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  • 1
    ISSN: 1573-0646
    Keywords: 5-ethyl-2′-deoxyuridine ; murine leukemia L1210 ; DNA synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A series of forty 5′-ester derivatives of 5-ethyl-2′-deoxyuridine (EDU) have been evaluated for their inhibitory effects on the growth and metabolism of murine leukemia L1210 cells. Several EDU esters proved as potent as EDU in their inhibitory effects on L1210 cell growth (inhibitory dose-50: 5–10 μg/ml), suggesting that these esters were readily hydrolyzed to release the parent compound EDU. That the EDU esters had to be hydrolyzed first to EDU was further suggested by the dependence of their antiproliferative action on the thymidine kinase activity of the cells. It was further ascertained that EDU and its esters acquired their antiproliferative effects by an interaction with dCTP biosynthesis, possibly at the CDP ribonucleotide reductase step. Under conditions where thymidine was readily incorporated, we were unable to demonstrate any incorporation of EDU into L1210 cell DNA.
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  • 2
    ISSN: 1573-739X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-904X
    Keywords: Caco-2 ; prodrug ; intestinal permeability ; intestinal metabolism ; bis(POM)-PMEA ; antiviral
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To evaluate intestinal transport, uptake and metabolism characteristics of the bis(pivaloyloxymethyl)-ester [bis(POM)-ester] of the antiviral agent 9-(2-phosphonylmethoxyethyl)adenine [PMEA]. Methods. Intestinal transport, uptake and metabolism of bis(POM)-PMEA were studied using an in vitro cell culture system of the intestinal mucosa (Caco-2 monolayers). Concentrations of bis(POM)-PMEA and its metabolites mono(POM)-PMEA and PMEA were determined using a reversed-phase HPLC method. Enzymatic stability of bis(POM)-PMEA was evaluated by incubation with purified liver carboxylesterase, homogenates of Caco-2 cells and scraped pig small intestinal mucosa. Results. The use of bis(POM)-PMEA as a prodrug of PMEA resulted in a significant increase in transport of total PMEA [bis(POM)-PMEA, mono(POM)-PMEA and PMEA] across Caco-2 monolayers. While transepithelial transport of PMEA (500 μM) was lower than 0.1% during a 3 hr incubation period, transport of total PMEA after addition of bis(POM)-PMEA (100 μM) amounted to 8.8% over the same incubation period. Only 23% of the amount transported appeared as intact bis-ester at the basolateral side, while 33% of this amount was free PMEA and 44% was mono(POM)-PMEA, suggesting susceptibility of the prodrug to chemical and enzymatic degradation. Uptake studies revealed that only negligible amounts of bis(POM)-PMEA (〈 0.2%) were present inside the cells. Very high intracellular concentrations of PMEA were found ≈ 1.2 mM, after a 3 hr incubation with 50 μM bis(POM)-PMEA), which suggests that PMEA was trapped inside the cells probably due to its negative charge. This explains that efflux of PMEA was relatively slow (25% of the intracellular amount in 3 hr). Enzymatic degradation of the prodrug by carboxylesterase was confirmed by incubation of bis(POM)-PMEA with purified enzyme (Km = 87 μM and Vmax = 9.5 μM/min). Incubation of bis(POM)-PMEA (10 μM) with cell homogenate of Caco-2 monolayers and pig small intestinal mucosa produced similar degradation profiles. Conclusions. The use of the bis(POM)-prodrug significantly enhances the intestinal permeability of PMEA. Intracellular trapping of PMEA in the intestinal mucosa may result in slow release of PMEA to the circulation after oral administration of bis(POM)-PMEA.
