• Subject must have a documented history of Lennox-Gastaut syndrome by:

∙ Evidence of more than one type of seizure, of which at least one should be an atonic or tonic seizure

‣ History of an electroencephalogram (EEG) reporting diagnostic criteria for LGS (abnormal background activity accompanied by slow, spike and wave pattern \<3.0 Hz)

‣ History of developmental delay

• Male or female subjects

• Subjects must be age 4-55 years at the time of consent/assent

• Must have been \<11 years old at the onset of LGS

• Subjects must have experienced at least 2 drop seizures with potential to fall (tonic, atonic, tonic-clonic) during the 4-week Baseline period preceding randomization (minimum of 4 drop seizures in the first two weeks and 4 in the last two weeks). Drop seizures are defined as a seizure involving the entire body, trunk, or head that led or could have led to a fall, injury, slumping in a chair, or hitting the subject's head on a surface. All drop seizure types must be countable (either as isolated seizures or as countable isolated seizures in a cluster).

• Subjects must have been receiving 1 to 4 concomitant anti-seizure medications (ASMs) at a stable dose for at least 4 weeks before Visit 1

• If not taking Epidiolex, subjects may take other approved cannabidiol or over the counter cannabidiol products. If taking cannabidiol other than Epidiolex, consult Medical Monitor to determine if it counts as a concomitant ASM.

• Dietary therapy and any CNS stimulator settings must be stable for 4 weeks prior to baseline and maintain stable regimen throughout the study. The dietary therapy and CNS stimulators are not counted as an ASM.

• Parents or caregivers must be able to keep accurate seizure diaries

⁃ Subject is either not of childbearing potential, defined as premenarchal, postmenopausal for at least 1 year or surgically sterile (bilateral tubal ligation, bilateral oophorectomy, or hysterectomy), if of childbearing potential, must comply with an acceptable method of birth control during the study, for at least 4 weeks prior to study entry and for 4 weeks following completion of the study, if able.

⁃ Subject and/or caregiver(s)/legal representative must be willing and able to give informed assent/consent for participation in the study

⁃ Subject and their caregiver must be willing and able (in the investigator's opinion) to comply with all study requirements

⁃ History of COVID-19 vaccination is permitted