Abstract

TMC-435, being developed by Tibotec Pharmaceuticals Ltd, is an orally administered, macrocyclic inhibitor of the HCV NS3/4A serine protease. HCV infection can cause chronic hepatitis, cirrhosis of the liver and hepatocellular carcinoma. The HCV NS3/4A enzyme is an essential component for viral replication, suggesting that this protein is a key therapeutic target. Biochemical assays demonstrated potent inhibition of HCV NS3/4A by TMC-435 in all HCV genotypes tested, with the exception of HCV-3. In cellular replicon models, the compound selectively inhibited HCV-1 replication and displayed additive effects with ribavirin, and had synergistic activity with IFNalpha and an NS5B polymerase inhibitor. Pharmacokinetic data demonstrated high exposure and good oral bioavailability, supporting once-daily dosing of TMC-435 in humans. In phase I and II clinical trials, the administration of TCM-435 to patients infected with HCV-1, alone or in combination with PEG-IFNalpha and ribavirin, produced significant reductions in HCV-RNA without any significant adverse effects, thus providing a basis for further development of this compound as an anti-HCV therapeutic agent. At the time of publication, phase II trials with TMC-435 were ongoing.