title: Synthesis and biological evaluation of a cytarabine phosphoramidate prodrug.
abstract: Recently, we reported a novel approach for the intracellular delivery of the anti-cancer nucleotide 5-fluoro-2'-deoxyuridine 5'-monophosphate (FdUMP) using phosphoramidate-based prodrugs. These phosphoramidate prodrugs contain an ester group that undergoes intracellular activation, liberating phosphoramidate anion, which in turn undergoes spontaneous cyclization and P-N bond cleavage to yield the nucleoside monophosphate quantitatively. This approach has now been extended to cytarabine [1-beta-D-arabinofuranosylcytosine (Ara-C)], an anti-cancer nucleoside that is limited in its utility because of poor intracellular transport characteristics and weak activity as a substrate for tumor cell kinases. The cytarabine phosphoramidate prodrug 1 has been synthesized and evaluated in comparison with cytarabine for growth inhibitory activity against wild-type, nucleoside transport-deficient, and nucleoside kinase-deficient CEM leukemia cell lines. The prodrug was comparable in growth inhibitory activity (IC50 = 32 nM) to cytarabine (IC50 = 16 nM) in wild-type CCRF-CEM cells following drug treatment for 72 h. The nucleoside transport-deficient CEM/AraC8C exhibited a high level of resistance (6400-fold) to cytarabine but was more sensitive (210-fold resistant vs CCRF-CEM cells) to prodrug 1. Similarly, the deoxycytidine kinase-deficient cell line (CEM/dCK-) was highly resistant to cytarabine (13900-fold) but more sensitive (106-fold resistant vs CCRF-CEM cells) to prodrug 1. These results indicate that prodrug 1 is significantly more potent than cytarabine against transport- and kinase-deficient cell lines and are consistent with a mechanism involving intracellular delivery of cytarabine 5'-monophosphate.
authors.affiliation: Department of Medicinal Chemistry and Molecular Pharmacology and Cancer Center, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Sandra C
authors.initials: SC
authors.lastname: Tobias
authors.forename: Richard F
authors.initials: RF
authors.lastname: Borch
mesh_terms: D000577:Amides / Q000138:chemical synthesis* / Q000494:pharmacology; D001692:Biological Transport; D002455:Cell Division; D045744:Cell Line, Tumor; D003561:Cytarabine / Q000138:chemical synthesis* / Q000494:pharmacology; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D010756:Phosphoric Acids / Q000138:chemical synthesis* / Q000494:pharmacology; D011355:Prodrugs / Q000138:chemical synthesis* / Q000494:pharmacology
chemical_list: D000577:Amides; D010756:Phosphoric Acids; D011355:Prodrugs; D003561:Cytarabine; C011067:phosphoramidic acid