9519Background: Ipi+Nivo is now FDA approved in the US to treat pts with melanoma. We report our clinical experience of toxicity in pts enrolled in the Ipi+Nivo EAP. Methods: 64 pts were treated on the Ipi+Nivo EAP from Dec. 2014 through Jan. 2016 at MSKCC. Ipi (3mg/kg) and nivo (1mg/kg) were administered q3 weeks for 4 doses. Afterwards, pts were offered Nivo (3mg/kg) q2wks or off-protocol pembrolizumab (2 mg/kg) q3wks until unacceptable toxicity, disease progression (POD), or complete response. Clinically significant immune-related adverse events (irAEs) were defined as CTCAE v4.0 grade ≥ 2 or grade 1 events requiring systemic steroids. Results: 15 pts (39.1%) received all 4 doses of Ipi+Nivo; 11 pts (17.2%) received 3 doses, 20 pts (31.3%) received 2 doses, and 8 pts (12.5%) received 1 dose. Minimum follow up after last Ipi+Nivo treatment was 1 month. 31 pts (79.5%) stopped early for toxicity, 7 (18.0%) for POD and 1 (2.6%) for death due to other causes. The median number of anti-PD-1 doses administere...