X0306 4 2019-01-23 0 0001604464 Atara Biotherapeutics, Inc. ATRA 0001612096 Ciechanover Isaac E. 611 GATEWAY BOULEVARD SUITE 900 SOUTH SAN FRANCISCO CA 94080 1 1 0 0 Chief Executive Officer Common Stock 2019-01-23 4 S 0 3000 34.84 D 301252 I See footnote Common Stock 2019-01-23 4 S 0 800 35.59 D 300452 I See footnote Common Stock 2019-01-23 4 S 0 100 36.58 D 300352 I See footnote Common Stock 2019-01-24 4 S 0 3470 34.98 D 296882 I See footnote Common Stock 2019-01-24 4 S 0 430 35.82 D 296452 I See footnote Common Stock 433111 D Transaction pursuant to Rule 10b5-1 Plan adopted January 23, 2018. The price in Column 4 is a weighted average sale price. The prices actually received ranged from $34.35 to $35.12. 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. Shares are held by the Isaac E. Ciechanover and Allison M. Ciechanover Family Trust dated 8/8/08, of which the Reporting Person is a trustee. The price in Column 4 is a weighted average sale price. The prices actually received ranged from $35.40 to $36.40. 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. The price in Column 4 is a weighted average sale price. The prices actually received ranged from $34.50 to $35.49. 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. The price in Column 4 is a weighted average sale price. The prices actually received ranged from $35.635 to $36.07. 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. /s/ David Tucker, Attorney-in-Fact for Isaac E. Ciechanover 2019-01-25