ABSTRACT
Our HCV research program investigated novel 2'-dihalogenated nucleoside HCV polymerase inhibitors and identified compound 1, a 5'-phosphoramidate prodrug of 2'-deoxy-2'-α-bromo-ß-chloro uridine. Although 1 had a favorable in vitro activity profile in HCV replicons, oral dosing in dog resulted in low levels of the active 5'-triphosphate (TP) in liver. Metabolism studies using human hepatocytes provided a simple assay for screening alternative phosphoramidate prodrug analogs. Compounds that produced high TP concentrations in hepatocytes were tested in dog liver biopsy studies. This method identified 2-aminoisobutyric acid ethyl ester (AIBEE) phosphoramidate prodrug 14, which provided 100-fold higher TP concentrations in dog liver in comparison to 1 (4 and 24 h after 5 mg/kg oral dose).
Subject(s)
Antiviral Agents/pharmacology , Deoxyuridine/analogs & derivatives , Deoxyuridine/pharmacology , Enzyme Inhibitors/pharmacology , Hepacivirus/drug effects , Prodrugs/pharmacology , Aminoisobutyric Acids/metabolism , Aminoisobutyric Acids/pharmacokinetics , Aminoisobutyric Acids/pharmacology , Animals , Antiviral Agents/metabolism , Antiviral Agents/pharmacokinetics , Deoxyuridine/metabolism , Deoxyuridine/pharmacokinetics , Dogs , Enzyme Inhibitors/metabolism , Enzyme Inhibitors/pharmacokinetics , Hepacivirus/enzymology , Hepatocytes/metabolism , Humans , Liver/metabolism , Microbial Sensitivity Tests , Organophosphorus Compounds/metabolism , Organophosphorus Compounds/pharmacokinetics , Organophosphorus Compounds/pharmacology , Prodrugs/metabolism , Prodrugs/pharmacokinetics , RNA-Dependent RNA Polymerase/antagonists & inhibitors , Viral Nonstructural Proteins/antagonists & inhibitors , Virus Replication/drug effectsABSTRACT
Hepatitis C virus (HCV) nucleoside inhibitors have been a key focus of nearly 2 decades of HCV drug research due to a high barrier to drug resistance and pan-genotypic activity profile provided by molecules in this drug class. Our investigations focused on several potent 2'-halogenated uridine-based HCV polymerase inhibitors, resulting in the discovery of novel 2'-deoxy-2'-dihalo-uridine analogs that are potent inhibitors in replicon assays for all genotypes. Further studies to improve in vivo performance of these nucleoside inhibitors identified aminoisobutyric acid ethyl ester (AIBEE) phosphoramidate prodrugs 18a and 18c, which provide high levels of the active triphosphate in dog liver. AIBEE prodrug 18c was compared with sofosbuvir (1) by co-dosing both compounds by oral administration in dog (5â¯mg/kg each) and measuring liver concentrations of the active triphosphate metabolite at both 4 and 24â¯h post dosing. In this study, 18c provided liver triphosphate concentrations that were 6-fold higher than sofosbuvir (1) at both biopsy time points, suggesting that 18c could be a highly effective agent for treating HCV infected patients in the clinic.
