Mechanism of activation of PSI-7851 and its diastereoisomer PSI-7977.
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Murakami E, Tolstykh T, Bao H, Niu C, Steuer HM, Bao D, Chang W, Espiritu C, Bansal S, Lam AM, Otto MJ, Sofia MJ, Furman PA
Mechanism of activation of PSI-7851 and its diastereoisomer PSI-7977.
J Biol Chem. 2010 Nov 5;285(45):34337-47. doi: 10.1074/jbc.M110.161802. Epub 2010 Aug 26.
- PubMed ID
- 20801890 [ View in PubMed]
- Abstract
A phosphoramidate prodrug of 2'-deoxy-2'-alpha-fluoro-beta-C-methyluridine-5'-monophosphate, PSI-7851, demonstrates potent anti-hepatitis C virus (HCV) activity both in vitro and in vivo. PSI-7851 is a mixture of two diastereoisomers, PSI-7976 and PSI-7977, with PSI-7977 being the more active inhibitor of HCV RNA replication in the HCV replicon assay. To inhibit the HCV NS5B RNA-dependent RNA polymerase, PSI-7851 must be metabolized to the active triphosphate form. The first step, hydrolysis of the carboxyl ester by human cathepsin A (CatA) and/or carboxylesterase 1 (CES1), is a stereospecific reaction. Western blot analysis showed that CatA and CES1 are both expressed in primary human hepatocytes. However, expression of CES1 is undetectable in clone A replicon cells. Studies with inhibitors of CatA and/or CES1 indicated that CatA is primarily responsible for hydrolysis of the carboxyl ester in clone A cells, although in primary human hepatocytes, both CatA and CES1 contribute to the hydrolysis. Hydrolysis of the ester is followed by a putative nucleophilic attack on the phosphorus by the carboxyl group resulting in the spontaneous elimination of phenol and the production of an alaninyl phosphate metabolite, PSI-352707, which is common to both isomers. The removal of the amino acid moiety of PSI-352707 is catalyzed by histidine triad nucleotide-binding protein 1 (Hint1) to give the 5'-monophosphate form, PSI-7411. siRNA-mediated Hint1 knockdown studies further indicate that Hint1 is, at least in part, responsible for converting PSI-352707 to PSI-7411. PSI-7411 is then consecutively phosphorylated to the diphosphate, PSI-7410, and to the active triphosphate metabolite, PSI-7409, by UMP-CMP kinase and nucleoside diphosphate kinase, respectively.
DrugBank Data that Cites this Article
- Drugs
- Drug Targets
Drug Target Kind Organism Pharmacological Action Actions Sofosbuvir RNA-dependent RNA-polymerase Protein Hepatitis C Virus YesInhibitorDetails - Drug Enzymes
Drug Enzyme Kind Organism Pharmacological Action Actions Sofosbuvir Carboxylesterase Protein Humans NoSubstrateDetails Sofosbuvir Histidine triad nucleotide-binding protein 1 Protein Humans UnknownSubstrateDetails Sofosbuvir Lysosomal protective protein Protein UnknownSubstrateDetails Sofosbuvir Nucleoside diphosphate kinase A Protein Humans UnknownSubstrateDetails Sofosbuvir UMP-CMP kinase Protein Humans UnknownSubstrateDetails - Drug Reactions
Reaction Details Details Details
