Utilizing its proprietary GEMS technology, PTC has identified a number of small molecules that selectively inhibit the translation of the hepatitis C virus (HCV) protein without inhibiting human host cell translation in in vitro studies. In March 2006, PTC entered into an exclusive collaboration with Merck & Co., Inc. (formally Schering-Plough Corporation) for the development and commercialization of the compounds in the HCV program.

Chronic HCV is an inflammatory liver disease associated with chronic infection by HCV. It is the leading cause of liver failure requiring liver transplantation in both the United States and Europe. According to the World Health Organization, approximately 170 million people, or roughly 2.7% of the world's population, are chronically infected with HCV. The Centers for Disease Control, or CDC, estimate that more than 2.7 million people in the United States have chronic HCV infection and that approximately 8,000 to 10,000 patients die annually in the United States from complications resulting from this infection. According to the National Institutes of Health Consensus Development Conference Panel Statement the prevalence of cirrhosis and the incidence of its complications, including various forms of liver cancer and liver related deaths, will increase dramatically over the next 10 to 20 years.

There are no available vaccines against HCV. The current standard of care for the treatment of HCV is a combination of two drugs, interferon and ribavirin. More than 50% of patients infected with the genotype 1 strain of HCV generally do not respond to this therapy. In addition, there are significant side effects to this therapy, which often result in dose reductions or premature treatment termination.