Pharmasset, Inc. is a clinical-stage pharmaceutical company focused on discovering, developing, and commercializing novel drugs to treat viral infections. The Company focuses on the development of nucleoside/tide analogs as oral therapeutics for the treatment of chronic hepatitis C virus (HCV) infection. Nucleoside/tide analogs are a class of compounds, which act as alternative substrates for the viral polymerase, thus inhibiting viral replication. The Company has three clinical-stage product candidates. It also has a series of preclinical candidates in preparation for clinical development. The three clinical product candidates include RG7128, PSI-7977 and PSI-938. In January 2012, Gilead Sciences, Inc. acquired Pharmasset, Inc.