for people ages 2-56 (full criteria)
at San Francisco, California and other locations
study started
completion around
Principal Investigator
by Joseph Sullivan
Headshot of Joseph Sullivan
Joseph Sullivan



The main aim of the study is to learn if soticlestat, when given as an add-on therapy, reduces the number of seizures in children and adults with Dravet Syndrome (DS) or Lennox-Gastaut Syndrome (LGS).

Participants will receive their standard anti-seizure therapy, plus tablets of soticlestat. There will be scheduled visits and follow-up phone calls throughout the study.

Official Title

A Phase 3, Prospective, Open-Label, Multisite, Extension of Phase 3 Studies To Assess the Long-Term Safety and Tolerability of Soticlestat as Adjunctive Therapy in Subjects With Dravet Syndrome or Lennox-Gastaut Syndrome (ENDYMION 2)


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.


Dravet Syndrome (DS), Lennox Gastaut Syndrome (LGS), Drug Therapy, Myoclonic Epilepsies, Lennox Gastaut Syndrome, Syndrome, Soticlestat


You can join if…

Open to people ages 2-56

  1. Participant must have:
  2. Been previously enrolled in a phase 3 soticlestat clinical study.

You CAN'T join if...

  1. Unstable, clinically significant neurologic (other than the disease being studied), psychiatric, cardiovascular, ophthalmologic, pulmonary, hepatic, renal, metabolic, gastrointestinal, urologic, immunologic, hematopoietic, endocrine disease, malignancy including progressive tumors, or other abnormality that may impact the ability to participate in the study or that may potentially confound the study results. It is the responsibility of the investigator to assess the clinical significance; however, consultation with the medical monitor may be warranted.
  2. Abnormal and clinically significant ECG abnormality at Visit 1 including QT interval with Fridericia correction method (QTcF) >450 milliseconds (ms) confirmed with a repeat ECG using manual measurement of QTcF.
  3. Participant is considered by the investigator to be at imminent risk of suicide or injury to self, others, or property. Participants who have positive answers on item numbers 4 or 5 on the CSSRS before dosing are excluded. This scale will only be administered to participants aged ≥6 years.


  • University of California Benioff Children's Hospital accepting new patients
    San Francisco California 94143 United States
  • David Geffen School of Medicine at UCLA not yet accepting patients
    Los Angeles California 90095 United States
  • Cook Children's Medical Center - Jane and John Justin Neurosciences Center accepting new patients
    Fort Worth Texas 76104 United States

Lead Scientist at UCSF

  • Joseph Sullivan
    Professor, Neurology, School of Medicine. Authored (or co-authored) 53 research publications


accepting new patients
Start Date
Completion Date
More about this study
Phase 3 research study
Study Type
Expecting 400 study participants
Last Updated