A Precision Prescription: New Genetic Guidelines for Safer Thiopurine Use
The Clinical Pharmacogenetics Implementation Consortium (CPIC) has released a crucial 2025 update to its guidelines for dosing thiopurine drugs, a class of immunosuppressants used in conditions like inflammatory bowel disease and leukemia. The update provides refined recommendations for adjusting starting doses of azathioprine, mercaptopurine, and thioguanine based on a patient’s genetic profile for two key enzymes: thiopurine methyltransferase (TPMT) and Nudix hydrolase 15 (NUDT15). Individuals carrying specific genetic variants that reduce or eliminate the function of these enzymes are at a significantly higher risk of severe, potentially life-threatening myelosuppression when given standard drug doses. The guidelines now also offer specific advice for patients with variants in both genes, aiming to personalize therapy and improve safety across diverse populations.
Why it might matter to you: This update directly impacts clinical immunology and pharmacology by moving precision medicine for immunosuppression from theory to actionable protocol. For clinicians, it provides a clear, evidence-based framework to mitigate a major adverse effect, enhancing patient safety in autoimmune and oncologic treatments. For the field, it underscores the growing necessity of integrating pharmacogenetic testing into standard care to optimize therapeutic outcomes and prevent treatment-related harm.
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