Study to Investigate LP352 in Subjects With Developmental and Epileptic Encephalopathies

Key Inclusion Criteria: 1. Male or non-pregnant, non-lactating female, age 12 to 65 years 2. Diagnosis of Dravet syndrome, Lennox-Gastaut syndrome, or other developmental and epileptic encephalopathy 3. Has a minimum number of seizures per 4-week period while taking 1 to 4 anti-seizure medications 4. All medications and epilepsy interventions must be stable for 4 weeks before screening and are expected to remain stable during the study 5. The patient/parent/caregiver is able and willing to attend study visits, complete the diary and take study drug as instructed Key Exclusion Criteria: 1. Current or past history of cardiovascular or cerebrovascular disease, such as cardiac valvulopathy, myocardial infarction, stroke, pulmonary arterial hypertension or abnormal blood pressure 2. Has glaucoma, renal impairment, liver disease or any other medical condition that would affect study participation or pose a risk to the subject 3. Current or recent history of moderate or severe depression, anorexia nervosa, bulimia or at risk of suicidal behavior 4. Currently taking anorectic agents, monoamine oxidase inhibitors; serotonin agonists or antagonists including fenfluramine, atomoxetine, vortioxetine, or other medications for weight loss 5. Positive test result on the drug screen, except tetrahydrocannabinol (THC) for patients taking prescribed cannabidiol