A synthetic nucleoside analogue with antineoplastic activity. Tiazofurin (TR) is anabolized intracellularly to an analogue of NAD, tiazole-4-carboxamide adenine dinucleotide (TAD), a potent inhibitor of IMP dehydrogenase (IMPDH); IMPDH is the rate-limiting enzyme for de novo purine synthesis. Inhibition of IMPDH results in reduced levels of guanylates, resulting in the inhibition tumor cell growth in vitro and in vivo. OR An anticancer drug being studied to stop cell growth.