X0306 4 2018-05-15 0 0001604464 Atara Biotherapeutics, Inc. ATRA 0001706400 Porter Derrell C/O ATARA BIOTHERAPEUTICS, INC. 611 GATEWAY BOULEVARD, SUITE 900 SOUTH SAN FRANCISCO CA 94080 0 1 0 0 SVP, Head of Global Commercial Common Stock 2018-05-15 4 M 0 16334 14.30 A 28834 D Common Stock 2018-05-15 4 S 0 16334 45.02 D 12500 D Employee Stock Option (Right to Buy) 14.30 2018-05-15 4 M 0 16334 0.00 D 2024-05-10 Common Stock 16334 113666 D Transaction pursuant to Rule 10b5-1 Plan adopted March 9, 2018. The price in Column 4 is a weighted average sale price. The prices actually received ranged from $45.00 to $45.05. The reporting person will provide to the issuer, any security holder of the issuer, or the SEC staff, upon request, information regarding the number of shares sold at each price within the range 25% of the shares subject to the option vest and become exercisable on May 10, 2018 and 1/48th of the shares subject to the stock option vest and become exercisable each full month thereafter. /s/ David Tucker, Attorney-in-Fact for Derrell Porter 2018-05-16