atra-defa14a_20210608.htm

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

☐	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

☒	No fee required.

☐	Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.

Title of each class of securities to which transaction applies:

Aggregate number of securities to which transaction applies:

Per unit price or other underlying value of transaction computed pursuant to Exchange Act Rule 0-11 (Set forth the amount on which the filing fee is calculated and state how it was determined):

Proposed maximum aggregate value of transaction:

Total fee paid:

☐	Fee paid previously with preliminary materials.

☐	Check box if any part of the fee is offset as provided by Exchange Act Rule 0-11(a)(2) and identify the filing for which the offsetting fee was paid previously. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

Amount Previously Paid:

Form, Schedule or Registration Statement No.:

Filing Party:

Date Filed:

Your Vote Counts! ATARA BIOTHERAPEUTICS, INC. 611 GATEWAY BLVD., SUITE 900 SOUTH SAN FRANCISCO, CA 94080 ATARA BIOTHERAPEUTICS, INC. 2021 Annual Meeting Vote by June 7, 2021 11:59 PM ET You invested in ATARA BIOTHERAPEUTICS, INC. and it’s time to vote! You have the right to vote on proposals being presented at the Annual Meeting. This is an important notice regarding the availability of proxy material for the stockholder meeting to be held on June 8, 2021. Vote in Person at the Meeting* June 8, 2021 9:00 AM, PDT Smartphone users Point your camera here and vote without entering a control number V1 For complete information and to vote, visit www.ProxyVote.com Control # D47738-P55168 Get informed before you vote View the Notice and Proxy Statement and Form 10-K online OR you can receive a free paper or email copy of the material(s) by requesting prior to May 25, 2021. If you would like to request a copy of the material(s) for this and/or future stockholder meetings, you may (1) visit www.ProxyVote.com, (2) call 1-800-579-1639 or (3) send an email to sendmaterial@proxyvote.com. If sending an email, please include your control number (indicated below) in the subject line. Unless requested, you will not otherwise receive a paper or email copy. 2430 Conejo Spectrum Street Thousand Oaks, CA 91320 *Please check the meeting materials for any special requirements for meeting attendance. At the meeting, you will need to request a ballot to vote these shares.

THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming stockholder meeting. Please follow the instructions on the reverse side to vote these important matters. Vote at www.ProxyVote.com Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click “Sign up for E-delivery”. Voting Items Board Recommends D47739-P55168 01) Eric L. Dobmeier 02) William K. Heiden 03) Beth Seidenberg, M.D. 1. Election of Directors Nominees: 2. To approve, on an advisory basis, the compensation of the Company’s named executive officers, as disclosed in the Proxy Statement. 3. To ratify the selection of Deloitte & Touche LLP as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2021. NOTE: Such other matters that may properly come before the meeting or any adjournment or postponement thereof will be voted on by the proxy holders in their discretion. For For For