Regarding ICI therapy, both anti-PD-1/PD-L1 and anti-CTLA-4 mAbs appear to confer greater therapeutic benefits on patients with cancers with higher tumor mutational burden (TMB), which is regarded as an independent predictor of response to immunotherapy in various cancers, particularly melanoma and non-small-cell lung cancer [29,30]. The gene discussed is PDCD1; the disease is cancer.