Sofosbuvir hepatitis C drug, molecular model. This antiviral drug, marketed as Sovaldi, is used to treat chronic hepatitis C infections. It works by inhibiting the enzyme RNA polymerase that the virus uses to replicate its RNA (ribonucleic acid) genome. The hepatitis C virus infects liver cells causing an inflammatory disease that can lead to degeneration and scarring (cirrhosis). When used in combination with the drug Ledipasvir, sofosbuvir cures 90 per cent of patients.