An Efficacy and Safety Study of Clemizole HCl in Patients With Lennox-Gastaut Syndrome

Key Inclusion Criteria:

1. Males or females, ages ≥2 to ≤55 years, at the time of Screening.

2. Participant/parent/legal authorized representative (LAR) willing and able to givewritten informed consent/assent.

3. Diagnosis of LGS, including:

• Evidence of at least one type of countable major motor seizure.

• History of electroencephalogram (EEG) consistent with LGS (abnormal backgroundactivity, and one of the following: 1) slow spike-wave discharges [<2.5 Hz], or

2. paroxysmal fast activity during sleep).

• Abnormal cognitive development.

• Onset of seizures at 11 years of age or younger.

Key Exclusion Criteria:

1. Known sensitivity, allergy, or previous exposure to clemizole HCl.

2. Known history of long QT syndrome or any significant history of a seriousabnormality of the electrocardiogram (ECG) (e.g., recent myocardial infarction,clinically significant arrhythmia).

3. Family history of sudden cardiac death, unexplained death, or death from a primarydysrhythmia potentially associated with QT prolongation in any family member.

4. Seizures secondary to illicit drug or alcohol use, infection, neoplasm,demyelinating disease, degenerative neurological disease, or progressive centralnervous system disease, metabolic illness, recent anoxic episode within the last 6months requiring resuscitation, or progressive degenerative disease or any othercondition, which in the opinion of the investigator, could affect seizure control.

5. Epilepsy surgery planned during the study or epilepsy surgery within 6 months priorto Screening.

6. Concomitant use of fenfluramine.

7. Prior or concomitant use of lorcaserin.