X0306 4 2022-03-01 0001604464 Atara Biotherapeutics, Inc. ATRA 0001809916 Murugan Amar C/O ATARA BIOTHERAPEUTICS, INC. 611 GATEWAY BOULEVARD,SUITE 900 SOUTH SAN FRANCISCO CA 94080 true SVP, GC & Secretary Common Stock 2022-03-01 4 A 0 51814 0 A 139535 D Common Stock 2022-03-01 4 S 0 1465 9.857 D 138070 D Common Stock 2022-03-01 4 S 0 1112 9.856 D 136958 D Employee Stock Option (Right to Buy) 10.21 2022-03-01 4 A 0 97398 0 A 2032-02-28 Common Stock 97398 97398 D These restricted stock units vest in 16 equal quarterly installments on each Company Quarterly Vesting Date (as defined below), with the initial installment vesting on May 15, 2022, subject to the reporting person's continuous service. Company Quarterly Vesting Date means March 1, May 15, August 15 and November 15 of each year. Shares sold pursuant to a 10b5-1 arrangement to satisfy tax obligations in connection with the vesting of previously granted restricted stock units. The sale price of the reporting person's shares represents the weighted average price of all shares sold by a broker on March 1, 2022 on behalf of a group of employees of the Issuer to satisfy the payment of withholding tax liability of such employee. 1/48th of the shares subject to the stock option vest and become exercisable each month with the initial installment vesting on April 1, 2022, subject to the reporting person's continuous service. Includes 181 shares purchased under the Issuer's Employee Stock Purchase Plan on November 30, 2021. /s/ David Tucker, Attorney-in-Fact for Amar Murugan 2022-03-03