CD274 and Merkel cell skin cancer: Anti-CTLA-4 alone or in combination with anti-PD-1 revealed an overall response (OR) in 31% of the patients; one patient with MCC refractory – anti-PD-1 and anti-CTLA-4–had tumor regression with anti-PD-L1.52 It is worth mentioning that this study is the largest case series to date describing the anti-tumor efficacy of anti-PD-L1 as a second-line treatment for MCC patients with anti-PD-1 refractory disease.