GEMZ Phase 3 study of fenfluramine shows positive response: states UCB

GEMZ Phase 3 study of fenfluramine shows positive response: states UCB

By, Admin 30 June 2025

Overview

UCB, a global biopharmaceutical company, today announced that the Phase 3 study investigating the safety and efficacy of adjunctive fenfluramine in CDKL5 deficiency disorder (CDD) met its primary and most key secondary endpoints.3 The study is a randomized, double-blind, placebo-controlled, fixed-dose, multi-center study examining the efficacy and safety of adjunctive fenfluramine treatment in 87 individuals aged one through 35, with a CDD diagnosis and uncontrolled seizures.4

Commnet from Fiona du Monceau: EVP, UCB

These results pave the way for creating significant therapeutic progress and represent an important milestone in UCB's mission to bring meaningful innovation to individuals and families affected by developmental and epileptic encephalopathies (DEEs). We are grateful to the patients, families, and researchers who made this progress possible, and we look forward to working with the health authorities to make treatment available as soon as possible,"" said Fiona du Monceau, Executive Vice President, Patient Evidence, UCB.

The study outcome

The primary endpoint of the study is based on the median percent change in countable motor seizure frequency (CMSF) between baseline and the titration plus maintenance phase, comparing fenfluramine with the placebo group. Full results will be presented at an upcoming scientific meeting.

About the disorder: CDKL5 deficiency disorder

  • CDD is an ultra-rare DEE with refractory infantile-onset epilepsy and severe global neurodevelopmental delays resulting in intellectual, motor, cortical visual, and sleep impairments as major features.
  • It is caused by pathogenic variants in the cyclin dependent kinase-like 5 (CDKL5) gene located on the X chromosome. 
  • It is estimated that CDD affects approximately 1 in 40,000 to 60,000 live births.

Safety profile of fenfluramine

In the study, fenfluramine was generally well tolerated, and the safety profile was consistent with previous studies in DS/LGS.3 UCB is currently conducting an open-label, flexible-dose, long-term 54-week extension phase of the study to characterize the long-term safety and tolerability of fenfluramine in pediatric and adult individuals with CDD.4

Indications for fenfluramine

  • 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. 
  • It is not approved for use in CDD by any regulatory authority worldwide.

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