PDCD1 and metastatic melanoma: After FMT was shown to be safe and successful in mice, the first human study of FMT and immunotherapy was conducted by Baruch et al. in 2020 on 10 patients with anti-PD-1 refractory metastatic melanoma, examining the safety and efficacy of FMT in the treatment of metastatic melanoma with anti-PD-1.