In Vitro Characterization of GSK2485852, a Novel Hepatitis C Virus Polymerase Inhibitor

Abstract

; GlaxoSmithKline, Collegeville, Pennsylvania, USA c GSK2485852 (referred to here as GSK5852) is a hepatitis C virus (HCV) NS5B polymerase inhibitor with 50% effective concentrations (EC 50 s) in the low nanomolar range in the genotype 1 and 2 subgenomic replicon system as well as the infectious HCV cell culture system. We have characterized the antiviral activity of GSK5852 using chimeric replicon systems with NS5B genes from additional genotypes as well as NS5B sequences from clinical isolates of patients infected with HCV of genotypes 1a and 1b. The inhibitory activity of GSK5852 remained unchanged in these intergenotypic and intragenotypic replicon systems. GSK5852 furthermore displays an excellent resistance profile and shows a <5-fold potency loss across the clinically important NS5B resistance mutations P495L, M423T, C316Y, and Y448H. Testing of a diverse mutant panel also revealed a lack of cross-resistance against known resistance mutations in other viral proteins. Data from both the newer 454 sequencing method and traditional population sequencing showed a pattern of mutations arising in the NS5B RNA-dependent RNA polymerase in replicon cells exposed to GSK5852. GSK5852 was more potent than HCV-796, an earlier inhibitor in this class, and showed greater reductions in HCV RNA during long-term treatment of replicons. GSK5852 is similar to HCV-796 in its activity against multiple genotypes, but its superior resistance profile suggests that it could be an attractive component of an all-oral regimen for treating HCV.

In Vitro Activity and Resistance Profile of Dasabuvir, a Nonnucleoside Hepatitis C Virus Polymerase Inhibitor

“…The palm I site overlaps with the palm II site near the C316 residue, as indicated by the fact that the C316Y variant is resistant to the known palm II inhibitor HCV-796. However, HCV-796 possesses significant inhibitory activity toward genotype 2a, 2b, and 3 polymerases (18). The observation that dasabuvir is not active against genotype 2 and 3 polymerases suggests that it is likely a palm I site binder.…”

“…Upper thumb (thumb I) binders, such as BI-207127 and BMS-791325, are associated with resistant variants P495A/S/L/T and V499A (16). The palm I and II sites are partially overlapping; palm II site inhibitors include HCV-796 and GSK5852 (17,18). HCV-796 selects a highly resistant variant, C316Y, whereas GSK5852 retains activity against C316Y but is less active against variants C316F, S365F/L/T, and C445F.…”

“…HCV-796 selects a highly resistant variant, C316Y, whereas GSK5852 retains activity against C316Y but is less active against variants C316F, S365F/L/T, and C445F. These palm II site inhibitors are differentiated from other nonnucleoside inhibitors in that they possess potent activity across genotype 1 to 4 polymerases (17,18). Palm I site inhibitors include multiple series of benzothiadiazine-containing compounds, which select resistant variants C316Y, M414T, Y448H, and G554D (19,20).…”

Preclinical Characterization and In Vivo Efficacy of GSK8853, a Small-Molecule Inhibitor of the Hepatitis C Virus NS4B Protein

“…The NS4B gene was amplified with the following primers for population sequencing: for genotype 1a, 5=-TCTCAGCACTTACC GTACATC-3= and 5=-CCCTTAGCCAGGAACCGGAGCATG-3=; and for genotype 1b, 5=-GCCTCACACCTCCCTTACATC-3= and 5=-CTCTT AGCCACGAGCCGGAGC-3=. Twenty-day HCV RNA reduction assay. Replicons of genotype 1b were treated with compound over a 20-day period to measure the effect of long-term dosing on replication of viral RNA, as described previously (33). Cells were seeded in flasks containing compound at a concentration of 10ϫ the calculated EC 90 .…”

A Review on Anti-HCV Agents Targeting Active Site and Allosteric Sites of Non-Structural Protein 5b [Ns5b]

“…Voitenleitner et al reported that GSK5852 showed good anti-HCV activity with EC50 values in the nanomolar range against HCV genotypes 1 and 2 and has an excellent resistant profile. This molecule is currently in clinic [147,148]. The Palm II nonnucleoside inhibitors that are currently in different phases of development are given in Table 7.…”