title: Biochemical study of the comparative inhibition of hepatitis C virus RNA polymerase by VX-222 and filibuvir.
abstract: Filibuvir and VX-222 are nonnucleoside inhibitors (NNIs) that bind to the thumb II allosteric pocket of the hepatitis C virus (HCV) RNA-dependent RNA polymerase. Both compounds have shown significant promise in clinical trials and, therefore, it is relevant to better understand their mechanisms of inhibition. In our study, filibuvir and VX-222 inhibited the 1b/Con1 HCV subgenomic replicon, with 50% effective concentrations (EC(50)s) of 70 nM and 5 nM, respectively. Using several RNA templates in biochemical assays, we found that both compounds preferentially inhibited primer-dependent RNA synthesis but had either no or only modest effects on de novo-initiated RNA synthesis. Filibuvir and VX-222 bind to the HCV polymerase with dissociation constants of 29 and 17 nM, respectively. Three potential resistance mutations in the thumb II pocket were analyzed for effects on inhibition by the two compounds. The M423T substitution in the RNA polymerase was at least 100-fold more resistant to filibuvir in the subgenomic replicon and in the enzymatic assays. This resistance was the result of a 250-fold loss in the binding affinity (K(d)) of the mutated enzyme to filibuvir. In contrast, the inhibitory activity of VX-222 was only modestly affected by the M423T substitution but more significantly affected by an I482L substitution.
authors.affiliation: Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana, USA.
authors.forename: Guanghui
authors.initials: G
authors.lastname: Yi
authors.forename: Jerome
authors.initials: J
authors.lastname: Deval
authors.forename: Baochang
authors.initials: B
authors.lastname: Fan
authors.forename: Hui
authors.initials: H
authors.lastname: Cai
authors.forename: Charlotte
authors.initials: C
authors.lastname: Soulard
authors.forename: C T
authors.initials: CT
authors.lastname: Ranjith-Kumar
authors.forename: David B
authors.initials: DB
authors.lastname: Smith
authors.forename: Lawrence
authors.initials: L
authors.lastname: Blatt
authors.forename: Leonid
authors.initials: L
authors.lastname: Beigelman
authors.forename: C Cheng
authors.initials: CC
authors.lastname: Kao
mesh_terms: D000998:Antiviral Agents / Q000378:metabolism / Q000494:pharmacology*; D001665:Binding Sites / Q000187:drug effects; D045744:Cell Line, Tumor; D003511:Cyclohexanols / Q000378:metabolism / Q000494:pharmacology*; D024882:Drug Resistance, Viral; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D016174:Hepacivirus / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D008958:Models, Molecular; D009154:Mutation / Q000187:drug effects; D011753:Pyrones / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D012367:RNA, Viral / Q000235:genetics; D012324:RNA-Dependent RNA Polymerase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012093:Replicon / Q000187:drug effects; D013698:Templates, Genetic; D013876:Thiophenes / Q000378:metabolism / Q000494:pharmacology*; D014230:Triazoles / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011743:Pyrimidines
chemical_list: D000998:Antiviral Agents; D003511:Cyclohexanols; D004791:Enzyme Inhibitors; D011753:Pyrones; D012367:RNA, Viral; D012324:RNA-Dependent RNA Polymerase; D013876:Thiophenes; D014230:Triazoles; C550357:filibuvir; D011743:Pyrimidines; C000592793:lomibuvir