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PTC725, an NS4B-Targeting Compound, Inhibits a Hepatitis C Virus Genotype 3 Replicon, as Predicted by Genome Sequence Analysis and Determined Experimentally.

ABSTRACT: PTC725 is a small molecule NS4B-targeting inhibitor of hepatitis C virus (HCV) genotype (gt) 1 RNA replication that lacks activity against HCV gt2. We analyzed the Los Alamos HCV sequence database to predict susceptible/resistant HCV gt's according to the prevalence of known resistance-conferring amino acids in the NS4B protein. Our analysis predicted that HCV gt3 would be highly susceptible to the activity of PTC725. Indeed, PTC725 was shown to be active against a gt3 subgenomic replicon with a 50% effective concentration of ∼5 nM. De novo resistance selection identified mutations encoding amino acid substitutions mapping to the first predicted transmembrane region of NS4B, a finding consistent with results for PTC725 and other NS4B-targeting compounds against HCV gt1. This is the first report of the activity of an NS4B targeting compound against HCV gt3. In addition, we have identified previously unreported amino acid substitutions selected by PTC725 treatment which further demonstrate that these compounds target the NS4B first transmembrane region.

SUBMITTER: Graci JD

PROVIDER: S-EPMC5118984 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Although a highly effective vaccine is available, the number of yellow fever cases has increased over the past 2 decades, which highlights the pressing need for antiviral therapeutics. In a high-throughput screening campaign, we identified an acetic acid benzodiazepine (BDAA) compound which potently inhibits yellow fever virus (YFV). Interestingly, while treatment of YFV-infected cultures with 2 ?M BDAA reduced the virion production by greater than 2 logs, the compound was not active against 21 other viruses from 14 different viral families. Selection and genetic analysis of drug-resistant viruses revealed that replacement of the proline at amino acid 219 (P219) of the nonstructural protein 4B (NS4B) with serine, threonine, or alanine conferred YFV with resistance to BDAA without apparent loss of replication fitness in cultured mammalian cells. However, replacement of P219 with glycine conferred BDAA resistance with significant loss of replication ability. Bioinformatics analysis predicts that the P219 amino acid is localized at the endoplasmic reticulum lumen side of the fifth putative transmembrane domain of NS4B, and the mutation may render the viral protein incapable of interacting with BDAA. Our studies thus revealed an important role and the structural basis for the NS4B protein in supporting YFV replication. Moreover, in YFV-infected hamsters, oral administration of BDAA protected 90% of the animals from death, significantly reduced viral load by greater than 2 logs, and attenuated virus infection-induced liver injury and body weight loss. The encouraging preclinical results thus warrant further development of BDAA or its derivatives as antiviral agents to treat yellow fever. IMPORTANCE Yellow fever is an acute viral hemorrhagic disease which threatens approximately 1 billion people living in tropical areas of Africa and Latin America. Although a highly effective yellow fever vaccine has been available for more than 7 decades, the low vaccination rate fails to prevent outbreaks in at-risk regions. It has been estimated that up to 1.7 million YFV infections occur in Africa each year, resulting in 29,000 to 60,000 deaths. Thus far, there is no specific antiviral treatment for yellow fever. To cope with this medical challenge, we identified a benzodiazepine compound that selectively inhibits YFV by targeting the viral NS4B protein. To our knowledge, this is the first report demonstrating in vivo safety and antiviral efficacy of a YFV NS4B inhibitor in an animal model. We have thus reached a critical milestone toward the development of specific antiviral therapeutics for clinical management of yellow fever.

Dataset Information

PTC725, an NS4B-Targeting Compound, Inhibits a Hepatitis C Virus Genotype 3 Replicon, as Predicted by Genome Sequence Analysis and Determined Experimentally.

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