Vincristine Pharmacokinetics in Infants

PRIMARY OBJECTIVE: I. To validate body surface area (BSA)-banded infant dosing tables by comparing vinCRIStine drug exposure, defined as the area under the concentration-time curve for the elimination phase (AUCelim), in infants and young children dosed according to the table to older children dosed according to BSA. SECONDARY OBJECTIVE: I. To estimate intra- and inter-age group variability (CV) using non-compartmental analysis (NCA) and population pharmacokinetic (PK) methods. EXPLORATORY OBJECTIVES: I. To correlate higher AUCelim with the presence of functionally impaired single nucleotide polymorphisms (SNP) of CYP3A4 and CYP3A5. II. To assess vinCRIStine dose modifications in infants receiving weekly vinCRIStine dosed according to the BSA-banded infant dosing tables. OUTLINE: Patients receive vincristine intravenously (IV) per standard of care (SOC). Patients undergo collection of blood samples at baseline (before first vincristine dose), and 2, 6-8, and 18-24 hours after a dose of vincristine. Patients may also undergo collection of blood samples with a second SOC vincristine dose at the same time points. Patients are followed for dose modifications for a period of 42 days (when receiving weekly dosing of vincristine).