UCB Presents Fenfluramine Data in Rare Epilepsies at EEC 2026

UCB is presenting 18 abstracts at the 16th European Epilepsy Congress in Athens, covering fenfluramine across Lennox-Gastaut syndrome (LGS), Dravet syndrome (DS), CDKL5 deficiency disorder (CDD), and Rett syndrome. The data extend beyond seizure reduction to executive functioning, daily activities, seizure-free days, and the development of new treatment options for rare developmental and epileptic encephalopathies (DEEs).

Fenfluramine data extend beyond seizure control

In adults with LGS, a post hoc analysis of a randomized controlled trial and its open-label extension evaluated behavioral regulation and everyday executive functioning using the caregiver-completed Behavior Rating Inventory of Executive Function-Adult Version (BRIEF-A).

Among patients receiving fenfluramine 0.7 mg/kg/day or 0.2 mg/kg/day, clinically meaningful improvements were observed across behavioral regulation, metacognition, and global executive functioning compared with placebo. In the randomized trial, improvements in behavioral regulation occurred in 17% to 33% of fenfluramine-treated adults versus 12% with placebo. Metacognition improved in 33% versus 4%, while global executive composite scores improved in 28% to 38% versus 8%.

A separate prospective evaluation in 10 patients with DS assessed outcomes before treatment and after one year. Among patients treated for more than six months, median generalized tonic-clonic seizure reduction reached 62.5% in children and 74.5% in adults. Although statistically significant improvements in non-seizure outcomes were not detected among the three patients who completed one-year follow-up, caregivers reported improvements in motor function, alertness, and daily living skills.

CDD program advances

UCB also presented two post hoc analyses from fenfluramine development in CDD, an ultra-rare DEE caused by pathogenic variants in the X-linked CDKL5 gene.

In a Phase 3 randomized, double-blind, placebo-controlled study of 86 patients, fenfluramine increased countable motor seizure-free days. Patients gained a median 6.4 seizure-free days per month compared with 0.1 day with placebo, and 71.4% achieved more than seven additional seizure-free days per month versus 31.8% with placebo.

Patients who gained at least seven seizure-free days per month were also more likely to be rated “much improved” or “very much improved” on the Clinical Global Impression-Improvement scale. A separate time-to-event analysis found that fenfluramine-treated patients took longer to return to baseline seizure counts than those receiving placebo.

Fenfluramine remains investigational for CDD and is not approved for this indication by any regulatory authority.

Phase 3 Rett syndrome program

UCB presented the design of an ongoing Phase 3 randomized, double-blind, placebo-controlled study with an open-label extension enrolling approximately 200 patients with Rett syndrome.

The coprimary endpoints assess change at Week 14 in the caregiver-completed Rett Syndrome Behaviour Questionnaire and investigator-rated Clinical Global Impression of Change. Secondary measures include sleep disturbance, communication ability, and caregiver assessment of seizure-related change.

Focus on acute seizure management and adult care

Additional research examined patient and caregiver preferences for acute seizure treatment. Across quantitative surveys and qualitative interviews, participants prioritized rapid seizure cessation and ease of administration. Most preferred fast-acting, non-rectal options, while 88% of survey respondents indicated they would wait 30 seconds to administer treatment, supporting the feasibility of early intervention strategies.

UCB also reported persistent gaps in transitioning people with rare and complex epilepsies from pediatric to adult care. In a survey of 57 EpiCare reference-network respondents, about half reported having no written transition protocol, while only 12% had dedicated transition coordinators and physical spaces.

The company will also host Expressing Epilepsy, an art exhibition featuring work by people living with epilepsy, during the congress.

Fenfluramine is approved in the European Union as an add-on treatment for seizures associated with DS and LGS in patients aged two years and older. It is not approved for CDD or Rett syndrome. UCB’s EEC 2026 program therefore provides a broader view of fenfluramine’s clinical development, spanning established indications, investigational rare epilepsies, and outcomes that extend beyond seizure frequency.

Reference

UCB presents data at EEC 2026 highlighting continued leadership in epilepsy and developmental and epileptic encephalopathies, UCB, 01 September 2026