Answer
Inherited variants can reduce the body's ability to inactivate thiopurine metabolites, increasing the risk of severe marrow suppression and other toxicity.
Sources for this answer
- Tioguanine 40 mg Tablets — Current selected SmPCemc · Summary of Product Characteristics
- NHSNHS · NHS medicine guidance
General medicine information. Follow the instructions for your own medicine and speak to a pharmacist or clinician about your individual circumstances.