In November 2011, Pharmasset Inc was acquired by Gilead Sciences Inc - itself having been SBIR involved in the firm's early days. Pharmasset, Inc. had been a clinical-stage pharmaceutical company committed to discovering, developing and commercializing novel drugs to treat viral infections. Organized around development of oral therapeutics for the treatment of hepatitis C virus (HCV), atthe time of acqusiiton the firm had two product candidates and a series of preclinical candidates nearing preparation for clinical development: * RG7128, a pro-drug of PSI-6130 for the treatment of HCV, is entering a phase 2b clinical trial through a collaboration with Roche; * PSI-7977, a chirally pure isomer of PSI-7851 is a second generation nucleotide analog for the treatment of HCV * Purine nucleotide series. Additionally, the firm was working on Racivir, for the treatment of HIV following the completion of a Phase 2 clinical trial. The firm's efforts centered on a class of compounds known as nucleoside analogs, which act to inhibit the enzymes required for viral replication. Applying expertise in nucleoside chemistry to the discovery and development of additional antiviral therapeutics for HCV.. In September 2003, Pharmasset entered into a collaborative licensing agreement with Incyte Corporation for the development and commercialization of Reverset. In October 2004, Pharmasset entered into a collaboration agreement with Hoffmann-La Roche for the development and commercialization of PSI-6130 for the treatment of Hepatitis C. Pharmasset retains proprietary development and commercialization rights to the balance of its clinical and preclinical pipeline.