ABSTRACT
The development of interferon-free regimens for the treatment of chronic HCV infection constitutes a preferred option that is expected in the future to provide patients with improved efficacy, better tolerability, and reduced risk for emergence of drug-resistant virus. We have pursued non-nucleoside NS5B polymerase allosteric inhibitors as combination partners with other direct acting antivirals (DAAs) having a complementary mechanism of action. Herein, we describe the discovery of a potent follow-up compound (BI 207524, 27) to the first thumb pocket 1 NS5B inhibitor to demonstrate antiviral activity in genotype 1 HCV infected patients, BILB 1941 (1). Cell-based replicon potency was significantly improved through electronic modulation of the pKa of the carboxylic acid function of the lead molecule. Subsequent ADME-PK optimization lead to 27, a predicted low clearance compound in man. The preclinical profile of inhibitor 27 is discussed, as well as the identification of a genotoxic metabolite that led to the discontinuation of the development of this compound.
Subject(s)
Acrylates/chemical synthesis , Antiviral Agents/chemical synthesis , Antiviral Agents/metabolism , Indoles/chemical synthesis , Viral Nonstructural Proteins/antagonists & inhibitors , Acrylates/metabolism , Acrylates/pharmacokinetics , Animals , Antiviral Agents/pharmacology , Cinnamates/chemical synthesis , Cinnamates/metabolism , Cinnamates/pharmacokinetics , Dogs , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/metabolism , Enzyme Inhibitors/pharmacokinetics , Hepatitis C, Chronic , Humans , Indoles/metabolism , Indoles/pharmacokinetics , Macaca mulatta , RNA-Dependent RNA Polymerase/antagonists & inhibitors , Rats , Structure-Activity RelationshipABSTRACT
We set out to find the "fenestrin" gene, a gene whose protein is associated with numerous cellular apertures, including the nuclear exchange junction in mating Tetrahymena thermophila. First we developed protocols for imaging and isolating intact nuclear exchange junctions from conjugating cells. Proteins from these junctions were purified using SDS-PAGE, subjected to limited proteolysis, and precise molecular weights were determined by mass spectrometry. Using Protein Prospector software and the published Tetrahymena Genome Database, genes for 15 of the most abundant proteins found in our extracts were identified. The most promising candidate was cloned by PCR, fused to yellow fluorescent protein (YFP), and placed under the control of an inducible metallothionein promoter. YFP-localization within live Tetrahymena transformants strongly suggested that one of these genes encoded the fenestrin protein, a result that was subsequently confirmed by Western blotting.
Subject(s)
Cell Nucleus/metabolism , Proteomics/methods , Protozoan Proteins/metabolism , Tetrahymena/metabolism , Animals , Blotting, Western , Cloning, Molecular/methods , Electrophoresis, Polyacrylamide Gel , Genome, Protozoan , Luminescent Proteins/genetics , Luminescent Proteins/metabolism , Mass Spectrometry , Microscopy, Fluorescence , Protozoan Proteins/genetics , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Tetrahymena/geneticsABSTRACT
Sildenafil revolutionised the treatment of erectile dysfunction (ED) on its introduction in 1998. Not only is it effective, but is, perhaps even more importantly, an extremely acceptable manner in which to treat ED (i.e., oral pharmacotherapy), compared to the other treatments that were available at that time (e.g., intracavernosal injection). Whilst sildenafil remains the market leader for ED treatment, it does have some shortcomings: its clinical efficacy is diminished in 'difficult to treat' patient groups, such as diabetics, side effects, such as blue-tinged vision and headache, and the need to time the ingestion of sildenafil to 1 h prior to expected time of sexual intercourse. Recently, newer phosphodiesterase inhibitors ('sons of viagra') have become available, and potentially to improve upon, what has become regarded as the gold standard for ED treatment. This review article discusses the differences between vardenafil, tadalafil and sildenafil, in order to allow the clinician to make an informed decision as to which phosphodiesterase inhibitor to prescribe when dealing with the ever expanding number of patients seeking help for ED.
Subject(s)
Impotence, Vasculogenic/drug therapy , Phosphodiesterase Inhibitors/therapeutic use , 3',5'-Cyclic-GMP Phosphodiesterases/antagonists & inhibitors , Carbolines/therapeutic use , Diabetes Complications/drug therapy , Drug Interactions , Humans , Imidazoles/therapeutic use , Impotence, Vasculogenic/etiology , Male , Phosphodiesterase Inhibitors/adverse effects , Phosphodiesterase Inhibitors/pharmacokinetics , Piperazines/therapeutic use , Purines , Sildenafil Citrate , Sulfones , Tadalafil , Triazines , Vardenafil DihydrochlorideABSTRACT
Hepatitis C virus (HCV) infection is a serious cause of chronic liver disease worldwide with more than 170 million infected individuals at risk of developing significant morbidity and mortality. Current interferon-based therapies are suboptimal especially in patients infected with HCV genotype 1, and they are poorly tolerated, highlighting the unmet medical need for new therapeutics. The HCV-encoded NS3 protease is essential for viral replication and has long been considered an attractive target for therapeutic intervention in HCV-infected patients. Here we identify a class of specific and potent NS3 protease inhibitors and report the evaluation of BILN 2061, a small molecule inhibitor biologically available through oral ingestion and the first of its class in human trials. Administration of BILN 2061 to patients infected with HCV genotype 1 for 2 days resulted in an impressive reduction of HCV RNA plasma levels, and established proof-of-concept in humans for an HCV NS3 protease inhibitor. Our results further illustrate the potential of the viral-enzyme-targeted drug discovery approach for the development of new HCV therapeutics.
