1558. A Population Pharmacokinetic Model for Posaconazole Intravenous Solution and Oral Powder for Suspension Formulations in Pediatric Patients With Neutropenia

BACKGROUND: Posaconazole is approved in adults for prophylaxis and treatment of invasive fungal disease. Two formulations that offer weight-based dosing—intravenous (IV) and oral powder for suspension (PFS)—are being evaluated in children. A population pharmacokinetic (popPK) approach was used to characterize and predict the PK exposure of posaconazole PFS and IV formulations in children to identify dosages associated with achieving a target PK of 1200 ng/mL as the mean C(avg) and individual C(avg) ≥500 ng/mL and <2500 ng/mL in ~90% of patients. METHODS: A popPK model was developed through nonlinear mixed-effects modeling using data obtained from a trial in children with neutropenia (ClinicalTrials.gov, NCT02452034; Merck protocol, MK-5592-097). Three dose cohorts (3.5, 4.5, and 6 mg/kg/day [≤300 mg/day]) were studied in two age groups (2–<7 years and 7–17 years). Posaconazole IV was administered twice on day 1 then once daily through at least day 10, followed by PFS once daily through day 28 at clinician discretion. A compartmental model, including both formulations, was fit to the data. Model selection was based on the Log-Likelihood Criterion, goodness-of-fit plots, and scientific plausibility. Significance of the covariates was assessed in a stepwise forward inclusion/backward procedure. An additional assessment characterized the impact of different food covariates on bioavailability. RESULTS: An open one-compartmental PK model with first-order absorption and estimated bioavailability, as well as allometrically scaled effects of body weight on clearance and volume, adequately described the PK of posaconazole IV and PFS formulations. Model predictions are shown in the Table. Effects of the different food covariates were not statistically significant. Simulations indicated that for the 6-mg/kg/d dose, model-predicted C(avg) generally met PK targets. Model-predicted C(avg) was ≥500 ng/mL in >90% of subjects in all cohorts. The 1200-ng/mL target geometric mean C(avg) was achieved for all but the 2–<7 years cohort receiving the PFS formulation. CONCLUSION: This popPK-based analysis demonstrated that the 6-mg/kg/d dose of IV or PFS posaconazole formulation (≤300 mg/days) is appropriate for children (2–17 years) and that PFS can be administered without regard to food. [Image: see text] DISCLOSURES: All authors: No reported disclosures.