A Phase 2, Prospective, Interventional, Open-Label, Multisite, 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)

This study is open to both adults and children aged 18 years and above, regardless of gender. You would generally be considered for this study if you have already participated in an earlier study involving the medication soticlestat (TAK-935) and have certain types of severe epilepsy.

The specific epilepsy conditions include Dravet Syndrome, Lennox-Gastaut Syndrome, CDKL5 Deficiency Disorder, Chromosome 15 Duplication Syndrome, or other similar severe epilepsies in adults. The main idea is that this study is a continuation for people who have already started treatment with this specific medicine in a past trial.

If you take part in this study, you'll continue to receive the study medication, soticlestat, as an add-on to any other epilepsy medicines you're already taking. You would have regular check-ups which involve various assessments. These assessments will include keeping track of any side effects you might experience, and looking at changes in your behaviour and how you manage everyday tasks. Doctors will also check your general health through blood tests, measurements like blood pressure and heart rate, body weight, and heart traces (ECGs).

There will also be questionnaires to understand your mood and behaviour. For children aged 6 and over, there are specific assessments for behaviour and, if aged 6 or over, questions about thoughts of self-harm. The study will also track how often seizures occur. The total duration of your participation will depend on how long the study continues, as it's an 'extension' study designed to gather long-term information.