Inhibition of Hepatitis C Replicon RNA Synthesis by β-D-2′-deoxy-2′-fluoro-2′-C-Methylcytidine: A Specific Inhibitor of Hepatitis C Virus Replication

Abstract

beta-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 (EC90)=4.6 +/- 2.0 microM. 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 EC90. 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 > or =100 mg/kg per day.

Genotype and Subtype Profiling of PSI-7977 as a Nucleotide Inhibitor of Hepatitis C Virus

“…PSI-7977 (prodrug of 2=-F-2=-C-methyluridine monophosphate) (38), PSI-352938 (prodrug of 2=-F-2=-C-methylguanosine monophosphate) (34), PSI-6130 (2=-F-2=-C-methylcytidine) (40), R1479 (4=-azidocytidine) (13), IDX-184 and INX-189 (prodrugs of 2=-C-meth-ylguanosine monophosphate) (43,48), NS5B nonnucleoside inhibitors NNI-1 (an indole analog), NNI-2 (a thiophene analog), NNI-3 (a benzothiadiazine analog), and HCV-796 (a benzofuran analog or NNI-4) (39), NS3 protease inhibitors telaprevir and RG7227 (ITMN-191) (21,22), NS3/4a inhibitor ACH-806 (46), and NS5A inhibitor BMS-790052 (8) were synthesized at Pharmasset and shown to be Ͼ95 to 99% pure by proton nuclear magnetic resonance, mass spectroscopy, and highperformance liquid chromatography analysis. Ribavirin was obtained from Sigma-Aldrich.…”

Characterization of the Metabolic Activation of Hepatitis C Virus Nucleoside Inhibitor β-d-2′-Deoxy-2′-fluoro-2′-C-methylcytidine (PSI-6130) and Identification of a Novel Active 5′-Triphosphate Species

“…Therefore, these nucleoside analogs are non-obligatory chain terminators despite the presence of a 3Ј-hydroxyl group. Recently, ␤-D-2Ј-deoxy-2Ј-fluoro-2Ј-C-methylcytidine (PSI-6130) has been identified as a potent and selective inhibitor of HCV replication in the subgenomic replicon system with little or no cytotoxicity in various human cell lines or bone marrow precursor cells (16). The corresponding triphosphate of PSI-6130 is an inhibitor of HCV NS5B competitive with natural CTP (17).…”

Mechanism of Activation of PSI-7851 and Its Diastereoisomer PSI-7977

“…The most advanced anti-HCV nucleoside, RG7128, is a diisobutyrate nucleoside prodrug of ␤-D-2Ј-deoxy-2Ј-␣-fluoro-2Ј-␤-C-methylcytidine (PSI-6130) and is currently in phase IIb clinical studies. PSI-6130 demonstrated potent activity in the subgenomic HCV replicon assay (9); the incubation of radiolabeled PSI-6130 with either replicon cells or primary human hepatocytes resulted in the formation of the 5Ј-mono-, di-, and triphosphate metabolites of PSI-6130 (10 -12). The triphosphate metabolite (PSI-6130-TP) was shown to be a potent inhibitor of HCV NS5B RNA-directed RNA polymerase (RdRp) (11).…”