rule 14a-6(e)(2))
☒		Definitive Proxy Statement
☐		Definitive Additional Materials
☐		Soliciting Material Pursuant to § 240.14a-12

Atara Biotherapeutics, Inc.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement if Other Than the Registrant)

Payment of Filing Fee (Check all boxes that apply):


☒	No fee required.
☐	Fee paid previously with preliminary materials.
☐	Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

ATARA BIOTHERAPEUTICS, INC.

1280 Rancho Conejo Boulevard

Thousand Oaks, CA 91320

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

To Be Held on June 9, 2026

Dear Stockholder:

You are cordially invited to attend the Annual Meeting of Stockholders (the “Annual Meeting”) of Atara Biotherapeutics, Inc., a Delaware corporation. The meeting will be held virtually via live audio webcast on June 9, 2026 at 9:00 a.m. Pacific time for the following purposes:

To elect our two nominees for director named in the accompanying Proxy Statement to hold office until the 2029 Annual Meeting of Stockholders;

To approve, on an advisory basis, the compensation of our named executive officers, as disclosed in the Proxy Statement accompanying this Notice;

To approve the first amendment to our 2024 Equity Incentive Plan to increase the number of shares of common stock reserved for issuance thereunder by 400,000;

To ratify the selection by the Audit Committee of our Board of Directors of Deloitte & Touche LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2026; and

To conduct any other business properly brought before the Annual Meeting.

These items of business are more fully described in the Proxy Statement accompanying this Notice. This Notice is not a form for voting and presents only an overview of the more complete proxy materials, which contain important information. You should access and review all proxy materials before voting. The Proxy Statement accompanying this Notice contains instructions on how to access our proxy materials and vote online, or in the alternative, request a paper copy of the proxy materials and a proxy card. The record date for the Annual Meeting is April 14, 2026 (the “Record Date”). Only stockholders of record at the close of business on that date may vote at the meeting or any adjournment thereof.

To increase access for all our stockholders, we have determined that it is prudent to hold this year’s Annual Meeting in a virtual-only format via live audio webcast. You may attend the virtual Annual Meeting at www.virtualshareholdermeeting.com/ATRA2026. To participate in the Annual Meeting, you will need the 16-digit control number that appears on your Notice of Internet Availability of Proxy Materials, proxy card or the instructions that accompanied your proxy materials. Refer to the “Questions and Answers About These Proxy Materials and Voting” section of the accompanying Proxy Statement for detailed procedures regarding attending, submitting questions and voting at the virtual Annual Meeting.

A list of stockholders entitled to vote at the meeting will be available for examination during normal business hours for ten days prior to the meeting for any purpose germane to the meeting at our corporate headquarters at 1280 Rancho Conejo Boulevard, Thousand Oaks, CA 91320.

By Order of the Board of Directors

/s/AnhCo Nguyen

AnhCo Nguyen, Ph.D.

President and Chief Executive Officer

Thousand Oaks, California

April 24, 2026

     Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting of Stockholders to Be Held on June 9, 2026 at 9:00 a.m. Pacific time held virtually at www.virtualshareholdermeeting.com/ATRA2026. The Proxy Statement and Atara’s Annual Report on Form 10-K for the fiscal year 2025 are available electronically at www.proxyvote.com.

    

     Proxy materials or this Notice are being first released or mailed on or about April 27, 2026, to all stockholders entitled to vote at the Annual Meeting. In accordance with rules and regulations adopted by the Securities and Exchange Commission, instead of mailing a printed copy of our proxy materials to each record stockholder, we may furnish proxy materials by providing internet access to those documents.

    

     You are cordially invited to attend the Annual Meeting virtually via live audio webcast. Whether or not you expect to attend the meeting, please complete, date, sign and return the proxy card mailed to you, or vote over the telephone or the internet as instructed in these materials, as promptly as possible in order to ensure your representation at the meeting. Stockholders who attend the virtual Annual Meeting should follow instructions at www.virtualshareholdermeeting.com/ATRA2026 to vote online during the Annual Meeting. Please note, however, that if your shares are held of record by a broker, bank or other nominee and you wish to vote at the virtual Annual Meeting, you must follow the instructions from that record holder.

    

TABLE OF CONTENTS


		Page
Questions and Answers About These Proxy Materials and Voting		1
Proposal 1: Election of Directors		7
Nominees for Election for a Three-Year Term Expiring at the 2029 Annual Meeting		7
Information Regarding the Board of Directors and Corporate Governance		9
Proposal 2: Advisory Vote on Executive Compensation		20
Proposal 3: Approval of the First Amendment to the Atara Biotherapeutics, Inc. 2024 Equity Incentive Plan		21
Proposal 4: Ratification of the Selection of Independent Registered Public Accounting Firm		30
Security Ownership of Certain Beneficial Owners and Management		31
Executive Officers		33
Executive Compensation		33
Transactions with Related Persons and Indemnification		48
Householding of Proxy Materials		49
Other Matters		49

ATARA BIOTHERAPEUTICS, INC.

1280 Rancho Conejo Boulevard, Thousand Oaks, CA 91320

PROXY STATEMENT

FOR THE 2026 ANNUAL MEETING OF STOCKHOLDERS

QUESTIONS AND ANSWERS ABOUT THESE PROXY MATERIALS AND VOTING

Why did I receive a notice regarding the availability of proxy materials on the internet?

Pursuant to rules adopted by the Securities and Exchange Commission (the “SEC”), we have elected to provide access to our proxy materials over the internet. Accordingly, we have sent you a Notice of Internet Availability of Proxy Materials (the “Notice”) because our Board of Directors (the “Board”) is soliciting your proxy to vote at the 2026 Annual Meeting of Stockholders (the “Annual Meeting”), including any votes related to adjournments or postponements of the meeting. All stockholders will have the ability to access the proxy materials on the website referred to in the Notice or request to receive a printed set of the proxy materials. Instructions on how to access the proxy materials over the internet or to request a printed copy may be found in the Notice. In this Proxy Statement, “we”, “us”, “our”, “Company” and “Atara” refer to Atara Biotherapeutics, Inc.

We intend to mail the Notice on or about April 27, 2026 to all stockholders of record entitled to vote at the Annual Meeting.

How do I attend the Annual Meeting?

The meeting will be held virtually via live audio webcast on June 9, 2026 at 9:00 a.m. Pacific time. The meeting will only be conducted virtually via webcast and there will be no physical meeting location.

Attending the Annual Meeting as a Stockholder of Record: Shares Registered in Your Name

Atara’s stockholders of record as of April 14, 2026 (the “Record Date”) can attend the Annual Meeting by accessing the meeting center at www.virtualshareholdermeeting.com/ATRA2026 and entering the 16-digit control number on the proxy card or Notice previously received. The webcast of the Annual Meeting will be archived for one year after the date of the Annual Meeting at www.virtualshareholdermeeting.com/ATRA2026. Instructions on how to connect to the Annual Meeting and participate via the Internet, including how to demonstrate proof of stock ownership, are also available at the meeting website. If you do not have your 16-digit control number, you will be able to access and listen to the Annual Meeting, but you will not be able to vote your shares or submit questions during the Annual Meeting. See below, “Attending the Annual Meeting as a Guest.”

Attending the Annual Meeting as a Beneficial Owner: Shares Registered in the Name of a Broker, Bank or Other Nominee

Beneficial stockholders as of the Record Date (i.e., shares held in “street name” through an intermediary, such as a broker, bank or other nominee), who want to attend the Annual Meeting can attend using the 16-digit control number found on the Notice and instructions received from their broker, bank or other nominee.

Attending the Annual Meeting as a Guest

Guests may enter the Annual Meeting in “listen-only” mode by entering the Annual Meeting at www.virtualshareholdermeeting.com/ATRA2026 and entering the information requested in the “Guest Login” section. Guests will not have the ability to vote or ask questions during the Annual Meeting.

What if I have technical difficulties or trouble accessing the virtual Annual Meeting?

If you encounter any difficulties accessing the virtual meeting or during the meeting time, please call the phone number posted on the date of the meeting at www.virtualshareholdermeeting.com/ATRA2026 for general technical questions.

Who can vote at the Annual Meeting?

Only stockholders of record at the close of business on the Record Date will be entitled to vote at the Annual Meeting. On this Record Date, there were 8,512,272 shares of common stock outstanding and entitled to vote. Each outstanding share of common stock shall entitle the holder thereof to one vote.

Stockholder of Record: Shares Registered in Your Name

If on the Record Date your shares were registered directly in your name with our transfer agent, Computershare Trust Company, N.A., then you are a stockholder of record for purposes of the Annual Meeting. As a stockholder of record, you may vote virtually at the Annual Meeting or vote by proxy. Whether or not you plan to attend the virtual Annual Meeting, we urge you to fill out and return a proxy card or vote by proxy over the telephone or on the internet as instructed below to ensure your vote is counted.

Beneficial Owner: Shares Registered in the Name of a Broker, Bank or Other Nominee

If on the Record Date your shares were held, not in your name, but rather in an account at a brokerage firm, bank or other similar organization, then you are the beneficial owner of shares held in “street name” and the Notice is being forwarded to you by that organization. The broker, bank or other nominee holding your account is considered to be the stockholder of record for purposes of voting at the Annual Meeting. As a beneficial owner, you have the right to direct the broker, bank or other nominee holding your account regarding how to vote the shares in your account. You are also invited to attend the virtual Annual Meeting and may vote during the meeting if you log in with the 16-digit control number provided on your proxy materials.

