Aims: Nivolumab, a fully human immunoglobulin G4 PD-1 immune-checkpoint inhibitor antibody, is tolerable and active in patients with advanced solid tumors. In this trial, long-term clinical activity, response off therapy, association of tumor PD-1 ligand 1 (PD-L1) expression with survival endpoints, and 3-year overall survival (OS) were investigated in patients with advanced MEL.
Methods: 107 previously treated ipilimumab-naïve advanced MEL patients received nivolumab (0.1, 0.3, 1, 3, or 10 mg/kg IV) every fortnight for ≤96 weeks and were evaluated for OS and progression-free survival (PFS). Tumour cell PD-L1 expression was assessed by a Dako immunohistochemistry assay.
Results: Among patients who initiated treatment with nivolumab, 25% had ≥3 prior therapies. Across doses, 1-, 2- and 3-year OS (95% CI) rates were 63% (53, 71), 48% (38, 57) and 41% (31, 51), respectively; and numbers of patients at risk were 63, 44 and 22, respectively. Thirty-four patients demonstrated objective responses by RECIST, 24 of whom stopped nivolumab for reasons other than disease progression. Of those 11 maintained responses for ≥24 weeks off drug (range: 24, 56+ weeks); and 4 had unconventional “immune-related” responses.
Median response duration was 22.9 months. In a subset of patients with evaluable tumor samples (41/107), patients with PD-L1(+) (i.e. ≥ 5% on tumour cells) and (–) tumours (n=18 and 23, respectively) had median OS of not reached and 12.5 months, respectively; median PFS was 9.1 months and 1.9 months, respectively. Safety was previously reported.
Conclusions: In advanced MEL patients, nivolumab demonstrated favorable 2- and 3-year OS rates, durable responses with a number persisting off therapy, and an acceptable safety profile. Additional analyses will be presented by patients’ characteristics across the full population, long-term survival subgroup, and PD-L1(+/–) tumor subgroups. Ongoing phase III trials are further evaluating nivolumab in MEL and PD-L1 as a potential predictive biomarker for response.