SELLAS Life Sciences Announces No Outcomes Analyses Were Performed, No Statistical Penalty Incurred In Its Phase 3 REGAL Trial Evaluating Galinpepimut-S

SELLAS Life Sciences Group, Inc. (NASDAQ: SLS) ("SELLAS'' or the "Company"), a late-stage clinical biopharmaceutical company focused on the development of novel therapies for a broad range of cancer indications, today provided an update on the ongoing Phase 3 REGAL trial evaluating GPS as a potential maintenance therapy in patients with AML after second complete remission (CR2).

Following the Independent Data Monitoring Committee (IDMC) recommendation in August 2025 that the Phase 3 REGAL trial continue without modification, it was expected that the 80th event (death) required to trigger the final analysis would occur before year-end. The REGAL trial is an overall survival study, and per the statistical analysis plan, the final analysis will be triggered once 80 events (deaths) have occurred.

SELLAS was informed by its contract research organization managing the REGAL trial that the pooled number of events was 72 as of December 26, 2025. SELLAS remains blinded to all efficacy and survival data outcomes and, as no outcomes analyses were performed and no statistical penalty has been incurred, this one-time update on the aggregate number of events does not impact future statistical analyses. Because the final analysis is event-driven, and the timing of studies with overall survival as an endpoint can vary, SELLAS will announce the 80th event when it occurs.