Prolonged fenfluramine use in open-label studies of Dravet or Lennox-Gastaut syndromes: Long-term safety, tolerability, patient global functioning, and considerations for interpreting effectiveness.

内容摘要

Long-term safety and global functioning are reported in patients with Dravet syndrome (DS) or Lennox-Gastaut syndrome (LGS) treated with fenfluramine in an open-label extension (OLE) study after participating in a previous open-label feeder study. Patients could enroll in this international, multicenter OLE (NCT03936777) after completing one of three fenfluramine open-label studies. The latest feeder study fenfluramine dose was continued, then flexibly titrated (maximum: .7 mg/kg/day [26 mg/day] without stiripentol or .4 mg/kg/day [17 mg/day] with stiripentol), with ≥1 concomitant antiseizure medication administered. Primary endpoint was fenfluramine long-term safety/tolerability. Global functioning using caregiver- and investigator-reported Clinical Global Impression of Improvement (CGI-I) ratings, globally and for subdomains (cognition, behavior, motor function), at last visit relative to study baseline was evaluated. Overall treatment exposure and age groups were analyzed post hoc. A total of 412 patients enrolled (DS: 265 [64.3%], LGS: 147 [35.7%]); 30.8% were ≥18 years old. Median fenfluramine treatment duration in this OLE was 729.5 days (range = 8-1544), and overall median fenfluramine exposure, including feeder studies, was 1464.5 days (range = 171-2800). In this OLE, ≥1 treatment-emergent adverse event (TEAE) was reported in 311 (75.5%) patients; fenfluramine-related (per investigator) serious TEAEs were reported in five (1.2%) patients. Three patients died in this OLE (deemed unrelated to fenfluramine by investigators). After starting this OLE already receiving fenfluramine, 373 of 401 (93.0%) and 376 of 401 (93.8%) patients were rated by caregiver and investigator, respectively, as "improved or no change" on CGI-I versus this study baseline; subdomain ratings of "improved or no change" were largely consistent with global assessment. In our OLE study of patients with DS or LGS treated with fenfluramine (up to 4 years), no new or unexpected safety signals were observed; global functioning was improved or stable (vs. study baseline) in >90% of patients, supporting long-term fenfluramine use in pediatric and adult patients with DS or LGS.