A Phase Ib Study of Selinexor in Combination with Pembrolizumab in Patients with Metastatic Melanoma

Introduction: Immune checkpoint inhibitors (ICIs) have substantially advanced the treatment of patients with malignant melanoma. However, improving therapeutic efficacy requires identifying drug combinations that elicit durable responses without inducing intolerable toxicity. Within that context, selinexor emerges as a possible combination option that has been shown in preclinical studies to enhance the efficacy of ICI therapy. Methods: In this phase 1b study, we investigated selinexor in combination with pembrolizumab in 25 patients with advanced non-uveal melanoma. Patients received selinexor at a dosage of 60 mg taken orally twice weekly, and pembrolizumab intravenously at a dosage of 200 mg every 3 weeks. Results: Despite the high incidence of adverse events (96%), most treatment-related toxicities were manageable with supportive care and dose reductions. The most common adverse events of any grade were nausea (n = 20; 80%), decreased white blood cell count (n = 15; 60%), vomiting (n = 14; 56%), anemia (n = 12; 48%), fatigue (n = 12; 48%), and decreased platelet count (n = 12; 48%). The 10 patients with treatment-naïve evaluable disease had an objective response rate (ORR) of 70% (n = 7, including three patients with complete response), which was significantly higher than that of the 14 patients with prior anti–programmed cell death protein 1 (anti-PD-1) therapy, whose ORR was 7% (n = 1; p = 0.002). Stable disease was observed in two patients (20%) with treatment-naïve disease and seven patients (50%) with prior anti-PD-1 therapy. Conclusion: Selinexor combined with pembrolizumab showed promising antitumor activity in patients with treatment-naïve metastatic melanoma. The toxicity profile of the combination was consistent with that reported for individual agents, with no additional safety concerns.