Can I ask questions during the virtual Annual Meeting?

If you are attending the virtual Annual Meeting and logged in as a stockholder, questions can be submitted by accessing the meeting center at www.virtualshareholdermeeting.com/ATRA2026 and entering your 16-digit control number. Instructions on how to participate in the Annual Meeting are available on the meeting website.

What am I voting on?

There are four matters scheduled for a vote:

•

Election of two directors named in this Proxy Statement to hold office until the 2029 Annual Meeting of Stockholders;

•

Advisory approval of the compensation of our named executive officers, as disclosed in this Proxy Statement in accordance with SEC rules;

•

Approval of the first amendment to our 2024 Equity Incentive Plan (the “2024 Plan”) to increase the number of shares of common stock reserved for issuance thereunder by 400,000; and

•

Ratification of selection by the Audit Committee of our Board of Deloitte & Touche LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2026.

What if another matter is properly brought before the Annual Meeting?

We currently know of no other matters that will be presented for consideration at the Annual Meeting. If any other matters are properly brought before the Annual Meeting, it is the intention of the proxyholders named in the accompanying proxy to vote on those matters in accordance with their best judgment, including any continuation, postponement or adjournment of the Annual Meeting.

How do I vote?

You may either vote “For” all the nominees to the Board or you may “Withhold” your vote for any nominee you specify. For each of the other matters to be voted on, you may either vote “For” or “Against” or abstain from voting.

The procedures for voting are as follows:

Stockholder of Record: Shares Registered in Your Name

If you are a stockholder of record, you may vote virtually during the Annual Meeting, vote by proxy over the telephone, vote by proxy through the internet or vote by proxy using a proxy card that you may request or that we may elect to deliver at a later time. Whether or not you plan to attend the Annual Meeting, we urge you to vote by proxy to ensure your vote is counted. You may still attend the Annual Meeting and vote during the virtual Annual Meeting even if you have already submitted a proxy.

•

To vote virtually during the Annual Meeting, enter the Annual Meeting using the 16-digit control number. Instructions on how to vote while participating in the Annual Meeting live via the Internet are posted at www.virtualshareholdermeeting.com/ATRA2026.

•

To vote over the telephone, dial toll-free 1-800-690-6903 using a touch-tone phone and follow the recorded instructions. You will be asked to provide the Company number and control number from the Notice. Your telephone vote must be received by 11:59 p.m. Eastern time on June 8, 2026 to be counted.

•

To vote through the internet, go to www.proxyvote.com to complete an electronic proxy card. You will be asked to provide the Company number and control number from the Notice. Your internet vote must be received by 11:59 p.m. Eastern time on June 8, 2026 to be counted.

•

To vote by mail using the proxy card, simply complete, sign and date the proxy card that may be delivered and return it promptly in the envelope provided. If you return your signed proxy card before the Annual Meeting, your proxyholder (one of the individuals named on your proxy card) will vote your shares as you direct.

Beneficial Owner: Shares Registered in the Name of Broker, Bank or Other Nominee

If you are a beneficial owner of shares registered in the name of your broker, bank or other nominee, you should receive a Notice containing voting instructions from that broker, bank or other nominee rather than from Atara. Simply follow the voting instructions in the Notice to ensure that your vote is counted. Follow the instructions from your broker, bank or other nominee included with the proxy materials, or contact your broker, bank or other nominee to request a proxy form. You are also invited to attend the virtual Annual Meeting and may vote during the meeting if you log in with the 16-digit control number provided on your proxy materials.

How many votes do I have?

On each matter to be voted upon, you have one vote for each share of common stock you owned as of the Record Date.

What happens if I do not vote?

Stockholder of Record: Shares Registered in Your Name

If you are a stockholder of record and do not vote by completing your proxy card, by telephone, through the internet or during the virtual Annual Meeting, your shares will not be voted.

Beneficial Owner: Shares Registered in the Name of Broker, Bank or Other Nominee

If you are a beneficial owner and do not instruct your broker, bank, or other nominee how to vote your shares, the question of whether your broker, bank or other nominee will still be able to vote your shares depends on whether the particular proposal is deemed to be a “routine” matter under the rules of various securities exchanges. Brokers, banks and nominees can use their discretion to vote “uninstructed” shares with respect to matters that are considered to be “routine,” but not with respect to “non-routine” matters. Under the applicable rules, “non-routine” matters are matters that may substantially affect the rights or privileges of stockholders, such as mergers, stockholder proposals, elections of directors (even if not contested), executive compensation (including any advisory stockholder votes on executive compensation and on the frequency of stockholder votes on executive compensation), and certain corporate governance proposals, even if supported by management. Accordingly, your nominee may not vote your shares on Proposals 1, 2 or 3 without your instructions, but may vote your shares on Proposal 4 even in the absence of your instruction.

What if I return a proxy card or otherwise vote but do not make specific choices?

If you return a signed and dated proxy card or otherwise vote without marking voting selections, your shares will be voted, as applicable, “For” the election of each of the nominees for director; “For” the advisory approval of named executive officer compensation; ”For” the first amendment to our 2024 Equity Incentive Plan to increase the number of shares of common stock reserved for issuance thereunder by 400,000; and “For” the ratification of selection by the Audit Committee of our Board of Deloitte & Touche LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2026. If any other matter is properly presented at the Annual Meeting, your proxyholder will vote your shares using their best judgment.

Who is paying for this proxy solicitation?

We will pay for the entire cost of soliciting proxies. Directors and employees will not be paid any additional compensation for soliciting proxies. We may also reimburse brokerage firms, banks, and other similar organizations for the cost of forwarding proxy materials to beneficial owners.

What does it mean if I receive more than one Notice?

If you receive more than one Notice, your shares may be registered in more than one name or in different accounts. Please follow the voting instructions on each of the Notices you receive to ensure that all of your shares are voted.

Can I change my vote after submitting my proxy?

Stockholder of Record: Shares Registered in Your Name

Yes. You can revoke your proxy at any time before the final vote at the Annual Meeting. If you are the record holder of your shares, you may revoke your proxy in any one of the following ways:

•

you may submit another properly completed proxy card with a later date;

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you may grant a subsequent proxy by telephone or through the internet;

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you may send a timely written notice that you are revoking your proxy to our Secretary at 1280 Rancho Conejo Boulevard, Thousand Oaks, California 91320 (such notice will be considered timely if it is received at the indicated address by close of business on the business day immediately preceding the date of the Annual Meeting); or

•

you may attend the Annual Meeting virtually and vote during the Annual Meeting by entering the 16-digit control number that appears on your Notice, proxy card or the instructions that accompanied your proxy materials. Instructions on how to vote while participating in the Annual Meeting live via the Internet are posted at www.virtualshareholdermeeting.com/ATRA2026.

Simply attending the Annual Meeting will not, by itself, revoke your proxy. Your most current proxy card or telephone or internet proxy is the one that is counted.

Beneficial Owner: Shares Registered in the Name of Broker or Bank

If your shares are held by your broker, bank or other similar organization as a nominee or agent, you should follow the instructions provided by your broker, bank, or other similar organization.

When are stockholder proposals due for next year’s annual meeting?

To be considered for inclusion in next year’s proxy materials, your proposal must be submitted in writing by December 28, 2026 to our Secretary at 1280 Rancho Conejo Boulevard, Thousand Oaks, CA 91320, and must comply with all applicable requirements of Rule 14a-8 promulgated under the Securities Exchange Act of 1934, as amended (the “Exchange Act”); provided, however, that if our 2027 Annual Meeting of Stockholders is held before May 10, 2027 or after July 9, 2027, then the deadline is a reasonable amount of time prior to the date we print and mail the Notice for the 2027 Annual Meeting of Stockholders. If you wish to submit a proposal (including a director nomination) that is not to be included in next year’s proxy materials, the proposal must be received by our Secretary not later than the close of business on March 11, 2027 nor earlier than the close of business on February 9, 2027; provided, however, that if our 2027 Annual Meeting of Stockholders is held before May 10, 2027 or after July 9, 2027, then the proposal must be received no earlier than the close of business on the 120th day prior to such meeting and not later than the close of business on the later of the 90th day prior to such meeting or the 10th day following the day on which public announcement of the date of such meeting is first made. You are also advised to review our bylaws, which contain additional requirements about advance notice of stockholder proposals and director nominations.

In order to comply with the universal proxy rules, stockholders who intend to solicit proxies in support of director nominees other than our nominees must provide notice that sets forth the information required by Rule 14a-19 under the Exchange Act no later than April 10, 2027; provided, however, that if our 2027 Annual Meeting of Stockholders is held before May 10, 2027 or after July 9, 2027, then the notice must be received by the later of 60 days prior to the date of the annual meeting or the 10th day following the day on which public announcement of the date of such meeting is made.

What are broker non-votes and what is broker discretionary voting?

