Based on the results of the randomised cohort B2 carried out within the phase 1 KEYNOTE-001 trial, Pembrolizumab was the first PD-1 inhibitor to be approved by the US FDA (September 2014), with a recommended dose of 2 mg/kg every three weeks for the treatment of patients with unresectable melanoma or metastatic melanoma who have progressed following treatment with ipilimumab or a BRAF inhibitor [45]. Here, PDCD1 is linked to metastatic melanoma.