A Clinical Trial for Participants With DEE to Assess Efficacy, Safety, Tolerability, and PK of Relutrigine

Inclusion Criteria:

• Has a documented diagnosis of a developmental and epileptic encephalopathy.

• Onset of seizures <12 years old.

• Has a weight >7 kg at the time of signing consent/assent.

Exclusion Criteria:

• Has a history of left bundle branch block, arrhythmias, Brugada syndrome, congenitalheart disease, familial short QT syndrome, or family history of sudden death orventricular arrhythmias, including idiopathic ventricular fibrillation.

• Had 2 or more episodes of convulsive status epilepticus requiring hospitalizationand intubation in the 6 months prior to Screening.

• Has an abnormal ECG reading, including a QT interval corrected for heart rate usingBazett's method (QTcB) <350 and >450 ms (males), or <360 and >460 ms (females) atScreening and/or on Day 1.

• Any nerve stimulation must have been placed at least 3 months prior to Screeningwith at least 1 month of stable settings prior to Screening.

• Has received any other experimental or investigational drug, device, or othertherapy within 30 days or 5 half-lives (whichever is longer) prior to Screening,including any prior use of gene therapy.

• Is currently pregnant or breastfeeding or is planning to become pregnant during theclinical trial or within 5 half-lives of the last study drug dose.