SELLAS Life Sciences Group, Inc. announced that it has started patient screening for its pivotal Phase 3 REGAL clinical trial of its lead clinical candidate, galinpepimut-S (GPS), in patients with acute myeloid leukemia (AML) who have achieved complete remission after second-line anti-leukemic therapy (CR2). The study is expected to enroll approximately 116 patients across approximately 50 clinical sites in the U.S. and Europe. GPS was previously granted Fast Track designation and orphan drug designation in AML by the U.S. Food and Drug Administration (FDA) and orphan drug designation by the European Medicines Agency (EMA). The REGAL study is a 1:1 randomized, open-label study comparing GPS monotherapy in the maintenance setting to investigators’ choice best available treatment in AML patients who have achieved hematologic complete remission, with or without thrombocytopenia (CR2/CR2p), after second-line antileukemic therapy and who are deemed ineligible for or unable to undergo allogeneic stem-cell transplantation. The primary endpoint is the overall survival (OS) from the time of study entry. Secondary endpoints include leukemia-free survival, antigen-specific T-cell immune response dynamics, measurable residual disease by multigene array, and assessments of AML clonal evolution and inflammasome molecular signatures in the tumor microenvironment in bone marrow biopsy samples. The Company anticipates interim analysis for safety and futility in the fourth quarter of 2021. In a previous Phase 2a study in AML patients in the CR2 setting, GPS demonstrated a clinically meaningful and statistically significant median OS of 16.3 months in AML CR2 patients vs. 5.4 months in contemporaneously assessed unvaccinated patients (p = 0.0175). Treatment-related adverse events were primarily comprised of Grade 1 or 2 local injection site reactions and one Grade 3 (transient leukopenia) adverse event. A second previous Phase 2 study of GPS in AML patients who achieved first complete remission (CR1) also met its primary endpoint with an OS rate at 3 years from first vaccination of 47%.