mk-7009 and danoprevir

The current standard of care for patients with chronic hepatitis C virus (HCV) infection is pegylated interferon alfa in combination with ribavirin. Treatment duration and efficacy depend heavily on HCV genotype. A sustained virologic response (SVR) is achieved only in approximately 40% of patients. Side effects of the current standard of care often make adherence to therapy difficult, further reducing the chance for an SVR. Numerous patient-related and virus-related factors can determine response to treatment. Nonresponders are a large proportion of the current HCV-infected population, and the number of patients with HCV infection is growing, necessitating newer therapies with higher efficacy and potentially fewer side effects. A new era of direct acting antiviral (DAA) compounds has emerged. The first 2 protease inhibitors for HCV infection, telaprevir and boceprevir, are coming to market in 2011. Other protease compounds in development include TMC-435, vaniprevir, BI-201335, BMS-650032, and danoprevir. The numerous other therapies that have potential in the treatment of HCV infection include nucleoside inhibitors, non-nucleoside inhibitors, NS5A inhibitors, DAA combinations, therapeutic vaccines, human monoclonal antibodies, immune modifiers, and interferon lambda.

Topics: Aminoisobutyric Acids; Cyclopropanes; Drug Resistance, Viral; Drug Therapy, Combination; Hepacivirus; Hepatitis C, Chronic; Heterocyclic Compounds, 3-Ring; Humans; Indoles; Isoindoles; Lactams; Lactams, Macrocyclic; Leucine; Oligopeptides; Proline; Quinolines; Simeprevir; Sulfonamides; Thiazoles; Treatment Outcome; Viral Load; Virus Replication

Hepatitis C virus (HCV) infects over 170 million people worldwide and is the leading cause of chronic liver diseases, including cirrhosis, liver failure, and liver cancer. Available antiviral therapies cause severe side effects and are effective only for a subset of patients, though treatment outcomes have recently been improved by the combination therapy now including boceprevir and telaprevir, which inhibit the viral NS3/4A protease. Despite extensive efforts to develop more potent next-generation protease inhibitors, however, the long-term efficacy of this drug class is challenged by the rapid emergence of resistance. Single-site mutations at protease residues R155, A156 and D168 confer resistance to nearly all inhibitors in clinical development. Thus, developing the next-generation of drugs that retain activity against a broader spectrum of resistant viral variants requires a comprehensive understanding of the molecular basis of drug resistance. In this study, 16 high-resolution crystal structures of four representative protease inhibitors--telaprevir, danoprevir, vaniprevir and MK-5172--in complex with the wild-type protease and three major drug-resistant variants R155K, A156T and D168A, reveal unique molecular underpinnings of resistance to each drug. The drugs exhibit differential susceptibilities to these protease variants in both enzymatic and antiviral assays. Telaprevir, danoprevir and vaniprevir interact directly with sites that confer resistance upon mutation, while MK-5172 interacts in a unique conformation with the catalytic triad. This novel mode of MK-5172 binding explains its retained potency against two multi-drug-resistant variants, R155K and D168A. These findings define the molecular basis of HCV N3/4A protease inhibitor resistance and provide potential strategies for designing robust therapies against this rapidly evolving virus.

Topics: Antiviral Agents; Cyclopropanes; Drug Resistance, Viral; Hepacivirus; Hepatitis C; Humans; Indoles; Isoindoles; Lactams; Lactams, Macrocyclic; Leucine; Models, Molecular; Oligopeptides; Proline; Protease Inhibitors; Protein Structure, Tertiary; Structure-Activity Relationship; Sulfonamides; Viral Nonstructural Proteins

The hepatitis C virus (HCV) genotype influences efficacy of interferon (IFN)-based therapy. HCV protease inhibitors are being licensed for treatment of genotype 1 infection. Because there are limited or no data on efficacy against HCV genotypes 2-7, we aimed at developing recombinant infectious cell culture systems expressing genotype-specific nonstructural (NS) protein 3 protease (NS3P).. Viability of J6/JFH1-based recombinants with genotypes 1-7 NS3P/NS4A was evaluated in Huh7.5 human hepatoma cells. Adaptive mutations were identified in reverse genetic studies. Efficacy of lead compound linear protease inhibitors VX-950 (telaprevir) and SCH503034 (boceprevir) and macrocyclic inhibitors TMC435350, ITMN-191 (danoprevir), and MK-7009 (vaniprevir) was determined in high-throughput infection assays.. For genotype(isolate) 2a(J6), 3a(S52), 5a(SA13), and 6a(HK6a), we developed culture systems producing supernatant infectivity titers of 3.5-4.0 log₁₀ focus forming units/mL. Against 2a(J6), 5a(SA13), and 6a(HK6a), all inhibitors showed similar efficacy; macrocyclic inhibitors had ~10-fold greater potency than linear inhibitors. However, compared with 2a recombinant J6/JFH1, efficacy against 3a(S52) was 16- to 70-fold lower for macrocyclic inhibitors and 2- to 7-fold lower for linear inhibitors. Testing of additional genotype 2a and 3a isolates showed that these differences were genotype specific. The resistance of 3a isolates was similar to J6/JFH1 with engineered resistance mutations originally observed for genotype 1 patients. In contrast, we found similar efficacy of NS5A inhibitor BMS-790052 and interferon-alfa2.. Novel HCV culture systems with genotype specific NS3P/NS4A revealed similar efficacy of protease inhibitors against genotypes 2a, 5a, and 6a and comparatively low but varying efficacy against genotype 3a isolates. These systems will facilitate genotype-specific studies of HCV protease inhibitors and of viral resistance.

Topics: Carcinoma, Hepatocellular; Carrier Proteins; Cell Line, Tumor; Cyclopropanes; Genotype; Hepacivirus; Hepatitis C; Humans; Indoles; Intracellular Signaling Peptides and Proteins; Isoindoles; Lactams; Lactams, Macrocyclic; Leucine; Liver Neoplasms; Molecular Sequence Data; Oligopeptides; Proline; Protease Inhibitors; Sulfonamides; Treatment Outcome; Viral Nonstructural Proteins

In order to assess the natural variation in susceptibility to hepatitis C virus (HCV) NS3 protease inhibitors (PIs) among untreated HCV patient samples, the susceptibilities of 39 baseline clinical isolates were determined using a transient-replication assay on a panel of HCV PIs, including two α-ketoamides (VX-950 and SCH-503034) and three macrocyclic inhibitors (MK-7009, ITMN-191, and TMC-435350). Some natural variation in susceptibility to all HCV PIs tested was observed among the baseline clinical isolates. The susceptibility to VX-950 correlated strongly with the susceptibility to SCH-503034. A moderate correlation was observed between the susceptibilities to ITMN-191 and MK-7009. In contrast, the phenotypic correlations between the α-ketoamides and macrocyclic inhibitors were significantly lower. This difference is partly attributable to reduced susceptibility of the HCV variants containing the NS3 polymorphism Q80K (existing in 47% of genotype 1a isolates) to the macrocyclic compounds but no change in the sensitivity of the same variants to the α-ketoamides tested. Our results suggest that the natural variation in baseline susceptibility may contribute to different degrees of antiviral response among patients in vivo, particularly at lower doses.

Topics: Antiviral Agents; Cell Line, Tumor; Cyclopropanes; Hepacivirus; Heterocyclic Compounds, 3-Ring; Humans; Indoles; Isoindoles; Lactams; Lactams, Macrocyclic; Leucine; Molecular Structure; Oligopeptides; Proline; Protease Inhibitors; Simeprevir; Sulfonamides