INHIBITION OF RIBONUCLEOTIDE REDUCTASE BY 2'-SUBSTITUTED DEOXYCYTIDINE ANALOGS - POSSIBLE APPLICATION IN AIDS TREATMENT

After phosphorylation to the corresponding diphosphates, 2'-azido-2'-d eoxycytidine and 2'-difluorocytidine act as powerful inhibitors of rib onucleotide reductase. Phosphorylation requires deoxycytidine kinase, an enzyme with particularly high activity in lymphoid cells. Therefore , the deoxycytidine analogs can be expected to inhibit the reductase w ith some specificity for the lymphoid system. Pretreatment of human CE M lymphoblasts with the analogs considerably increased the phosphoryla tion of 3'-deoxy-3'-azidothymidine (AzT). The increased phosphorylatio n of AzT is caused by a prolongation of the S phase of the cell cycle. Our results suggest the possibility of a combination of 2'-substitute d deoxycytidine analogs with AzT in the treatment of AIDS. Gao et al. [Gao, W.-Y., Cara, A., Gallo, R. C. & Lori, F. (1993) Proc. Natl; Acad . Sci. USA 90, 8925-8928] have suggested the use of the ribonucleotide reductase inhibitor hydroxyurea for this purpose, since the resulting decrease in the size of deoxyribonucleotide pools decreases the proce ssivity of the HIV reverse transcriptase. From our results it would ap pear that the 2'-substituted deoxycytidine analogs might be preferable to hydroxyurea.