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TPMT in the treatment of Crohn's disease with azathioprine

L Lennard1

  • 1Academic Unit of Molecular and Clinical Pharmacology, School of Medicine, University of Sheffield, UK. L.Lennard@sheffield.ac.uk

Gut
|July 16, 2002
PubMed

Insights

Thiopurine S-methyltransferase (TPMT) deficiency identifies patients at risk for severe myelosuppression from azathioprine. TPMT testing is crucial for predicting early bone marrow toxicity but not long-term outcomes in Crohn

Area of Science:

  • Pharmacogenomics
  • Immunosuppressive Therapy
  • Gastroenterology

Background:

  • Azathioprine and mercaptopurine are thiopurine drugs used in treating inflammatory conditions like Crohn's disease.
  • Thiopurine S-methyltransferase (TPMT) deficiency is a known genetic factor leading to severe myelosuppression in patients receiving thiopurines.
  • Identifying individuals at risk for adverse drug reactions is critical for safe and effective treatment.

Purpose of the Study:

  • To evaluate the role of TPMT activity measurement in predicting azathioprine-induced myelosuppression.
  • To determine the predictive value of TPMT status for early and long-term toxicity and clinical response in patients with Crohn's disease.

Main Methods:

  • Review of documented cases and clinical evidence regarding azathioprine-induced myelosuppression.
  • Analysis of the utility of TPMT activity testing at the initiation of thiopurine therapy.
  • Assessment of TPMT's predictive power for toxicity and response in both early and established phases of azathioprine treatment.

Main Results:

  • TPMT deficiency affects approximately 1 in 300 patients, predisposing them to severe myelosuppression with standard thiopurine doses.
  • TPMT activity measurement is valuable for identifying patients at risk of early bone marrow toxicity during the initial months of azathioprine therapy.
  • TPMT status does not reliably predict long-term clinical response or drug toxicity in patients already established on azathioprine.

Conclusions:

  • TPMT activity testing is essential for predicting and preventing early-onset myelosuppression associated with azathioprine and mercaptopurine.
  • In Crohn's disease patients on long-term azathioprine, myelosuppression is multifactorial, necessitating ongoing blood cell count monitoring irrespective of TPMT status.
  • TPMT testing plays a key role in managing initial thiopurine therapy but not in long-term patient management or outcome prediction.

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