Later-line treatments for melanoma can be of limited benefit for patients without activating class 1 BRAF mutations, with objective response rates to single-agent ipilimumab following single-agent anti-PD1 therapy as low as 9%, although combination therapy with ipilimumab and nivolumab in this context is more promising, offering response rates of 28% [52]. Here, PDCD1 is linked to melanoma.