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

The drug being tested in this study is called soticlestat (TAK-935). Soticlestat administered long-term in pediatric and adult participants who participated in an antecedent soticlestat Phase 3 clinical study will be assessed for additional safety and tolerability data along with efficacy analysis, as well as palatability and acceptability of soticlestat in the pediatric population.

The study will enroll approximately 400 participants.

All participants will receive soticlestat based on their weight in the 2-week Titration Period (for participants who roll over from an antecedent double-blind study). Following the Titration Period, participants will continue to receive the same dose in the Maintenance Period. At the end of maintenance period, the dose will be down-tapered (unless already at the lowest dose) and then stopped. Participants not tolerating minimum dose of 100 mg twice a day (BID) will be discontinued from the study.

This multi-center trial will be conducted worldwide. The overall time to participate in the study will be approximately 4 years, or until the study is stopped at the discretion of the sponsor, or the product is approved and launched. Participants who discontinue study drug treatment before the completion of the study, will continue to be followed per protocol and maintain a daily seizure diary until the final follow-up phone call.