Chowell et al., analyzed HLA-I genotype (HLA-A, -B and -C) in solid tumors from a cohort of cancer patients (NSCLC and melanoma) treated with anti-CTLA-4 or anti-PD-1 therapy and discovered that maximal heterozygosity at HLA-I loci improved overall survival after ICB compared with patients who were homozygous for at least one HLA locus [17]. The gene discussed is CTLA4; the disease is cancer.