CTLA4 and metastatic melanoma: Peter et al. [135], in studies on 27 metastatic melanoma patients, also demonstrated the correlation between gut microbiota composition and ICI therapy effects (anti-PD-1 therapy, n = 14; anti-CTLA-4 therapy, n = 1; anti-PD-1/anti-CTLA-4 therapy, n = 12).