Design, synthesis, and pharmacological evaluation of fluorinated tetrahydrouridine derivatives as inhibitors of cytidine deaminase

Several 2'-fluorinated tetrahydrouridine derivatives were synthesized as inhibitors of cytidine deaminase (CDA). (4R)-2'-Deoxy-2',2'-difluoro-3,4,5,6-tetrahydrouridine (7a) showed enhanced acid stability over tetrahydrouridine (THU) 5 at its N-glycosyl bond. As a result, compound 7a showed an improved oral pharmacokinetic profile with a higher and more reproducible plasma exposure in rhesus monkeys compared to 5. Co-administration of 7a with decitabine, a CDA substrate, boosted the plasma levels of decitabine in rhesus monkeys. These results demonstrate that compound 7a can serve as an acid-stable alternative to 5 as a pharmacoenhancer of drugs subject to CDA-mediated metabolism.