Pharmacokinetics and metabolism of the novel synthetic C-nucleoside, 1-(2-deoxy-beta-D-ribofuranosyl)-2,4-difluoro-5-iodobenzene: a potential mimic of 5-iodo-2'-deoxyuridine.

1-(2-Deoxy-beta-D-ribofuranosyl)-2,4-difluoro-5-iodobenzene (5-IDFPdR) is one of the several unnatural 1-(2-deoxy-beta-D-ribofuranosyl)-2,4-difluoro-5-substituted-benzenes recently synthesized for evaluation as anticancer, antiviral and diagnostic imaging agents. This class of C-nucleosides was designed to exploit several potential advantages relative to classical 5-substituted-2'-deoxyuridines, including stability towards phosphorolysis by pyrimidine phosphorylase, increased lipophilicity that may alter their ability to cross the blood-brain-barrier, and a greater resistance towards catabolism and deiodination. The physiochemical evaluation of 5-IDFPdR showed high lipophilicity (log P = 2.8), moderately high protein binding (70-75%), stability towards phosphorolysis (e.g. no evidence of metabolic deglycosylation) by thymidine phosphorylase, and minimal microsomal metabolism in vitro. Pharmacokinetic studies of 5-IDFPdR in rat were characterized by a short elimination half-life (9-12 min), modest urinary elimination in pooled 0-24 h urine specimens (10-14%, including 2% as unconjugated drug) and high oral bioavailability (F = 0.96). Both glucuronide and sulfate metabolites were present in urine. Glucuronidation was the predominant conjugation pathway.