scholarly journals Mechanistic Characterization of GS-9190 (Tegobuvir), a Novel Nonnucleoside Inhibitor of Hepatitis C Virus NS5B Polymerase

2011 ◽  
Vol 55 (9) ◽  
pp. 4196-4203 ◽  
Author(s):  
I-hung Shih ◽  
Inge Vliegen ◽  
Betty Peng ◽  
Huiling Yang ◽  
Christy Hebner ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Mechanism Of Action ◽  
Cross Resistance ◽  
Resistance Pattern ◽  
Hcv Rna ◽  
Wild Type ◽  
Nonstructural Proteins ◽  
Antiviral Activities

ABSTRACTGS-9190 (Tegobuvir) is a novel imidazopyridine inhibitor of hepatitis C virus (HCV) RNA replicationin vitroand has demonstrated potent antiviral activity in patients chronically infected with genotype 1 (GT1) HCV. GS-9190 exhibits reduced activity against GT2a (JFH1) subgenomic replicons and GT2a (J6/JFH1) infectious virus, suggesting that the compound's mechanism of action involves a genotype-specific viral component. To further investigate the GS-9190 mechanism of action, we utilized the susceptibility differences between GT1b and GT2a by constructing a series of replicon chimeras where combinations of 1b and 2a nonstructural proteins were encoded within the same replicon. The antiviral activities of GS-9190 against the chimeric replicons were reduced to levels comparable to that of the wild-type GT2a replicon in chimeras expressing GT2a NS5B. GT1b replicons in which the β-hairpin region (amino acids 435 to 455) was replaced by the corresponding sequence of GT2a were markedly less susceptible to GS-9190, indicating the importance of the thumb subdomain of the polymerase in this effect. Resistance selection in GT1b replicon cells identified several mutations in NS5B (C316Y, Y448H, Y452H, and C445F) that contributed to the drug resistance phenotype. Reintroduction of these mutations into wild-type replicons conferred resistance to GS-9190, with the number of NS5B mutations correlating with the degree of resistance. Analysis of GS-9190 cross-resistance against previously reported NS5B drug-selected mutations showed that the resistance pattern of GS-9190 is different from other nonnucleoside inhibitors. Collectively, these data demonstrate that GS-9190 represents a novel class of nonnucleoside polymerase inhibitors that interact with NS5B likely through involvement of the β-hairpin in the thumb subdomain.

scholarly journals In VitroandIn VivoAntiviral Activity and Resistance Profile of the Hepatitis C Virus NS3/4A Protease Inhibitor ABT-450

2014 ◽  
Vol 59 (2) ◽  
pp. 988-997 ◽  
Author(s):  
Tami Pilot-Matias ◽  
Rakesh Tripathi ◽  
Daniel Cohen ◽  
Isabelle Gaultier ◽  
Tatyana Dekhtyar ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Antiviral Agents ◽  
Cross Resistance ◽  
Hcv Rna ◽  
Genotype 1 ◽  
Common Amino Acid ◽  
Direct Acting Antiviral ◽  
Genotype 1A

ABSTRACTThe development of direct-acting antiviral agents is a promising therapeutic advance in the treatment of hepatitis C virus (HCV) infection. However, rapid emergence of drug resistance can limit efficacy and lead to cross-resistance among members of the same drug class. ABT-450 is an efficacious inhibitor of HCV NS3/4A protease, with 50% effective concentration values of 1.0, 0.21, 5.3, 19, 0.09, and 0.69 nM against stable HCV replicons with NS3 protease from genotypes 1a, 1b, 2a, 3a, 4a, and 6a, respectively.In vitro, the most common amino acid variants selected by ABT-450 in genotype 1 were located in NS3 at positions 155, 156, and 168, with the D168Y variant conferring the highest level of resistance to ABT-450 in both genotype 1a and 1b replicons (219- and 337-fold, respectively). In a 3-day monotherapy study with HCV genotype 1-infected patients, ABT-450 was coadministered with ritonavir, a cytochrome P450 3A4 inhibitor shown previously to markedly increase peak, trough, and overall drug exposures of ABT-450. A mean maximum HCV RNA decline of 4.02 log10was observed at the end of the 3-day dosing period across all doses. The most common variants selected in these patients were R155K and D168V in genotype 1a and D168V in genotype 1b. However, selection of resistant variants was significantly reduced at the highest ABT-450 dose compared to lower doses. These findings were informative for the subsequent evaluation of ABT-450 in combination with additional drug classes in clinical trials in HCV-infected patients. (Study M11-602 is registered at ClinicalTrials.gov under registration no. NCT01074008.)

