CHARACTERIZATION OF 2',3'-DIDEOXYCYTIDINE DIPHOSPHOCHOLINE AND 2',3'-DIDEOXYCYTIDINE DIPHOSPHOETHANOLAMINE - PROMINENT PHOSPHODIESTER METABOLITES OF THE ANTI-HIV NUCLEOSIDE 2',3'-DIDEOXYCYTIDINE

2',3'-Dideoxycytidine (ddCyd) is among the most potent of the antihuma n immunodeficiency virus (HIV) agents of the dideoxynucleoside class. Its pharmacologically active metabolite 2',3'-dideoxycytidine 5'-triph osphate (ddCTP) is an effective inhibitor of HIV reverse transcriptase and thus of HIV replication. ddCyd differs, however, from other dideo xynucleoside agents such as 3'-azido-3'-deoxythymidine and 2',3'-dideo xyinosine in its capacity to generate phosphodiester metabolites (i.e. ddCDP choline and ddCDP ethanolamine). We have synthesized and charac terized these two diesters, and established their identity with the me tabolites formed in ddCyd-treated Molt-4 cells. Toward this end, the b iologically generated metabolites have been isolated on a preparative scale and compared with the synthetic compounds mass spectroscopically , chromatographically, and enzymatically (i.e. their relative suscepti bility to the catabolic enzymes alkaline phosphatase and venom phospho diesterase). The concentration reached by each of these two phosphodie sters within cells can, under certain conditions, equal or exceed that of ddCTP, and their half-times of disappearance are long, indicating that they may serve as depot forms of ddCyd. The possible role of thes e phosphodiesters in contributing to the unusual toxicity of ddCyd is discussed.