One retrospective cohort study (n = 55 patients) observed trending improvements in overall and progression-free survival in study participants with metastatic malignant melanoma who receive the metformin in combination with ICB (ipilimumab [anti-cytotoxic T-lymphocyte-associated protein 4 or CTLA-4], nivolumab [anti-PD-1], and/or pembrolizumab); however, these changes failed to reach statistical significance compared to ICB alone (69). Here, CTLA4 is linked to metastatic melanoma.