CTLA4 and hepatocellular carcinoma: Currently, the US Food and Drug Administration (FDA) has approved four immune checkpoint inhibitors as single or combined therapy for the first-line/second-line treatment of HCC: atilizumab (programmed death-ligand 1 (PD-L1)) combined with bevacizumab (vascular endothelial growth factor (VEGF)), ipilimumab (cytotoxic T lymphocyte-associated antigen 4 (CTLA-4)) combined with nivolumab (programmed cell death protein 1 (PD1)), and single pembrolizumab (PD1) or single nivolumab.