Pembrolizumab, an immune checkpoint inhibitor, is an anti-human programmed cell death-1 (PD-1) monoclonal antibody and used for the treatment of non-small cell lung carcinoma (NSCLC) and melanoma with high expression of programmed cell death ligand-1 (PD-L1) and high microsatellite instability (MSI) status solid cancer [1–3]. Here, PDCD1 is linked to melanoma.