Exhibit 99.1 Atara Biotherapeutics Announces Fourth Quarter and Full Year 2023 Financial Results and Operational Progress Tab-cel U.S. BLA on Track for Submission in Q2 2024 Following Positive Pre-BLA Meeting Allogeneic CAR T Pipeline Expands Into Autoimmune Disease With Plans To Initiate a ATA3219 Lupus Nephritis Study in H2 2024, and Initial Clinical Data Expected H1 2025 ATA3219 NHL Study Enrolling With Initial Clinical Data Expected in Q4 2024 Cash Runway Into 2027 Enables Key Pipeline Readouts THOUSAND ...