PURPOSE: Disease progression during or after anti-PD-1-based treatment is common in advanced melanoma. Sotigalimab is a CD40 agonist antibody with unique epitope specificity and Fc-receptor binding profile optimized for activation of CD40-expressing antigen presenting cells. Preclinical data indicated that CD40 agonists combined with anti-PD1 could overcome resistance to anti-PD-1. METHODS: We conducted a multi-center, open-label, phase II trial to evaluate the combination of sotigalimab 0.3mg/kg and nivolumab 360mg q3wk in patients with advanced melanoma following confirmed disease progression on anti-PD-1. The primary objective was to determine the objective response rate (ORR). RESULTS: Thirty-eight subjects were enrolled and evaluable for safety. Thirty-three were evaluable for activity. Five confirmed partial responses (PR) were observed for an ORR of 15%. Two PRs are ongoing at 45.9+ and 26+ months while the other 3 responders relapsed at 41.1, 18.7, and 18.4 months. Median duration of response was at least 26 months. Two additional patients had stable disease for > 6 months. Thirty-four patients (89%) experienced at least one adverse event (AE) and 13% experienced a grade 3 AE related to sotigalimab. The most common AEs were pyrexia, chills, nausea, fatigue, pruritus, elevated liver function, rash, vomiting, headache, arthralgia, asthenia, myalgia, and diarrhea. There were no treatment-related SAEs, deaths, or discontinuation of sotigalimab due to AEs. CONCLUSIONS: Sotigalimab plus nivolumab had a favorable safety profile consistent with the toxicity profiles of each agent. The combination resulted in durable and prolonged responses in a subset of patients with anti-PD-1-resistant melanoma, warranting further evaluation in this setting.