A Phase 3 Study to Examine the Efficacy and Safety of ZX008 in Subjects With CDKL5 Deficiency Disorder.

To be considered for this study, individuals must have a confirmed diagnosis of CDKL5 Deficiency Disorder caused by a specific gene change, with their epilepsy starting within their first year of life, along with motor and developmental delays. They should be between 1 and 35 years old.

It's important that their seizures haven't improved adequately despite trying at least two different epilepsy medicines in the past or currently. They also need to be taking at least one epilepsy treatment already (which could be medication, a special diet, or a device like a VNS). All current epilepsy treatments must be stable before starting the study and expected to remain stable throughout. During a screening visit, the parent or caregiver must report that the individual has at least 4 major motor seizures per week.

However, some health conditions or allergies would prevent someone from joining. For instance, if they are allergic to the study medicine (fenfluramine) or its ingredients, or if they have a history of certain serious heart or lung conditions. Any significant health issue that could make taking part unsafe or affect the study results would also mean they cannot join.

If you decide to join this study, it could last for a long time, potentially over two years. First, there's a main part (Part 1) that lasts about 20 weeks. During this time, for 14 weeks, participants will either receive the active study medicine (ZX008) or a dummy medicine (placebo). This is done without you or your doctor knowing which one you are getting. Following this, if you're still doing well and wish to continue, you might move into longer-term open-label extension parts (Part 2 and Part 3) where everyone receives the active study medicine.

Throughout the study, there will be regular visits to the clinic for check-ups, assessments, and to pick up your medicine. There will be specific periods for slowly increasing the medication dose, followed by longer periods where the dose stays the same. You'll need to keep all your other epilepsy treatments stable during the study. If you leave the study early at any point, there will be a follow-up heart check-up visit about 6 months after your last dose of the medicine.