Skip to content
Clinical Trials – home

Rare diseases

Investigational molecules

Locations

Our offerNewsroom

Not recruitingRare disease

Study on Long-Term Safety of Soticlestat for Adults and Children with Developmental Epileptic Encephalopathies

Verified siteInvestigationalNo placebo
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying the long-term safety and tolerability of a medication called soticlestat (also known by its code name TAK-935). The study is designed for individuals with certain types of rare epilepsies, specifically Developmental Epileptic Encephalopathies. These include conditions such as Dravet Syndrome, Lennox Gastaut Syndrome, CDKL5 Deficiency Disorder, and Chromosome 15 Duplication Syndrome. The purpose of the study is to see how well soticlestat can be tolerated when used alongside other treatments for seizures, such as anti-seizure medications, a vagal nerve stimulator, or special diets like the ketogenic or modified Atkins diet.

Participants in this study will take soticlestat in the form of a tablet, which is taken orally. The study will follow participants over a period to monitor their health and any side effects they might experience. The maximum daily dose of soticlestat is 600 milligrams, and the treatment period can last up to 96 weeks. Throughout the study, researchers will keep track of any adverse events, changes in behavior, and other health indicators to ensure the safety of the participants.

This study is an extension of previous research, meaning that participants have already been involved in earlier studies of soticlestat. The goal is to gather more information about how the medication affects people over a longer period. By doing so, researchers hope to better understand the potential benefits and risks of using soticlestat as a treatment for these rare epileptic conditions.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, you will be informed about the purpose and procedures involved. This study aims to assess the long-term safety and tolerability of soticlestat as an additional therapy for certain types of epilepsy.

    You will be required to have participated in a previous soticlestat study and meet specific conditions to be eligible.

  2. Step 2

    Medication administration

    You will receive soticlestat in the form of a tablet, which you will take orally. The dosage and frequency will be determined by the study team based on your individual needs and previous study participation.

    The medication will be administered alongside at least one other anti-seizure therapy, which may include anti-epileptic drugs, a vagal nerve stimulator, or a special diet like the ketogenic or modified Atkins diet.

  3. Step 3

    Regular assessments

    Throughout the study, you will undergo regular assessments to monitor your health and the effects of the medication. These assessments will include checking vital signs, body weight, and conducting laboratory tests.

    Behavioral and functional measures will be evaluated using specific scales, such as the Vineland Adaptive Behavior Scale and the Aberrant Behavior Checklist.

  4. Step 4

    Monitoring and reporting

    You will be asked to report any side effects or changes in your condition. The study team will monitor the incidence of adverse events and any significant changes in clinical safety tests.

    Your seizure frequency will be tracked, and any changes from the baseline will be recorded to assess the effectiveness of the treatment.

  5. Step 5

    Completion of the study

    The study is expected to continue until May 2026. Upon completion, you will have a final assessment to evaluate the overall impact of the treatment.

    The results will contribute to understanding the long-term safety and benefits of soticlestat for individuals with developmental epileptic encephalopathies.

Who can join the trial?

6 criteria

  • Participants must have been part of a previous study involving the drug soticlestat.
  • Participants should have either successfully completed a previous soticlestat study or received at least 10 weeks of treatment with soticlestat in a previous study.
  • Participants must not have experienced any serious or severe side effects from the study drug that would make it unsafe to continue using it, according to the study doctor or sponsor.
  • In the opinion of the study doctor, participants should have the potential to benefit from taking soticlestat.
  • Participants can be of any gender.
  • The study includes individuals from vulnerable populations, which means people who might need extra protection or care.

Who cannot join the trial?

5 criteria

  • Patients who have a medical condition other than the specific types of **epileptic encephalopathies** being studied, such as Dravet Syndrome, Lennox Gastaut Syndrome, CDKL5 Deficiency Disorder, Chromosome 15 Duplication Syndrome, or other adult developmental and epileptic encephalopathies (DEEs).
  • Patients who are not currently using at least one **anti-seizure therapy**. This includes medications specifically for seizures, a device called a **vagal nerve stimulator**, or special diets like the **ketogenic diet** or **modified Atkins diet**.
  • Patients who are not within the specified age range for the study.
  • Patients who are not willing or able to follow the study procedures.
  • Patients who have any other medical condition or situation that the study doctors believe would make it unsafe or inappropriate for them to participate.
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.

