A Study of Soticlestat in Adults and Children With Rare Epilepsies

A Phase 2, Prospective, Interventional, Open-Label, Multi-Site, Extension Study to Assess the Long-Term Safety and Tolerability of Soticlestat (TAK-935) as Adjunctive Therapy in Subjects With Developmental Epileptic Encephalopathies Including Dravet Syndrome, Lennox Gastaut Syndrome, CDKL5 Deficiency Disorder, and Chromosome 15 Duplication Syndrome (ENDYMION 1)

The main aim is to assess the long-term safety and tolerability of soticlestat when used along with other anti-seizure treatment.

Participants will receive soticlestat twice a day. Participants will visit the study clinic every 2-6 months throughout the study.

Study treatments may continue as long as the participant is receiving benefit from it.

The drug being tested in this study is called soticlestat (TAK-935). This global, open-label extension (OLE) study will assess the long-term safety and tolerability of soticlestat in participants with developmental and epileptic encephalopathy (DEE) who participated in previous short-term efficacy/safety studies of soticlestat. All participants will receive Soticlestat treatment.

Participants who rollover from previous blinded study will undergo up to 2 weeks of Dose Optimization Period (depending on the previous study) followed by Maintenance Period. Participants who rollover from an open-label study will continue on their current dose until development is stopped by the sponsor, or the product is approved for marketing, or at any time at the discretion of the sponsor. There will be a 4-week Safety Follow-up Period after the last dose in Maintenance Period, including a 2-week dose Tapering Period.

Inclusion Criteria:

1. Participants must have participated in a previous soticlestat study and meet one of the following conditions:

   • Successfully completed a soticlestat clinical study.
   • Received at least 10 weeks of treatment with the study drug in an antecedent placebo-controlled blinded soticlestat clinical study and the participant did not have a serious or severe AE that, in the investigator's or sponsor's opinion, was related to the study drug and would make it unsafe for the participant to continue receiving the study drug.

2. In the opinion of the investigator, the participant has the potential to benefit from the administration of soticlestat

Exclusion Criteria:

1. Clinically significant disease, that, in the investigator's opinion, precludes study participation.
2. Enrollment in any other clinical trial involving an investigational drug, device, or treatment in the past 90 days (with the exception of an antecedent study involving Soticlestat).
3. Participant is currently pregnant or breastfeeding or is planning to become pregnant during the study or within 30 days of the last study drug administration.
4. Suicide attempt within the last year, at significant risk of suicide (either in the opinion of the investigator or defined as 'yes' to suicidal ideation question 4 or 5 on the C-SSRS at Screening) or appearing suicidal per investigator judgment.