scholarly journals The Combination of Grazoprevir, a Hepatitis C Virus (HCV) NS3/4A Protease Inhibitor, and Elbasvir, an HCV NS5A Inhibitor, Demonstrates a High Genetic Barrier to Resistance in HCV Genotype 1a Replicons

2016 ◽  
Vol 60 (5) ◽  
pp. 2954-2964 ◽  
Author(s):  
Frederick C. Lahser ◽  
Karin Bystol ◽  
Stephanie Curry ◽  
Patricia McMonagle ◽  
Ellen Xia ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Protease Inhibitor ◽  
Cross Resistance ◽  
Hcv Rna ◽  
Wild Type ◽  
Genetic Barrier ◽  
Potent Effect ◽  
Ns5a Inhibitor ◽  
Genotype 1A

ABSTRACTThe selection of resistance-associated variants (RAVs) against single agents administered to patients chronically infected with hepatitis C virus (HCV) necessitates that direct-acting antiviral agents (DAAs) targeting multiple viral proteins be developed to overcome failure resulting from emergence of resistance. The combination of grazoprevir (formerly MK-5172), an NS3/4A protease inhibitor, and elbasvir (formerly MK-8742), an NS5A inhibitor, was therefore studied in genotype 1a (GT1a) replicon cells. Both compounds were independently highly potent in GT1a wild-type replicon cells, with 90% effective concentration (EC90) values of 0.9 nM and 0.006 nM for grazoprevir and elbasvir, respectively. No cross-resistance was observed when clinically relevant NS5A and NS3 RAVs were profiled against grazoprevir and elbasvir, respectively. Kinetic analyses of HCV RNA reduction over 14 days showed that grazoprevir and elbasvir inhibited prototypic NS5A Y93H and NS3 R155K RAVs, respectively, with kinetics comparable to those for the wild-type GT1a replicon. In combination, grazoprevir and elbasvir interacted additively in GT1a replicon cells. Colony formation assays with a 10-fold multiple of the EC90values of the grazoprevir-elbasvir inhibitor combination suppressed emergence of resistant colonies, compared to a 100-fold multiple for the independent agents. The selected resistant colonies with the combination harbored RAVs that required two or more nucleotide changes in the codons. Mutations in the cognate gene caused greater potency losses for elbasvir than for grazoprevir. Replicons bearing RAVs identified from resistant colonies showed reduced fitness for several cell lines and may contribute to the activity of the combination. These studies demonstrate that the combination of grazoprevir and elbasvir exerts a potent effect on HCV RNA replication and presents a high genetic barrier to resistance. The combination of grazoprevir and elbasvir is currently approved for chronic HCV infection.

scholarly journals In Vitro RNA Replication Directed by Replicase Complexes Isolated from the Subgenomic Replicon Cells of Hepatitis C Virus

2003 ◽  
Vol 77 (3) ◽  
pp. 2295-2300 ◽  
Author(s):  
Vicky C. H. Lai ◽  
Shannon Dempsey ◽  
Johnson Y. N. Lau ◽  
Zhi Hong ◽  
Weidong Zhong
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Synthesis ◽  
Divalent Cations ◽  
Hcv Rna ◽  
Nonstructural Proteins ◽  
Subgenomic Replicon ◽  
Free System ◽  
Potential Inhibitors

ABSTRACT Replication of hepatitis C virus (HCV) RNA in virus-infected cells is believed to be catalyzed by viral replicase complexes (RCs), which may consist of various virally encoded nonstructural proteins and host factors. In this study, we characterized the RC activity of a crude membrane fraction isolated from HCV subgenomic replicon cells. The RC preparation was able to use endogenous replicon RNA as a template to synthesize both single-stranded (ss) and double-stranded (ds) RNA products. Divalent cations (Mg2+ and Mn2+) showed different effects on RNA synthesis. Mg2+ ions stimulated the synthesis of ss RNA but had little effect on the synthesis of ds RNA. In contrast, Mn2+ ions enhanced primarily the synthesis of ds RNA. Interestingly, ss RNA could be synthesized under certain conditions in the absence of ds RNA, and vice versa, suggesting that the ss and ds RNA were derived either from different forms of replicative intermediates or from different RCs. Pulse-chase analysis showed that radioactivity incorporated into the ss RNA was chased into the ds RNA and other larger RNA species. This observation indicated that the newly synthesized ss RNA could serve as a template for a further round of RNA synthesis. Finally, 3′ deoxyribonucleoside triphosphates were able to inhibit RNA synthesis in this cell-free system, presumably through chain termination, with 3′ dGTP having the highest potency. Establishment of the replicase assay will facilitate the identification and evaluation of potential inhibitors that would act against the entire RC of HCV.

