A Study to Investigate the Efficacy and Safety of ZX008 in Subjects With CDKL5 Deficiency Disorder

Inclusion Criteria:

• Subject has a confirmed pathogenic or likely pathogenic mutation in the CDKL5 geneand a clinical diagnosis of CDD with epilepsy onset in the first year of life, plusmotor and developmental delays.

• Subject is male or female, aged 1 to 35 years, inclusive, as of the day of theScreening Visit.

• Subject must have failed to achieve seizure control despite previous or current useof 2 or more AETs.

• Subject is currently receiving at least 1 concomitant antiseizure treatment:antiseizure medication (ASM), vagus nerve stimulation (VNS), responsiveneurostimulation (RNS), or ketogenic diet (KD).

• All medications or interventions for epilepsy (including VNS, RNS, and KD) must bestable prior to screening and are expected to remain stable throughout the study.

• At the Screening Visit, parent/caregiver reports that subject has ≥ 4 countablemotor seizures(CMS) per week.

Exclusion Criteria:

• Subject has a known hypersensitivity to fenfluramine or any of the excipients in thestudy drug.

• Subject has a diagnosis of pulmonary arterial hypertension.

• Subject has a clinically significant medical condition, including chronicobstructive pulmonary disease, interstitial lung disease, or portal hypertension, orhas had clinically relevant symptoms or a clinically significant illness currentlyor in the 4 weeks prior to the Screening Visit, other than epilepsy, that wouldnegatively impact study participation, collection of study data, or pose a risk tothe subject.

• Subject has current or past history of cardiovascular or cerebrovascular disease,such as cardiac valvulopathy, myocardial infarction or stroke, severe ventriculararrhythmias, or clinically significant structural cardiac abnormality, including butnot limited to mitral valve prolapse, atrial or ventricular septal defects, patentductus arteriosus, and patent foramen ovale with reversal of shunt. (Note: Patentforamen ovale or a bicuspid aortic valve are not considered exclusionary).

• Subject has moderate to severe hepatic impairment.

• Subject has current eating disorder that suggests anorexia nervosa or bulimia.

• Subject has a current or past history of glaucoma.

• Subject is taking > 4 concomitant ASMs. Rescue medications are not included in thecount.

• Subject is receiving concomitant treatment with cannabidiol (CBD) other thanEpidiolex/Epidyolex or is being actively treated with tetrahydrocannabinol (THC) orany marijuana product for any condition.

• Subject has participated in another interventional clinical trial within 30 days ofthe Screening Visit or is currently receiving an investigational product.

• Subject has previously been treated with Fintepla® (fenfluramine) prior to theScreening Visit.