PDCD1 and cancer: To put this in perspective, until recently dacarbazine was the treatment of choice for metastatic melanoma with a 2-year survival rate for patients (with normal LDH levels) of only 40% [4]; however, the inclusion of checkpoint inhibitors nivolumab (α-PD-1) and ipilimumab (α-CTLA-4) has doubled the 1- and 2-year survival rates to 85% and 79%, respectively, [5,6,7] thus marking a sharp turn in cancer therapeutics for melanoma and sparking multiple new clinical trials with checkpoint inhibitor therapy for other cancers [8,9,10,11].