Inhibition of hepatitis C replicon RNA synthesis by beta-D-2'-deoxy-2'-fluoro-2'-C-methylcytidine: a specific inhibitor of hepatitis C virus replication

β-D-2'-Deoxy-2'-fluoro-2'-C-methylcytidine (PSI-6130) is a cytidine analogue with potent and selective anti-hepatitis C virus (HCV) activity in the subgenomic HCV replicon assay, 90% effective concentration (EC 90 )=4.6 ±2.0 μM. The spectrum of activity and cytotoxicity profile of PSI-6130 was evaluated against a diverse panel of viruses and cell types, and against two additional HCV-1b replicons. The S282T mutation, which confers resistance to 2'-C-methyl adenosine and other 2'-methylated nucleosides, showed only a 6.5-fold increase in EC 90 . When assayed for activity against bovine diarrhoea virus (BVDV), which is typically used as a surrogate assay to identify compounds active against HCV, PSI-6130 showed no anti-BVDV activity. Weak antiviral activity was noted against other flaviviruses, including West Nile virus, Dengue type 2, and yellow fever virus. These results indicate that PSI-6130 is a specific inhibitor of HCV. PSI-6130 showed little or no cytotoxicity against various cell types, including human peripheral blood mononuclear and human bone marrow progenitor cells. No mitochondrial toxicity was observed with PSI-6130. The reduced activity against the RdRp S282T mutant suggests that PSI-6130 is an inhibitor of replicon RNA synthesis. Finally, the no-effect dose for mice treated intraperitoneally with PSI-6130 for six consecutive days was ≥ 100 mg/kg per day.