PDCD1 and melanoma: Moreover, an important subset of melanoma patients remains unresponsive to these therapies or develops resistance over time; 15–20% of melanoma tumors harboring the BRAFV600E mutation do not respond to targeted therapies such as BRAF and MEK inhibitors (BRAFi, MEKi, respectively) [5], and treatment with ICB such as anti-PD-1 (programmed cell death protein 1) or anti-CTLA4 (cytotoxic T-lymphocyte–associated antigen 4) does not confer a therapeutic benefit to 40–60% of patients [6].