PDCD1 and metastatic melanoma: Since 2011, several immune checkpoint inhibitors have been approved for patients with unresectable or metastatic melanoma by the US Food and Drug Administration (FDA), including anti-PD-1 (nivolumab and pembrolizumab), anti-PDL-1 (avelumab and atezolizumab), and anti-CTLA-4 inhibitors (ipilimumab).[14,15,16,17] Notably, Dr. James P. Allison and Dr. Tasuku Honjo were awarded the 2018 Nobel Prize in Physiology or Medicine for their discovery of cancer therapy by inhibition of CTLA-4 and PD-1, respectively.