Zalcitabine (2'-3'-dideoxycytidine, ddC), is a derivative of the naturally existing deoxycytidine, made by replacing the hydroxyl group in position 3' with a hydrogen. It is phosphorylated in the T cell into its active triphosphate form, ddCTP. This active metabolite works as a substrate for the reverse transcriptase, and also by incorporation into the viral DNA, hence terminating the chain elongation due to the missing hydroxyl group. ...