CTLA4 and renal cell carcinoma: Nivolumab, an anti-PD-1 antibody, was approved in Japan in 20161, and ICI-based combination therapies, such as the anti-PD-1 antibody nivolumab with the anti-CTLA-4 antibody ipilimumab, have become the primary treatment option for metastatic RCC since 20182.