Background: Ipilimumab (Ipi), a fully human monoclonal antibody that binds to cytotoxic T-lymphocyte antigen-4 expressed on T cells, and vemurafenib (Vem), a small molecule inhibitor of BRAF V600-mutated kinase, are both approved treatments for AM. Ipi has shown improved overall survival (OS) in two randomized phase III trials of patients with previously treated (3 mg/kg monotherapy) and previously untreated (10 mg/kg plus dacarbazine) AM. Vem has shown improved OS in a randomized phase III trial of patients that harbor the BRAF V600E mutation. The most common drug-related adverse events (AEs) with Ipi monotherapy were immune-related GI tract and skin toxicities, which were generally manageable using treatment guidelines. The most common AEs with Vem were arthralgia, rash, and fatigue. Vem can induce rapid and substantial responses, and resistance mechanisms are a focus of current investigation. This study will evaluate the safety of Vem lead-in followed by Ipi (prior to resistance) in patients with BRAF V600-mutated AM. Methods: An estimated 45 patients will be enrolled. Eligible patients include those ≥18 years old with previously untreated AM, a BRAF V600 mutation, and an ECOG PS of 0 or 1. Major exclusion criteria are primary ocular melanoma, active brain metastases, and autoimmune disease. Patients will initially receive Vem for 6 weeks (960 mg twice daily). After a washout period of 3-10 days (per protocol), patients will be initiated on Ipi at 10 mg/kg (every 3 wk for 4 doses, then once every 12 wk beginning at week 24, until disease progression or unacceptable toxicity). Vem will be restarted at the time of disease progression on Ipi (no minimum time to restart) or unacceptable toxicity on Ipi (restart minimum of 1 mo after the last dose of Ipi). Vem will be restarted at the last dose level tolerated at the end of the lead-in phase. Patients will be followed every 12 weeks for toxicity and/or disease progression, and subsequently will be followed every 12 weeks for survival. The objectives of this study are to estimate the incidence of grade 3-4 drug-related AEs. Exploratory objectives include the evaluation of efficacy (OS). Clinical trial information: NCT01673854.