scholarly journals VX-950, a Novel Hepatitis C Virus (HCV) NS3-4A Protease Inhibitor, Exhibits Potent Antiviral Activities in HCV Replicon Cells

2006 ◽  
Vol 50 (5) ◽  
pp. 1813-1822 ◽  
Author(s):  
Kai Lin ◽  
Robert B. Perni ◽  
Ann D. Kwong ◽  
Chao Lin
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Antiviral Agents ◽  
Alpha Interferon ◽  
Hcv Rna ◽  
Resistance Mutations ◽  
In Vitro Characterization ◽  
Antiviral Activities

ABSTRACT The NS3-4A serine protease of hepatitis C virus (HCV) is essential for viral replication and therefore has been one of the most attractive targets for developing specific antiviral agents against HCV. VX-950, a highly selective, reversible, and potent peptidomimetic inhibitor of the HCV NS3-4A protease, is currently in clinical development for the treatment of hepatitis C. In this report, we describe the in vitro characterization of anti-HCV activities of VX-950 in subgenomic HCV replicon cells. Incubation with VX-950 resulted in a time- and dose-dependent reduction of HCV RNA and proteins in replicon cells. Moreover, following a 2-week incubation with VX-950, a reduction in HCV RNA levels of 4.7 log10 was observed, and this reduction resulted in elimination of HCV RNA from replicon cells, since there was no rebound in replicon RNA after withdrawal of the inhibitor. The combination of VX-950 and alpha interferon was additive to moderately synergistic in reducing HCV RNA in replicon cells with no significant increase in cytotoxicity. The benefit of the combination was sustained over time: a 4-log10 reduction in HCV RNA level was achieved following a 9-day incubation with VX-950 and alpha interferon at lower concentrations than when either VX-950 or alpha interferon was used alone. The combination of VX-950 and alpha interferon also suppressed the emergence of in vitro resistance mutations against VX-950 in replicon cells.

scholarly journals In Vitro Antiviral Profile of Ruzasvir, a Potent and Pangenotype Inhibitor of Hepatitis C Virus NS5A

2018 ◽  
Vol 62 (11) ◽  
Author(s):  
Ernest Asante-Appiah ◽  
Rong Liu ◽  
Stephanie Curry ◽  
Patricia McMonagle ◽  
Sony Agrawal ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Antiviral Activity ◽  
De Novo ◽  
Antiviral Agents ◽  
Cross Resistance ◽  
Hcv Rna ◽  
Direct Acting Antiviral ◽  
Direct Acting

ABSTRACT Inhibition of NS5A has emerged as an attractive strategy to intervene in hepatitis C virus (HCV) replication. Ruzasvir (formerly MK-8408) was developed as a novel NS5A inhibitor to improve upon the potency and barrier to resistance of early compounds. Ruzasvir inhibited HCV RNA replication with 50% effective concentrations (EC50s) of 1 to 4 pM in Huh7 or Huh7.5 cells bearing replicons for HCV genotype 1 (GT1) to GT7. The antiviral activity was modestly (10-fold) reduced in the presence of 40% normal human serum. The picomolar potency in replicon cells extended to sequences of clinical isolates available in public databases that were synthesized and tested as replicons. In GT1a, ruzasvir inhibited common NS5A resistance-associated substitutions (RASs), with the exception of M28G. De novo resistance selection studies identified pathways with certain amino acid substitutions at residues 28, 30, 31, and 93 across genotypes. Substitutions at position 93 were more common in GT1 to -4, while changes at position 31 emerged frequently in GT5 and -6. With the exception of GT4, the reintroduction of selected RASs conferred a ≥100-fold potency reduction in the antiviral activity of ruzasvir. Common RASs from other classes of direct-acting antiviral agents (DAAs) did not confer cross-resistance to ruzasvir. The interaction of ruzasvir with an NS3/4A protease inhibitor (grazoprevir) and an NS5B polymerase prodrug (uprifosbuvir) was additive to synergistic, with no evidence of antagonism or cytotoxicity. The antiviral profile of ruzasvir supported its further evaluation in human trials in combination with grazoprevir and uprifosbuvir.

