Vol. 56, Issue 6, 1354-1361, December 1999

Intracellular Metabolism of CycloSaligenyl 3'-Azido-2',3'-dideoxythymidine Monophosphate, a Prodrug of 3'-Azido-2',3'-dideoxythymidine (Zidovudine)

Jan Balzarini, Lieve Naesens, S. Aquaro, T. Knispel, C.-F. Perno, E. De Clercq, and C. Meier

Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium (J.B., L.N., E. De C.); Department of Experimental Medicine, University of Rome "Tor Vergata," Rome, Italy (S.A., C.-F.P.); Institut für Organische Chemie, Universität Hamburg, Hamburg, Germany (T.K., C.M.); and IRCCS L. Spallanzani, Rome, Italy (C.-F.P.)

The administration of CycloSaligenyl 3'-azido-2',3'-dideoxythymidine monophosphate (CycloSal-AZTMP) to CEM cells resulted in a concentration- and time-dependent conversion to the 5'-monophosphate (AZTMP), 5'-diphosphate (AZTDP), and 5'-triphosphate (AZTTP) derivatives. High ratios of AZTMP/AZTTP were found in the CEM cell cultures treated with CycloSal-AZTMP. The intracellular T_1/2 of AZTTP in CEM cell cultures treated with either AZT and CycloSal-AZTMP was approximately 3 h. A variety of human T- and B-lymphocyte cell lines efficiently converted the prodrug to the AZT metabolites, whereas peripheral blood lymphocytes and primary monocyte/macrophages showed at least 10-fold lower metabolic conversion of the prodrug. CycloSal-AZTMP failed to generate marked levels of AZT metabolites in thymidine kinase-deficient CEM/TK cells, an observation that is in agreement with the substantial loss of antiviral activity of CycloSal-AZTMP in CEM/TK cells. The inability of CycloSal-AZTMP to generate AZTMP in CEM/TK cells is presumably due to a relatively high hydrolysis rate of AZTMP to the parent nucleoside AZT, combined with the inability of CEM/TK cells to phosphorylate AZT to AZTMP through the cytosolic salvage enzyme thymidine kinase.