for people ages 2-35 (full criteria)
at San Francisco, California and other locations
study started
estimated completion



The aims of the study are: - to learn if soticlestat, when given as add-on therapy, reduces the number of major motor drop seizures in children, teenagers, and adults with Lennox-Gastaut Syndrome. - to assess the safety profile of soticlestat when given in combination with other therapies. Participants will receive their standard anti-seizure therapy, plus either tablets of soticlestat or placebo. A placebo looks just like soticlestat but will not have any medicine in it. Participants will take soticlestat or placebo for 16 weeks, followed by a gradual dose reduction for 1 week. Then, participants will be followed up for 2 weeks.

Official Title

A Multicenter, Randomized, Double-Blind, Placebo-Controlled, Parallel Group Study to Evaluate the Efficacy, Safety, and Tolerability of Soticlestat as Adjunctive Therapy in Pediatric and Adult Subjects With Lennox-Gastaut Syndrome (LGS)


The drug being tested in this study is called soticlestat (TAK-935). Soticlestat will be assessed for efficacy, safety, and tolerability in pediatric and adult participants with Lennox-Gastaut syndrome (LGS). The study will enroll approximately 234 patients. Participants will be randomly assigned (by chance, like flipping a coin) in a 1:1 ratio to receive standard of care (SOC) plus one of the following adjunctive therapies which will remain undisclosed to the participant and study doctor during the study (unless there is an urgent medical need): 1. Soticlestat 2. Placebo (dummy inactive pill - this is a tablet/mini-tablet that looks like the study drug but has no active ingredient) Participants will receive soticlestat or matching placebo based on their weight in the 4-week Titration Period. Following the Titration Period, participants will continue to receive the same dose in the Maintenance Period. The dose will then be down-tapered. This multi-center trial will be conducted worldwide. The overall time to participate in the study will be from 22-25 weeks. Participants will then have an option to either enter the Open-label Extension (OLE) Study or discontinue. If participants discontinue, they will be followed-up for safety.


Lennox Gastaut Syndrome (LGS) Drug therapy Lennox Gastaut Syndrome Syndrome Soticlestat


You can join if…

Open to people ages 2-35

  1. Has documented clinical diagnosis of Lennox-Gastaut Syndrome (LGS).
  2. Has ≥8 major motor drop (MMD) seizures each month in the 3 months prior to Screening based on the historical information and has ≥8 MMD seizures per 28 days during the 4 to 6 week prospective Baseline Period.
  3. Weighs ≥10 kg at the Screening Visit (Visit 1).
  4. Failure to control seizures despite appropriate trials of at least 2 anti-seizure medications (ASMs) based on historical information, and is currently on an anti-seizure therapy or other treatment options considered as standard of care (SOC).
  5. Currently taking 0 to 3 ASMs at stable doses for at least 4 weeks before the Screening Visit (Visit 1); ASM dosing regimen must remain constant throughout the study.

You CAN'T join if...

  1. Admitted to a medical facility and intubated for treatment of status epilepticus 2 or more times in the 3 months immediately before Screening (Visit 1). Status epilepticus is defined as continuous seizure activity lasting longer than 5 minutes or repeated seizures without return to Baseline in between seizures.
  2. 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.
  3. Considered by the investigator to be at imminent risk of suicide or injury to self, others, or property, or the participant has attempted suicide within 12 months before the Screening Visit (Visit 1). Participants who have positive answers on item numbers 4 or 5 on the Columbia suicide severity rating scale (C-SSRS) before randomization/dosing (Visit 2) are excluded. This scale will only be administered to participants aged ≥6 years.


  • University of California Benioff Children's Hospital in progress, not 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


accepting new patients at some sites,
but this study is not currently recruiting here
Start Date
Completion Date
Related Info
Phase 3 Lennox-Gastaut Syndrome Research Study
Study Type
Expecting 234 study participants
Last Updated