UCB’s Fintepla (fenfluramine) has been associated with a nearly 50% reduction in countable motor seizure frequency (CMSF) in adult and paediatric patients with cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder (CDD).
The company announced data from the Phase III GEMZ trial (NCT05064878) at the American Epilepsy Society (AES) meeting, which took place in Atlanta, US, from 5 to 9 December 2025.
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In the study, patients treated with Fintepla experienced a 47.6% median reduction in CMSF from baseline, compared with 2.8% for placebo. This translated into an estimated median reduction of 52.7% between treatment groups over the 14-week titration and maintenance period.
Within the Fintepla-treated patients, 45.2% achieved at least a 50% reduction in CMSF, compared to 4.5% of placebo patients. This translates as an additional six seizure free days per month in the treatment cohort, compared to baseline.
Investigators rated 38.1% of patients on Fintepla as ‘much improved’ or ‘very much improved’ on the Clinical Global Impression–Improvement (CGI-I) scale compared with 6.8% of those on placebo.
Caregivers reported an even higher CGI-I rating, with 53.7% reporting a ‘much improved’ or ‘very much improved’ rating for patients treated with Fintepla compared with 2.3% in the placebo group.
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By GlobalDataUCB’s patient evidence executive vice-president Fiona du Monceau said: “Families affected by this ultra-rare condition face immense daily challenges with frequent, treatment-resistant seizures that are profoundly disruptive to daily life. These trial results emphasise the impact that seizure control can have on the lives of patients and their families, and we look forward to working with health authorities to make this treatment available as soon as possible.”
UCB previously confirmed that the randomised, placebo controlled, double-blind GEMZ trial met its primary and secondary endpoints; however, data was not released at the time. The trial enrolled 86 adult and paediatric patients aged between one and 35 years, with a CDD diagnosis and uncontrolled seizures.
The drug was generally well tolerated in the trial, with no new safety signals identified and no cases of valvular heart disease (VHD) or pulmonary arterial hypertension (PAH) occurring.
Serious treatment-emergent adverse events (TEAEs) were experienced in 14.3% of treated patients compared with 6.7% who received placebo. Serious TEAEs in the treatment cohort included urinary tract infection, metapneumovirus infection, RSV pneumonia, decreased appetite, and dyskinesia.
The company is now conducting an open-label, flexible-dose, long-term 54-week extension phase of the study to characterise the long-term safety profile and tolerability of Fintepla in patients with CDD.
CDD landscape periled by unmet needs
CDD is an ultra-rare, developmental and epileptic encephalopathy (DEE) characterised by multiple types of drug-resistant seizures, plus severe global neurodevelopmental delays resulting in intellectual, motor, cortical visual, gastrointestinal and sleep impairments as major features.
It is caused by pathogenic variants in the CDKL5 gene, located on the X chromosome, and affects four times more females than males. It is estimated that CDD affects approximately one in 40,000 to 60,000 live births, with a median age of onset of six weeks.
Fintepla is already approved for use in the US, EU and Japan for patients with Dravet syndrome or Lennox-Gastaut syndrome as an add-on therapy to other anti-epileptic medicines for patients two years of age and older.
While it is not approved for use in CDD by any regulatory authority worldwide, UCB is seeking global approval of the drug. The company has not disclosed information as to when applications would be submitted.
The CDD space is plagued with unmet needs, as only one drug is approved specifically for CDD. Ztalmy (ganaxolone) gained approval in CDD by the US Food and Drug Administration (FDA) in 2022. It has since been approved in the EU and UK. It is, however, only approved in patients aged over two years of age, meaning that UCB’s drug would allow earlier intervention in patients aged one and over.
UCB will be happy with the potential label expansion after it invested $1.9bn to acquire Fintepla’s developer, Zogenix, in 2022, bringing the anti-seizure medication into its portfolio. Shortly after this acquisition, the candidate gained approval for Lennox-Gastaut syndrome.