If you are a beneficial owner of shares held in a brokerage account and you do not instruct your broker, bank or other agent how to vote your shares, your broker, bank or other agent may still be able to vote your shares in its discretion. Under the rules of the New York Stock Exchange, which are also applicable to Nasdaq-listed companies, brokers, banks and other securities intermediaries that are subject to New York Stock Exchange rules may use their discretion to vote your “uninstructed” shares on matters considered to be “routine” under New York Stock Exchange rules but not with respect to “non-routine” matters. A broker non-vote occurs when a broker, bank or other agent has not received voting instructions from the beneficial owner of the shares and the broker, bank or other agent cannot vote the shares because the matter is considered “non-routine” under NYSE rules. The Company believes that Proposal 4 is the only “routine” matter to be presented at the Annual Meeting on which brokers will be permitted to vote shares on your behalf, even without voting instructions. If your broker votes these shares on your behalf, your shares will be counted as present for purposes of establishing a quorum at the Annual Meeting.

Other than Proposal 4, the Company believes that all proposals set forth in this Proxy Statement are considered “non-routine” matters and brokers will not be able to vote on behalf of their clients if no voting instructions have been furnished. A “broker non-vote” share will not affect the determination of whether the matter is approved. Please give your broker voting instructions on all proposals to ensure your shares are represented in the vote.

How many votes are needed to approve each proposal?

The following table summarizes the minimum vote needed to approve each proposal and the effect of abstentions and broker non-votes.


Proposal Number	Proposal Description	Vote Required for Approval	Effect of Abstentions	Effect of Broker Non-Votes
1	Election of directors	Plurality of the votes of shares present in person, present by remote communication, if applicable, or represented by proxy and entitled to vote on the matter	None	None
2	Advisory approval of the compensation of our named executive officers	“For” votes from the holders of a majority of shares present in person, present by remote communication, if applicable, or represented by proxy and entitled to vote on the matter	Against	None
3	Approval of the first amendment to our 2024 Equity Incentive Plan to increase the number of shares of common stock reserved for issuance thereunder by 400,000	“For” votes from the holders of a majority of shares present in person, present by remote communication, if applicable, or represented by proxy and entitled to vote on the matter	Against	None
4	Ratification of the selection of Deloitte & Touche LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2026	“For” votes from the holders of a majority of shares present in person, present by remote communication, if applicable, or represented by proxy and entitled to vote on the matter	Against	Not applicable; brokers have discretion to vote

What is the quorum requirement?

A quorum of stockholders is necessary to hold a valid Annual Meeting. A quorum will be present if stockholders holding at least a majority of the outstanding shares entitled to vote are present at the Annual Meeting in person by remote communication or represented by proxy. On the Record Date, there were 8,512,272 shares outstanding and entitled to vote. Thus, the holders of 4,256,137 shares must be present in person by remote communication or represented by proxy at the Annual Meeting to have a quorum.

Your shares will be counted towards the quorum only if you submit a valid proxy (or one is submitted on your behalf by your nominee) or if you vote in person by remote communication at the Annual Meeting. Abstentions and broker non-votes will be counted towards the quorum requirement. If there is no quorum, the holders of a majority of shares present at the Annual Meeting in person by remote communication or represented by proxy may adjourn the Annual Meeting to another date.

How can I find out the results of the voting at the Annual Meeting?

Preliminary voting results will be announced at the Annual Meeting. In addition, final voting results will be published in a current report on Form 8-K that we expect to file within four business days after the Annual Meeting. If final voting results are not available to us in time to file a Form 8-K within four business days after the Annual Meeting, we intend to file a Form 8-K to publish preliminary results and, within four business days after the final results are known to us, file an additional Form 8-K to publish the final results.

PROPOSAL 1

ELECTION OF DIRECTORS

The Board is divided into three classes. Each class has a three-year term. Vacancies on the Board may be filled only by persons elected by a majority of the remaining directors. A director elected by the Board to fill a vacancy in a class, including vacancies created by an increase in the number of directors, shall serve for the remainder of the full term of that class and until the director’s successor is duly elected and qualified.

The Board presently has seven members. There is one director in the class whose term of office expires in 2026. Carol Gallagher, Pharm.D., a current director whose term expires at the Annual Meeting will cease to be a director upon the expiration of her term at the conclusion of the Annual Meeting. In order to rebalance the Board classes upon the expiration of Dr. Gallagher’s term, Dr. Nguyen and Mr. Subramanian will stand for election at the Annual Meeting, each with a term to expire at the 2029 Annual Meeting of Stockholders. Immediately following the Annual Meeting, the size of the Board will be reduced to six. Dr. Nguyen was previously elected to the Board by our stockholders. Mr. Subramanian was appointed by the Board in 2025. Each of the nominees listed below is currently a member of our Board who has been recommended for reelection by the Nominating and Corporate Governance Committee and nominated for reelection by the Board. If elected at the Annual Meeting, each of these nominees would serve until the 2029 Annual Meeting of Stockholders and until his successor has been duly elected and qualified, or, if sooner, until the director’s death, resignation or removal. It is our policy to invite and encourage directors and nominees for director to attend the Annual Meeting. All of our then-serving directors other than Messrs. Mallik and Huang and Dr. Roncarolo attended our 2025 Annual Meeting of Stockholders.

Directors are elected by a plurality of the votes of the holders of shares present in person, present by remote communication, if applicable, or represented by proxy and entitled to vote on the election of directors. For the Annual Meeting, this means that the two nominees receiving the highest number of affirmative votes, even if less than a majority of the shares outstanding on the Record Date, will be elected. Shares represented by executed proxies will be voted, if authority to do so is not withheld, for the election of the two nominees named below. If any nominee becomes unavailable for election as a result of an unexpected occurrence, shares that would have been voted for that nominee will instead be voted for the election of a substitute nominee proposed by the Board. Each person nominated for election has agreed to serve if elected. We have no reason to believe that any nominee will be unable to serve. The following is a brief biography of each nominee and each director whose term will continue after the Annual Meeting.

Nominees for Election for a Three-Year Term Expiring at the 2029 Annual Meeting

AnhCo Nguyen, Ph.D., 53, has served as our President and Chief Executive Officer and a member of the Board since September 2024. Dr. Nguyen joined the Company in May 2021 as Senior Vice President, Chief Scientific Officer and assumed the role of Executive Vice President, Chief Scientific and Technical Officer in May 2023. Prior to joining the Company in May 2021, Dr. Nguyen held roles of increasing responsibility in research and development at Fate Therapeutics, Inc., most recently as its Vice President, Research and Development Innovation. Previously, from April 2018 to November 2019, Dr. Nguyen served as Senior Director, Oncology Research and Development at Pfizer. Dr. Nguyen received his undergraduate degree in biology from Harvard College and a Ph.D. in Immunology from Washington University in St. Louis. He was a Postdoctoral Associate at the Center for Cancer Research at the Massachusetts Institute of Technology. We believe that Dr. Nguyen is qualified to serve on our Board due to his role as our President and Chief Executive Officer, his deep industry knowledge and experience leading research efforts in the field.

Nachi Subramanian, 42, has served as a member of the Board since May 2025. Mr. Subramanian was appointed to the Board in connection with the purchase of shares of the Company’s common stock and pre-funded warrants by Redmile Group in May 2025. Mr. Subramanian is a Managing Director at Redmile Group, a healthcare-focused investment firm based in San Francisco and New York. He joined the firm in December 2021. Prior to Redmile, Nachi spent fourteen years at J.P. Morgan, where he held senior roles across the Private Markets and Global Cash Equities businesses. He began his career in Institutional Equities at Bear Stearns. Nachi holds a B.A. in Political Science and Economics from the University of California, Irvine. We believe that Mr. Subramanian is qualified to serve on our Board due to his extensive experience in finance, his leadership and business experience.

THE BOARD OF DIRECTORS RECOMMENDS

A VOTE IN FAVOR OF EACH NAMED NOMINEE.

Directors Continuing in Office Until the 2027 Annual Meeting

William K. Heiden, 66, has served as a member of the Board since November 2015. Mr. Heiden served as the President and Chief Executive Officer, and as a member of the board of directors, of AMAG Pharmaceuticals, Inc. (acquired by Covis Pharma GmbH), a pharmaceutical company, from May 2012 until April 2020. Prior to joining AMAG, Mr. Heiden served as President and Chief Executive Officer of GTC Biotherapeutics, Inc. (now part of LFB, S.A.), a biotherapeutics company, from June 2010 to May 2012. From September 2004 until December 2008, Mr. Heiden served as President and Chief Executive Officer of Elixir Pharmaceuticals, Inc., (“Elixir”) a biopharmaceutical company. Prior to joining Elixir, Mr. Heiden served as President and Chief Operating Officer of Praecis Pharmaceuticals Incorporated (which was acquired by GlaxoSmithKline), from 2002 to 2004. From 1987 to 2002, Mr. Heiden progressed through various positions of increasing responsibility at Schering-Plough Corporation (which was acquired by Merck & Co.), including managing a number of businesses in the United States, Europe and Canada. Mr. Heiden has served on the board of directors of Macrogenics, Inc. since May 2022. Mr. Heiden holds an M.B.A. from Cornell University’s Johnson Graduate School of Management, a M.I.M. degree from the University of Louvain, and a B.A. degree from the University of Florida. We believe that Mr. Heiden is qualified to serve on our Board due to his extensive experience as a pharmaceutical and biotechnology executive.

