Final analysis of open-label extension (OLE) study of Fintepla®▼ (fenfluramine) in Lennox-Gastaut syndrome published in Epilepsy and Behavior

• Long-term data on the treatment of children and adults living with Lennox-Gastaut syndrome (LGS) with fenfluramine¹ demonstrated sustained reduction in frequency of seizures associated with a fall and improvement in global functioning²
• No new safety signals were reported, reinforcing the consistent safety profile seen in previous studies²
• Additionally, parents/caregivers reported improvements in overall quality of life and a reduction in levels of their own anxiety and depression from baseline through month 12 of the OLE period²

Brussels (Belgium), October 14, 2025 – 07:00 (CET) – UCB, a global biopharmaceutical company, today announced that the final analysis of an open-label extension (OLE) study on Fintepla (fenfluramine) in Lennox-Gastaut syndrome (LGS) was published in Epilepsy and Behavior.² Children and adults aged 2-35 years treated with fenfluramine showed a significant sustained reduction in frequency of seizures associated with a fall (drop seizures) from Month 2 of OLE to end of study compared with baseline and an improvement in global functioning reported by caregivers and investigators. No new or unexpected treatment-emergent adverse events (TEAEs) were reported.² Parents/caregivers reported improvements in social interactions and activities, feelings of stigma, general health, quality of life, and their own anxiety.² These results follow final analysis of OLE study evaluating safety and effectiveness of fenfluramine in Dravet Syndrome earlier this year, showing sustained reduction in monthly convulsive seizure frequency and long-term tolerability.³

Kelly G Knupp, Associate Professor of Pediatrics and Neurology at the CU Anschutz School of Medicine, and coauthor of the paper, said, “These data reinforce the long-term safety and tolerability of fenfluramine in children and adults living with Lennox-Gastaut syndrome, a condition with a significant unmet medical need. The sustained reduction in seizure frequency, coupled with the meaningful improvements in quality of life for both patients and their families, underscores the importance of addressing not just the clinical but also the emotional and social challenges faced by these families every day.”

Highlights from the OLE

247 patients (mean age 14.3±7.6 years) were enrolled from study sites in North America, Europe, and Australia, with a median fenfluramine exposure of 364 days (range: 19–537) and a mean daily dose of 0.4±0.1 mg/kg/day (n=246). Meaningful improvements were seen across the key study endpoints listed below:²

• Common treatment-emergent adverse events (TEAEs) reported in ≥10% of patients included decreased appetite, fatigue, nasopharyngitis, seizures, and pyrexia, with no cases of valvular heart disease or pulmonary arterial hypertension observed.  Only 5.3% (n=13) of patients discontinued the study due to TEAEs.
• A significant median percentage change in the frequency of seizures associated with a fall from month 2 to the end of the study (−31.1%, P<0.0001, n=240, mITT population), with reductions of −27.6% in pediatric patients (n=170, P=0.0005) and −40.0% in adults (n=70, P<0.0001). 
• At the last visit, parents/caregivers and investigators reported any improvement in 59.9% (n=142/237) and 57.0% (n=135) of patients, respectively, on the Clinical Global Impression—Improvement (CGI-I) scale. 
• The Quality of Life in Childhood Epilepsy Questionnaire (QOLCE) was completed by parents/caregivers at pre-RCT baseline and at Month 12 of the OLE. From baseline through Month 12 of the OLE period, the mean change in the overall QoL score, calculated as the average of 16 subscale scores, was 2.9 points (n=148, P=0.0166), indicating improvement.

In the European Union (EU), fenfluramine is approved for the treatment of seizures associated with Dravet syndrome and Lennox-Gastaut syndrome as an add-on therapy to other anti-epileptic medicines for patients 2 years of age and older.¹ In the United States, fenfluramine oral solution is indicated for the treatment of seizures associated with Dravet syndrome and Lennox-Gastaut syndrome in patients 2 years of age and older.⁴ In Japan, fenfluramine is approved for treating seizures associated with Dravet syndrome and Lennox-Gastaut syndrome (LGS) as an add-on therapy to other anti-epileptic medicines for patients 2 years and older.⁵ 

About Lennox-Gastaut syndrome (LGS)

Lennox-Gastaut Syndrome (LGS) is a rare, severe developmental and epileptic encephalopathy (DEE) characterized by the presence of tonic seizures and at least one additional seizure type and severe developmental delays. It typically starts during childhood and persists into adulthood.^6,7 Approximately 50% of infants with a severe DEE evolve over time to LGS.⁷ LGS has far-reaching effects beyond seizures; impairments with developmental delay culminating in cognitive impairment, communication, psychiatric symptoms, sleep, behavioral challenges and mobility are common.⁷ Seizures largely remain drug-resistant on currently available medications.⁷ Sudden unexpected death in epilepsy (SUDEP) is a major concern for patients and families with LGS.⁸ 

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