Document Detail


Use of rat and human in vitro systems to assess the effectiveness and enzymology of deoxy-guanine analogues as prodrugs of an antiviral agent.
MedLine Citation:
PMID:  8149871     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
BRL 55792, BRL 55791, and BRL 55039 are prodrugs of an active anti-viral agent 9-(3-hydroxypropoxy) guanine, (BRL 44385). The prodrugs were 6-deoxygenated analogues of BRL 44385 with ether groups substituted at the 9-position: BRL 55792 with an (isopropoxymethyloxy)propoxy group, BRL 55791 with a (methoxymethyloxy)propoxy group, and BRL 55039 with an ethoxypropoxy group. Conversion of the prodrugs to BRL 44385 had been demonstrated in vivo in rat and involved 6-oxidation followed by dealkylation. Metabolism was studied in rat liver in vitro systems to find a model to evaluate BRL 44385 production. Rat hepatocytes performed both reaction steps and were used to assess which of the three prodrugs demonstrated greatest production of the active drug. BRL 55792 demonstrated greatest conversion in vitro and this was in agreement with in vivo data. The production of BRL 44385 from BRL 55792 was also demonstrated in human hepatocyte incubations providing evidence that these reactions can occur in man thereby increasing confidence that BRL 55792 would be a suitable prodrug for human therapy. Further experiments were performed to investigate the enzymes involved in these conversions. The 6-oxidation step occurred in the cytosol. Use of allopurinol and menadione (xanthine and aldehyde oxidase inhibitors) indicated that these conversions were catalyzed exclusively by xanthine oxidase in the rat but mainly by aldehyde oxidase in man. The dealkylation reaction was detected in hepatocytes but not in homogenates or subcellular fractions. Inhibition of this reaction by aminobenzotriazole and ketoconazole (P-450 inhibitors) indicated that it was mediated by cytochrome P-450.
Authors:
A W Harrell; S M Wheeler; P East; S E Clarke; R J Chenery
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Drug metabolism and disposition: the biological fate of chemicals     Volume:  22     ISSN:  0090-9556     ISO Abbreviation:  Drug Metab. Dispos.     Publication Date:    1994 Jan-Feb
Date Detail:
Created Date:  1994-05-06     Completed Date:  1994-05-06     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  9421550     Medline TA:  Drug Metab Dispos     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  124-8     Citation Subset:  IM    
Affiliation:
Department of Drug Metabolism and Pharmacokinetics, SmithKline Beecham, Welwyn, Herts, U.K.
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MeSH Terms
Descriptor/Qualifier:
Animals
Antiviral Agents / metabolism*
Cytochrome P-450 Enzyme System / antagonists & inhibitors,  metabolism
Guanine / analogs & derivatives*,  metabolism*
Humans
Liver / cytology,  enzymology
Models, Biological
Prodrugs / metabolism*
Rats
Rats, Sprague-Dawley
Xanthine Oxidase / metabolism
Chemical
Reg. No./Substance:
0/Antiviral Agents; 0/Prodrugs; 73-40-5/Guanine; 9035-51-2/Cytochrome P-450 Enzyme System; EC 1.17.3.2/Xanthine Oxidase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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