Thymidine as an anticancer agent, alone or in combination. A biochemical appraisal.

The value of thymidine as a cytotoxic drug alone or in combination with other pyrimidine antimetabolites has received considerable attention in recent years. In this paper, the biochemical basis for the cytotoxicity of thymidine and its interaction with other pyrimidine antimetabolites is described. It is indicated that early clinical trials have largely failed to substantiate data from experimental studies that have shown thymidine to be an effective antimetabolite and capable of potentiating the antineoplastic effect of several other agents. It is suggested that tumours likely to respond to thymidine alone or in combination may be identified by measuring in clinical tumour specimens known biochemical determinants of thymidine efficacy.