A Study to Evaluate Safety, Tolerability, and Pharmacokinetics of Fenfluramine (Hydrochloride) in Infants 1 Year to Less Than 2 Years of Age With Dravet Syndrome

Inclusion Criteria:

• Participant is ≥1 to <2 years of age as of the day of the first administration ofstudy drug

• Participant has a documented diagnosis or likely diagnosis of Dravet syndromeaccording to the International League Against Epilepsy (ILAE) criteria and as agreedby the Epilepsy Study Consortium (ESC)

• Participant must be currently receiving ≥1 concomitant anti seizure medication (ASM)at a stable dose for ≥4 weeks prior to the Screening Visit and is expected to remainstable throughout the study. Rescue medications for seizures are not counted towardsthe total number of ASMs

• Participant must have drug resistant epilepsy as defined as a history of failure ofadequate trials of 2 tolerated, appropriately chosen and used antiepileptic drugschedules (whether as monotherapies or in combination) to achieve sustained seizurefreedom

• Participants must have ≥1 countable motor seizures (CMS) during the Baseline Period.The CMS include distinct seizures of generalized tonic-clonic, bilateral clonic,focal motor, bilateral tonic, atonic (drop), bilateral tonic/atonic, or focal tobilateral tonic-clonic type. If the participant fails to have ≥1 qualifying seizuresin 28 days, the Baseline Period may be extended by an additional 14 days withSponsor approval. Participants with an extended Baseline Period must still have ≥1CMS in the 28 days immediately prior to the day of the first administration of studydrug

• Body weight is ≥8 kg

• Males and females

Exclusion Criteria:

• Participant has a known hypersensitivity to fenfluramine hydrochloride (HCl) or anyof the excipients in the study drug

• Participant has an exclusionary cardiovascular or cardiopulmonary abnormality basedon echocardiogram (ECHO), electrocardiogram (ECG), or physical examination and isnot approved for entry by the central cardiac reader

• Participant has a diagnosis of pulmonary arterial hypertension

• Participant 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 in theopinion of the Investigator would negatively impact study participation, collectionof study data, or pose a risk to the participant

• Participant has current or past history of cardiovascular or cerebrovasculardisease, such as cardiac valvulopathy, myocardial infarction or stroke, severeventricular arrhythmias, or clinically significant structural cardiac abnormality,including but not limited to mitral valve prolapse, atrial or ventricular septaldefects, patent ductus arteriosus, and patent foramen ovale with reversal of shunt. (Note: Patent foramen ovale or a bicuspid aortic valve are not consideredexclusionary.)

• Participant has a current or past history of glaucoma

• Participant has moderate to severe hepatic impairment, assessed based on theChild-Pugh classification system

• Participant has moderate to severe renal impairment (estimated glomerular filtrationrate <50 mL/min/1.73 m^2 calculated with the updated Bedside Schwartz equation forchildren

• QT interval corrected (QTc) >450 msec

• Participant is taking >4 concomitant ASMs

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

• Participant is receiving concomitant therapy with any of the following:centrally-acting anorectic agents; monoamine-oxidase inhibitors; anycentrally-acting compound with clinically appreciable amount of serotonin agonist orantagonist properties, including serotonin reuptake inhibition; othercentrally-acting noradrenergic agonists, including atomoxetine; or cyproheptadine.Disallowed medications are subject to washout of ≥5 half-lives before the first dayof study drug administration

• Participant is currently receiving another investigational product(s) or hasreceived another investigational product within 30 days or within <5 times thehalf-life of that investigational product, whichever is longer, prior to theScreening Visit

• Participant has previously been treated with Fintepla (fenfluramine HCl) prior tothe Screening Visit