Yuan H, Li N, Lai Y
Evaluation of in vitro Models for Screening Alkaline Phosphatase Mediated Bioconversion of Phosphate Ester Prodrugs. [JOURNAL ARTICLE]
Drug Metab Dispos 2009 Apr 16.
Generating a phosphate prodrug is one of the common approaches for circumventing poor solubility issues of a parent drug. Alkaline phosphatase level was determined in rat intestine mucosa scraps, Caco-2 cell and MDCK cell to characterize in vitro models for alkaline phosphatase mediated phosphate prodrug conversion. In addition, fosphenytoin and fosfluconazole were used as probe prodrugs to evaluate the models. The highest amount of ALP was detected in rat intestinal mucosa scraps, while alkaline phosphatase in 5-day cultured MDCK cells was minimal. As anticipated, alkaline phosphatase levels correlated with the parent drug conversion, and the shortest cleavage half-life (t1/2) was observed in rat mucosa scraps and MDCK cells showed the slowest conversion. Furthermore, the polarized conversion for the prodrugs was observed in Caco-2 monolayer cells, suggesting the polarized localization of alkaline in differentiated Caco-2 cells. The rate of alkaline phosphatase mediated conversion was prodrug concentration dependent with Michaelis-Menten constants of 1160 microM and 351 microM for fosphenytoin and fosfluconazole, respectively, determined in Caco-2 cells. The result revealed that while the intestinal mucosa scraps reserved the highest ALP activities and demonstrated as a promising in vitro tool for screening the bioconversion of phosphate prodrug, Caco-2 monolayers could provide the predictive information of bioconversion and further offer the capability in characterizing the permeability of prodrug and parent drug.
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