Onconova Therapeutics, Inc. announced 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. 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.