Outcomes in metastatic melanoma have dramatically shifted since the introduction of antibodies targeting immune system checkpoints (immune checkpoint blockade [ICB]).1 In particular, dual blockade of both programmed cell death-1 and cytotoxic T-lymphocyte–associated antigen 4 (CTLA-4), with nivolumab and ipilimumab, respectively (combination ICB), generates durable responses and median overall survival (OS) beyond 5 years.2,3. This evidence concerns the gene PDCD1 and metastatic melanoma.