BACKGROUND:There is limited real-world data on the efficacy and safety of combination programmed cell death protein-1 (PD-1) inhibitor, nivolumab and the cytotoxic T-lymphocyte antigen (CTLA-4) inhibitor ipilimumab. METHOD:We retrospectively identified patients (pts) with metastatic melanoma treated with three-weekly nivolumab (1 mg/kg) in combination with ipilimumab (3 mg/kg) for four cycles followed by nivolumab monotherapy (3 mg/kg) fortnightly. Patient demographics and treatment parameters were collected and outcomes determined. RESULTS:A total of 45 pts received combination treatment with a median follow up of 8.7 months (range 0.33-25.9 months). A total of 67% were male, and BRAF V600 mutations detected in 38%. At treatment commencement, 14 (31%) pts had brain metastases, 51% had an elevated LDH and 18 (40%) were treatment-naive. Almost a third (30%) required corticosteroids for symptom control or management of prior toxicities. Nineteen (42%) patients had prior anti-PD-1 therapy. The disease control rate (DCR) was 54% and objective response rate (ORR) was 29%. Of pts treated with prior immune checkpoint inhibitors, the DCR and ORR were 50% and 33%, respectively. Intracranial responses were observed in 18% (n = 2). The median progression-free survival (PFS) was 5.8 months (95% Confidence interval (CI), 2.9-14.1 months). PFS was higher in treatment naïve patients compared to those who had prior immunotherapy (6.2 months vs 4.9 months, P = 0.59). The median OS was 17.4 months (95% CI, 7.1-NR). pts requiring corticosteroids had a shorter PFS (4.9 months vs 6.8 months) and OS (7.1 months vs NR, P = 0.01).Treatment-related adverse events of any grade were experienced by 88% of pts, with 54% having grade 3-4 adverse events. Treatment discontinuation due to adverse events occurred in 44% of pts. CONCLUSION:In this study, responses to combination immunotherapy were lower than reported. Patients treated with prior immunotherapy had similar responses as treatment-naïve pts. The toxicity profile seen in this study is similar to those reported in clinical trials.