SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this Agreement ) is dated as of

SECURITIES PURCHASE AGREEMENT

This Securities Purchase Agreement (this Agreement ) is dated as of September 3, 2024, between Atara Biotherapeutics,

Inc., a corporation incorporated under the laws of the state of Delaware (the Company ), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a Purchaser and

collectively the Purchasers ).

WHEREAS, subject to the terms and conditions set forth in this Agreement and pursuant to

an effective registration statement under the Securities Act (as defined below), the Company desires to issue and sell to each Purchaser, and each Purchaser, severally and not jointly, desires to purchase from the Company, securities of the Company

as more fully described in this Agreement.

NOW, THEREFORE, IN CONSIDERATION of the mutual covenants contained in this Agreement, and for

other good and valuable consideration the receipt and adequacy of which are hereby acknowledged, the Company and each Purchaser agree as follows:

1.1 Definitions. In addition to the terms defined elsewhere in this Agreement, for all purposes of this Agreement, the following

terms have the meanings set forth in this Section 1.1:

Acquiring Person shall have the meaning ascribed to such

term in Section 4.5.

Action means any action, suit, inquiry, notice of violation, proceeding (including any

partial proceeding such as a deposition) or investigation pending or, to the Company s Knowledge, threatened in writing against or affecting the Company, any Subsidiary or any of their respective properties or any officer, director or employee

of the Company or any Subsidiary acting in his or her capacity as an officer, director or employee before or by any federal, state, county, local or foreign court, arbitrator, governmental or administrative agency, regulatory authority, stock

market, stock exchange or trading facility.

Affiliate means any Person directly or indirectly controlled by, controls

or is under common control with a Person as such terms are used in and construed under Rule 405 under the Securities Act.

Allocation Schedule means the allocation schedule of a Purchaser delivered to the Company at Closing in accordance with

Section 2.3(b) hereof, in the form of Exhibit B hereto.

Board of Directors means the board of directors of

Business Day means any day other than Saturday, Sunday or other day on which commercial banks in The City

of New York are authorized or required by law to remain closed; provided, however, for clarification, commercial banks shall not be deemed to be authorized or required by law to remain closed due to stay at home , shelter-in-place , non-essential employee or any other similar orders or restrictions or the closure of any

physical branch locations at the direction of any governmental authority so long as the electronic funds transfer systems (including for wire transfers) of commercial banks in The City of New York generally are open for use by customers on such day.

Closing means the closing of the purchase and sale of the Securities pursuant to Section 2.1.

Closing Date means September 5, 2024.

Commission means the United States Securities and Exchange Commission.

Common Stock means the common stock of the Company, par value $0.0001 per share, and any other class of securities

into which such securities may hereafter be reclassified or changed.

Common Stock Equivalents means any securities of

the Company or its Subsidiaries which would entitle the holder thereof to acquire at any time Common Stock, including, without limitation, any debt, preferred stock, right, option, warrant or other instrument that is at any time convertible into or

exercisable or exchangeable for, or otherwise entitles the holder thereof to receive, Common Stock.

Common Stock Per Share

Purchase Price equals $8.25, subject to adjustment for reverse and forward stock splits, stock dividends, stock combinations and other similar transactions of the Common Stock that occur after the date of this Agreement.

Company Counsel means Sidley Austin LLP, with offices located at 555 California Street, Suite 2000, San Francisco,

Company s Knowledge means with respect to any statement made to the Company s Knowledge,

that the statement is based upon the actual knowledge, following reasonable due inquiry, of the executive officers (as defined in Rule 16a-1(f) of the Exchange Act) of the Company having responsibility for the

matter or matters that are the subject of the statement.

Disclosure Time means, (i) if this Agreement is signed

on a day that is not a Trading Day or after 9:00 a.m. (New York City time) and before midnight (New York City time) on any Trading Day, 9:01 a.m. (New York City time) on the Trading Day immediately following the date hereof, unless otherwise agreed

in writing as to an earlier time by the Company and the Purchasers, and (ii) if this Agreement is signed between midnight (New York City time) and 9:00 a.m. (New York City time) on any Trading Day, no later than 9:01 a.m. (New York City time)

on the date hereof, unless otherwise agreed in writing as to an earlier time by the Company and the Purchasers.

Date means, the date on which the Company s certifying officers have evaluated the effectiveness of the Company s disclosure controls and procedures as of the end of the period covered by the Company s most recently filed

periodic report under the Exchange Act.

Exchange Act means the Securities Exchange Act of 1934, as amended, and the

rules and regulations promulgated thereunder.

