TMC435 is a small-molecule inhibitor of the NS3/4A serine protease of hepatitis C virus (HCV) currently in phase 2 development. The in vitro resistance profile of TMC435 was characterized by selection experiments with HCV genotype 1 replicon cells and the genotype 2a JFH-1 system. In 80% (86/109) of the sequences from genotype 1 replicon cells analyzed, a mutation at NS3 residue D168 was observed, with changes to V or A being the most frequent. Mutations at NS3 positions 43, 80, 155, and 156, alone or in combination, were also identified. A transient replicon assay confirmed the relevance of these positions for TMC435 inhibitory activity. The change in the 50% effective concentrations (EC 50 s) observed for replicons with mutations at position 168 ranged from <10-fold for those with the D168G or D168N mutation to ϳ2,000-fold for those with the D168V or D168I mutation, compared to the EC 50 for the wild type. Of the positions identified, mutations at residue Q80 had the least impact on the activity of TMC435 (<10-fold change in EC 50 s), while greater effects were observed for some replicons with mutations at positions 43, 155, and 156. TMC435 remained active against replicons with the specific mutations observed after in vitro or in vivo exposure to telaprevir or boceprevir, including most replicons with changes at positions 36, 54, and 170 (<3-fold change in EC 50 s). Replicons carrying mutations affecting the activity of TMC435 remained fully susceptible to alpha interferon and NS5A and NS5B inhibitors. Finally, combinations of TMC435 with alpha interferon and NS5B polymerase inhibitors prevented the formation of drug-resistant replicon colonies.Hepatitis C is a blood-borne infection that can ultimately result in severe liver diseases, including fibrosis, cirrhosis, and hepatocellular carcinoma (7). The chronic nature of the disease and the significant possibility of long-term liver damage have led to the current global health burden, with an estimated 180 million people being infected, of whom 130 million are chronic hepatitis C virus (HCV) carriers (54).The current standard-of-care therapy for HCV-infected patients consists of a combination of weekly injected pegylated alpha interferon (Peg-IFN-␣) and twice-daily oral ribavirin. Treatment of HCV genotype 1-infected patients with this regimen for 48 weeks has a limited success rate (a 40 to 50% sustained virological response [SVR]) and is associated with a wide range of side effects, including flu-like symptoms, anemia, and depression, leading to treatment discontinuation in a significant proportion of patients (31, 48). Therefore, specifically targeted antiviral therapies for hepatitis C (STAT-C) have been a major focus of drug discovery efforts. Treatments with several NS3/4A protease inhibitors and NS5A and NS5B polymerase inhibitors, alone or in combination with Peg-IFN-␣-ribavirin, have recently shown encouraging results in clinical trials (17,36).HCV NS3 is an essential, bifunctional, multidomain protein that possesses protease and RNA helicase activiti...

TMC125 is a potent new investigational nonnucleoside reverse transcriptase inhibitor (NNRTI) that is

ABSTRACTHepatitis C virus (HCV) infection is a major global health burden and is associated with an increased risk of liver cirrhosis and hepatocellular carcinoma. There remains an unmet medical need for efficacious and safe direct antivirals with complementary modes of action for combination in treatment regimens to deliver a high cure rate with a short duration of treatment for HCV patients. Here we report thein vitroinhibitory activity, mode of action, binding kinetics, and resistance profile of TMC647055, a novel and potent nonnucleoside inhibitor of the HCV NS5B RNA-dependent RNA polymerase.In vitrocombination studies with an HCV NS3/4A protease inhibitor demonstrated potent suppression of HCV RNA replication, confirming the potential for combination of these two classes in the treatment of chronic HCV infection. TMC647055 is a potent nonnucleoside NS5B polymerase inhibitor of HCV replication with a promisingin vitrobiochemical, kinetic, and virological profile that is currently undergoing clinical evaluation.

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Structure-based macrocyclization of a 6-carboxylic acid indole chemotype has yielded potent and selective finger-loop inhibitors of the hepatitis C virus (HCV) NS5B polymerase. Lead optimization in conjunction with in vivo evaluation in rats identified several compounds showing (i) nanomolar potency in HCV replicon cells, (ii) limited toxicity and off-target activities, and (iii) encouraging preclinical pharmacokinetic profiles characterized by high liver distribution. This effort culminated in the identification of TMC647055 (10a), a nonzwitterionic 17-membered-ring macrocycle characterized by high affinity, long polymerase residence time, and broad genotypic coverage. In vitro results of the combination of 10a with the HCV protease inhibitor TMC435 (simeprevir) supported an evaluation of this combination in patients with regard to virus suppression and resistance emergence. In a phase 1b trial with HCV genotype 1-infected patients, 10a was considered to be safe and well-tolerated and demonstrated potent antiviral activity, which was further enhanced in a combination study with TMC435.