Determine the safety, tolerability, dose-limiting toxicities (DLTs), maximum tolerated dose (MTD), and recommended Phase 2 dose (RP2D) of ACY-241 in combination with ipilimumab at 1 mg/kg and nivolumab at 3 mg/kg every 3 weeks for 4 doses each during a 12-week induction period, then administered with nivolumab at a flat dose of 240 mg every 2 weeks in maintenance for up to 1 year in patients with unresectable Stage III/Stage IV melanoma.