The first retrospective study to investigate the impact of ICI therapy on testicular function and spermatogenesis included seven patients (age range: 23–78 years) treated with anti-CTLA-4 (ipilimumab) and anti-PD-1 (nivolumab) for over a month, at Johns Hopkins University Hospital, who ultimately succumbed to metastatic melanoma [68]. Here, CTLA4 is linked to metastatic melanoma.