Inhibitors of 3C Cysteine Proteinases from Picornaviridae

The Picornaviridae are among the smallest icosahedral positive-sense single stranded RNA containing viruses known, and comprise one of the largest and most important families of human and animal pathogens. The hepatitis A virus (HAV) and human rhinovirus (HRV) are important pathogens that belong to the picornavirus family. All picornaviruses have a 3C proteinase that processes an initially biosynthesized precursor protein and is crucial for viral maturation and replication. Although it is a cysteine proteinase, this 3C enzyme has a topology similar to those of the chymotrypsin-like serine proteinases. A series of inhibitors of HAV and HRV 3C proteinases were synthesized and tested as potential lead compounds for the design of therapeutic agents for human picornaviral pathogens. This research shows that thiol-reactive groups or “warheads” such as iodoacetamides, β-lactones, Michael acceptors, ketones and pseudoxazolones can be used as effective tools to inhibit the HAV and HRV 3C proteinase enzymes. In addition, studies based on enzyme-inhibitor kinetics, mass spectrometry and NMR spectroscopy were effectively used to gain knowledge concerning enzyme-inhibitor mechanism of action and enzyme-inhibitor regiospecific reactivity.