Biomaterial Database

Metabolic activation of the anti-hepatitis C virus nucleotide prodrug PSI-352938. 2012

Congrong Niu, and Tatiana Tolstykh, and Haiying Bao, and Yeojin Park, and Darius Babusis, and Angela M Lam, and Shalini Bansal, and Jinfa Du, and Wonsuk Chang, and P Ganapati Reddy, and Hai-Ren Zhang, and Joseph Woolley, and Li-Quan Wang, and Piyun B Chao, and Adrian S Ray, and Michael J Otto, and Michael J Sofia, and Phillip A Furman, and Eisuke Murakami

Pharmasset, Inc, Princeton, New Jersey, USA.

PSI-352938 is a novel cyclic phosphate prodrug of β-D-2'-deoxy-2'-α-fluoro-2'-β-C-methylguanosine-5'-monophosphate with potent anti-HCV activity. In order to inhibit the NS5B RNA-dependent RNA polymerase, PSI-352938 must be metabolized to the active triphosphate form, PSI-352666. During in vitro incubations with PSI-352938, significantly larger amounts of PSI-352666 were formed in primary hepatocytes than in clone A hepatitis C virus (HCV) replicon cells. Metabolism and biochemical assays were performed to define the molecular mechanism of PSI-352938 activation. The first step, removal of the isopropyl group on the 3',5'-cyclic phosphate moiety, was found to be cytochrome P450 (CYP) 3A4 dependent, with other CYP isoforms unable to catalyze the reaction. The second step, opening of the cyclic phosphate ring, was catalyzed by phosphodiesterases (PDEs) 2A1, 5A, 9A, and 11A4, all known to be expressed in the liver. The role of these enzymes in the activation of PSI-352938 was confirmed in primary human hepatocytes, where prodrug activation was reduced by inhibitors of CYP3A4 and PDEs. The third step, removal of the O(6)-ethyl group on the nucleobase, was shown to be catalyzed by adenosine deaminase-like protein 1. The resulting monophosphate was consecutively phosphorylated to the diphosphate and to the triphosphate PSI-352666 by guanylate kinase 1 and nucleoside diphosphate kinase, respectively. In addition, formation of nucleoside metabolites was observed in primary hepatocytes, and ecto-5'-nucleotidase was able to dephosphorylate the monophosphate metabolites. Since CYP3A4 is highly expressed in the liver, the CYP3A4-dependent metabolism of PSI-352938 makes it an effective liver-targeted prodrug, in part accounting for the potent antiviral activity observed clinically.