Exempt Issuance means the issuance of (a) shares of Common Stock or

options to employees, officers, directors or consultants of the Company pursuant to any stock or option plan duly adopted for such purpose, by a majority of the non-employee members of the Board of Directors

or a majority of the members of a committee of non-employee directors established for such purpose for services rendered to the Company; provided that the issuance of any such securities to any consultant

(i) are issued as restricted securities (as defined in Rule 144) and carry no registration rights that require or permit the filing of any registration statement in connection therewith during the prohibition period in

Section 4.11(a) herein or (ii) are subject to a written lock-up agreement for the term of prohibition period in Section 4.11 herein, (b) securities upon the exercise or exchange of or

conversion of any Securities issued hereunder, and/or other securities exercisable or exchangeable for or convertible into shares of Common Stock issued and outstanding on the date of this Agreement, provided that such securities have not been

amended since the date of this Agreement to increase the number of such securities or to decrease the exercise price, exchange price or conversion price of such securities (other than in connection with stock splits or combinations) or to extend the

term of such securities and (c) securities issued pursuant to acquisitions or strategic

transactions approved by a majority of the disinterested directors of the Company, provided that such securities (i) are issued as restricted securities (as defined in Rule 144)

and carry no registration rights that require or permit the filing of any registration statement in connection therewith during the prohibition period in Section 4.11(a) herein or (ii) are subject to a written lock-up agreement, and provided that any such issuance shall only be to a Person (or to the equityholders of a Person) which is, itself or through its subsidiaries, an operating company or an owner of an asset in a

business synergistic with the business of the Company, but shall not include a transaction in which the Company is issuing securities primarily for the purpose of raising capital or to an entity whose primary business is investing in securities.

FCPA means the Foreign Corrupt Practices Act of 1977, as amended.

FDA means the Food and Drug Administration of the U.S. Department of Health and Human Services.

GAAP means U.S. generally accepted accounting principles, as applied by the Company.

Intellectual Property Rights shall have the meaning ascribed to such term in Section 3.1(p).

Liens means a lien, charge, pledge, security interest, encumbrance, right of first refusal, preemptive right or other

Material Adverse Change shall have the meaning ascribed to such term in Section 3.1(j).

Material Adverse Effect means (i) a material adverse effect on the results of operations, assets, prospects, business

or financial condition of the Company and its Subsidiaries, taken as a whole, or (ii) a material adverse effect on the Company s ability to perform in any material respect on a timely basis its obligations under any Transaction Document;

except that, with respect to the foregoing clause (i), any of the following, either alone or in combination, shall not be deemed a Material Adverse Effect: (A) effects caused by changes or circumstances affecting general market conditions in

the U.S. economy or which are generally applicable to the industry in which the Company operates, provided that such effects are not borne disproportionately by the Company, (B) effects resulting from or relating to the announcement or

disclosure of the sale of the Securities or other transactions contemplated by this Agreement, or (C) effects caused by any event, occurrence or condition resulting from or relating to the taking of any action in accordance with this Agreement.

Material Contract means any contract, instrument or other agreement to which the Company is a party or by which it is

bound which is material to the business of the Company, including those that have been filed as an exhibit to the SEC Reports pursuant to Item 601(b)(10) of Regulation S-K.

Material Permits shall have the meaning ascribed to such term in Section 3.1(n).

Person means an individual or corporation, partnership, trust, incorporated or unincorporated association, joint venture,

limited liability company, joint stock company, government (or an agency or subdivision thereof) or other entity of any kind.

Proceeding means an action, claim, suit, arbitration, hearing, investigation or proceeding (including, without limitation,

an informal investigation or partial proceeding, such as a deposition), whether commenced or threatened.

means the prospectus included in the Registration Statement, including the information incorporated by reference therein, at the time it was declared effective by the Commission.

Prospectus Supplement means the supplement to the Prospectus complying

with Rule 424(b) of the Securities Act containing certain supplemental information regarding the Securities and the terms of the offering of the Securities that will be filed with the Commission, including the information incorporated by reference

therein, and delivered by the Company to each Purchaser on or prior to the date hereof.

Purchaser Party shall have the

meaning ascribed to such term in Section 4.8.

Registration Statement means the Registration Statement on Form S-3 (File No. 333-275256) filed by the Company with the Commission and declared effective on November 13, 2023, including the information incorporated by reference

Required Approvals shall have the meaning ascribed to such term in Section 3.1(e).

Rule 144 means Rule 144 promulgated by the Commission pursuant to the Securities Act, as such Rule may be amended or

interpreted from time to time, or any similar rule or regulation hereafter adopted by the Commission having substantially the same purpose and effect as such Rule.

Rule 424 means Rule 424 promulgated by the Commission pursuant to the Securities Act, as such Rule may be amended or

interpreted from time to time, or any similar rule or regulation hereafter adopted by the Commission having substantially the same purpose and effect as such Rule.

SEC Reports shall have the meaning ascribed to such term in Section 3.1(h).

Securities means, collectively, the Shares, the Warrants and the Warrant Shares.

Securities Act means the Securities Act of 1933, as amended, and the rules and regulations promulgated thereunder.

Shares means the shares of Common Stock issued to each Purchaser on the Closing Date.

Short Sales means all short sales as defined in Rule 200 of Regulation SHO under the Exchange Act (but shall

not be deemed to include locating and/or borrowing shares of Common Stock).

Subscription Amount means, as to each

Purchaser, the aggregate amount to be paid for the Shares and/or Warrants, as applicable, purchased hereunder as specified below in such Purchaser s Allocation Schedule and next to the heading Subscription Amount, in United States

dollars and in immediately available funds.

Subsidiary means the subsidiary of the Company as set forth in the SEC

Reports, and shall, where applicable, also include any direct or indirect subsidiary of the Company formed or acquired after the date hereof.

Trading Day means a day on which the principal Trading Market is open for trading.