ABSTRACT
HCV NS3/4a protease inhibitors are proven therapeutic agents against chronic hepatitis C virus infection, with boceprevir and telaprevir having recently received regulatory approval as add-on therapy to pegylated interferon/ribavirin for patients harboring genotype 1 infections. Overcoming antiviral resistance, broad genotype coverage, and a convenient dosing regimen are important attributes for future agents to be used in combinations without interferon. In this communication, we report the preclinical profile of MK-5172, a novel P2-P4 quinoxaline macrocyclic NS3/4a protease inhibitor currently in clinical development. The compound demonstrates subnanomolar activity against a broad enzyme panel encompassing major hepatitis C virus (HCV) genotypes as well as variants resistant to earlier protease inhibitors. In replicon selections, MK-5172 exerted high selective pressure, which yielded few resistant colonies. In both rat and dog, MK-5172 demonstrates good plasma and liver exposures, with 24-h liver levels suggestive of once-daily dosing. When administered to HCV-infected chimpanzees harboring chronic gt1a or gt1b infections, MK-5172 suppressed viral load between 4 to 5 logs at a dose of 1 mg/kg of body weight twice daily (b.i.d.) for 7 days. Based on its preclinical profile, MK-5172 is anticipated to be broadly active against multiple HCV genotypes and clinically important resistance variants and highly suited for incorporation into newer all-oral regimens.
Subject(s)
Hepacivirus/drug effects , Protease Inhibitors/pharmacology , Quinoxalines/pharmacology , Quinoxalines/pharmacokinetics , Viral Nonstructural Proteins/antagonists & inhibitors , Amides , Animals , Antiviral Agents/pharmacology , Carbamates , Cyclopropanes , Dogs , Drug Resistance, Viral , Genotype , Hepacivirus/enzymology , Hepacivirus/genetics , Hepatitis C, Chronic/drug therapy , Hepatitis C, Chronic/virology , Liver/drug effects , Pan troglodytes , Quinoxalines/metabolism , Rats , Sulfonamides , Viral Load/drug effectsABSTRACT
Thieno[3,2-b]pyrroles are a novel class of allosteric inhibitors of HCV NS5B RNA-dependent RNA polymerase which show potent affinity for the NS5B enzyme. Introduction of a polar substituent in the position N1 led to a compound that efficiently blocks subgenomic HCV RNA replication in HUH-7 cells with an EC50 of 2.9 microM.
Subject(s)
Protease Inhibitors/chemistry , Pyrroles/chemistry , Viral Nonstructural Proteins/antagonists & inhibitors , Allosteric Regulation , Protease Inhibitors/pharmacology , Pyrroles/pharmacologyABSTRACT
Infections caused by hepatitis C virus (HCV) are a significant world health problem for which novel therapies are in urgent demand. The polymerase of HCV is responsible for the replication of viral RNA. We recently disclosed dihydroxypyrimidine carboxylates 2 as novel, reversible inhibitors of the HCV NS5B polymerase. This series was further developed into 5,6-dihydroxy-2-(2-thienyl)pyrimidine-4-carboxylic acids such as 34 (EC50 9.3 microM), which now show activity in the cell-based HCV replication assay. The structure-activity relationship of these inhibitors is discussed in the context of their physicochemical properties and of the polymerase crystal structure. We also report the results of mutagenesis experiments which support the proposed binding model, which involves pyrophosphate-like chelation of the active site Mg ions.
Subject(s)
Antiviral Agents/chemical synthesis , Hepacivirus/drug effects , Hepacivirus/enzymology , Methylurea Compounds/chemical synthesis , Models, Molecular , Pyrimidines/chemical synthesis , Thiophenes/chemical synthesis , Viral Nonstructural Proteins/antagonists & inhibitors , Viral Nonstructural Proteins/genetics , Antiviral Agents/chemistry , Antiviral Agents/pharmacology , Binding Sites , Cell Line , Chelating Agents/chemistry , Crystallization , Humans , Methylurea Compounds/chemistry , Methylurea Compounds/pharmacology , Mutagenesis , Protein Conformation , Pyrimidines/chemistry , Pyrimidines/pharmacology , Structure-Activity Relationship , Thiophenes/chemistry , Thiophenes/pharmacology , Viral Nonstructural Proteins/chemistry , Virus Replication/drug effectsABSTRACT
Infections caused by hepatitis C virus (HCV) are a significant world health problem for which novel therapies are in urgent demand. Compounds that block replication of subgenomic HCV RNA in liver cells are of interest because of their demonstrated antiviral effect in the clinic. In followup to our recent report that indole-N-acetamides (e.g., 1) are potent allosteric inhibitors of the HCV NS5B polymerase enzyme, we describe here their optimization as cell-based inhibitors. The crystal structure of 1 bound to NS5B was a guide in the design of a two-dimensional compound array that highlighted that formally zwitterionic inhibitors have strong intracellular potency and that pregnane X receptor (PXR) activation (an undesired off-target activity) is linked to a structural feature of the inhibitor. Optimized analogues devoid of PXR activation (e.g., 55, EC(50) = 127 nM) retain strong cell-based efficacy under high serum conditions and show acceptable pharmacokinetics parameters in rat and dog.
Subject(s)
Acetamides/chemical synthesis , Antiviral Agents/chemical synthesis , Hepacivirus/enzymology , Indoles/chemical synthesis , RNA, Viral/drug effects , RNA-Dependent RNA Polymerase/antagonists & inhibitors , Viral Nonstructural Proteins/antagonists & inhibitors , Acetamides/chemistry , Acetamides/pharmacology , Allosteric Regulation , Animals , Antiviral Agents/chemistry , Antiviral Agents/pharmacology , Biological Availability , Cell Line, Tumor , Dogs , Genome, Viral , Half-Life , Hepacivirus/genetics , Humans , Indoles/chemistry , Indoles/pharmacology , Models, Molecular , Pregnane X Receptor , RNA-Dependent RNA Polymerase/chemistry , Rats , Rats, Sprague-Dawley , Receptors, Cytoplasmic and Nuclear/agonists , Receptors, Steroid/agonists , Structure-Activity Relationship , Tissue Distribution , Viral Nonstructural Proteins/chemistryABSTRACT
Allosteric inhibition of the hepatitis C virus (HCV) NS5B RNA-dependent RNA polymerase enzyme has recently emerged as a viable strategy toward blocking replication of viral RNA in cell-based systems. We report here a novel class of allosteric inhibitor of NS5B that shows potent affinity for the NS5B enzyme and effective inhibition of subgenomic HCV RNA replication in HUH-7 cells. Inhibitors from this class have promising characteristics for further development as anti-HCV agents.
Subject(s)
Acetamides/chemical synthesis , Hepacivirus/drug effects , Indoles/chemical synthesis , RNA-Dependent RNA Polymerase/antagonists & inhibitors , Viral Nonstructural Proteins/antagonists & inhibitors , Acetamides/pharmacokinetics , Acetamides/pharmacology , Administration, Oral , Allosteric Regulation , Animals , Biological Availability , Cell Line, Tumor , Hepacivirus/genetics , Humans , Indoles/chemistry , Indoles/pharmacology , RNA, Viral/biosynthesis , RNA, Viral/drug effects , Rats , Structure-Activity RelationshipABSTRACT
The Na+ transporting properties of the first member of a new class of artificial ionophores, based on a C2-symmetric polyhydroxylated steroid dimer, are described.