UI	MeSH Term	Description	Entries
D009701	Nucleoside-Diphosphate Kinase	An enzyme that is found in mitochondria and in the soluble cytoplasm of cells. It catalyzes reversible reactions of a nucleoside triphosphate, e.g., ATP, with a nucleoside diphosphate, e.g., UDP, to form ADP and UTP. Many nucleoside diphosphates can act as acceptor, while many ribo- and deoxyribonucleoside triphosphates can act as donor. EC 2.7.4.6.	Deoxynucleoside Diphosphate Kinases,GDP Kinase,Nucleoside Diphosphokinases,Nucleoside-Diphosphate Kinases,Diphosphate Kinases, Deoxynucleoside,Diphosphokinases, Nucleoside,Kinase, GDP,Kinase, Nucleoside-Diphosphate,Kinases, Deoxynucleoside Diphosphate,Kinases, Nucleoside-Diphosphate,Nucleoside Diphosphate Kinase,Nucleoside Diphosphate Kinases
D009705	Nucleosides	Purine or pyrimidine bases attached to a ribose or deoxyribose. (From King & Stansfield, A Dictionary of Genetics, 4th ed)	Nucleoside,Nucleoside Analog,Nucleoside Analogs,Analog, Nucleoside,Analogs, Nucleoside
D010727	Phosphoric Diester Hydrolases	A class of enzymes that catalyze the hydrolysis of one of the two ester bonds in a phosphodiester compound. EC 3.1.4.	Phosphodiesterase,Phosphodiesterases,Hydrolases, Phosphoric Diester
D002478	Cells, Cultured	Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.	Cultured Cells,Cell, Cultured,Cultured Cell
D003498	Cyclic P-Oxides		Heterocyclic P-Oxides,Cyclic P Oxides,Heterocyclic P Oxides,Oxides, Cyclic P,P Oxides, Cyclic,P-Oxides, Cyclic,P-Oxides, Heterocyclic
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000998	Antiviral Agents	Agents used in the prophylaxis or therapy of VIRUS DISEASES. Some of the ways they may act include preventing viral replication by inhibiting viral DNA polymerase; binding to specific cell-surface receptors and inhibiting viral penetration or uncoating; inhibiting viral protein synthesis; or blocking late stages of virus assembly.	Antiviral,Antiviral Agent,Antiviral Drug,Antivirals,Antiviral Drugs,Agent, Antiviral,Agents, Antiviral,Drug, Antiviral,Drugs, Antiviral
D016174	Hepacivirus	A genus of FLAVIVIRIDAE causing parenterally-transmitted HEPATITIS C which is associated with transfusions and drug abuse. Hepatitis C virus is the type species.	Hepatitis C virus,Hepatitis C-Like Viruses,Hepaciviruses,Hepatitis C Like Viruses,Hepatitis C viruses,Hepatitis C-Like Virus
D051528	Guanylate Kinases	Catalyzes the ATP-dependent PHOSPHORYLATION of GMP to generate GDP and ADP.	Guanylate Kinase,ATP-(d)GMP Phosphotransferase,Erythrocyte protein p55,GMP Kinase,Guanosine Monophosphate Kinase,Guanylate Kinase 1,MAGUK Proteins,Membrane-Associated Guanylate Kinase,Membrane-Associated Guanylate Kinases,Guanylate Kinase, Membrane-Associated,Guanylate Kinases, Membrane-Associated,Kinase 1, Guanylate,Kinase, GMP,Kinase, Guanosine Monophosphate,Kinase, Guanylate,Kinase, Membrane-Associated Guanylate,Kinases, Guanylate,Kinases, Membrane-Associated Guanylate,Membrane Associated Guanylate Kinase,Membrane Associated Guanylate Kinases,Monophosphate Kinase, Guanosine,Proteins, MAGUK,p55, Erythrocyte protein,protein p55, Erythrocyte
D051544	Cytochrome P-450 CYP3A	A cytochrome P-450 suptype that has specificity for a broad variety of lipophilic compounds, including STEROIDS; FATTY ACIDS; and XENOBIOTICS. This enzyme has clinical significance due to its ability to metabolize a diverse array of clinically important drugs such as CYCLOSPORINE; VERAPAMIL; and MIDAZOLAM. This enzyme also catalyzes the N-demethylation of ERYTHROMYCIN.	CYP3A,CYP3A4,CYP3A5,Cytochrome P-450 CYP3A4,Cytochrome P-450 CYP3A5,Cytochrome P-450IIIA,Cytochrome P450 3A,Cytochrome P450 3A4,Cytochrome P450 3A5,Erythromycin N-Demethylase,Taurochenodeoxycholate 6-alpha-Monooxygenase,3A5, Cytochrome P450,6-alpha-Monooxygenase, Taurochenodeoxycholate,Cytochrome P 450 CYP3A,Cytochrome P 450 CYP3A4,Cytochrome P 450 CYP3A5,Cytochrome P 450IIIA,Erythromycin N Demethylase,N-Demethylase, Erythromycin,P-450 CYP3A, Cytochrome,P-450 CYP3A4, Cytochrome,P-450 CYP3A5, Cytochrome,P-450IIIA, Cytochrome,P450 3A, Cytochrome,P450 3A5, Cytochrome,Taurochenodeoxycholate 6 alpha Monooxygenase