Inclusion Criteria:  Has documented clinical diagnosis of Dravet Syndrome (DS). Has ≥4 convulsive seizures in each 1-month period in the 3 months before screening based on the historical information and has ≥4 convulsive seizures per 28 days during the 4- to 6-week prospective baseline period. Weighs ≥10 kg at the screening visit (Visit 1). Failure to control seizures despite appropriate trials of at least 2 ASMs based on historical information and is currently on an antiseizure therapy or other treatment options considered as SOC. Currently taking 0 to 4 antiseizure medication (ASMs) at stable doses for at least 4 weeks before the screening visit (Visit 1); benzodiazepines used chronically (daily) to treat seizures are considered ASMs. ASM dosing regimen must remain constant throughout the study.  Exclusion Criteria:  1. Unstable, clinically significant neurologic (other than the disease being studied), psychiatric, cardiovascular, ophthalmologic, pulmonary, hepatic, renal, metabolic, gastrointestinal, urologic, immunologic, hematopoietic, endocrine disease, malignancy including progressive tumors, or other abnormality that may impact the ability to participate in the study or that may potentially confound the study results. It is the responsibility of the investigator to assess the clinical significance; however, consultation with the medical monitor may be warranted.