NS5B

About: NS5B is a research topic. Over the lifetime, 1314 publications have been published within this topic receiving 59534 citations.

A review on anti-hcv agents targeting active site and allosteric sites of non-structural protein 5b [ns5b]

Abstract: Hepatitis C, a chronic disease affecting the global population significantly is caused majorly by Hepatitis C virus [HCV]. Among the several druggable targets explored for Hepatitis C, the viral protein, non-structural protein 5B [NS5B] is the target of choice for researchers as it is the key enzyme in the HCV replication and its active site is conserved among all genotypes. In the recent years the landscape of Hepatitis C therapies, have evolved from Peg-Interferon [PEG-INF]/Ribavirin, to directly acting anti-virus along with PEG-INF and finally, INF free regimens with greater than 90% sustained virological response [SVR]. The launch of Sofosbuvir, a nucleotide inhibitor of NS5B marks the major paradigm in hepatitis C research. Sofosbuvir exhibits, pan-genotypic activity, low barrier to resistance, highly effective and safe. However, the high prices of these medications limit their universal access. This review will focus on progress towards the discovery and development of NS5B inhibitors targeting allosteric sites and active site, covering the chemical class and structure-activity relationships.

Mutations Identified in the Hepatitis C Virus (HCV) Polymerase of Patients with Chronic HCV Treated with Ribavirin Cause Resistance and Affect Viral Replication Fidelity.

Abstract: Ribavirin has been used for 25 years to treat patients with chronic hepatitis C virus (HCV) infection; however, its antiviral mechanism of action remains unclear. Here, we studied virus evolution in a subset of samples from a randomized 24-week trial of ribavirin monotherapy versus placebo in chronic HCV patients, as well as the viral resistance mechanisms of the observed ribavirin-associated mutations in cell culture. Thus, we performed next-generation sequencing of the full-length coding sequences of HCV recovered from patients at weeks 0, 12, 20, 32 and 40 and analyzed novel single nucleotide polymorphisms (SNPs), diversity, and mutation-linkage. At week 20, increased genetic diversity was observed in 5 ribavirin-treated compared to 4 placebo-treated HCV patients due to new synonymous SNPs, particularly G-to-A and C-to-U ribavirin-associated transitions. Moreover, emergence of 14 nonsynonymous SNPs in HCV nonstructural 5B (NS5B) occurred in treated patients, but not in placebo controls. Most substitutions located close to the NS5B polymerase nucleotide entry site. Linkage analysis showed that putative resistance mutations were found in the majority of genomes in ribavirin-treated patients. Identified NS5B mutations from genotype 3a patients were further introduced into the genotype 3a cell-culture-adapted DBN strain for studies in Huh7.5 cells. Specific NS5B substitutions, including DBN-D148N+I363V, DBN-A150V+I363V, and DBN-T227S+S183P, conferred resistance to ribavirin in long-term cell culture treatment, possibly by reducing the HCV polymerase error rate. In conclusion, prolonged exposure of HCV to ribavirin in chronic hepatitis C patients induces NS5B resistance mutations leading to increased polymerase fidelity, which could be one mechanism for ribavirin resistance.

Virtual screening of imidazole analogs as potential hepatitis C virus NS5B polymerase inhibitors

Abstract: Hepatitis C virus (HCV) infection is a global health threat and current therapies warrant the need for novel HCV therapies. Several synthetic analogs targeting HCV serine protease and RNA-dependent RNA polymerase have entered clinical development. To investigate the novel HCV NS5B RdRp polymerase inhibitor, screening of a designed data set consisting of benzimidazole analogs by the FlexX docking approach was performed. Binding interactions at the active sites (PDB ID: 2DXS) were evaluated leading to the rationalization of further synthesis and evaluation procedures.

Rare haplotype load as marker for lethal mutagenesis.

Abstract: RNA viruses replicate with a template-copying fidelity, which lies close to an extinction threshold. Increases of mutation rate by nucleotide analogues can drive viruses towards extinction. This transition is the basis of an antiviral strategy termed lethal mutagenesis. We have introduced a new diversity index, the rare haplotype load (RHL), to describe NS5B (polymerase) mutant spectra of hepatitis C virus (HCV) populations passaged in absence or presence of the mutagenic agents favipiravir or ribavirin. The increase in RHL is more prominent in mutant spectra whose expansions were due to nucleotide analogues than to multiple passages in absence of mutagens. Statistical tests for paired mutagenized versus non-mutagenized samples with 14 diversity indices show that RHL provides consistently the highest standardized effect of mutagenic treatment difference for ribavirin and favipiravir. The results indicate that the enrichment of viral quasispecies in very low frequency minority genomes can serve as a robust marker for lethal mutagenesis. The diagnostic value of RHL from deep sequencing data is relevant to experimental studies on enhanced mutagenesis of viruses, and to pharmacological evaluations of inhibitors suspected to have a mutagenic activity.