Exhibit 99.1 SELLAS Life Sciences Reports First Quarter 2024 Financial Results and Provides Corporate Update - Announced Independent Data Monitoring Committee’s (IDMC) Recommendation to Continue the Phase 3 REGAL Study in Patients with Acute Myeloid Leukemia (AML) Without Modifications: IDMC to Reconvene in June - - Completed Enrollment in Phase 3 REGAL Study of Galinpepimut-S - - Announced Positive Phase 2 Data of SLS009 Demonstrating 100% Response Rate in r/r AML Patients with ASXL1 Mutation at 30 mg BIW ...