SELLAS Shares Surge as GPS Immunotherapy Shows Encouraging Survival Extension in AML Study

SELLAS Life Sciences Group Inc. (SLS) shares closed trading yesterday at $3.35, reflecting a robust 16.72% gain following the company’s disclosure of positive trial momentum. The stock has fluctuated within the range of $0.85 to $3.43 over the past twelve months, underscoring investor interest in the biotech firm’s pipeline advancement.

The strength comes as SELLAS revealed that its Phase 3 REGAL trial evaluating Galinpepimut-S (GPS) as a maintenance therapy is progressing more favorably than initially projected. As of December 26, 2025, the trial has registered 72 clinical events out of the 80 deaths required to unlock the final overall survival analysis in patients with acute myeloid leukemia (AML). This delay in reaching the endpoint threshold suggests that treated patients are experiencing extended survival durations compared to historical expectations.

The REGAL Trial: Addressing a Critical Clinical Gap

The REGAL investigation focuses on AML patients who have achieved a second complete remission (CR2) but are ineligible for transplantation—a particularly challenging population historically managed with hypomethylating agents and BCL-2 inhibitors. In this setting, median overall survival typically spans approximately eight months, highlighting the substantial therapeutic void that GPS aims to fill.

GPS, a WT1-targeting immunotherapeutic licensed from Memorial Sloan Kettering Cancer Center, represents a novel approach to extending survival in this difficult-to-treat cohort. The mechanism targets Wilms tumor antigen 1, leveraging immunological pathways to combat disease progression. Remarkably, SELLAS remains completely blinded to all efficacy and survival data, maintaining the integrity of the ongoing analysis.

Regulatory and Monitoring Developments

The Independent Data Monitoring Committee (DMC) previously advised in August 2025 that the trial should proceed unmodified, signaling confidence in the study design and execution. The extended survival observed may positively influence the probability of demonstrating a clinically meaningful benefit, as emphasized by key opinion leaders during SELLAS’s recent research and development event.

No interim efficacy assessments have been performed to date, and no statistical penalties have accumulated. The company will announce the occurrence of the 80th event, at which point the study will be unblinded and comprehensive final analyses will commence.

Expanding Portfolio Beyond GPS

In parallel, SELLAS is progressing SLS009 (tambiciclib), a highly selective CDK9 inhibitor currently in Phase 2a testing for relapsed or refractory AML in patients who have previously failed or become refractory to venetoclax-based regimens. This candidate follows successful completion of a Phase 1 study in hematologic malignancies and is complemented by an ongoing monotherapy investigation in relapsed or refractory peripheral T-cell lymphoma, broadening the therapeutic potential across multiple hematologic cancers.