Background: In the phase III CheckMate 037 study, NIVO improved the objective response rate and progression-free survival with less toxicity vs chemotherapy in patients (pts) with MEL who progressed after prior IPI treatment. We report the first efficacy and updated safety data from pts with MEL in CheckMate 172, including those with rare melanoma subtypes (uveal, mucosal), brain metastases, or an ECOG performance status (PS) of 2. Methods: In this ongoing phase II, single-arm, open-label, multicenter study, pts with MEL who progressed on or after IPI were treated with NIVO 3 mg/kg Q2W for up to 2 years until progression or unacceptable toxicity (NCT02156804). We report efficacy and updated safety data from 734 treated pts with ≥1 year of follow-up (database lock: November 2016). Results: Of 734 pts, 50% had LDH>ULN, 7% ECOG PS 2, 66% M1c disease, 15% a history of brain metastases, and 23% received ≥3 prior therapies. Overall, 593 pts (81%) received more than 4 doses of NIVO. Overall, response rate at 12 weeks was 32%, with a complete response in 1% (Table). The 1-year overall survival (OS) rate was 63%. Any grade and grade 3/4 treatment-related adverse events (AEs) occurred in 66% and 17% of pts, respectively. Discontinuations due to treatment-related AEs occurred in 4% of pts. The most common treatment-related select (potentially immune-related) AEs were diarrhea (12%), hypothyroidism (9%), and pruritus (7%). Conclusions: CheckMate 172 is the largest study of NIVO efficacy and safety in pts with MEL who progressed on or after IPI. NIVO demonstrated a safety profile consistent with that of prior clinical trials. Efficacy outcomes were encouraging in some difficult-to-treat subgroups of pts with poor prognostic factors, such as mucosal melanoma and brain metastases. Clinical trial information: NCT02156804

*Assessed in evaluable pts on treatment for ≥12 weeks; NR=not reached.