X0306 4 2017-11-15 0 0001604464 Atara Biotherapeutics, Inc. ATRA 0001612094 Clark Mitchall G. 611 GATEWAY BOULEVARD SUITE 900 SOUTH SAN FRANCISCO CA 94080 0 1 0 0 EVP & Chief R & QA Officer Common Stock 2017-11-15 4 M 0 7212 0.00 A 166342 D Common Stock 2017-11-16 4 S 0 3290 14.20 D 163052 D Restricted Stock Unites 2017-11-15 4 M 0 7212 0.00 D Common Stock 7212 12019 D Shares issued upon settlement of vested restricted stock units ("RSUs"). Shares sold to cover tax obligation from settlement of vested restricted stock units. Transaction pursuant to Rule 10b5-1 Plan adopted October 12, 2016. Each restricted stock unit represents a contingent right to receive one share of the Issuer's common stock or a cash settlement. The RSUs were granted with both (a) a liquidity event-based vesting condition and (b) a service-based vesting condition, both of which conditions must be satisfied in order for the RSUs to vest. The liquidity event-based condition was satisfied upon the closing of the Issuer's initial public offering (the "IPO"). The shares that vested on the closing date of the IPO, and the shares that vested thereafter through May 15, 2015, were settled on May 15, 2015. The service-based vesting condition provides that 25% of the total number of shares on March 17, 2015 and 1/48th of the total number of shares monthly thereafter, subject to the holder's continuous service through each such date. The earlier of (i) March 27, 2021 or (ii) the recepient's termination date. /s/ Tina Gullotta, Attorney-in-Fact for Mitchall G. Clark 2017-11-17