# Therapeutic drug monitoring of imatinib in paediatric chronic myeloid leukaemia: Data from a real‐world setting

## TL;DR

This study shows that monitoring imatinib levels in children with leukemia helps adjust doses and improve treatment outcomes in real-world settings.

## Contribution

The study provides real-world evidence that therapeutic drug monitoring of imatinib improves personalized treatment in pediatric CML.

## Key findings

- Children under 13 received significantly higher imatinib doses than older patients.
- Imatinib levels above 1000 ng/mL correlated with better molecular response rates at 3 months.
- Therapeutic drug monitoring identified non-adherence in 3 patients and linked high drug levels to adverse events.

## Abstract

Imatinib (IMA) therapy for paediatric chronic myeloid leukemia (pCML) requires age‐dependent dose adjustments. Assessment of therapeutic drug monitoring (TDM) under ‘real‐world’ conditions was performed. Collection of blood and TDM‐relevant data, calculation of individual dosage exposure, measurement of plasma C
min (IMA, Nor‐IMA) by HPLC/MS‐MS and recording of adverse event (AE). Two hundred and forty‐six specimens from 66 patients were analysed. Individual median IMA dosage exposure was 253 mg/m2 (range: 128–504). Children <13 years received a median of 43 mg/m2 more than older patients (p < 0.0001). Median C
min of IMA and Nor‐IMA was 1017 ng/mL (range: 51–3976) and 269 ng/mL (range: 21–981), respectively, correlating significantly with the prescribed dose. At 5/246 visits, non‐adherence was confirmed by very low IMA C
min in 3/66 patients, all ≥13 years old. Correlation of IMA C
min >1000 ng/mL with achieving OMR demonstrated in each 63% (N = 24/37, N = 27/43, respectively) patients at months 3 and 6. In the cohort with lower levels, only 23% and 50%, respectively, achieved these milestones. This difference was significant only at month 3. Of 66 patients, 30 reported 125 AEs with gastrointestinal and musculoskeletal as leading complaints. In 9.3% of AEs, the correlated IMA C
min was ≥3000 ng/mL. TDM is a simple and rapid additional tool for managing pCML under ‘real‐world conditions’.

Therapeutic drug monitoring (TDM) of imatinib is reported from a real‐world study in 66 children with paediatric Chronic Myeloid Leukemia (pCML). TDM allows dose adjustments, improving molecular response rates and is a step forward in personalized pCML care.