Immune checkpoint inhibitors (ICIs) have shown promising results in cancer treatment; in particular, ICIs targeting CTLA-4, PD-1, and PD-L1 have yielded unprecedented and durable responses in a significant percentage of cancer patients in recent years, leading to the US Food and Drug Administration (FDA) approval of six ICIs for numerous cancer indications since 2011 [24]. Here, CTLA4 is linked to cancer.