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  • 4
    ISSN: 1573-904X
    Keywords: fruit extracts ; esterase inhibition ; bis(POC)-PMPA ; ester prodrug ; Caco-2 cells ; absorption enhancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To explore the usefulness of fruit extracts as enhancers of the oral absorption of esterase-sensitive prodrugs. Methods. Inhibition of esterase-mediated degradation by nature-identical fruit extracts was evaluated using 1) p-nitrophenylacetate (model substrate for esterase-activity) in rat intestinal homogenates and 2) bis(isopropyloxycarbonyloxymethyl)-(R)-9-[(2-phosphonomethoxy) propyl]adenine [bis(POC)-PMPA] (esterase-sensitive prodrug of the antiviral agent PMPA) in Caco-2 cell homogenates and in intestinal homogenates from rat, pig and man. Subsequently, transport of the ester prodrug was studied across Caco-2 monolayers in the presence or absence of fruit extracts. Results. In homogenates from rat ileum, the esterase activity could be reduced significantly by the inclusion of fruit extracts (1%): the initial enzymatic degradation of p-nitrophenylacetate was inhibited by 77% (strawberry), 16% (passion fruit) and 57% (banana). A similar inhibition of bis(POC)-PMPA metabolism by fruit extracts was observed in intestinal homogenates from several species and in homogenates from Caco-2 cells. Transport of total PMPA across Caco-2 monolayers was enhanced 3-fold by co-incubation with strawberry extract (1%). The fraction of intact prodrug appearing in the acceptor compartment increased from virtually zero to 67%. Conclusions. The results suggest that co-incubation with nature-identical fruit extracts might be useful as a strategy to enhance the transepithelial transport of esterase-sensitive prodrugs through inhibition of intracellular metabolism of the prodrug.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Investigational new drugs 1 (1983), S. 103-115 
    ISSN: 1573-0646
    Keywords: diarylamidines ; diarylimidazolines ; murine leukemia L1210 ; DNA synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A series of 96 diarylamidine (and diarylimidazoline) derivatives were evaluated for their inhibitory effects on the growth and DNA synthesis of murine leukemia L1210 cells. The amidino- and imidazolino-substituted aryl moieties of the compounds consisted of phenyl, indole, indene, benzofuran, benzo[b]thiophene or benzimidazole. Several of these compounds were found to inhibit L1210 cell proliferation with an ID50 (50% inhibitory dose) of 1 μg/ml or lower. Structure-function analysis revealed that the antitumor cell activity of the diarylamidines depended on the planarity of the molecule, the presence of amidino- (or, preferably, imidazolino-) groups on both aryl moieties, the nature of the bridge connecting the two aryl moieties (preferably no bridge at all, phenoxy or ethene) and, finally, the nature of the aryl moieties (preferably, benzofuran or benzo[b]thiophene). Hence, compound 20 (6-(2-imidazolin-2-yl)-2-[4-(2-imidazolin-2-yl)phenyl] benzo[b]thiophene) emerged as the most potent inhibitor of L1210 cell growth (ID50: 0.21 μg/ml). Its inhibitory potency was similar to that of the well-known trypanocidal drug ethidium bromide (compound 98). For all diarylamidine derivatives taken together, some correlation (r = 0.612) was noted between the log ID50 for L1210 cell proliferation and the log ID50 for L1210 cell DNA synthesis (as monitored by [methyl 3H]dThd incorporation). These findings suggest that the inhibitory effects of the diarylamidines on L1210 cell proliferation may at least partially reside in an inhibition of DNA synthesis. Compound 41 (2,2′-vinylenedi-1-benzofuran-5-carboxamidine), that exhibited a potent antitumor activity in vitro (ID50: 1.5 μg/ml), was further evaluated for its antitumor efficacy in vivo and found to increase the median survival time of L1210 cell-inoculated BDF1 mice up to 204%, if administered at a dose of 200 mg/kg.
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  • 6
    Publication Date: 1983-06-01
    Print ISSN: 0167-6997
    Electronic ISSN: 1573-0646
    Topics: Chemistry and Pharmacology , Medicine
    Published by Springer
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  • 7
    Publication Date: 1984-03-01
    Print ISSN: 0167-6997
    Electronic ISSN: 1573-0646
    Topics: Chemistry and Pharmacology , Medicine
    Published by Springer
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