scholarly journals Cyclophilin A Is an Essential Cofactor for Hepatitis C Virus Infection and the Principal Mediator of Cyclosporine Resistance In Vitro

2008 ◽  
Vol 82 (11) ◽  
pp. 5269-5278 ◽  
Author(s):  
Feng Yang ◽  
Jason M. Robotham ◽  
Heather B. Nelson ◽  
Andre Irsigler ◽  
Rachael Kenworthy ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Cyclophilin A ◽  
Hcv Rna ◽  
Wild Type ◽  
Replication Assay ◽  
Cellular Cofactor ◽  
Interfering Rna ◽  
Cypa Expression

ABSTRACT Cyclosporine (CsA) and its derivatives potently suppress hepatitis C virus (HCV) replication. Recently, CsA-resistant HCV replicons have been identified in vitro. We examined the dependence of the wild-type and CsA-resistant replicons on various cyclophilins for replication. A strong correlation between CsA resistance and reduced dependency on cyclophilin A (CyPA) for replication was identified. Silencing of CyPB or CyPC expression had no significant effect on replication, whereas various forms of small interfering RNA (siRNA) directed at CyPA inhibited HCV replication of wild-type but not CsA-resistant replicons. The efficiency of a particular siRNA in suppressing CyPA expression was correlated with its potency in inhibiting HCV replication, and expression of an siRNA-resistant CyPA cDNA rescued replication. In addition, an anti-CyPA antibody blocked replication of the wild-type but not the resistant replicon in an in vitro replication assay. Depletion of CyPA alone in the CsA-resistant replicon cells eliminated CsA resistance, indicating that CyPA is the chief mediator of the observed CsA resistance. The dependency on CyPA for replication was observed for both genotype (GT) 1a and 1b replicons as well as a GT 2a infectious virus. An interaction between CyPA and HCV RNA as well as the viral polymerase that is sensitive to CsA treatment in wild-type but not in resistant replicons was detected. These findings reveal the molecular mechanism of CsA resistance and identify CyPA as a critical cellular cofactor for HCV replication and infection.

scholarly journals Genotypic and Phenotypic Analyses of Hepatitis C Virus from Patients Treated with JTK-853 in a Three-Day Monotherapy

2012 ◽  
Vol 57 (1) ◽  
pp. 436-444 ◽  
Author(s):  
Naoki Ogura ◽  
Yukiyo Toyonaga ◽  
Izuru Ando ◽  
Kunihiro Hirahara ◽  
Tsutomu Shibata ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Amino Acid ◽  
Viral Resistance ◽  
Hcv Rna ◽  
Amino Acid Substitutions ◽  
Sequencing Analysis ◽  
Resistance Mutations ◽  
In The Wild

ABSTRACTJTK-853, a palm site-binding NS5B nonnucleoside polymerase inhibitor, shows antiviral activityin vitroand in hepatitis C virus (HCV)-infected patients. Here, we report the results of genotypic and phenotypic analyses of resistant variants in 24 HCV genotype 1-infected patients who received JTK-853 (800, 1,200, or 1,600 mg twice daily or 1,200 mg three times daily) in a 3-day monotherapy. Viral resistance in NS5B was investigated using HCV RNA isolated from serum specimens from the patients. At the end of treatment (EOT) with JTK-853, the amino acid substitutions M414T (methionine [M] in position 414 at baseline was replaced with threonine [T] at EOT), C445R (cysteine [C] in position 445 at baseline was replaced with arginine [R] at EOT), Y448C/H (tyrosine [Y] in position 448 at baseline was replaced with cysteine [C] or histidine [H] at EOT), and L466F (leucine [L] in position 466 at baseline was replaced with phenylalanine [F] at EOT), which are known to be typical resistant variants of nonnucleoside polymerase inhibitors, were observed in a clonal sequencing analysis. These substitutions were also selected by a treatment with JTK-853in vitro, and the 50% effective concentration of JTK-853 in the M414T-, C445F-, Y448H-, and L466V-harboring replicons attenuated the susceptibility by 44-, 5-, 6-, and 21-fold, respectively, compared with that in the wild-type replicon (Con1). These findings suggest that amino acid substitutions of M414T, C445R, Y448C/H, and L466F are thought to be viral resistance mutations in HCV-infected patients receiving JTK-853 in a 3-day monotherapy.

