GS-9451 + tegobuvir + peginterferon alfa-2a + ribavirin

This is a **four-drug combination regimen** targeting chronic hepatitis C virus (HCV) infection, specifically genotype 1. The regimen consists of: - **GS-9451**: A potent, selective small molecule inhibitor of the HCV NS3 protease, blocking viral replication. - **tegobuvir (GS-9256)**: A non-nucleoside inhibitor of the HCV NS5B RNA-dependent RNA polymerase, impeding HCV RNA synthesis. - **peginterferon alfa-2a**: A pegylated interferon that stimulates immune defenses against HCV and has a broad antiviral effect. - **ribavirin**: A nucleoside analog that acts through multiple mechanisms, including interference with viral RNA synthesis, mutagenesis, immunomodulation, and inhibition of inosine monophosphate dehydrogenase. The combination was studied for enhancing sustained virological response rates in patients for whom standard therapy was unsuccessful or who were infected with difficult-to-treat genotypes. These drugs act synergistically on different stages of the HCV lifecycle, aiming to prevent viral replication and clear infection.