Class/mechanism: Purine (guanine) analog, antimetabolite that interferes with DNA synthesis. Thioguanine competes with hypoxanthine and guanine for the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) and is converted to 6-thioguanylic acid (TGMP). TGMP interferes with several processes involving the synthesis of guanine nucleotides. It exerts pseudo-feedback inhibition of glutamine-5-phosphoribosylpyrophosphate amidotransferase, an early enzyme in the de novo pathway for purine ribonucleotide synthesis. TGMP is a competitive inhibitor of inosinic acid (IMP) dehydrogenase, interfering with the conversion of IMP to xanthylic acid (XMP). Thioguanylic acid is converted to thioguanosine diphosphate (TGDP) and thioguanosine triphosphate (TGTP), and they are eventually incorporated into RNA and DNA, which may cause additional cytotoxicity. Thioguanine is structurally and functionally similar to Mercaptopurine (6-MP).
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Diseases for which it is used
Patient drug information
History of changes in FDA indication
- 1/18/1966: Initial FDA approval
Also known as
- Generic names: 6-TG, 6-thioguanine, 2-Amino-6-Mercaptopurine
- Brand name: Tabloid