An Open-Label Study to Investigate the Safety of Single and Multiple Ascending Doses in Children and Adolescents With Dravet Syndrome

Inclusion Criteria: * Diagnosis of Dravet Syndrome (DS) with onset of recurrent focal motor or hemiconvulsive or generalized tonic-clonic seizures prior to 12 months of age, which are often prolonged and triggered by hyperthermia. * No history of causal MRI lesion * No other known etiology * Normal development at seizure onset. * Documented pathogenic, likely pathogenic variant, or variant of uncertain significance in the SCN1A gene associated with DS. * Use of at least 2 prior treatments for epilepsy that either had lack of adequate seizure control (requiring an additional AED) or had to be discontinued due to an AE(s). * Currently taking at least one AED at a dose which has been stable for at least 4 weeks prior to Screening. * Stable epilepsy medications or interventions for epilepsy (including ketogenic diet or vagal nerve stimulator) for at least 4 weeks prior to Screening. Exclusion Criteria: * Known pathogenic mutation in another gene that causes epilepsy * Currently treated with an AED acting primarily as a sodium channel blocker, as maintenance treatment, including: phenytoin, carbamazepine, oxcarbazepine, lamotrigine, lacosamide, or rufinamide. * Clinically significant unstable medical conditions other than epilepsy. * Clinically relevant symptoms or a clinically significant illness in the 4 weeks prior to Screening or prior to dosing on Day 1, other than epilepsy. * History of brain or spinal cord disease (other than epilepsy or DS), or history of bacteri…