James Huang, 60, has served as a member of the Board since May 2025. Mr. Huang was appointed to the Board in connection with the purchase of shares of the Company’s common stock and pre-funded warrants by Panacea Capital (formerly Panacea Venture) in May 2025. Mr. Huang has over 37 years of biotech experience and has served as the Founder and Managing Partner of Panacea Capital since 2018. Prior to Panacea Capital, Mr. Huang was a Managing Partner at Kleiner Perkins (KPCB) China where he focused on the firm’s life sciences practice, and a managing partner at Vivo Ventures where he led numerous investments in China. He was also the president of Anesiva, a biopharmaceutical company focused on pain-management treatments. Earlier in his career, he held senior roles in business development, sales, marketing, and R&D with Tularik Inc. (acquired by Amgen), GlaxoSmithKline LLC, Bristol-Myers Squibb and ALZA Corp. (acquired by Johnson & Johnson). In addition to our Board, Mr. Huang also serves as a director on the board of directors of Kindstar Globalgene Technology Inc., which he joined in January 2012, Connect Biopharma Holdings Limited, which he joined in February 2024, Lee’s Pharmaceutical Holdings Limited, which he joined in July 2024, and CASI Pharmaceuticals, Inc., which he joined in September 2025. Mr. Huang also serves as a director of several private companies. He received an M.B.A. from the Stanford Graduate School of Business and a B.S. degree in chemical engineering from the University of California, Berkeley. We believe that Mr. Huang is qualified to serve on our Board due to his extensive experience in private equity, the biotechnology industry, his leadership and business experience.

Directors Continuing in Office Until the 2028 Annual Meeting

Matthew K. Fust, 61, has served as a member of the Board since March 2014. Mr. Fust is a board member and advisor to life sciences companies. Mr. Fust has served on the board of directors of Crinetics Pharmaceuticals, Inc. since February 2018, Ultragenyx Pharmaceutical, Inc. since January 2014, and Neumora Therapeutics, Inc. since December 2020. Mr. Fust was previously Executive Vice President and Chief Financial Officer of Onyx Pharmaceuticals, Inc., a biopharmaceutical company, from January 2009 through its acquisition by Amgen in October 2013. Mr. Fust continued as an employee of Amgen until January 2014. From May 2003 to December 2008, Mr. Fust served as Chief Financial Officer at Jazz Pharmaceuticals, Inc., a specialty pharmaceutical company. From 2002 to 2003, Mr. Fust served as Chief Financial Officer at Perlegen Sciences, a biopharmaceutical company. Previously, he was Senior Vice President and Chief Financial Officer at ALZA Corporation, a pharmaceutical company, where he was an executive from 1996 until 2002. From 1991 until 1996, Mr. Fust was a manager in the healthcare strategy practice at Andersen Consulting. Mr. Fust holds a B.A. from the University of Minnesota and an M.B.A. from the Stanford Graduate School of Business. We believe that Mr. Fust is qualified to serve on our Board due to his extensive experience as a chief financial officer in the life sciences industry, his leadership and management experience, and his service as a director of other biopharmaceutical companies.

Gregory A. Ciongoli, 50, has served as a member of the Board since September 2024. Mr. Ciongoli was appointed to the Board in connection with the purchase of shares of the Company’s common stock and pre-funded warrants by Adiumentum Capital Management in September 2024. Mr. Ciongoli is the Founder and Managing Partner of Adiumentum Capital Management, a Boston-based investment firm. Prior to Adiumentum, he was a Partner at the Baupost Group from 2007 to 2024, where he worked on a broad range of public and private equity investments. Mr. Ciongoli has served on the board of directors of Zymeworks, Inc. since August 2025. Mr. Ciongoli is Chair of the Advisory Board for the James Madison Institute of American Ideals and Institutions at Princeton University, and he is actively involved in a number of local not-for-profit organizations. Mr. Ciongoli graduated from Princeton University with an A.B. and received his M.B.A. from Harvard Business School. We believe that Mr. Ciongoli is qualified to serve on our Board due to his extensive experience in private equity, his leadership and business experience.

INFORMATION REGARDING THE BOARD OF DIRECTORS AND CORPORATE GOVERNANCE

Independence of the Board of Directors

Generally, under the listing requirements and rules of The Nasdaq Stock Market (“Nasdaq”), independent directors must comprise a majority of a listed company’s board of directors. The Board has undertaken a review of its composition, the composition of its committees and the independence of each director. The Board has determined that, other than Dr. Nguyen, none of our directors has a relationship that would interfere with the exercise of independent judgment in carrying out the responsibilities of a director and that each is “independent” as that term is defined under the listing requirements and rules of Nasdaq. Accordingly, a majority of the members of the Board is independent, as required under applicable Nasdaq rules. In making this determination, the Board considered the current and prior relationships that each non-employee director has with the Company and all other facts and circumstances the Board deemed relevant in determining their independence, including the beneficial ownership of our capital stock by each non-employee director.

Board Leadership Structure

Mr. Ciongoli, an independent director, was appointed as chair of the Board in September 2025 when Dr. Pascal Touchon voluntarily resigned from the Board. Dr. Gallagher, an independent director, served as lead independent director of the Board until September 2025 when Mr. Ciongoli was appointed as chair of the Board. Accordingly, the positions of chair and Chief Executive Officer are currently separated. Separating these positions allows our Chief Executive Officer to focus on our day-to-day business, while allowing our chair to lead our Board in its fundamental role of providing advice to, and oversight of, other members of management. Our Board recognizes the time, effort and energy that the Chief Executive Officer must devote to his position in the current business environment, as well as the commitment required to serve as our chair. Although our bylaws and Corporate Governance Guidelines do not require that we separate the chair and Chief Executive Officer positions, our Board believes that having separate positions is the appropriate leadership structure for us at this time. Our Board recognizes that, depending on the circumstances, other leadership models, such as combining the role of chair with the role of Chief Executive Officer, might be appropriate. Accordingly, our Board may periodically review its leadership structure. Our Corporate Governance Guidelines provide that in the event that the chair is not an independent director, our Board may designate one of the independent directors to serve as lead independent director. We believe that separation of the positions of the chair of the Board and Chief Executive Officer at this time, and the designation of a lead independent director when the chair of the Board is not an independent director, reinforces the independence of the Board in its oversight of the business and affairs of the Company.

Role of the Board in Risk Oversight

One of the Board’s key functions is informed oversight of our risk management process. The Board does not have a standing risk management committee, but rather administers this oversight function directly through the Board as a whole, as well as through various Board standing committees that address risks inherent in their respective areas of oversight. In particular, the Board is responsible for monitoring and assessing strategic risk exposure, including a determination of the nature and level of risk appropriate for the Company. The Audit Committee has the responsibility to consider and discuss our major financial and cybersecurity risk exposures, insurance coverage, and the steps management has taken to monitor and control these exposures, including guidelines and policies designed to mitigate risks identified. The Audit Committee also monitors compliance with legal and regulatory requirements, in addition to oversight of the performance of our internal audit function. The Nominating and Corporate Governance Committee monitors the effectiveness of our corporate governance guidelines, including whether they are successful in preventing illegal or improper liability-creating conduct. The Nominating and Corporate Governance Committee also has oversight of the Company’s practices with respect to enterprise risk assessment and risk management, while management is responsible for day-to-day risk management processes. The Human Capital Committee assesses and monitors whether any of our compensation policies and programs has the potential to encourage excessive risk-taking. It is the responsibility of the committee chairs to report findings regarding material risk exposures to the Board as quickly as possible. The Board has delegated to the chair of the Board the responsibility of coordinating between the Board and management with regard to the determination and implementation of responses to any problematic risk management issues.

Meetings of the Board of Directors

The Board met 28 times during 2025. Each Board member, except for Mr. Huang, attended 75% or more of the aggregate number of meetings of the Board and of the committees on which they served during the portion of the last fiscal year for which they were a director or committee member. Mr. Huang was appointed to the Board in May 2025 and to the Human Capital Committee in September 2025. Mr. Huang's attendance rate reflected scheduling conflicts during his initial transition onto the Board. In 2025, our non-employee directors met 22 times in regularly scheduled executive sessions at which only non-employee directors were present.

Information Regarding Committees of the Board of Directors

The Board had four standing committees: an Audit Committee, a Human Capital Committee, a Nominating and Corporate Governance Committee, and a Research and Development Committee. In September 2025, the Board reconsidered the committee composition and dissolved the Research and Development Committee. The following table provides membership and meeting information for each of the Board committees in 2025:


Name	Audit	Human Capital	Nominating and Corporate Governance	Research and Development(1)
AnhCo Nguyen, Ph.D.
Pascal Touchon, D.V.M.(2)				X*
Matthew K. Fust	X*
Carol Gallagher, Pharm.D.(3)	X
William K. Heiden	X	X*
Gregory A. Ciongoli (4)			X(5)
James Huang(6)		X(7)
Nachi Subramanian(8)			X*(9)
Ameet Mallik(10)		X	X*
Maria Grazia Roncarolo, M.D.(11)			X	X
Total meetings in 2025	4	4	3	0

* Committee Chair.

