The Lack of Effect of Food on the Pharmacokinetics of ZX008 (Fenfluramine Oral Solution): Results of a Single-dose, Two-period Crossover Study

Abstract

Purpose: Fenfluramine is being developed as a low-dose adjunctive treatment for seizures in patients with Dravet syndrome and other epileptic encephalopathies, including Lennox-Gastaut syndrome. Most patients with Dravet syndrome receive multiple antiepileptic drugs, making it challenging for caregivers to track correct administration times. The present Phase I study was conducted to determine the effect of food on the pharmacokinetic properties of fenfluramine.

Methods: Healthy nonsmoking subjects aged 18 to 50 years were enrolled in an open-label, crossover, Phase I pharmacokinetic and safety profile study and received 2 single 0.8-mg/kg doses of ZX008 (fenfluramine hydrochloride oral solution), 1 after a 10-hour overnight fast and the other 30 minutes after the start of consumption of a high-fat breakfast, in a randomly assigned order. A washout period of at least 9 days separated the 2 treatment periods. Venous blood samples were taken before each dose and periodically for 72 hours after each dose for determination of concentrations of fenfluramine and its active metabolite norfenfluramine. Plasma pharmacokinetic parameters were estimated for each subject by noncompartmental analysis.

Findings: In the 13 subjects completing both treatment periods, food had no effect on the rate or extent of absorption and bioavailability of fenfluramine as assessed by fed vs fasted adjusted geometric mean observed plasma C_max (59.1 vs 56.7 ng/mL; NS) and AUC_0-∞ (1640 vs 1600 ng · h/mL; NS). Additionally, there was no impact of food on systemic exposure of norfenfluramine. Seven subjects reported at least 1 treatment-emergent adverse event; all treatment-emergent adverse events were mild in severity.

Implications: The bioequivalence and tolerability of single 0.8-mg/kg oral doses of ZX008 in the fed and fasted states support ZX008 administration without regard to meals.

Keywords: fenfluramine; food; norfenfluramine; pharmacokinetics.