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Glecaprevir is an inhibitor of the HCV NS3/4A protease, which is a viral enzyme necessary for the proteolytic cleavage of the HCV encoded polyprotein into mature forms of the NS3, NS4A, NS4B, NS5A, and NS5B proteins. These multifunctional proteins, including NS3, are essential for viral replication. The N-terminal of NS3 protein confers serine protease activity, whileThe C-terminus of NS3 encodes a DExH/D-box RNA helicase which hydyolyzes NTP as an energy source to unwind double-stranded RNA in a 3′ to 5′ direction during replication of viral genomic RNA. NS4A is a cofactor for NS3 that directs the localization of NS3 and modulates its enzymatic activities. Glecaprevir disrupts the intracellular processes of the viral life cycle through inhibiting the NS3/4A protease activity of cleaving downstream junctions of HCV polypeptide and proteolytic processing of mature structural protein.
NS5A is a phosphoprotein that plays an essential role in replication, assembly and maturation of infectious viral proteins. The basal phosphorylated form of NS5A, which is maintained by C-terminal serine cluster, is key in ensuring its interaction with the viral capsid protein, or the core protein. By blocking this interaction, pibrentasvir inhibits the assembly of proteins and production of mature HCV particles. NS5A also interacts with viral and cellular proteins to form the HCV replicase complex, and supports the RNA replication of HCV