This study focuses on Developmental and Epileptic Encephalopathies (DEE), a group of severe conditions that cause frequent seizures and affect brain development. The research evaluates a new medication called LP352 (bexicaserin), which is given as an oral solution. The study aims to determine if this medication can effectively reduce seizures in children and adults with this condition.

The study uses LP352 or placebo in the form of an oral solution, which can be given through the mouth or through a feeding tube. Participants will take the medication or placebo for approximately 17 weeks. The maximum daily dose of the medication is 36 milligrams, and participants will continue taking their regular anti-seizure medications during the study.

The research focuses on people who experience various types of seizures, including tonic seizures (stiffening of muscles), atonic seizures (sudden loss of muscle strength), focal seizures (seizures that start in one part of the brain), and tonic-clonic seizures (convulsions with both stiffening and jerking). The study particularly includes people with Lennox-Gastaut Syndrome, a severe form of epilepsy that begins in childhood.