Exhibit 99.1 SELLAS Life Sciences Reports Third Quarter 2025 Financial Results and Provides Corporate Update Recent Corporate Highlights: Phase 3 REGAL Trial of GPS: Following the positive IDMC recommendation announced in August to continue the trial without modification, the Phase 3 REGAL trial of GPS in patients with acute myeloid leukemia (AML) who have achieved complete remission following second-line salvage therapy (CR2) remains on track and continues to execute as planned. The final analysis will be ...