SELLAS Life Sciences Group (SLS) Study Update summary

Study milestone and context

• The pivotal phase III REGAL study for GPS in AML patients in complete remission after second-line salvage therapy reached the interim analysis trigger of 60 events.

• REGAL is an open-label, event-driven, registrational Phase 3 trial with overall survival as the primary endpoint and 126 patients enrolled.

• Interim analysis represents 48% of the study population; final analysis will occur at 80 events (63%).

• A conservative O'Brien-Fleming boundary will be used to determine statistical significance at interim and final analyses.

• A webcast was scheduled to discuss the process and potential outcomes of the interim analysis.

IDMC process and possible outcomes

• The IDMC will review efficacy, futility, and safety data at a meeting scheduled for January 2025, using unblinded data.

• The IDMC will hold closed and open sessions to review unblinded and blinded data, respectively, and provide recommendations.

• Recommendations may include continuing the trial, modifying it, or discontinuing based on efficacy or futility; discontinuation could result from either futility or exceptional efficacy observed at interim analysis.

• If the trial proceeds to 80 events, it may indicate GPS extends survival and is a positive sign.

• Any recommendation to stop for efficacy will be communicated to the FDA before public disclosure.

Study design and objectives

• IDMC is responsible for periodic reviews of safety, efficacy, and futility, ensuring scientific and clinical validity.