The nucleoside compound 2-β-D-ribofuranosylthiazole-4-carboxamide (NSC 286193; tiazofurin; see Fig. 1) has recently been shown to possess significant antitumor activity against L1210 and P388 murine leukemias (1,2). Its demonstrated antitumor efficacy in treating mice with Lewis lung carcinoma (2), a tumor refractory to many chemotherapeutic drugs, is of considerable potential significance. Anabolism of the compound is required for its antitumor activity and involves the production of a state of guanine nucleotide depletion secondary to inhibition of inosine monophosphate (IMP) dehydrogenase (3). Thiazolecarboxamide adenine dinucleotide is formed in the metabolism of tiazofurin and appears to be responsible for the inhibition of IMP dehydrogenase (4, 5).
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