Exhibit 99.1 SELLAS Life Sciences Reports Full Year 2023 Financial Results and Provides Corporate Update – Announced Phase 2a study of SLS009 in r/r AML Showing 50% Response Rate in the Selected Optimal Dose of 30 mg BIW Exceeding the Targeted 20% and 100% Response Rate in Patients with Identified Biomarkers - – Completed Enrollment in Phase 3 REGAL Study of Galinpepimut-S in Patients with Acute Myeloid Leukemia; Steering Committee Guided Interim Analysis May Be Imminent; IDMC Scheduled in Late April- – Pha ...