Four recent studies analyzed the impact of FMT on the efficacy of ICIs (Table 2) and reported that FMT from donors who had been previously treated with anti-PD-1 monotherapy for metastatic melanoma achieved a complete or partial response, while patients with anti-PD-1 refractory metastatic melanoma demonstrated a clinical response to ICIs in a subgroup of patients when they were treated with the association of FMT with anti-PD-1 immunotherapy. This evidence concerns the gene PDCD1 and metastatic melanoma.