Pharmacokinetics of PEGasparaginase in Infants with Acute Lymphoblastic Leukemia

Background: PEGasparaginase is known to be a critical drug for treating pediatric acute lymphoblastic leukemia (ALL), however, there is insufficient evidence to determine the optimal dose for infants who are less than one year of age at diagnosis. This international study was conducted to identify the pharmacokinetics of PEGasparaginase in infants with newly diagnosed ALL and gather insight into the clearance and dosing of this population. Methods: Infants with ALL who received treatment with PEGasparaginase were included in our population pharmacokinetic assessment employing non-linear mixed effects modelling (NONMEM). Results: 68 infants with ALL, with a total of 388 asparaginase activity samples, were included. PEGasparaginase doses ranging from 400 to 3,663 IU/m were administered either intravenously or intramuscularly. A one-compartment model with time-dependent clearance, modeled using a transit model, provided the best fit to the data. Body weight was significantly correlated with clearance and volume of distribution. The final model estimated a half-life of 11.7 days just after administration, which decreased to 1.8 days 14 days after administration. Clearance was 19.5% lower during the post-induction treatment phase compared to induction. Conclusion: The pharmacokinetics of PEGasparaginase in infants diagnosed under one year of age with ALL is comparable to that of older children (1–18 years). We recommend a PEGasparaginase dosing at 1,500 IU/m for infants without dose adaptations according to age, and implementing therapeutic drug monitoring as standard practice.