NS5B inhibitor

Non-structural protein 5B (NS5B) inhibitors are a class of direct-acting antivirals widely used in the treatment of chronic hepatitis C. Depending on site of action and chemical composition, NS5B inhibitors may be categorized into three classes—nucleoside active site inhibitors (NIs), non-nucleoside allosteric inhibitors, and pyrophosphate analogues. Subsequently, all three classes are then subclassified. All inhibit RNA synthesis by NS5B but at different stages/sites resulting in inability of viral RNA replication. Expression of direct-acting NS5B inhibitors does not take place in cells that are not infected by hepatitis C virus, which seems to be beneficial for this class of drugs.

Low efficacy, serious side effects, development of resistance of previously available hepatitis C treatments were the greatest concerns prior to the development of direct-acting antivirals, and remained a problem at the beginning of their development. Therefore, combinational direct-acting antiviral therapies were preferable. Research has demonstrated that specific anti-hepatitis C virus agents such as NS5B inhibitors lead to improved efficacy and tolerability.