PDCD1 and melanoma: A multicenter randomized phase 2 trial, the ABC trial, compared the efficacy of anti-PD-1 monotherapy and combination IPI+anti-PD-1 in melanoma patients with asymptomatic brain metastases and showed that patients treated with the combination achieved higher rates of response both intracranially (ORR = 46%, and ORR = 56% for drug treatment naïve) and extracranially (ORR = 57%, and ORR = 63% for drug treatment naive) compared to anti-PD-1 alone (ORR = 20% intracranially, and ORR = 21% for drug treatment naïve) and extracranially (ORR = 29%, and ORR = 29% for drug treatment naïve)) (92).