We usually reply within a few days

Verified sites

All sites with verified contact details – recruitment status may not be available; ask directly

Trial locations

Where you can join this trial

Countries are shaded by recruitment status. Click a recruiting country to ask about joining there.

Not recruiting
Not finding your country?

Not sure what to do next?

Joining a clinical trial can seem overwhelming. We guide you step by step, so you know exactly what to expect and how we support you through the process.

See the full process and FAQ

Investigated drugs

Soticlestat (TAK-935) is a medication being studied for its potential to help people with certain types of epilepsy, which are conditions that cause frequent seizures. In this trial, soticlestat is used alongside other treatments that patients are already taking for their epilepsy. The goal is to see if soticlestat can be safely used over a long period and if it is well-tolerated by patients. This means researchers want to know if patients can take it without experiencing too many side effects. Soticlestat is being tested in people with specific rare forms of epilepsy, such as Dravet Syndrome and Lennox Gastaut Syndrome, to see if it can help reduce their seizures when used with their current treatments.

What is already known about the treatment

Soticlestat – Soticlestat is administered orally and is being studied as an additional treatment for people with certain types of epilepsy, such as Dravet Syndrome and Lennox Gastaut Syndrome. It is currently in clinical trials to evaluate its long-term safety and how well people tolerate it when used alongside other seizure treatments. Soticlestat works by targeting specific enzymes in the brain to help reduce the frequency of seizures. It is classified as an investigational antiepileptic drug, meaning it is still being researched and is not yet widely available for general medical use.

Investigated diseases

  • Dravet Syndrome

    Dravet Syndrome is a severe form of epilepsy that begins in infancy. It is characterized by prolonged seizures that are often triggered by fever or hot temperatures. As the child grows, other types of seizures may develop, including myoclonic and absence seizures. The condition can lead to developmental delays and cognitive impairment. Over time, individuals may experience difficulties with balance and coordination. Behavioral issues and sleep disturbances are also common as the disease progresses.

  • Lennox-Gastaut Syndrome

    Lennox-Gastaut Syndrome is a complex, rare form of epilepsy that typically appears in early childhood. It is marked by multiple types of seizures, including tonic and atonic seizures, which can lead to sudden falls. Cognitive dysfunction and developmental delays are common, often worsening over time. The condition is also associated with behavioral problems and learning difficulties. Seizures in Lennox-Gastaut Syndrome are often resistant to treatment and can be frequent and severe. The syndrome can significantly impact daily life and development.

  • CDKL5 Deficiency Disorder

    CDKL5 Deficiency Disorder is a rare genetic condition that causes severe neurodevelopmental impairment. It is characterized by early-onset seizures, often beginning in infancy. The disorder leads to significant developmental delays, affecting motor skills, communication, and cognitive abilities. Individuals may experience difficulties with feeding and have poor muscle tone. As the disorder progresses, it can result in scoliosis and other orthopedic issues. Behavioral challenges, such as irritability and sleep disturbances, are also common.

  • Chromosome 15 Duplication Syndrome

    Chromosome 15 Duplication Syndrome is a genetic disorder caused by an extra copy of a segment of chromosome 15. It is associated with developmental delays, intellectual disability, and autism spectrum disorder. Seizures are common and can vary in type and severity. The condition often leads to hypotonia, or reduced muscle tone, and may affect motor skills. Individuals may also experience behavioral issues, such as anxiety and hyperactivity. The syndrome can impact communication and social interaction abilities.

  • Developmental and Epileptic Encephalopathies (DEEs)

    Developmental and Epileptic Encephalopathies are a group of severe epilepsy disorders that begin in infancy or early childhood. They are characterized by frequent and severe seizures that can lead to developmental regression or delays. The condition affects cognitive, motor, and behavioral development, often resulting in significant impairment. Seizures in DEEs are typically resistant to treatment and can vary widely in type. Over time, individuals may experience a decline in skills they previously acquired. The condition can also lead to sleep disturbances and other neurological issues.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2022-502801-13-00Protocol codeTAK-935-18-001Estimated enrolment156 patientsSponsorTakeda Development Center Americas Inc.

sourced from the EU Clinical Trials Register and site verification

Want to learn more about this trial or check if you can participate?

Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.