PDCD1 and melanoma: Recently, Ribas et al. have demonstrated the efficacy of mAbs against immune checkpoint receptors, such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), programmed cell death 1 (PD-1), and programmed cell death protein ligand (PD-L1) to treat multiple advanced cancers, such as NSCLC, melanoma, bladder, and head and neck cancers [79].