Sofosbuvir works by directly targeting the hepatitis C virus to prevent it from multiplying in the liver. It attaches to the viral RNA to block the virus from making copies of itself. Daclatasvir is a direct-acting antiviral (DAA) that also targets the hepatitis C virus to stop its replication.

Sofosbuvir is an inhibitor of the hepatitis C virus (HCV) NS5B RNA-dependent RNA polymerase, which is essential for viral replication. It is a nucleotide prodrug that is metabolized inside the cells to form the active compound GS-461203. This active form is incorporated into HCV RNA by the NS5B polymerase and works as a chain terminator to stop the virus from multiplying. Laboratory studies show that GS-461203 effectively inhibits NS5B polymerase activity from HCV genotypes 1b, 2a, 3a, and 4a at very low concentrations. GS-461203 does not inhibit human DNA or RNA polymerases, nor mitochondrial RNA polymerase.

Daclatasvir blocks HCV viral RNA replication and protein production by directly inhibiting the NS5A protein. NS5A is essential for viral transcription and translation, so its inhibition prevents the virus from reproducing.

Hepatic viral infections (Hepatitis C)