A Phase 3, Randomized, Multi-Center, Double-Blind, Placebo-Controlled Clinical Trial to Evaluate the Efficacy, Safety, Tolerability, and Pharmacokinetics of Relutrigine in Participants with Developmental and Epileptic Encephalopathies Followed by an Open-Label Extension

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, congenital heart disease, familial short QT syndrome, or family history of sudden death or ventricular arrhythmias, including idiopathic ventricular fibrillation.
• Had 2 or more episodes of convulsive status epilepticus requiring hospitalization and intubation in the 6 months prior to Screening.
• Has an abnormal ECG reading, including a QT interval corrected for heart rate using Bazett's method (QTcB) <350 and >450 ms (males), or <360 and >460 ms (females) at Screening and/or on Day 1.
• Any nerve stimulation must have been placed at least 3 months prior to Screening with at least 1 month of stable settings prior to Screening.
• Has received any other experimental or investigational drug, device, or other therapy 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 the clinical trial or within 5 half-lives of the last study drug dose.