Exhibit 99.1 Atara Biotherapeutics Announces First Quarter 2024 Financial Results and Operational Progress Tab-cel® U.S. BLA on Track for Submission in Q2 2024 Initiation of ATA3219 Lupus Nephritis Study Expected in Q4 2024, with Initial Clinical Data Expected in H1 2025 Initiation of New ATA3219 Cohort Without Lymphodepletion in Severe Systemic Lupus Erythematosus Planned for Q4 2024, with Initial Clinical Data Expected in H2 2025 Enrolling ATA3219 Non-Hodgkin’s Lymphoma Study, with Initial Clinical Data E ...