To optimize voriconazole dosing in pediatric hematopoietic cell transplantation (HCT), we conducted a phase I study with a modified 3 + 3 dose-escalation followed by an expansion cohort at the maximum tolerated, minimum efficacious dose (MTD/MED). Patients ≤21 years who required voriconazole for prevention or treatment of an invasive fungal infection were assigned to three age groups. Of the 59 evaluable patients, 13 were <2 years, 23 were 2–11, and 23 were 12–21. Therapeutic serum voriconazole troughs (1.5–5 µg/mL) drawn at 7 days after initiation determined efficacy. The MTD/MED was 12 mg/kg/dose q12 h × 2 loading doses, then 10 mg/kg/dose q12 h in patients <2, and was 10 mg/kg/dose q12 h in patients 2–11. The 12–21 age group had no dose-limiting toxicity at 8 mg/kg/dose q12 h; however, the MED was not reached. Drug-related AEs ≥grade 3 included increased bilirubin, transaminases, and creatinine, all occurring in <10%. There was no significant association between supra-therapeutic troughs and AEs. Five of 17 patients who had supra-therapeutic troughs (29%) had an AE, compared to 8 of 42 who did not (19%, p = 0.38). Observational population pharmacokinetic analysis demonstrated that inter-individual variability on voriconazole clearance was >100% CV, and clearance increased with age.
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