144 0001977970 XXXXXXXX LIVE 0001604464 Atara Biotherapeutics, Inc. 001-36548 c/o Atara Biotherapeutics, Inc. 1280 Rancho Conejo Boulevard Thousand Oaks CA 91320 805-623-4211 Nguyen AnhCo Director Officer Common Stock Morgan Stanley Smith Barney LLC

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

5981 62680.88 9371144 05/18/2026 NASDAQ Common Stock 05/15/2026 Settlement of vested RSUs issued under an S-8 Registration Plan Issuer N 13887 05/15/2026 Equity compensation for services rendered N AnhCo Nguyen

1280 Rancho Conejo Boulevard Thousand Oaks CA 91320

Common Stock 03/02/2026 2996 15237.36 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 AnhCo Nguyen