PSI-7976 is the isomer of PSI-7977. PSI-7977 is an active inhibitor of HCV RNA replication in the HCV replicon assay, demonstrates potent anti-hepatitis C virus ( HCV ) activity. In Vitro PSI-7851 is a mixture of two diastereoisomers, PSI-7976 and PSI-7977, with PSI-7977 being the more active inhibitor of HCV RNA replication in the HCV replicon assay. Carboxylesterase 1 (CES1) preferentially hydrolyzes PSI-7976 over PSI-7977. The kinetic data also indicates that PSI-7976 is a better substrate for CES1 than for cathepsin A (CatA)MCE has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid