TY - JOUR T1 - Cyclosaligenyl-2′,3′-didehydro-2′,3′-dideoxythymidine Monophosphate: Efficient Intracellular Delivery of d4TMP JF - Molecular Pharmacology JO - Mol Pharmacol SP - 928 LP - 935 DO - 10.1124/mol.58.5.928 VL - 58 IS - 5 AU - Jan Balzarini AU - Stefano Aquaro AU - Tina Knispel AU - Chiara Rampazzo AU - Vera Bianchi AU - Carlo-Federico Perno AU - Erik De Clercq AU - Chris Meier Y1 - 2000/11/01 UR - http://molpharm.aspetjournals.org/content/58/5/928.abstract N2 - Cyclosaligenyl-2′,3′-didehydro-2′,3′-dideoxythymidine-5′-monophosphate (cycloSal-d4TMP) is a potent and selective inhibitor of human immunodeficiency virus replication in cell culture and differs from other nucleotide prodrug approaches in that it is designed to selectively deliver the nucleotide 5′-monophosphate by a controlled, chemically induced hydrolysis. Its antiviral efficacy in cell culture is at least as good as, if not superior to, that of d4T. CycloSal-d4TMP was found to lead to the efficient intracellular release of d4TMP in a variety of cell lines, including both wild-type CEM and thymidine kinase-deficient CEM/TK− cells. Under similar experimental conditions, exposure of CEM/TK− cells to d4T failed to result in significant d4TTP levels. The intracellular conversion of cycloSal-d4TMP proved to be both time and dose dependent. The half-life of d4TTP generated intracellularly from d4T- or cycloSal-d4TMP-treated CEM cells was ∼3.5 h, and the intracellular ratios of d4TTP/d4TMP in cells exposed to cycloSal-d4TMP gradually increased from 1 to 3.4 upon prolonged incubation. Radiolabeled cycloSal-d4TMP could be separated as its two R p and S pdiastereomers on high-performance liquid chromatography. TheR p diastereomer of cycloSal-d4TMP was 3- to 7-fold more efficient in releasing d4TMP and generating d4TTP than theS p cycloSal-d4TMP diastereomer. This correlated well with the 5-fold more pronounced antiviral activity of the R p diastereomer versus theS p diastereomer. d4TMP is a poor substrate for the cytosolic 5′(3′)-deoxyribonucleotidase (V max/K m for d4TMP: 0.08 ofV max/K m for dTMP) and is only slowly hydrolyzed to d4T. This contributes to the efficient conversion of the prodrug of d4TTP. ER -