PURPOSE: The aim of this study was to synthesize amino acid ester prodrugs of 5-fluoro-2'-deoxyuridine (floxuridine) to enhance intestinal absorption and resistance to glycosidic bond metabolism. METHODS: Amino acid ester prodrugs were synthesized and examined for their hydrolytic stability in human plasma, in Caco-2 cell homogenates, and in the presence of thymidine phosphorylase. Glycyl-L: -sarcosine uptake inhibition and direct uptake studies with HeLa/PEPT1 cells [HeLa cells overexpressing oligopeptide transporter (PEPT1)] were conducted to determine PEPT1-mediated transport and compared with permeability of the prodrugs across Caco-2 monolayers. RESULTS: Isoleucyl prodrugs exhibited the highest chemical and enzymatic stability. The prodrugs enhanced the stability of the glycosidic bond of floxuridine. Thymidine phosphorylase rapidly cleaved floxuridine to 5-fluorouracil, whereas with the prodrugs no detectable glycosidic bond cleavage was observed. The 5'-L: -isoleucyl and 5'-L: -valyl monoester prodrugs exhibited 8- and 19-fold PEPT1-mediated uptake enhancement in HeLa/PEPT1 cells, respectively. Uptake enhancement in HeLa/PEPT1 cells correlated highly with Caco-2 permeability for all prodrugs tested. Caco-2 permeability of 5'-L: -isoleucyl and 5'-L: -valyl prodrugs was 8- to 11-fold greater compared with floxuridine. CONCLUSIONS: Amino acid ester prodrugs such as isoleucyl floxuridine that exhibit enhanced Caco-2 transport and slower rate of enzymatic activation to parent, and that are highly resistant to metabolism by thymidine phosphorylase may improve oral delivery and therapeutic index of floxuridine.
PURPOSE: The aim of this study was to synthesize amino acid ester prodrugs of 5-fluoro-2'-deoxyuridine (floxuridine) to enhance intestinal absorption and resistance to glycosidic bond metabolism. METHODS:Amino acid ester prodrugs were synthesized and examined for their hydrolytic stability in human plasma, in Caco-2 cell homogenates, and in the presence of thymidine phosphorylase. Glycyl-L: -sarcosine uptake inhibition and direct uptake studies with HeLa/PEPT1 cells [HeLa cells overexpressing oligopeptide transporter (PEPT1)] were conducted to determine PEPT1-mediated transport and compared with permeability of the prodrugs across Caco-2 monolayers. RESULTS: Isoleucyl prodrugs exhibited the highest chemical and enzymatic stability. The prodrugs enhanced the stability of the glycosidic bond of floxuridine. Thymidine phosphorylase rapidly cleaved floxuridine to 5-fluorouracil, whereas with the prodrugs no detectable glycosidic bond cleavage was observed. The 5'-L: -isoleucyl and 5'-L: -valyl monoester prodrugs exhibited 8- and 19-fold PEPT1-mediated uptake enhancement in HeLa/PEPT1 cells, respectively. Uptake enhancement in HeLa/PEPT1 cells correlated highly with Caco-2 permeability for all prodrugs tested. Caco-2 permeability of 5'-L: -isoleucyl and 5'-L: -valyl prodrugs was 8- to 11-fold greater compared with floxuridine. CONCLUSIONS:Amino acid ester prodrugs such as isoleucyl floxuridine that exhibit enhanced Caco-2 transport and slower rate of enzymatic activation to parent, and that are highly resistant to metabolism by thymidine phosphorylase may improve oral delivery and therapeutic index of floxuridine.
Authors: Duxin Sun; Hans Lennernas; Lynda S Welage; Jeffery L Barnett; Christopher P Landowski; David Foster; David Fleisher; Kyung-Dall Lee; Gordon L Amidon Journal: Pharm Res Date: 2002-10 Impact factor: 4.200
Authors: Teresa N Faria; Julita K Timoszyk; Terry R Stouch; Balvinder S Vig; Christopher P Landowski; Gordon L Amidon; C David Weaver; Doris A Wall; Ronald L Smith Journal: Mol Pharm Date: 2004-01-12 Impact factor: 4.939
Authors: Wei Shen; Jae-Seung Kim; Phillip E Kish; Jie Zhang; Stefanie Mitchell; Brian G Gentry; Julie M Breitenbach; John C Drach; John Hilfinger Journal: Bioorg Med Chem Lett Date: 2008-12-10 Impact factor: 2.823