Development of an Aryloxazole Class of Hepatitis C Virus Inhibitors Targeting the Entry Stage of the Viral Replication Cycle

Abstract

Reliance on hepatitis C virus (HCV) replicon systems and protein-based screening assays has led to treatments that target HCV viral replication proteins. The model does not encompass other viral replication cycle steps such as entry, processing, assembly and secretion, or viral host factors. We previously applied a phenotypic high-throughput screening platform based on an infectious HCV system and discovered an aryloxazole-based anti-HCV hit. Structure– activity relationship studies revealed several compounds exhibiting EC50 values below 100 nM. Lead compounds showed inhibition of the HCV pseudoparticle entry, suggesting a different mode of action from existing HCV drugs. Hit 7a and lead 7ii both showed synergistic effects in combination with existing HCV drugs. In vivo pharmacokinetics studies of 7ii showed high liver distribution and long half-life without obvious hepatotoxicity. The lead compounds are promising as preclinical candidates for the treatment of HCV infection and as molecular probes to study HCV pathogenesis.

Fluoxazolevir inhibits hepatitis C virus infection in humanized chimeric mice by blocking viral membrane fusion

“…Fluoxazolevir can achieve complete inhibition against all 7 HCV chimeric genotypes in vitro with varying efficacies. Fluoxazolevir is most active against HCV genotypes 2a and 2b, which is not unexpected as HCV genotype 2a was used to discover fluoxazolevir 18 . The in vivo studies in which fluoxazolevir is effective against genotypes 1b, 2a and 3 without the emergence of RASs support the broad genotypic coverage of fluoxazolevir.…”

“…In a previous study, fluoxazolevir ( Fig. 1a ) was shown to target the entry step of the HCV life cycle using a HCV pseudoparticle assay 18 . To confirm fluoxazolevir’s role in inhibiting HCV entry, a time-of-addition assay was performed 19 .…”

“…We previously identified a promising aryloxazole-based series of HCV entry inhibitors, which have a structural scaffold different from other described HCV entry inhibitors 17 . After further structure-activity relationship optimization, we identified the compound 18a (NCGC00351982 or fluoxazolevir), as the lead candidate for preclinical development based on the best combined profile of efficacy, cytotoxicity and in vitro ADME (EC 50 =0.0188 μM, CC 50 =13.0 μM, selectivity index CC 50 /EC 50 >600) 18 . We report here the mechanism of action of fluoxazolevir, including in vitro efficacy against various HCV genotypes, synergy with other currently FDA-approved HCV drugs, in vivo pharmacokinetics in mice, rats and dogs, and efficacy in a humanized chimeric mouse model against HCV genotype 1b, 2a or 3 infection.…”

Discovery of small molecule inhibitors against the NS3/4A serine protease of Hepatitis C virus genotype 3 via highthroughput virtual screening and in vitro evaluations

“…The oxazole structure in compound A is interesting as it is able to form hydrogen bonds with two important residues; Ser139 and Gly137. Oxazole-based derivative compounds, aryloxazole and benzoxazole, have been used to develop inhibitors against HCV replication by targeting viral entry and NS5B polymerase, respectively (Ismail et al, 2013;He et al, 2017). There has also been development of many medicinal drugs that use oxazole and its derivatives such as antifungal (Wani et al, 2015), anti-bacterial (Prakash et al, 2014), anti-cancer (Choi et al, 2013), and anti-inflammatory (Pedada et al, 2016).…”

The activity prediction of indole inhibitors against HCV NS5B polymerase

“…Hepatitis C is one of the five (A, B, C, D, E) infectious diseases, which primarily affects the liver and causes both acute and chronic hepatitis (He et al, ). Hepatitis C virus (HCV) is a terrible virus with a positive‐ and single‐stranded RNA and is found in the Flaviviridae family (Venkatesan & Dass ).…”