Chemical Component Summary

FormulaC5 H5 N5 S
Molecular Weight167.19
Isomeric SMILESNc1nc2[nH]cnc2c(=S)[nH]1

Chemical Details

Formal Charge0
Atom Count16
Chiral Atom Count0
Chiral Atomsn/a
Bond Count17
Aromatic Bond Count5
Leaving Atomsn/a

Drug Info: DrugBank

DrugBank IDDB00352 Different stereochemistry
DescriptionAn antineoplastic compound which also has antimetabolite action. The drug is used in the therapy of acute leukemia. [PubChem]
  • 2-Amino 6mp
  • 2-Amino-1,7-dihydro-6H-purine-6-thione
  • 2-amino-1,9-Dihydropurine-6-thione
  • 2-amino-1H-purine-6(7H)-thione
  • 2-Amino-6-mercaptopurine
Brand Names
  • Lanvis
  • Tabloid
  • Tioguanina
  • Tioguanine
Affected OrganismHumans and other mammals
IndicationFor remission induction and remission consolidation treatment of acute nonlymphocytic leukemias.
PharmacologyThioguanine is an antineoplastic anti-metabolite used in the treatment of several forms of leukemia including acute nonlymphocytic leukemia. Anti-metabolites masquerade as purine or pyrimidine - which become the building blocks of DNA. They prevent these substances becoming incorporated in to DNA during the "S" phase (of the cell cycle), stopping normal development and division. Thioguanine was first synthesized and entered into clinical trial more than 30 years ago. It is a 6-thiopurine analogue of the naturally occurring purine bases hypoxanthine and guanine. Intracellular activation results in incorporation into DNA as a false purine base. An additional cytotoxic effect is related to its incorporation into RNA. Thioguanine is cross-resistant with mercaptopurine. Cytotoxicity is cell cycle phase-specific (S-phase).
Mechanism of actionThioguanine competes with hypoxanthine and guanine for the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) and is itself converted to 6-thioguanilyic acid (TGMP), which reaches high intracellular concentrations at therapeutic doses. TGMP interferes with the synthesis of guanine nucleotides by its inhibition of purine biosynthesis by pseudofeedback inhibition of glutamine-5-phosphoribosylpyrophosphate amidotransferase, the first enzyme unique to the de novo pathway of purine ribonucleotide synthesis. TGMP also inhibits the conversion of inosinic acid (IMP) to xanthylic acid (XMP) by competition for the enzyme IMP dehydrogenase. Thioguanine nucleotides are incorporated into both the DNA and the RNA by phosphodiester linkages, and some studies have shown that incorporation of such false bases contributes to the cytotoxicity of thioguanine. Its tumor inhibitory properties may be due to one or more of its effects on feedback inhibition of de novo purine synthesis; inhibition of purine nucleotide interconversions; or incorporation into the DNA and RNA. The overall result of its action is a sequential blockade of the utilization and synthesis of the purine nucleotides.
Route of administrationOral
  • Antimetabolites
  • Antimetabolites, Antineoplastic
  • Antineoplastic Agents
  • Antineoplastic and Immunomodulating Agents
  • Chemical Actions and Uses
CAS number154-42-7

Drug Targets

NameSequence SearchPharmacological ActionActions
Drug Info/Drug Targets: DrugBank 3.0: a comprehensive resource for 'omics' research on drugs. Knox C, Law V, Jewison T, Liu P, Ly S, Frolkis A, Pon A, Banco K, Mak C, Neveu V, Djoumbou Y, Eisner R, Guo AC, Wishart DS. Nucleic Acids Res. 2011 Jan; 39 (Database issue):D1035-41. | PMID:21059682