On May 25, 2023 Onconova Therapeutics, Inc. (NASDAQ: ONTX), ("Onconova"), a clinical-stage biopharmaceutical company focused on discovering and developing novel products for patients with cancer, reported that the first participant has been dosed in an investigator-sponsored Phase 2 trial of oral rigosertib plus the PD-1 inhibitor pembrolizumab in patients with metastatic melanoma who have progressed on prior PD-1/L1 inhibitor therapy (Press release, Onconova, MAY 25, 2023, View Source [SID1234632089]).

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"There is an urgent need for new treatment approaches in metastatic melanoma, as 40 to 60% of these patients currently see little to no clinical benefit from PD-1 inhibitors," said Ann Richmond, Ph.D., Ingram Professor of Pharmacology and Medicine at the Vanderbilt University School of Medicine and Senior Research Career Scientist at TVHS, Department of Veterans Affairs (Nashville). "The limited efficacy of these agents is often due to ‘cold’ tumor microenvironments (TME) that prevent the infiltration of immune effector cells. Peer-reviewed preclinical studies1 suggest rigosertib can enhance the efficacy of immune checkpoint blockade in metastatic melanoma by reversing cold TMEs, providing a strong scientific rationale for this clinical trial."

Douglas B. Johnson, M.D., M.S.C.I., Associate Professor of Medicine of Hematology/Oncology at Vanderbilt University Medical Center and Principal Investigator of the trial commented, "Rigosertib combined with anti-PD-1 therapy has shown clinical activity in checkpoint inhibitor refractory lung cancer patients, and we believe this promising finding may translate to melanoma. The newly initiated Phase 2 study has been thoughtfully designed to begin exploring this hypothesis and will afford participants the opportunity to receive a novel therapeutic combination that may lead to improved clinical outcomes. I look forward to conducting the study and to the important scientific insights I expect it will provide."

The investigator-sponsored Phase 2 trial is an open-label, two-stage, single arm study. Stage 1 of the trial is expected to include ten patients. If a pre-specified response criteria is met, the study will then proceed to Stage 2, during which an additional 19 patients are expected to be enrolled. Patients in the study will receive 560 mg of oral rigosertib twice daily on days 1-21 of 28-day treatment cycles, plus 400 mg of pembrolizumab administered via intravenous infusion every six weeks. The primary endpoint of the trial is overall response rate, while key secondary endpoints include assessments of safety, tolerability, progression-free survival, and overall survival. Correlative biomarker assessments will also be conducted.

Steven M. Fruchtman, M.D., President and Chief Executive Officer of Onconova, commented, "Rigosertib’s investigator-sponsored trials are an important component of our corporate strategy that allows us to diversify the indications studied with our pipeline while remaining internally focused on our lead narazaciclib program. We are thrilled to be collaborating with Vanderbilt’s world-class physician-scientists on this latest trial and look forward to its advancement."

For additional information on the Phase 2 trial, see Clincialtrials.gov identifier NCT05764395.