Fenfluramine provides clinically meaningful reduction in frequency of drop seizures in patients with Lennox–Gastaut syndrome: Interim analysis of an open-label extension study

Abstract

Objective: This study was undertaken to evaluate the long-term safety and effectiveness of fenfluramine in patients with Lennox–Gastaut syndrome (LGS). Methods: Eligible patients with LGS who completed a 14-week phase 3 randomized clinical trial enrolled in an open-label extension (OLE; NCT03355209). All patients were initially started on.2 mg/kg/day fenfluramine and after 1 month were titrated by effectiveness and tolerability, which were assessed at 3-month intervals. The protocol-specified treatment duration was 12 months, but COVID-19-related delays resulted in 142 patients completing their final visit after 12 months. Results: As of October 19, 2020, 247 patients were enrolled in the OLE. Mean age was 14.3 ± 7.6 years (79 [32%] adults) and median fenfluramine treatment duration was 364 days; 88.3% of patients received 2–4 concomitant antiseizure medications. Median percentage change in monthly drop seizure frequency was −28.6% over the entire OLE (n = 241) and −50.5% at Month 15 (n = 142, p