scholarly journals Cellular RNA Helicase p68 Relocalization and Interaction with the Hepatitis C Virus (HCV) NS5B Protein and the Potential Role of p68 in HCV RNA Replication

2004 ◽  
Vol 78 (10) ◽  
pp. 5288-5298 ◽  
Author(s):  
Phuay-Yee Goh ◽  
Yee-Joo Tan ◽  
Siew Pheng Lim ◽  
Y. H. Tan ◽  
Seng Gee Lim ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Cell Line ◽  
Rna Helicase ◽  
Hcv Rna ◽  
Activity Levels ◽  
Nonstructural Proteins ◽  
Negative Strand ◽  
Replicon Cell Line ◽  
Rna Helicase P68

ABSTRACT Chronic infection by hepatitis C virus (HCV) can lead to severe hepatitis and cirrhosis and is closely associated with hepatocellular carcinoma. The replication cycle of HCV is poorly understood but is likely to involve interaction with host factors. In this report, we show that NS5B, the HCV RNA-dependent RNA polymerase (RdRp), interacts with a human RNA helicase, p68. Transient expression of NS5B alone, as well as the stable expression of all the nonstructural proteins in a HCV replicon-bearing cell line (V. Lohmann, F. Korner, J.-O. Koch, U. Herian, L. Theilmann, and R. Bartenschlager, Science 285:110-113), causes the redistribution of endogenous p68 from the nucleus to the cytoplasm. Deletion of the C-terminal two-thirds of NS5B (NS5BΔC) dramatically reduces its coimmunoprecipitation (co-IP) with endogenous p68, while the deletion of the N-terminal region (NS5BΔN1 and NS5BΔN2) does not affect its interaction with p68. In consistency with the co-IP results, NS5BΔC does not cause the relocalization of p68 whereas NS5BΔN1 does. With a replicon cell line, we were not able to detect a change in positive- and negative-strand synthesis when p68 levels were reduced using small interfering RNA (siRNA). In cells transiently transfected with a full-length HCV construct, however, the depletion (using specific p68 siRNA) of endogenous p68 correlated with a reduction in the transcription of negative-strand from positive-strand HCV RNA. Overexpression of NS5B and NS5BΔN1, but not that of NS5BΔC, causes a reduction in the negative-strand synthesis, indicating that overexpressed NS5B and NS5BΔN1 sequesters p68 from the replication complexes (thus reducing their replication activity levels). Identification of p68 as a cellular factor involved in HCV replication, at least for cells transiently transfected with a HCV expression construct, is a step towards understanding HCV replication.

scholarly journals Protein-Protein Interactions between Hepatitis C Virus Nonstructural Proteins

2003 ◽  
Vol 77 (9) ◽  
pp. 5401-5414 ◽  
Author(s):  
Maria Dimitrova ◽  
Isabelle Imbert ◽  
Marie Paule Kieny ◽  
Catherine Schuster
Keyword(s):  
Endoplasmic Reticulum ◽  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Protein Interactions ◽  
Laser Scanning ◽  
Ex Vivo ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Nonstructural Proteins

ABSTRACT Replication of the hepatitis C virus (HCV) genome has been proposed to take place close to the membrane of the endoplasmic reticulum in membrane-associated replicase complexes, as is the case with several other plus-strand RNA viruses, such as poliovirus and flaviviruses. The most obvious benefits of this property are the possibility of coupling functions residing in different polypeptidic chains and the sequestration of viral proteins and nucleic acids in a distinct cytoplasmic compartment with high local concentrations of viral components. Indeed, HCV nonstructural (NS) proteins were clearly colocalized in association with membranes derived from the endoplasmic reticulum. This observation, together with the demonstration of the existence of several physical interactions between HCV NS proteins, supports the idea of assembly of a highly ordered multisubunit protein complex(es) probably involved in the replication of the viral genome. The objective of this study, therefore, was to examine all potential interactions between HCV NS proteins which could result in the formation of a replication complex(es). We identified several interacting viral partners by using a glutathione S-transferase pull-down assay, by in vitro and ex vivo coimmunoprecipitation experiments in adenovirus-infected Huh-7 cells allowing the expression of HCV NS proteins, and, finally, by using the yeast two-hybrid system. In addition, by confocal laser scanning microscopy, NS proteins were clearly shown to colocalize when expressed together in Huh-7 cells. We have been able to demonstrate the existence of a complex network of interactions implicating all six NS proteins. Our observations confirm previously described associations and identify several novel homo- and heterodimerizations.

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