Downey et al showed that melanoma patients with grade 3 to 4 IrAEs had duration of response more than doubled than those with grade 1 to 2 IrAEs.[9] Sanlorenzo et al showed that melanoma patient developing cutaneous adverse events while on Pembrolizumab had significantly longer progression-free survival (PFS) compared with patients who did not.[19] Indini et al reported IrAEs correlated with improved OS and PFS in patients undergoing anti-PD-1 immunotherapy for metastatic melanoma.[20]. Here, PDCD1 is linked to metastatic melanoma.