PDCD1 and melanoma: The cytotoxic T-lymphocyte associated protein-4 (CTLA-4) inhibitor ipilimumab and the programmed cell death-1 (PD-1) inhibitors including nivolumab and pembrolizumab are the monoclonal antibodies (MoAbs) that have particularly shown promising results in several clinical trials conducted in patients with advanced melanoma [10].