• Diagnosis of DS must fulfill all of the following criteria:

‣ Participants with seizure onset age \>1 and \<20 months

⁃ The participant has a history of at least 1 of the following seizure type(s): prolonged generalized tonic-clonic, hemiclonic, myoclonic, tonic, atonic, atypical absence, focal impaired awareness, nonconvulsive status epilepticus

• The participant has a current occurrence of at least 1 of the following countable motor seizure types: generalized tonic-clonic, tonic (bilateral), clonic (bilateral), atonic (bilateral) with truncal/leg involvement, focal motor (including hemiclonic), and focal to bilateral tonic-clonic

• The participant has demonstrated an average of at least 4 countable motor seizures per month for the 3 months prior to Screening.

• The participant has been taking 1 to 4 antiseizure medications (ASMs) at a stable dose for at least 4 weeks prior to Screening.

• The participant, parent, or caregiver is willing and able (in the judgment of the investigator) to comply with completion of the diaries throughout the study.

• The participant must be willing and able to provide written informed consent.