Samatasvir (IDX71) is a potent, orally active NS5A inhibitor of HCV replication. Samatasvir is effective and selective against infectious HCV and replicons, with EC50s falling within a tight range of 2 to 24 pM in genotype 1 through 5 replicons.In Vitro: Samatasvir (IDX719) retains full activity in the presence of HIV and hepatitis B virus (HBV) antivirals and is not cross-resistant with HCV protease, nucleotide, and nonnucleoside polymerase inhibitor classes.