Individualized dosing guidelines for PEGasparaginase and factors influencing the clearance: a population pharmacokinetic model

Considerable inter- and intra-patient variability exist in serum activity levels of PEGasparaginase, essential for pediatric acute lymphoblastic leukemia (ALL) treatment. A population pharmacokinetic (popPK) model was developed, identifying patient characteristics that explain these variabilities. Patients (n=92) were treated according to the Dutch Childhood Oncology Group (DCOG) ALL-11 protocol, using therapeutic drug monitoring to individualize PEGasparaginase doses. Non-linear mixed effects modeling (NONMEM) was used to analyze popPK evaluating several covariates. The final model was validated using an independent database (n=28). Guidelines for starting doses and dose adjustments were developed. A one-compartment model with timedependent clearance was adequately described in popPK. Normalization of clearance and volume of distribution by body surface area reduced inter-individual variability. Clearance was 0.084 L/day/m² for 12.7 days, increasing by 0.082 L/day/m²/day thereafter. Clearance was 38% higher during an infection, and 11-19% higher during induction treatment than during intensification and maintenance (P<0.001). In order to target an asparaginase activity level of 100 IU/L, a loading dose of 800 IU/m² (induction) and 600 IU/m² (intensification) is advised. In conclusion, variability of PEGasparaginase activity levels can be explained by body surface area, the treatment phase and the occurrence of an infection. With this popPK model, PEGasparaginase treatment can be individualized further, taking into account the covariates and the dosing guidelines provided. (clinicaltrials gov. Identifier [CCMO register]: NL50250.078.14).