(1) The Research and Development Committee was dissolved in September 2025.

(2) Dr. Touchon resigned from the Board in September 2025.

(3) Dr. Gallagher served as lead independent director until the appointment of Mr. Ciongoli as chair of the Board in September 2025. Dr. Gallagher’s term expires at the Annual Meeting and she will cease to be a director upon the expiration of her term at the conclusion of the Annual Meeting.

(4) Mr. Ciongoli was appointed as chair of the Board in September 2025.

(5) Mr. Ciongoli was appointed to the Nominating and Corporate Governance Committee in September 2025.

(6) Mr. Huang was appointed to the Board in May 2025.

(7) Mr. Huang was appointed to the Human Capital Committee in September 2025.

(8) Mr. Subramanian was appointed to the Board in May 2025.

(9) Mr. Subramanian was appointed as chair of the Nominating and Corporate Governance Committee in September 2025.

(10) Mr. Mallik resigned from the Board in September 2025.

(11) Dr. Roncarolo resigned from the Board in September 2025.

Audit Committee

The Board has determined that each member of the Audit Committee is independent under Nasdaq listing standards and Rule 10A-3(b)(1) promulgated under the Exchange Act. The Board has also determined that Mr. Fust is an “audit committee financial expert” within the meaning of SEC regulations. Each member of the Audit Committee has the requisite financial expertise required under the applicable requirements of Nasdaq. In arriving at this determination, the Board examined each Audit Committee member’s scope of experience and the nature of their employment in the corporate finance sector. The primary functions of this committee include, among others:

•

reviewing and pre-approving the engagement of our independent registered public accounting firm to perform audit services and any permissible non-audit services;

•

evaluating the performance of our independent registered public accounting firm and deciding whether to retain its services;

•

monitoring the rotation of partners on the engagement team of our independent registered public accounting firm;

•

reviewing our annual and quarterly financial statements and reports and discussing the statements and reports with our independent registered public accounting firm and management, including a review of disclosures under “Management’s Discussion and Analysis of Financial Condition and Results of Operations”, and conferring with our independent registered public accounting firm and management regarding the scope, adequacy and effectiveness of internal control over financial reporting;

•

considering and approving or disapproving of related party transactions;

•

reviewing, with our independent registered public accounting firm and management, significant issues that may arise regarding accounting principles and financial statement presentation, as well as matters concerning the scope, adequacy and effectiveness of our financial controls;

•

assessing our financial risk assessment and management of those risks;

•

oversight of cyber risk management and the integrity of our information technology systems, processes and data, and our incident response plans and contingency plans;

•

reviewing and assessing our director’s and officer’s indemnification and insurance;

•

preparing the report required by the rules of the SEC to be included in our annual proxy statement or annual report;

•

reviewing our compliance with legal or regulatory requirements;

•

establishing procedures for the receipt, retention and treatment of complaints received by us regarding financial controls, accounting or auditing matters; and

•

reviewing and evaluating, at least annually, the performance of the Audit Committee and the adequacy of its charter.

The Audit Committee met four times during 2025. The Audit Committee is briefed regularly on cybersecurity matters, such as our cybersecurity defense measures, current trends and cybersecurity incidents, including our responses to such incidents, if appropriate, and updates to our continuous and comprehensive employee cybersecurity training programs.

The Audit Committee has authority to engage legal counsel or other experts or consultants, as it deems appropriate to carry out its responsibilities. The Board has adopted a written Audit Committee charter that is available to stockholders on our website at http://investors.atarabio.com/governance.

Report of the Audit Committee of the Board of Directors1

The Audit Committee has reviewed and discussed the audited financial statements for the fiscal year ended December 31, 2025 with our management. The Audit Committee has discussed with the independent registered public accounting firm the matters required to be discussed by the applicable requirements of the Public Company Accounting Oversight Board (“PCAOB”) and the SEC. The Audit Committee has also received the written disclosures and the letter from the independent registered public accounting firm required by applicable requirements of the PCAOB regarding the independent accountants’ communications with the Audit Committee concerning independence and has discussed with the independent registered public accounting firm the accounting firm’s independence. Based on the foregoing, the Audit Committee has recommended to the Board that the audited financial statements be included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2025.

Matthew K. Fust

Carol Gallagher

William K. Heiden

The material in this report is not “soliciting material,” is being furnished and shall not be deemed “filed” with the Commission, and is not to be incorporated by reference in any filing of Atara under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended, whether made before or after the date hereof and irrespective of any general incorporation language in any such filing.

Human Capital Committee

The Board has determined that each member of the Human Capital Committee is independent under Nasdaq listing standards and Rule 10c-1 promulgated under the Exchange Act, and a “non-employee director” as defined in Rule 16b-3 promulgated under the Exchange Act. The primary functions of this committee include, among others:

•

determining the compensation and other terms of employment of our Chief Executive Officer and other executive officers and reviewing and approving corporate performance goals and objectives relevant to such compensation;

•

determining the compensation of our non-employee directors;

•

evaluating, adopting and administering our equity incentive plans, compensation plans and similar programs, as well as reviewing the results of any advisory stockholder votes on executive compensation and recommending to the Board the adoption, modification or termination of our plans and programs in light of such votes;

•

establishing policies with respect to equity compensation arrangements;

•

reviewing and assessing the elements of our compensation program as they relate to enterprise risk and the management of any such risks;

•

assessing the independence of each compensation consultant, legal counsel and other advisor to the Human Capital Committee, in accordance with and to the extent required by applicable law and Nasdaq;

•

reviewing with management any required disclosures under the caption “Compensation Discussion and Analysis” and recommending to the Board its inclusion in our periodic reports to be filed with the SEC;

•

developing, implementing, and periodically reviewing with management, our Incentive Compensation Recoupment Policy (“Clawback Policy”) and Stock Ownership Guidelines for the Company’s directors and executive officers, and monitor compliance with such guidelines;

•

periodically reviewing with the Chief Executive Officer the plans for succession for the Company’s executive officers;

•

reviewing and designing policies and strategies relating to talent management and development, talent acquisition, culture, and employee engagement;

•

preparing the report on executive compensation to be included in the Company’s annual proxy statement;

•

reviewing and recommending to the Board the annual corporate goals of the Company for approval by the Board and assessing the achievement of the Company’s such corporate goals annually and report to the Board on such assessment, for approval by the Board;

•

reviewing and discussing with management the Company policies and training and developing programs designed to support the long-term goals of the Company, including but not limited to goals relating to employee health, safety and well-being; environmental, social, and governance; and diversity and inclusion; and

•

reviewing and evaluating, at least annually, the performance of the Human Capital Committee and the adequacy of its charter.

The Human Capital Committee has authority to engage legal counsel or other experts or consultants, as it deems appropriate to carry out its responsibilities. The Board has adopted a written Human Capital Committee charter that is available to stockholders on our website at http://investors.atarabio.com/governance.

Human Capital Committee Processes and Procedures

The Human Capital Committee met four times during 2025. The agenda for each meeting is usually developed by our Chief Executive Officer, Chief People Officer, and Head of Legal in consultation with the Chair of the Human Capital Committee and our outside compensation consultants, if applicable. The Human Capital Committee meets regularly in executive session. However, from time to time, various members of management and other employees, as well as outside advisors or consultants, may be invited by the Human Capital Committee to make presentations, to provide financial or other background information or advice or to otherwise participate in Human Capital Committee meetings. The Chief Executive Officer does not and will not participate in, or be present during, any deliberations or determinations of the Human Capital Committee regarding their compensation. The charter of the Human Capital Committee grants the Human Capital Committee full access to all of our books, records, facilities and personnel. In addition, under the charter, the Human Capital Committee has authority to engage legal counsel or other experts or consultants, as it deems appropriate to carry out its responsibilities. The Human Capital Committee has the authority to retain compensation consultants to assist in its evaluation of executive and director compensation, including the authority to approve the consultant’s reasonable fees and other retention terms. Under the charter, the Human Capital Committee may select, or receive advice from, a compensation consultant, legal counsel or other advisor to the Human Capital Committee (other than in-house legal counsel and certain other types of advisors), only after assessing their independence in accordance with, and to the extent required by, applicable law and the listing requirements of Nasdaq; however, there is no requirement that any advisor be independent.

During 2025, the Human Capital Committee engaged Pearl Meyer & Partners, LLC (“Pearl Meyer”) as its independent compensation consultant. After considering all of the factors required by applicable Nasdaq rules, the Human Capital Committee was satisfied with Pearl Meyer’s independence and requested that its independent compensation consultants evaluate and help us refine our employee and non-employee director compensation strategies and practices. As part of its engagement, Pearl Meyer was requested by the Human Capital Committee to advise on compensation related topics including an annual merit increase to the employees, retention bonus strategy and executive compensation. Following a dialogue with Pearl Meyer, the Human Capital Committee considered the recommendations and approved the recommendations subject to certain modifications deemed appropriate by the Human Capital Committee. With respect to the executive officers, the Chief Executive Officer in consultation with Pearl Meyer developed recommendations that were presented to the Human Capital Committee for its consideration. Following discussion with the Chief Executive Officer and with Pearl Meyer, the Human Capital Committee considered the recommendations and approved the recommendations subject to certain modifications deemed appropriate by the Human Capital Committee.

