SELLAS Life Sciences (SLS) Reports Positive Follow-Up Phase 1/2 Clinical Data for Galinpepimut-S in Acute Myeloid Leukemia

SELLAS Life Sciences Group, Inc. (NASDAQ: SLS) today announced final follow-up data for its Phase 1/2 study of GPS in patients with acute myeloid leukemia (AML) in second complete remission (CR2). The final data show a median overall survival (OS) of 21.0 months, at a median follow-up of 30.8 months, in patients receiving GPS therapy compared to 5.4 months in the AML CR2 patients treated with best standard care, a statistically significant difference (p-value < 0.02). Final analysis also showed that GPS therapy continued to be well-tolerated throughout the study.

“We’re extremely pleased with this follow-up data, which show that GPS may have potential as a longer-term therapy for AML patients in CR2, an aggressive disease where the majority of patients typically relapse and have a survival rate of approximately 5 months with best standard therapy,” said Angelos Stergiou, MD, ScD h.c., President and Chief Executive Officer of SELLAS. “The 21-month survival data observed further increases our confidence in the potential of GPS as a maintenance treatment for AML patients in CR2, the same patient population as our pivotal Phase 3 study, known as REGAL.”

“These follow-up data build upon the initially published clinical results from the Phase 1/2 study of GPS in AML patients in CR2 and provide further evidence that this novel immunotherapeutic vaccine approach may improve outcomes for patients in this setting, who often harbor measurable residual disease and have a poor prognosis if they are unable to undergo allotransplant,” said Javier Pinilla-Ibarz, MD, PhD, Director of Immunotherapy for Malignant Hematology at the H. Lee Moffitt Cancer Center, and principal investigator of the Phase 1/2 study. “With this persistently positive efficacy signal, low toxicity burden, and CD4+ and CD8+ T cell responses, GPS has significant potential to serve as a maintenance therapy in AML patients in CR2, a patient population at great risk of leukemic relapse.”

The Company previously reported initial data from the Phase 1/2 study of GPS in AML patients in CR2 at a median follow-up of 19.3 months, showing median OS in GPS-treated patients of 16.3 months vs. 5.4 months in a patient cohort contemporaneously treated with best standard therapy (p = 0.0175). The final analysis, at a median follow-up of 30.8 months, now shows a median OS of 21 months in the GPS-treated patient cohort.

“Given these results, it is particularly exciting to be involved in the ongoing pivotal Phase 3 REGAL study of GPS in AML patients in CR2,” said Hagop M. Kantarjian, MD, Professor and Chair of the Department of Leukemia at the University of Texas - MD Anderson Cancer Center, and principal investigator of the Phase 3 REGAL study. “We are working to rapidly enroll patients who meet entry criteria for this study and believe these compelling results will enhance the visibility of this novel therapy and encourage broader participation in the pivotal Phase 3 trial. I look forward to initial results from the REGAL study, as I remain supportive of GPS’s potential promise as an immunotherapeutic agent in the AML CR2 setting.”

SELLAS is currently enrolling patients in the ongoing Phase 3 REGAL study, 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 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. SELLAS expects an interim analysis for safety and futility in the fourth quarter of 2021.

For further information on enrolling in the REGAL study, please visit: https://www.clinicaltrials.gov/ct2/show/NCT04229979?term=galinpepimut-S&draw=2&rank=3.

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