PDCD1 and melanoma: included 359 patients with advanced melanoma with disease progression after the use of ipilimumab and compared the efficacy of chemotherapy, anti-programmed cell death-1 (PD-1) inhibitor at 2 mg/kg, and anti-PD-1 antibody at 10 mg/kg, and found that reapplication of ICIs showed superior tumor control compared to chemotherapy, with ORRs of 23.4% and 4.5%, respectively, and the incidence of TRAEs of grade 2 or higher was lower (12.6% vs. 26.3%) (12).