Abstract
2-Bromo-5,6-dichloro-1-(β-d-ribofuranosyl)benzimidazole (BDCRB) is a potent and selective inhibitor of human cytomegalovirus (HCMV), but it lacks clinical utility due to rapid in vivo metabolism. We hypothesized that amino acid ester prodrugs of BDCRB may enhance both in vitro potency and systemic exposure of BDCRB through evasion of BDCRB-metabolizing enzymes. To this end, eight different amino acid prodrugs of BDCRB were tested for N-glycosidic bond stability, ester bond stability, Caco-2 cell uptake, antiviral activity, and cytotoxicity. The prodrugs were resistant to metabolism by BDCRB-metabolizing enzymes, and ester bond cleavage was rate-limiting in metabolite formation from prodrug. Thus, BDCRB metabolism could be controlled by the selection of promoiety. In HCMV plaque-formation assays, l-Asp-BDCRB exhibited 3-fold greater selectivity than BDCRB for inhibition of HCMV replication. This potent and selective antiviral activity in addition to favorable stability profile made l-Asp-BDCRB an excellent candidate for in vivo assessment and pharmacokinetic comparison with BDCRB. In addition to rapid absorption and sufficient prodrug activation after oral administration to mice, l-Asp-BDCRB exhibited a 5-fold greater half-life than BDCRB. Furthermore, the sum of area under the concentration-time profile (AUC)BDCRB and AUCprodrug after l-Asp-BDCRB administration was roughly 3-fold greater than AUCBDCRB after BDCRB administration, suggesting that a reservoir of prodrug was delivered in addition to parent drug. Overall, these findings demonstrate that amino acid prodrugs of BDCRB exhibit evasion of metabolizing enzymes (i.e., bioevasion) in vitro and provide a modular approach for translating this in vitro stability into enhanced in vivo delivery of BDCRB.
Footnotes
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This work was performed in the laboratories of G.L.A. and J.C.D. (University of Michigan College of Pharmacy and School of Dentistry) and was made possible by National Institutes of Health Grants R01-GM37188 and P01-AI46390. P.L.L. was supported by Training Grant GM07767 from the National Institute of General Medical Sciences. The contents are solely the responsibility of the authors and do not necessarily represent the official views of National Institute of General Medical Sciences.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.104.082412.
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ABBREVIATIONS: BDCRB, 2-bromo-5,6-dichloro-1-(β-d-ribofuranosyl)benzimidazole; HCMV, human cytomegalovirus; OGG1, 8-oxoguanine DNA glycosylase; MPG, N-methylpurine DNA glycosylase; TCRB, 2,5,6-trichloro-1-(β-d-ribofuranosyl)benzimidazole; TFA, trifluoroacetic acid; hOGG1, human 8-oxoguanine DNA glycosylase; HPLC, high-performance liquid chromatography; HFF, human foreskin fibroblast; LC/MS/MS, liquid chromatography/tandem mass spectrometry.
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↵1 Current address: Genomics and Bioinformatics Group, Laboratory of Molecular Pharmacology, National Cancer Institute, National Institutes of Health, Bethesda, MD.
- Received December 18, 2004.
- Accepted May 16, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
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