6-Thioguanine (6-TG) mechanism

, a purine analog, is primarily used in the treatment of acute nonlymphocytic leukemia in combination with daunorubicin and cytarabine. Like 6-MP, 6-TG is converted intracellularly to TGMP (also called 6-thioguanylic acid) by the enzyme HGPRT. TGMP is further converted to the di- and triphosphates, thioguanosine diphosphate and thioguanosine triphosphate, which then inhibit the biosynthesis of purines and also the phosphorylation of GMP to guanosine diphosphate. The nucleotide form of 6-TG is incorporated into DNA that leads to cell-cycle arrest.