In vitro antiviral activity of SCH446211 (SCH6), a novel inhibitor of the hepatitis C virus NS3 serine protease

Background: Current hepatitis C virus (HCV) therapies may cure ∼60% of infections. They are often contraindicated or poorly tolerated, underscoring the need for safer and more effective drugs. A novel, α-ketoamide-derived, substrate-based inhibitor of the HCV serine protease (SCH446211) was developed. Compared with earlier reported inhibitors of similar chemical class, it has a P1′-P2′ extension which provides extended interaction with the protease active site. The aim of this study was to evaluate the in vitro antiviral activity of SCH446211. Methods: Binding constant of SCH446211 to HCV NS3 protease was measured with the chromogenic substrate in vitro cleavage assay. Cell-based activity of SCH446211 was evaluated in replicon cells, which are Huh-7 hepatoma cells stably transfected with a subgenomic HCV RNA as reported previously. After 72 h of incubation with SCH446211, viral transcription and protein expression were measured by real-time RT-PCR (TaqMan), quantitative in situ hybridization, immunoblot and indirect immunofluorescence. Results: The binding constant of SCH446211 to HCV NS3 protease was 3.8 ± 0.4 nM. HCV replication and protein expression were inhibited by SCH446211 in replicon cells as consistently shown by four techniques. In particular, based on quantitative real-time RT-PCR measurements, the IC50 and IC90 of SCH446211 were estimated to be 40 ± 20 and 100 ± 20 nM (n = 17), respectively. Long-term culture of replicon cells with SCH446211 reduced replicon RNA to <0.1 copy per cell. SCH446211 did not show cellular toxicity at concentrations up to 50 μM. Conclusions: SCH446211 is a potent inhibitor of HCV protease in vitro. Its extended interaction with the HCV NS3 protease active site is associated with potent in vitro antiviral activity. This observation is potentially a useful guide for development of future potent inhibitors against HCV NS3 proteas

Key steps in the structure-based optimization of the hepatitis C virus NS3/4A protease inhibitor SCH503034

Crystal structures of protease/inhibitor complexes guided optimization of the buried nonpolar surface area thereby maximizing hydrophobic binding. The resulting potent tripeptide inhibitor is in clinical trials

Expanding the tools for identifying mononuclear phagocyte subsets in swine: Reagents to porcine CD11c and XCR1

International audiencePig is a domestic species of major importance in the agro-economy and in biomedical research. Mononuclear phagocytes (MNP) are organized in subsets with specialized roles in the orchestration of the immune response and new tools are awaited to improve MNP subset identification in the pig. We cloned pig CD11c cDNA and generated a monoclonal antibody to pig CD11c which showed a pattern of expression by blood and skin MNP subsets similar to humans. We also developed a porcine XCL1-mCherry dimer which specifically reacted with the XCR1-expressing dendritic cell subset of the type 1 lineage in blood and skin. These original reagents will allow the efficient identification of pig MNP subsets to study their role in physiological and pathological processes and also to target these cells in novel intervention and vaccine strategies for veterinary applications and preclinical evaluations. (C) 2016 Elsevier Ltd. All rights reserved