A Study of Soticlestat as an Add-on Therapy in Children and Young Adults With Dravet Syndrome

Study Overview
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Brief Summary
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The main aim of the study is to learn if soticlestat, when given as an add-on therapy, reduces the number of convulsive seizures in children and young adults with DS. Participants will receive their standard antiseizure therapy, plus either a tablet of soticlestat or placebo for 16 weeks. A placebo looks just like soticlestat but will not have any medicine in it. Participants may continue treatment in an extension study, based on the extension study's entry criteria. Those that want to stop treatment will have a gradual dose reduction during 1 week and then be followed up for 2 weeks.

Detailed Description
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The drug being tested in this study is called soticlestat (TAK-935). Soticlestat as an adjunctive therapy will be assessed for efficacy, safety, and tolerability in pediatric and adult participants with DS. The study will enroll approximately 142 pediatric and young adult patients. Participants will be randomized at a 1:1 ratio to receive standard of care (SOC) plus one of the following adjunctive therapies: Soticlestat or Placebo The total daily dose of study drug will be calculated based on body weight in the 4 weeks Titration Period. Following the Titration Period, participants will continue to receive the same dose in the 12-weeks Maintenance Period. This multi-center trial will be conducted worldwide. The overall time to participate in the study will be from 22-25 weeks. At the end of the treatment period, participants have the option to either complete the study and taper off the investigational product or to enter the OLE if they meet eligibility requirements. If participants discontinue, they will be followed-up on phone call approximately 14 days after the last dose of study drug for safety.

Official Title
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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 Young Adult Subjects With Dravet Syndrome (DS)

Conditions
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Dravet Syndrome (DS)

Intervention / Treatment
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* Drug: Soticlestat
* Drug: Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Has documented clinical diagnosis of DS. Had ≥12 convulsive seizures over 12 weeks before screening based on the historical information and has had ≥4 convulsive seizures per 28 days during the 4- to 6-week prospective baseline period. Weighs ≥10 kg at the screening visit (Visit 1). Failure to control seizures despite appropriate trials of at least 1 ASM based on historical information and is currently on an antiseizure therapy or other treatment options considered as SOC. Artisanal cannabidiols are allowed at a stable dose for at least 4 weeks before the screening visit (Visit 1); the dosing regimen and manufacturer should remain constant throughout the study (Artisanal cannabidiols will not be counted as ASMs.). Currently taking 0 to 4 ASMs at stable doses for at least 4 weeks before the screening visit (Visit 1); benzodiazepines used chronically (daily) to treat seizures are considered ASMs. Fenfluramine and cannabidiol (Epidiolex) are allowed where available and should be counted as an ASM. ASM dosing regimen must remain constant throughout the study. Exclusion Criteria: 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.