Historically, the Human Capital Committee has made most of the significant adjustments to annual compensation and determined bonus and equity awards at one or more meetings held during the first quarter of the year. The Human Capital Committee also considers matters related to individual compensation, such as compensation for new executive hires, as well as high-level strategic issues, such as the efficacy of our compensation strategy, potential modifications to that strategy, risks created by that strategy and new trends, retention concerns and plans or approaches to compensation, at various meetings throughout the year. For executives other than the Chief Executive Officer, the Human Capital Committee solicits and considers evaluations and recommendations submitted to the Committee by the Chief Executive Officer. In the case of the Chief Executive Officer, the evaluation of his performance is conducted by the Human Capital Committee with feedback from the Board as well as the executives, which determines any adjustments to Chief Executive Officer’s compensation as well as awards to be granted. For all executives and directors as part of its deliberations, the Human Capital Committee may review and consider, as appropriate, materials that it deems relevant. These materials may include financial reports and projections, operational data, tax and accounting information, tally sheets that set forth the total compensation that may become payable to executives in various hypothetical scenarios, executive and director stock ownership information, company stock performance data, analyses of historical executive compensation levels and current compensation levels across our Company and recommendations of the Human Capital Committee’s compensation consultant, including advice and recommendations by Pearl Meyer and agreed upon by the Human Capital Committee).

Human Capital Committee Interlocks and Insider Participation

None of the members of the Human Capital Committee is currently or has been at any time one of our officers or employees. None of our executive officers currently serves, or has served during the last year, as a member of the board of directors or compensation committee of any entity that has one or more executive officers serving as a member of the Board or the Human Capital Committee.

Nominating and Corporate Governance Committee

The Board has determined that each member of the Nominating and Corporate Governance Committee is independent under the Nasdaq listing standards. The primary functions of this committee include:

•

periodically reviewing and evaluating director performance on the Board and its committees, and recommending to the Board and management areas for improvement;

•

interviewing, evaluating, nominating and recommending individuals for membership on the Board and its committees;

•

developing and recommending to the Board an orientation program and continuing education for all directors, as appropriate;

•

reviewing periodically with the Company’s VP, Head of Legal, or appropriate delegates, the Company’s compliance with legal and regulatory requirements;

•

reviewing and assessing the Company’s practices with respect to enterprise risk assessment and enterprise risk management;

•

reviewing and recommending to the Board any amendments to our corporate governance policies; and

•

reviewing and assessing, at least annually, the performance of the Nominating and Corporate Governance Committee and the adequacy of its charter.

The Nominating and Corporate Governance Committee met three times during 2025. The Nominating and Corporate Governance Committee has authority to engage advisors or consultants (including legal counsel and search firms), as it deems appropriate to carry out its responsibilities. The Board has adopted a written Nominating and Corporate Governance Committee charter that is available to stockholders on our website at http://investors.atarabio.com/governance.

The Nominating and Corporate Governance Committee believes that candidates for director should have certain minimum qualifications, including the ability to read and understand basic financial statements, being over 21 years of age and having the highest personal integrity and ethics. In evaluating director nominee candidates, the Nominating and Corporate Governance Committee typically also considers factors such as: possessing relevant expertise upon which to be able to offer advice and guidance to management, having sufficient time to devote to our affairs, demonstrated excellence in their field, having the ability to exercise sound business judgment and having the commitment to rigorously represent the long-term interests of our stockholders and other factors deemed appropriate given then-current needs of the Board and Atara, to maintain a balance of knowledge, experience and capability. However, the Nominating and Corporate Governance Committee retains the right to modify the above qualifications from time to time.

The Board believes that diversity of viewpoints, background, experience, and other characteristics, such as race, gender, ethnicity, sexual orientation, culture and nationality, are an important part of its makeup, and the Nominating and Corporate Governance Committee and the Board actively seek these characteristics in identifying director candidates.

Candidates for director nominees are reviewed in the context of the current composition of the Board, our operating requirements, Nasdaq listing standards, applicable law and regulations and the long-term interests of stockholders. The Nominating and Corporate Governance Committee also determines whether a nominee is independent for Nasdaq purposes based upon Nasdaq listing standards, SEC rules and regulations and the advice of counsel, if necessary. The Nominating and Corporate Governance Committee conducts any appropriate and necessary inquiries into the backgrounds and qualifications of potential director candidates. The Nominating and Corporate Governance Committee meets to discuss and consider the candidates’ qualifications and ultimately recommend director nominees to the Board.

In the case of incumbent directors whose terms of office are set to expire, the Nominating and Corporate Governance Committee reviews these directors’ overall service to Atara during their terms, including the number of meetings attended, level of participation, quality of performance and any other relationships and transactions that might impair the directors’ independence.

The Nominating and Corporate Governance Committee will consider director candidates recommended by stockholders. The Nominating and Corporate Governance Committee does not intend to alter the manner in which it evaluates candidates, including the minimum criteria set forth above, based on whether or not the candidate was recommended by a stockholder. Stockholders who wish to recommend individuals for consideration by the Nominating and Corporate Governance Committee to become nominees for election to the Board may do so by delivering a written recommendation to the Nominating and Corporate Governance Committee at the following address: 1280 Rancho Conejo Boulevard, Thousand Oaks, CA 91320 not less than six months prior to any meeting at which directors are to be elected. Submissions must include the full name of the proposed nominee, a description of the proposed nominee’s business experience for at least the previous five years, complete biographical information, a description of the proposed nominee’s qualifications as a director and a representation that the nominating stockholder is a beneficial or record holder of our common stock and has been a holder for at least one year. Any such submission must be accompanied by the written consent of the proposed nominee to be named as a nominee and to serve as a director if elected.

Research and Development Committee

The Research and Development Committee provided advice and support to the Company in relation to the Company’s research and development activities and strategy. The primary function of this committee was to confer with the Chief Executive Officer and the Company’s research and development leadership team regarding:

•

the Company’s research and development activities and strategy;

•

significant emerging regulatory, research, scientific, and medical trends and developments relevant to the Company’s research and development activities and strategy, including their potential impact on the Company’s programs or plans;

•

infrastructure and resources made available by the Company for its research and development activities and clinical trial programs; and

•

research and development, scientific, medical and intellectual property aspects of any proposed material transactions such as significant investments, acquisitions and licenses.

The Research and Development Committee was dissolved in September 2025 in connection with the re-composition of the Board and its committees to align with the Company’s operations.

Ad Hoc Transactions Committee

The ad hoc Transactions Committee meets as needed to review and advise the Company in relation to key corporate transactions, including potential collaborations and licensing arrangements. The primary function of this ad hoc committee is to confer on such matters with the Chief Executive Officer and the Company’s corporate development, finance and legal leadership teams. The members of the ad hoc Transactions Committee are Dr. Gallagher, and Messrs. Fust and Heiden, each of whom have significant expertise in structuring, evaluating and advising on biotechnology collaboration and licensing transactions.

Summary of Current Director Core Experiences, Skills and Board Tenure

Our Board members are a diverse group of highly qualified leaders in their respective fields. Most of our directors have senior leadership experience at large public and private companies and have significant and diverse management experience (including strategic, planning, financial reporting, compliance, risk management, leadership development, scientific and healthcare industry expertise). The Board believes the skills, qualities, attributes, experience and diversity of our directors provide us with a range of perspectives to effectively represent the best interests of our stockholders. The chart below summarizes our directors’ strengths.


Experience / Skills*	Nguyen	Ciongoli	Fust	Gallagher1	Heiden	Huang	Subramanian
Healthcare Industry, Providers and Payers			✓	✓	✓	✓
Research and Development	✓			✓		✓
Regulatory / Compliance	✓		✓	✓		✓
Public Company Governance		✓	✓	✓	✓	✓	✓
Financial / Accounting		✓	✓	✓	✓	✓	✓
Executive Leadership	✓	✓	✓	✓	✓	✓	✓
M&A / Transactions	✓	✓	✓	✓	✓	✓	✓
Board Tenure (Year Joined)	2024	2024	2014	2013	2015	2025	2025

*The lack of a mark for a particular item does not mean the director does not possess the specific qualification, characteristic, skill or experience. Each of our directors has experience and/or skills in the enumerated areas, the mark is intended to indicate the director has a particular strength in such area.

(1) Dr. Gallagher’s term expires at the Annual Meeting and she will cease to be a director upon the expiration of her term at the conclusion of the Annual Meeting.

Board Diversity

Our Board is comprised of several individuals who self-identify as women or are from underrepresented communities. Our Board is committed to continuously align the composition of the Board and its leadership structure with our long-term strategic needs. The Nominating and Corporate Governance Committee identifies, evaluates, and makes recommendations to the Board. The Nominating and Corporate Governance Committee considers current Board skills, background, diversity, independence, experience, tenure, and anticipated retirements to identify gaps that may need to be filled on the Board. We recognize there is always more that can be done to promote diversity and inclusion and we actively seek ways to embrace diversity, inclusion, and equitable representation at all levels of our organization.

