144 0002064348 XXXXXXXX LIVE 0001604464 Atara Biotherapeutics, Inc. 001-36548 c/o Atara Biotherapeutics, Inc. 1280 Rancho Conejo Boulevard Thousand Oaks CA 91320 805-623-4211 Grant-Huerta Yanina Officer Common Stock Morgan Stanley Smith Barney LLC

Executive Services 200 W Civic Center Drive, 4th Floor Sandy UT 84070

2754 28861.92 9371144 05/18/2026 NASDAQ Common Stock 05/15/2026 Settlement of vested RSUs issued under an S-8 Registration Plan Issuer N 6393 05/15/2026 Equity compensation for services rendered N Yanina Grant-Huerta

1280 Rancho Conejo Boulevard Thousand Oaks CA 91320

Common Stock 03/02/2026 2104 10690.91 Shares sold automatically to satisfy tax withholding obligations in connection with the vesting of previously granted restricted stock units, pursuant to a sale-to-cover provision in the award agreement. 05/18/2026 /s/ John Chao, Attorney-in-Fact for Yanina Grant-Huerta