SELLAS Life Sciences Extends Survival Timeline In GPS Maintenance Study For AML Patients

SELLAS Life Sciences Group Inc. (SLS) has demonstrated notable progress in its pivotal Phase 3 REGAL investigation, with patient survival outlasting initial projections and pushing back the statistical milestone needed to complete the trial’s primary analysis. The stock reflected investor confidence, closing yesterday up 16.72% at $3.35 after trading within a $0.85 to $3.43 range over the preceding twelve months.

Extended Survival Data Points to Trial Momentum

As of late December 2025, SELLAS’s research partner reported that 72 clinical events had been recorded in the REGAL study—still below the required 80 events that will unlock the final overall survival assessment. This slower-than-typical event accumulation actually carries strategic implications for the trial’s success potential, as experts noted during SELLAS’s recent investor conference.

The REGAL program is investigating Galinpepimut-S (GPS) as a post-remission therapeutic for acute myeloid leukemia patients who have reached a second complete remission (CR2) but cannot pursue stem cell transplantation. This represents a challenging patient population with limited options, typically managed with hypomethylating compounds or BCL-2 antagonists, where historical median survival stands around eight months—underscoring the urgent therapeutic void in this setting.

How Extended Timelines Could Reshape Outcomes

GPS, a WT1-directed immunotherapeutic sourced from Memorial Sloan Kettering Cancer Center, targets this gap by potentially prolonging survival duration. The Independent Data Monitoring Committee provided clearance in August 2025 for REGAL to continue without protocol adjustments, and the company remains completely blinded regarding efficacy metrics and survival distributions.

Because REGAL operates as an event-driven design, SELLAS will make a public disclosure once the 80th clinical event transpires. At that juncture, the study database will be unmasked and comprehensive statistical evaluations will commence. Notably, the organization has not performed interim efficacy reviews and has avoided any associated statistical penalties, positioning the trial favorably for its conclusion phase.

Pipeline Expansion: CDK9 Inhibitor Advances

Beyond GPS, SELLAS is progressing SLS009 (tambiciclib), a selective CDK9 inhibitor currently in Phase 2a development for refractory or relapsed acute myeloid leukemia in patients with resistance to venetoclax-based regimens. This program emerged from an earlier Phase 1 study in hematologic cancers, with a parallel monotherapy investigation continuing in relapsed or refractory peripheral T-cell lymphoma populations, broadening the therapeutic scope of SELLAS’s clinical portfolio.