Based on TPMT status, start with normal starting dose (e.g., 75 mg/m2/day or 1.5 mg/kg/day) and adjust doses of mercaptopurine (and of any other myelosuppressive therapy) without any special emphasis on mercaptopurine compared to other agents. Allow at least 2 weeks to reach steady-state after each dose adjustment (PMID 20354201, 16401827, 11302950). NUDT15 phenotype could not be assigned based on genotyping. If thiopurines are required and either TPMT or NUDT15 status is unknown, monitor closely for toxicity.