In vitro activity: Ledipasvir (also known as GS5885) is a HCV NS5A polymerase inhibitor that is used for the treatment of hepatitis C virus infection. The combination product of ledipasvir 90 mg/sofosbuvir 400 mg (trade name Harvoni) was approved by FDA in October 2014. The ledipasvir/sofosbuvir combination is a direct-acting antiviral agent that interferes with HCV replication and can be used to treat patients with genotypes 1a or 1b without PEG-interferon or ribavirin. Ledipasvir has an extended plasma half-life of 37-45 h in healthy volunteers and produces a rapid>3 log viral load reduction in monotherapy at oral doses of 3 mg or greater with once-daily dosing in genotype 1a HCV-infected patients. It has been shown to be safe and efficacious, with SVR12 rates up to 100% when used in combination with direct-acting antivirals having complementary mechanisms.

Kinase Assay: GT1a replicon EC50 = 31 pM

Cell Assay: Ledipasvir is a specific inhibitor of HCV NS5A protein to inhibit HCV replication in the HCV subgenomic replicon system. NS5A replication complex inhibitors are novel antiviral factors for HCV treatment. Typically, these inhibitors have high efficiency and low viral resistance when compared to traditional HCV replication inhibitor targeted on NS3 helicase and NS5B RNA polymerasae. NS5A inhibitors are supposed to bind across the NS5A dimer interface, proximal to N-terminal domain 1. The binding is thought to distort dimer association directly or allosterically, which may disrupt NS5A function in HCV RNA replication. When a JFH1/3a-NS5A hybrid replicon was used to assess susceptibility to NS5A, another inhibitor DCV was shown to be more potent than ledipasvir. Additionally, NS5A-A30K and -Y93H variants exhibited reduced sensitivity to ledpasvir (EC50 value of 1770 nM and 4300 nM respectively).