Board Diversity Matrix


Total Number of Directors	7
Part I: Gender Identity	Female	Male
Directors*	1	5
Part II: Demographic Background
Asian	0	3
White	1	3

LGBTQ+	0	1
*One director declined to respond

Stockholder Communications with the Board

The Board has adopted a formal process by which stockholders may communicate with the Board or any of its directors. This information is available on our website at http://investors.atarabio.com/governance. Any interested person may also communicate directly with the chair of the Board or the independent or non-employee directors. Persons interested in communicating directly with the independent or non-employee directors regarding their concerns or issues are referred to the procedures for such communications on our website at http://investors.atarabio.com/governance/contact-board.

Code of Conduct

The Board has adopted a code of conduct that applies to all of our corporate employees, officers and directors, including those officers and employees responsible for financial reporting. Our code of conduct is available on our website at https://investors.atarabio.com/governance/governance-documents. We intend to disclose any amendments to this policy, or any waivers of its requirements, on our website or in public filings to the extent required by applicable SEC rules or exchange requirements.

Corporate Governance Guidelines

The Board has adopted Corporate Governance Guidelines to assure that the Board will have the necessary authority and practices in place to review and evaluate our business operations as needed and to make decisions that are independent of our management. The guidelines are also intended to align the interests of directors and management with those of our stockholders. The Corporate Governance Guidelines set forth the practices the Board intends to follow with respect to board composition and selection, board meetings and involvement of senior management, Chief Executive Officer performance evaluation and succession planning, conflicts of interest, and board committees and compensation. The Corporate Governance Guidelines also formalize the Board’s belief that a diversity of viewpoints, background, experience and other characteristics, such as race, gender, ethnicity, sexual orientation, culture and nationality, are an important part of its makeup, and that it actively seeks these characteristics in identifying director candidates.

Our Corporate Governance Guidelines are available on our website at https://investors.atarabio.com/governance/governance-documents.

Compliance Program

Our Compliance Program is designed to promote ethical business conduct and compliance with applicable laws and regulations. Key components of our compliance program include policies and procedures, compliance training and educational opportunities, maintaining avenues for staff to raise concerns without fear of retaliation, including anonymously through a business conduct hotline, and responding appropriately to compliance-related events.

Stock Ownership Guidelines

Our Stock Ownership Guidelines for our directors and named executive officers further align their financial interests with those of our stockholders, as well as promote sound corporate governance. For a detailed description of our Stock Ownership Guidelines see “Other Compensation Policies and Guidelines – Stock Ownership Guidelines” below.

Insider Trading Policy (including Anti-Hedging and Anti-Pledging)

Our Insider Trading Policy prohibits all employees (including executive officers) and directors from engaging in short sales, transactions in put or call options, hedging transactions or similar inherently speculative transactions with respect to our stock at any time. For a detailed description of our Insider Trading Policy see “Other Compensation Policies and Guidelines – Insider Trading Policy (including Anti-Hedging and Anti-Pledging)” below.

Clawback Policy

For a detailed description of our Clawback Policy see “Other Compensation Policies and Guidelines – Clawback Policy” below.

Environmental, Social, and Governance

Our mission is to transform the lives of patients with serious diseases through pioneering science, teamwork and a commitment to excellence.

We are committed to building a safe, environmentally sustainable and ethical business that provides long-term value for all Atara stakeholders.

As part of this commitment, we support Environmental, Social and Governance (“ESG”) initiatives aligned to our mission, culture and core values. These values provide the foundation for us to demonstrate our dedication to patients, staff, our environment and local communities. Our Board oversees the ESG initiatives and associated risks relevant to the Company.

Governance

We are committed to good corporate governance and conducting our business in an ethical manner. We have adopted numerous policies and guidelines to facilitate legal and ethical conduct and to further align the interests of our employees and directors with our stockholders and other key stakeholders, including the patients we serve. For a detailed description of several of these policies and guidelines, see “Information Regarding the Board of Directors and Corporate Governance” above.

Transparency, Respect, Accountability, Integrity, and Trust (“TRAIT”) Values

We have formalized a set of company values to guide us in how we conduct our business, interact with colleagues and execute our corporate strategy.

Environmental Sustainability

We are committed to operating our facilities in an environmentally responsible way to reduce environmental impacts and protect our people, our business, the environment and the communities where we operate. In light of the potential impact our business may have on the environment, we have set goals and adopted a number of internal policies and management systems designed to eliminate, reduce, or substitute hazardous materials and waste and reduce water and energy consumption. For example, we constructed our Atara Research Center in Thousand Oaks, California with provisions made to comply with Title 24 requirements, including exterior wall insulation, LED lighting with energy reducing controls system, low flow restroom fixtures, drought tolerant landscaping design, waste stream segregation for landfill and recyclables, and elimination of chlorofluorocarbons and other harmful chemicals during construction.

Community

We are committed to fostering the growth of the next generation of leaders through our involvement in our communities. Through active engagement with local schools, we discuss careers in Science, Technology, Engineering, & Mathematics.

We also collaborate with other biotech companies and our local community through Biocom California, the Healthcare Businesswoman’s Association, and the Conejo Valley Chamber of Commerce, amongst others. We look forward to continuing our community involvement to advance innovation and diversity in our industry.

Staff Engagement

We are dedicated to providing an inclusive, safe, and collaborative environment for all staff. Staff engagement and feedback is an integral part of helping us create and maintain an inclusive, safe and collaborative environment for our staff.

Cybersecurity and Data Security

We have established policies and processes designed to assess, identify, and manage material risk from cybersecurity threats, and have integrated these processes into our overall risk management systems and processes. We routinely assess material risks from cybersecurity threats, including any potential unauthorized occurrence on or conducted through our information systems that may result in adverse effects on the confidentiality, integrity, or availability of our information systems or any information residing therein. We monitor our environments to identify cybersecurity threats, as well as assess our environments in the event of a material change in our business practices that may affect information systems that are vulnerable to such cybersecurity threats. These risk assessments include identification of reasonably foreseeable internal and external risks, the likelihood and potential damage that could result from such risks, and the sufficiency of existing policies, procedures, systems, and safeguards in place to manage such risks.

Following our monitoring, we adjust, implement and maintain reasonable safeguards to minimize identified risks; reasonably address any identified gaps in existing safeguards; and regularly monitor the effectiveness of our safeguards. Primary responsibility for assessing, monitoring and managing our cybersecurity risks rests with our executive leadership team, who reports to our Chief Executive Officer, to manage any identified risks and mitigation process. As part of our overall cyber security framework, we monitor and test our safeguards and train our employees on these safeguards, in collaboration with our information technology department and management. Personnel at all levels and departments are made aware of our cybersecurity policies through ongoing training.

We engage third-party vendors in connection with our cybersecurity risk monitoring and processes. These service providers assist in our design and implementation of our cybersecurity policies and procedures, as well as to monitor and test our safeguards. We require each third-party service provider to certify that it has the ability to implement and maintain appropriate security measures, consistent with all applicable laws, to implement and maintain reasonable security measures in connection with their work with us, and to promptly report any suspected breach of its security measures that may affect our company.

We also maintain insurance coverage that is intended to address certain aspects of cybersecurity risks.

Notwithstanding any of these measures, our systems and networks remain potentially vulnerable to known or unknown cybersecurity attacks and other threats, any of which could have a material adverse effect on our consolidated results of operations, financial condition and cash flows. We have experienced, and will continue to experience, cyber incidents in the normal course of our business. As of the date of this report, we have not identified any risks from cybersecurity threats, including those from any previous cybersecurity incidents, that have materially affected us, our business strategy, results of operation or financial condition. However, there can be no assurances that a cybersecurity threat or incident that could have a material impact on us will not occur in the future.

The Audit Committee of the Board of Directors is responsible for the primary oversight of our information security programs, including relating to cybersecurity. The Audit Committee receives status updates on at least a semi-annual basis from our executive leadership team on, among other things, our cyber risks and threats, the status of projects to strengthen our information security systems, assessments of our security program, and our views of the emerging threat landscape. The Chair of the Audit Committee regularly reports to the Board on cybersecurity risks and other matters reviewed by the Audit Committee. In addition, all Board members have access to the materials for each Audit Committee meeting.

Our executive leadership team is responsible for the oversight of our cybersecurity risks. We have implemented a security incident response plan and use this incident response framework as part of the process we employ to keep the Audit Committee and our executive management informed about cybersecurity risks and to monitor the prevention, detection, mitigation and remediation of cybersecurity incidents. The plan is a set of procedures and tasks that our incident response team, under the direction of the executive leadership team, executes with the goal of ensuring timely identification and appropriate resolution of cybersecurity incidents. In addition, we validate compliance with our internal data security controls through the use of security monitoring tools.

Supplier Code of Conduct

We are committed to maintaining the highest standards of legal and ethical conduct and to reflect our TRAIT values. We expect our suppliers to demonstrate a similar commitment to legal and ethical business practices. Our Supplier Code of Conduct conveys our minimum expectations for our suppliers, and their respective subcontracts and suppliers, to: (i) operate in full compliance with all laws, rules, and regulations; (ii) conduct business ethically and act with integrity; (iii) uphold the human rights of workers and to treat workers with dignity and respect; (iv) provide a safe and healthy working environment; and (v) operate in an environmentally responsible and efficient manner. Our Supplier Code of Conduct can be found on our website at https://www.atarabio.com/suppliers.

