Serine protease inhibitors as anti-hepatitis C virus agents

Approximately 3% of the worldwide population (i.e., more than 170 million people) are chronically infected with the hepatitis C virus (HCV). An estimated 20% of these patients will develop liver cirrhosis within a mean of 20 years, and 2-5% of cirrhotic patients will die of end-stage liver disease or hepatocellular carcinoma. The currently approved antiviral therapy with pegylated interferon (pegIFN) and ribavirin induces a sustained virological response (SVR) in 40-50% of patients infected with genotype 1, the most prevalent HCV type. In this review, we focus on the development and clinical application of serine protease inhibitors as anti-HCV agents. Although highly active in inducing a significant decline of serum HCV RNA, the rapid development of resistance must be counteracted in combination with other antiviral agents, currently pegIFN-alpha and ribavirin. Two serine protease inhibitors have reached clinical Phase III trials, increasing SVR rates and shortening treatment duration when combined with pegIFN and ribavirin. Trials of interferon-free targeted combination therapies are currently underway.