CTLA4 and hepatocellular carcinoma: Ipilimumab was approved by the FDA in 2011, yet the second anti-CTLA-4 monoclonal antibody, tremelimumab, was not approved until 2022 for the treatment of unresectable hepatocellular carcinoma, and then only in combination with the anti-PD-L1 antibody duralimumab.