PRIMARY OBJECTIVE:~I. To determine the efficacy of rigosertib plus pembrolizumab in patients with metastatic melanoma who are refractory to treatment with a PD-1 inhibitor.~SECONDARY OBJECTIVES:~I. To evaluate progression-free survival (PFS) in patients with PD-1 inhibitor refractory metastatic melanoma receiving rigosertib plus pembrolizumab.~II. To evaluate safety, tolerability and adverse event profile of rigosertib plus pembrolizumab in patients with PD-1 inhibitor refractory metastatic melanoma.~III. To evaluate overall survival (OS) in patients with PD-1 inhibitor refractory metastatic melanoma receiving rigosertib plus pembrolizumab.~EXPLORATORY OBJECTIVE:~I. To evaluate change in tumor-infiltrating lymphocytes (TILs) upon treatment with rigosertib plus pembrolizumab in patients with metastatic melanoma that is refractory to PD-1 inhibitor.~OUTLINE:~Patients receive rigosertib orally (PO) plus pembrolizumab intravenously (IV) throughout the study. Patients undergo computed tomography (CT) or magnetic resonance imaging (MRI) and blood sample collection at screening and on study, and may also undergo tissue biopsy at screening and on study.
This phase II clinical trial tests how well rigosertib plus pembrolizumab workings in treating patients with melanoma which cannot be removed by surgery (unresectable) or that has spread from where it first started (primary site) to other places in the body (metastatic), and that has not responded to previous treatment with PD-1 or PD-L1 inhibitors (refractory). Rigosertib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth and may change the immune system to make immunotherapy more effective. Immunotherapy with monoclonal antibodies, such as pembrolizumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Giving rigosertib in combination with pembrolizumab may be more effective in treating patients with unresectable metastatic melanoma that has not responded to previous treatment with PD-1 or PD-L1 inhibitors than giving either drug alone.