A Study of Soticlestat as an Add-on Therapy in Children and Adults With Dravet Syndrome or Lennox-Gastaut Syndrome

Number of Participants With At Least One Treatment Emergent Adverse Event (TEAE) [Time Frame: Up to 4 years]

Change from Baseline in Columbia-Suicide Severity Rating Scale (C-SSRS) Score [Time Frame: Up to 4 years]

Change from Baseline in Body Weight for All Age Groups [Time Frame: Up to 4 years]

Change from Baseline in Height for All Age Groups [Time Frame: Up to 4 years]

Absolute Value for Tanner Stage for Children 6 to 17 Years of Age During the Study [Time Frame: Up to 4 years]

Absolute Value for Insulin-like Growth Factor 1 (IGF-1) for Children 2 to 17 Years of Age During the Study [Time Frame: Up to 4 years]

Percent Change from Baseline in Total Seizure Frequency per 28 Days for DS and LGS Participants [Time Frame: Up to 4 years]

Percent Change from Baseline in Convulsive Seizure Frequency per 28 Days in DS Cohort [Time Frame: Up to 4 years]

Percent Change from Baseline in Major Motor Drop (MMD) Seizure Frequency per 28 Days in LGS Cohort [Time Frame: Up to 4 years]

Clinical Global Impression of Improvement (CGI-I) Score [Time Frame: Up to 4 years]

Caregiver Global Impression of Improvement (Care GI-I) Score [Time Frame: Up to 4 years]

CGI-I Seizure Intensity and Duration Score [Time Frame: Up to 4 years]

CGI-I Nonseizure Symptoms Score [Time Frame: Up to 4 years]

Change in Quality of Life Inventory-Disability (QI-Disability) Score [Time Frame: Up to 4 years]