Boceprevir is a protease inhibitor that covalently, yet reversibly, binds (Ki = 14 nM) to the catalytic site (Ser139) of hepatitis C virus (HCV) nonstructural protein 3/4A (NS3/4A), a serine protease that is essential for viral replication. It was shown to inhibit the NS3/4A protease in an in vitro HCV replicon system with an EC50 value of 200 nM. Boceprevir can inhibit the activity of recombinant HCV genotype 1a and 1b NS3/4A protease enzymes in vitro with Ki values of 14 nM for each subtype. It has been evaluated in phase III clinical studies in combination with the current standard of care for treatment of HCV.
