In a retrospective study of 60 individuals with acral (n = 25)/mucosal (n = 35) melanoma treated with anti-PD-1 (either nivolumab or pembrolizumab), ORR was 32% and median PFS was 4.1 months in patients with acral melanomas and ORR was 23% and median PFS was 3.9 months in patients with mucosal melanomas (15). Here, PDCD1 is linked to melanoma.