PROPOSAL 2

Advisory Vote on Executive Compensation

Under the Dodd-Frank Wall Street Reform and Consumer Protection Act, and Section 14A of the Exchange Act, the Company’s stockholders are entitled to vote to approve, on an advisory basis, the compensation of the Company’s named executive officers as disclosed in this Proxy Statement in accordance with SEC rules.

This vote is not intended to address any specific item of compensation, but rather the overall compensation of the Company’s named executive officers and the philosophy, policies and practices described in this Proxy Statement. The compensation of the Company’s named executive officers subject to the vote is disclosed in the Compensation Discussion and Analysis, the compensation tables and the related narrative disclosure contained in this Proxy Statement. As discussed in those disclosures, the Company believes that its compensation policies and decisions are designed to meet two objectives: (i) to attract and retain talented and skilled executives by paying for performance; and (ii) to align compensation of our executives with our stockholders through an appropriate mix of short-term and long-term compensation. Compensation of the Company’s named executive officers is designed to enable the Company to attract and retain talented and experienced executives to lead the Company successfully in a competitive environment.

Accordingly, the Board is asking the stockholders to indicate their support for the compensation of the Company’s named executive officers as described in this Proxy Statement by casting a non-binding advisory vote “FOR” the following resolution:

“RESOLVED, that the compensation paid to the Company’s named executive officers, as disclosed pursuant to Item 402 of Regulation S-K, including the Compensation Discussion and Analysis, compensation tables and narrative discussion that accompanies the compensation tables, is hereby APPROVED.”

Because the vote is advisory, it is not binding on the Board, the Human Capital Committee or the Company. Nevertheless, the views expressed by the stockholders, whether through this vote or otherwise, are important to the Board and the Human Capital Committee, and, accordingly, the Board and the Human Capital Committee intend to consider the results of this vote in making determinations in the future regarding executive compensation arrangements.

Advisory approval of this proposal requires the vote of the holders of a majority of the shares present in person, present by remote communication, if applicable, or represented by proxy and entitled to vote on the matter at the Annual Meeting. Unless the Board decides to modify its policy regarding the frequency of soliciting advisory votes on the compensation of the Company’s named executives, the next scheduled say-on-pay vote will be at the 2027 Annual Meeting of Stockholders.

The Board Of Directors Recommends

A Vote In Favor Of Proposal 2

PROPOSAL 3

APPROVAL OF THE FIRST AMENDMENT TO THE ATARA BIOTHERAPEUTICS, INC. 2024 EQUITY INCENTIVE PLAN

Background

As of April 16, 2026, there were 69,657 shares of common stock remaining available for future issuances under the Atara Biotherapeutics, Inc. 2024 Equity Incentive Plan (the “2024 Plan”). Given the limited number of shares that currently remain available under the 2024 Plan, the Board and management believe it is important that the Plan Amendment (as defined below) be approved in order to maintain the Company’s ability to attract, motivate, reward and retain a talented team who will contribute to our success. The Board believes that the Company has used equity in a reasonable manner under the 2024 Plan and its prior equity plans, with a three-year average burn rate of approximately 9.0% of the Company’s outstanding shares of common stock.

Proposed Amendment

On April 16, 2026, the Board approved an amendment to the 2024 Plan, subject to approval by the Company’s stockholders, that would increase the total remaining number of shares available for issuance under the amended 2024 Plan by 400,000 (the “Plan Amendment”). After adding the shares of common stock that remained available for future issuances under the 2024 Plan as of April 16, 2026 to the additional shares approved by the Plan Amendment, there will be a total of 469,657 shares available for future issuance under the 2024 Plan. If the Plan Amendment is not approved by the Company’s stockholders, the Company will continue to operate the 2024 Plan pursuant to its current provisions.

Equity Grant Practices

Dilution

Annual dilution from our equity compensation program is measured as the total number of shares subject to equity awards granted in a given year, less cancellations and other shares returned to the reserve that year, divided by total shares outstanding at the end of that year. Annual dilution from our equity compensation program for fiscal year 2025 was 1.2%. Overhang is another measure of the dilutive impact of our equity compensation program. Our overhang is equal to the number of shares subject to outstanding equity compensation awards plus the number of shares available to be granted, divided by the total number of outstanding shares. As of the Record Date, our overhang was 7.3%. As of the Record Date, the 400,000 shares being requested under the Plan Amendment would bring our aggregate overhang to approximately 12.0%. Overhang percentages are based on 8,512,272 shares of common stock outstanding as of the Record Date and does not include 6,190,060 pre-funded warrants issued and outstanding as of such date.

Burn Rate

Burn rate is a measure of the number of shares subject to equity awards that we grant annually, which helps indicate the life expectancy of our equity plans and is another measure of stockholder dilution. We determine our burn rate by dividing the aggregate number of shares subject to awards granted during a given year by the weighted average number of shares outstanding during that year. Our three-year average burn rate is 9.0% excluding pre-funded warrants, and 6.7% including pre-funded warrants, and our burn rate for each of the past three fiscal years has been as follows:


Year	Stock Options Granted (A)	Full-Value Awards Granted (RSUs) (B)	Total (A)+(B)(1)	Basic Weighted Average Common Shares Outstanding	Burn Rate (2)	Burn Rate Including Warrants Outstanding (3)
2025	—	386,068	386,068	6,684,047	5.8%	3.1%
2024	—	548,774	548,774	5,063,222	10.8%	7.3%
2023	4,693,897	5,635,916	10,329,813	99,885,158	10.3%	9.8%

(1) Includes shares forfeited by former employees upon termination of their employment and subsequently re-issued, from time to time, to then current employees, in each case, in accordance with the 2024 Plan.

(2) Does not include issued and outstanding pre-funded warrants. As of December 31, 2025, 5,860,078 pre-funded warrants were issued and outstanding.

(3) Includes issued and outstanding pre-funded warrants. As of December 31, 2025, 5,860,078 pre-funded warrants were issued and outstanding

Certain Features of the 2024 Plan

The following features of the 2024 Plan are designed to reinforce alignment between the equity compensation arrangements awarded pursuant to the 2024 Plan and our stockholders’ interests:

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No discounting of stock options or stock appreciation rights;

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No repricing or replacement of underwater stock options or stock appreciation rights without stockholder approval;

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No dividend equivalents on stock options or stock appreciation rights;

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No dividends or dividend equivalents paid on unearned awards;

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No liberal share recycling provision;

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Annual non-employee director compensation limit; and

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No liberal definition of “change in control.”

Purposes of the 2024 Plan

Equity-based compensation is a significant component of our compensation program and the 2024 Plan is intended to help the Company secure and retain the services of eligible award recipients, provide incentives for such persons to exert maximum efforts for the success of the Company and any affiliate and provide a means by which the eligible recipients may benefit from increases in value of our common stock.

Under the 2024 Plan, the Company may grant:

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Non-qualified stock options;

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Incentive stock options (within the meaning of Section 422 of the Internal Revenue Code);

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Stock appreciation rights (“SARs”);

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Restricted stock, restricted stock units and other stock awards (collectively, “Stock Awards”); and

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Performance awards.

Description of the 2024 Plan

The following description is qualified in its entirety by reference to the 2024 Plan, as amended by the Plan Amendment, and the Plan Amendment, copies of which are attached as Appendices A and B and which are incorporated into this Proxy Statement by reference. The following does not purport to be a complete description of all of the provisions of the 2024 Plan, as amended by the Plan Amendment.

Administration

The 2024 Plan is administered by the Compensation Committee of the Board (the “Plan Committee”). Each member of the Plan Committee is intended to be (i) a “non-employee director” within the meaning of Rule 16b-3 under the Exchange Act and (ii) “independent” within the meaning of the rules of Nasdaq.

Subject to the express provisions of the 2024 Plan, the Plan Committee has the authority to select eligible persons to receive awards and determine all of the terms and conditions of each award. All awards will be evidenced by an agreement containing such terms and conditions not inconsistent with the 2024 Plan as the Plan Committee approves. The Plan Committee also has authority to establish rules and regulations for administering the 2024 Plan and to decide questions of interpretation or application of any provision of the 2024 Plan. The Plan Committee may take any action to (1) accelerate, in whole or in part, the time at which an award may be exercised or vest or (2) provide that any performance measures applicable to any outstanding award be deemed satisfied at the target, maximum or any other level.

The Plan Committee may delegate some or all of its power and authority under the 2024 Plan to a subcommittee of the Board, a member of the Board or an officer of the Company as the Plan Committee deems appropriate, except that it may not delegate its power and authority to a member of the Board or any officer with regard to awards to persons subject to Section 16 of the Exchange Act.

Available Shares

Under the 2024 Plan, as amended by the Plan Amendment, the number of shares of common stock available for all awards, other than substitute awards granted in connection with corporate transactions, will be 975,000 shares (the “Share Reserve”), which represents 575,000 shares initially authorized for issuance, plus 400,000 shares that will become available for issuance if the Company’s stockholders approve the Plan Amendment. This amount is subject to adjustment in the event of any equity restructuring that causes the per-share value of shares of common stock to change, including, without limitation, a merger, stock dividend, stock split, combination of shares or recapitalization through a

SEC Form DEF 14A filed by Atara Biotherapeutics Inc.