X0508 4 2026-03-02 0001604464 Atara Biotherapeutics, Inc. ATRA 0002064348 Grant-Huerta Yanina C/O ATARA BIOTHERAPEUTICS, INC. 1280 RANCHO CONEJO BOULEVARD THOUSAND OAKS CA 91320 true Chief Accounting Officer false Common Stock 2026-03-02 4 S 0 24 5.077 D 33830 D Common Stock 2026-03-02 4 S 0 1603 5.081 D 32227 D Common Stock 2026-03-02 4 S 0 377 5.082 D 31850 D Common Stock 2026-03-02 4 S 0 100 5.083 D 31750 D 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. The sale price of the reporting person's shares represents the weighted average price of all shares sold by a broker on March 2, 2026 on behalf of a group of employees of the Issuer to satisfy the payment of withholding tax liability of such employees. This amount includes 400 shares purchased under the Issuer's Employee Stock Purchase Plan on November 28, 2025. /s/ John Chao, Attorney-in-Fact for Yanina Grant-Huerta 2026-03-04