American Journal of Pharmacogenomics

, Volume 4, Issue 1, pp 1–8

Clinical Utility of Thiopurine S-Methyltransferase Genotyping

Practical Pharmacogenomics

DOI: 10.2165/00129785-200404010-00001

Cite this article as:
Corominas, H. & Baiget, M. Am J Pharmacogenomics (2004) 4: 1. doi:10.2165/00129785-200404010-00001


Thiopurine S-methyltransferase (TPMT) is a cytosolic enzyme that plays a major role in the metabolism of thiopurine drugs such as mercaptopurine and azathioprine. The interindividual differences in response to thiopurine administration is in part due to the presence of genetic polymorphisms in the gene that regulates TPMT activity. TPMT genotype correlates well with the in vivo enzyme activity within erythrocytes. Patients with genetically determined decreased TPMT activity develop severe myelosuppression when treated with standard doses of thiopurine drugs because an excess of thioguanine nucleotides accumulates in hematopoietic tissues.

TPMT genotyping provides clinicians with a reliable method for identifying TPMT-deficient patients who can benefit from low doses of thiopurine drugs in order to reduce the risk of developing adverse effects. Moreover, the administration of higher doses of the drug could improve therapeutic response in patients in whom the TPMT genotyping demonstrates the absence of mutated alleles.

Copyright information

© Adis Data Information BV 2004

Authors and Affiliations

  1. 1.Rheumatology Unit, Department of Internal MedicineHospital de la Santa Creu i Sant PauBarcelonaSpain
  2. 2.Department of GeneticsHospital de la Santa Creu i Sant PauBarcelonaSpain

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