from Kevin X. Chen and F. George Njoroge writing in Hepatitis C: Antiviral Drug Discovery and Development:
The hepatitis C virus (HCV) NS3 protease is essential for viral replication. It is one of the most attractive targets for developing novel antiviral therapies. Two distinct classes of NS3 protease inhibitors have emerged with different mechanisms of action: non-covalent classical inhibitors and covalent inhibitors. Several types of warheads for covalent bonding have been studied. Among them, the ketoamides have been the most successful class of covalent inhibitors. In fact, the two most clinically advanced HCV NS3 protease drug candidates are both ketoamides: boceprevir and telapravir, in phase III clinical trials. This chapter reviews the evolution and development of covalent NS3 protease inhibitors from early structure-activity-relationship investigations to late stage clinical candidates.
Further reading: Hepatitis C: Antiviral Drug Discovery and Development