Sofosbuvir is a nucleotide analog inhibitor of hepatitis C virus NS5B polymerase - the key enzyme mediating HCV RNA replication. Sofosbuvir is a prodrug and after ingestion it is rapidly converted to GS-331007, the predominant circulating drug that accounts for greater than 90% of the systemically active drug. The compound GS-331007 is efficiently taken up by hepatocytes, whereby cellular kinases convert GS-331007 to its pharmacologically active uridine analog 5’-triphosphate form (GS-461203). This triphosphate compound mimics the natural cellular uridine nucleotide and is incorporated by the HCV RNA polymerase into the elongating RNA primer strand, resulting in chain termination. The active form GS-461203 targets the NS5B catalytic site and acts as a non-obligate chain terminator. The active compound (GS-461203) does not inhibit host DNA polymerases, RNA polymerases, or mitochondrial RNA polymerase. Sofosbuvir (alone or in in combination with other medications) is used to treat Hepatitis C.

Ombitasvir (ABT-267) is an antiviral drug for the treatment of hepatitis C virus (HCV) infection. Ombitasvir is a potent inhibitor of the hepatitis C virus protein NS5A, has favorable pharmacokinetic characteristics and is active in the picomolar range against genotype 1 - 6. In 2015, it was approved by FDA for use in combination with paritaprevir, ritonavir and dasabuvir in the product Viekira Pak for the treatment of HCV genotype 1.

Dasabuvir is a non-nucleoside inhibitor of the hepatitis C virus (HCV) NS5B palm polymerase inhibitor. It is used in the treatment of adult patients with chronic hepatitis C virus infection in combination with ombitasvir, paritaprevir, and ritonavir as the combination product Viekira Pak. Viekira PAK combines three direct-acting antiviral agents with distinct mechanisms of action and non-overlapping resistance profiles to target HCV at multiple steps in the viral lifecycle. Dasabuvir is extensively evaluated in large clinical trials and shown excellent sustained virological response among hepatitis C virus genotype1 patient population in combination with other oral direct acting antivirals, with good safety profile and tolerance.