The purpose of this study is to determine the optimal dose and assess the safety and effectiveness of combining an investigational drug called GC33 with sorafenib in patients with advanced hepatocellular carcinoma (liver cancer). GC33 is a type of drug called a monoclonal antibody. It binds to the glypican-3 (GPC3) protein, which is found on many liver tumor cells. GC33 also binds to very powerful cells of the immune system called natural killer cells. GC33 causes the tumor to die by bringing the tumor cells in contact with natural killer cells.
Sorafenib (Nexavar®) is already approved for the treatment of liver cancer. It works by stopping a signal made by cancer cells that they need to multiply and grow, and through inhibiting blood supply to cancer cells. Sorafenib is a capsule that is taken by mouth.