PDCD1 and melanoma: More recently, adjuvant therapy with immune checkpoint blockade has demonstrated significant relapse-free survival (RFS) benefits, leading to US Food and Drug Administration (FDA) approval of single-agent ipilimumab (CTLA-4 blockade), nivolumab (PD-1 blockade) and pembrolizumab (PD-1 blockade) for adjuvant treatment of patients with high-risk stage III melanoma following complete resection [3–10].