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Title: Comparison of the disposition of ester prodrugs of the antiviral agent 9-(2-phosphonylmethoxyethyl)adenine [PMEA] in Caco-2 monolayers
Authors: Annaert, Pieter ×
Gosselin, G
Pompon, A
Benzaria, S
Valette, G
Imbach, J L
Naesens, Lieve
Hatse, Sigrid
De Clercq, Erik
Van den Mooter, Guy
Kinget, Renaat
Augustijns, Patrick #
Issue Date: Feb-1998
Publisher: Plenum publishing corporation
Series Title: Pharmaceutical Research vol:15 issue:2 pages:239-245
Abstract: PURPOSE: To evaluate the potential of several bis-ester prodrugs of the antiviral agent 9-(2-phosphonylmethoxyethyl)adenine (PMEA, adefovir) to enhance the oral absorption of PMEA. METHODS: Caco-2 monolayers were used to estimate intestinal transport and metabolism of the bis(pivaloyloxymethyl)-ester [bis(POM)-] and a series of bis(S-acyl-2-thioethyl)-esters [bis(SATE)-] of PMEA. An LC-MS method was used for the identification of unknown metabolites which were formed from the SATE-esters. RESULTS: During transport across Caco-2 monolayers, all esters were extensively degraded as could be concluded from the appearance of the mono-ester and free PMEA in apical as well as basolateral compartments. Incubation of SATE-esters with the monolayers resulted in the formation of two additional metabolites, which were identified as 2-thioethyl-PMEA and its dimerisation product. All ester prodrugs resulted in enhanced transepithelial transport of total PMEA (i.e. the bis-esters and their corresponding metabolites, including PMEA), but significant differences could be observed between the various esters. Transport of total PMEA ranged from 0.4 +/- 0.1% for the bis[S(methyl) ATE]-ester to 15.3 +/- 0.9% for the more lipophilic bis[S(phenyl)ATE]-PMEA. A relationship between total transport of the esters and their lipophilicity (as estimated by their octanol/water partition coefficient) was established (r2 = 0.87). Incubation of prodrug esters with homogenates from Caco-2 cells showed large differences in susceptibility of the compounds to esterases, the half-lives of the bis-esters varying from 4.3 +/- 0.3 min for the bis[S(phenyl)ATE]-PMEA to 41.5 +/- 0.8 min for its methyl analogue. In addition, intracellularly formed PMEA was observed to be further converted by the cells to the diphosphorylated PMEA (PMEApp). CONCLUSIONS: Several SATE-esters of PMEA can be considered as potential alternatives to bis(POM)-PMEA, due to enhanced epithelial transport, sufficient chemical and enzymatic stability and adequate release of PMEA. Toxicological studies as well as in vivo experiments are required in order to further explore the potential of those SATE-esters as prodrugs for oral delivery of PMEA.
URI: 
ISSN: 0724-8741
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Drug Delivery and Disposition
Laboratory of Virology and Chemotherapy (Rega Institute)
Laboratory of Experimental Oncology
× corresponding author
# (joint) last author

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