Ages Eligible for Study
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Minimum Age: 2 Years
Maximum Age: 21 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Soticlestat<br>Participants weighing <45kg: Soticlestat, mini-tablets, at the dose of 40mg to 200mg, orally or via gastrostomy tube (G-tube) or low-profile gastric tube (MIC-KEY button) or jejunostomy tube (J-tube), twice daily (BID) based on the body weight up to 4 weeks in Titration Period. Participants will continue to receive dose that they are on at the end of Titration Period, for 12 weeks in Maintenance Period. The total duration of the treatment will be up to 16 weeks (Treatment Period). The dose will be tapered down if participants decide to discontinue the treatment. Participants weighing ≥45kg: Soticlestat mini-tablets or tablets with a starting dose of 100mg BID followed by 200 mg BID and, then 300mg BID, up to 4 weeks in Titration Period. Participants will continue to receive 300mg BID for 12 weeks in the Maintenance Period. The total duration of the treatment will be up to 16 weeks (Treatment Period). The dose will be tapered down if participants decide to discontinue the treatment. | Drug: Soticlestat<br>* Soticlestat mini-tablets or tablets.<br>* Other names: TAK-935;|
| Placebo Comparator: Placebo<br>Soticlestat placebo-matching mini-tablets or tablets, orally or via G-tube or MIC-KEY button or J-tube, BID, up to 4 weeks in the Titration Period. Participants will continue to receive the soticlestat placebo-matching mini-tablets or tablets for 12 weeks in the Maintenance Period. The total duration of the treatment will be up to 16 weeks. Soticlestat matching tapering will be done to maintain the blind if participants decide to discontinue the treatment. | Drug: Placebo<br>* Soticlestat placebo-matching mini-tablets or tablets.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percent Change From Baseline in Convulsive Seizure Frequency per 28 days During the Full Treatment Period | Convulsive seizure frequency per 28 days is defined as total number of convulsive seizures reported during the period divided by number of days during the period seizures were assessed multiplied by 28. Percent change from Baseline will be defined as (frequency of seizures per 28 days during Treatment Period - frequency of seizures per 28 days at Baseline) divided by the frequency of seizures per 28 days at Baseline multiplied by 100. | Baseline up to Week 16 | 
| Percent Change From Baseline in Convulsive Seizure Frequency per 28 days During the Maintenance Period (EMA Region Specific) | Convulsive seizure frequency per 28 days is defined as total number of convulsive seizures reported during the period divided by number of days during the period seizures were assessed multiplied by 28. Percent change from Baseline will be defined as (frequency of seizures per 28 days during Maintenance Period - frequency of seizures per 28 days at Baseline) divided by the frequency of seizures per 28 days at Baseline multiplied by 100. This outcome measure is European Medicines Agency (EMA) specific. | Baseline up to Week 16 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percentage of Responders During Maintenance Period | Responders are defined as those with ≥50% reduction from baseline in convulsive seizures during the Maintenance Period. | Baseline up to Week 16 | 
| Percentage of Responders During the Full Treatment Period | Responders are defined as those with ≥50% reduction from baseline in convulsive seizures during the full Treatment Period. | Baseline up to Week 16 | 
| Percentage of Participants with ≤0%, >0% to ≤25%, >25% to ≤50%, >50% to ≤75%, and >75% to ≤100% Reduction in Convulsive Seizures in a Cumulative Response Curve |  | Baseline up to Week 16 | 
| Caregiver Global Impression of Improvement (Care GI-I) Score | The Care GI-I is a 7-point Likert scale that the caregiver uses to rate improvement in overall seizure control, behavior, safety and tolerability after the initiation of study drug relative to Baseline (before treatment with study drug). The participant will be rated as follows: 1 (very much improved), 2 (much improved), 3 (minimally improved), 4 (no change), 5 (minimally worse), 6 (much worse), and 7 (very much worse). The parent/caregiver will complete the Care GI-I via interview. Higher score will indicate worse symptoms. | Baseline up to Week 16 | 
| Clinical Global Impression of Improvement (CGI-I) Score | The CGI-I Clinician is a 7-point Likert scale that the investigator uses to rate a participant's change (improvement) in overall seizure control, behavior, safety and tolerability, after the initiation of study drug relative to Baseline (before treatment with study drug). The participant will be rated as follows: 1 (very much improved), 2 (much improved), 3 (minimally improved), 4 (no change), 5 (minimally worse), 6 (much worse), and 7 (very much worse). Higher score will indicate worse symptoms. | Baseline up to Week 16 | 
| CGI-I Nonseizure Symptoms Score | The CGI-I nonseizure symptoms instrument is a series of single-item assessments that the investigator uses to rate improvement in the symptoms and impacts in select nonseizure domains since initiating the study drug. The participant will be rated on 7-point scale by the investigator as follows: 1 (very much improved), 2 (much improved), 3 (minimally improved), 4 (no change), 5 (minimally worse), 6 (much worse), and 7 (very much worse). At baseline, a symptoms form is completed by the clinician in collaboration with the primary caregiver to assess the participants status based on the presence of any nonseizure symptoms. Higher score will indicate worse symptoms. | Baseline up to Week 16 | 
| Change in Quality of Life Inventory-Disability (QI-Disability) Score | The QI-Disability tool is a parent/caregiver-reported questionnaire that evaluates quality of life in children with intellectual disabilities. It contains 32 items covering 6 domains of quality of life: physical health, positive emotions, negative emotions, social interaction, leisure and the outdoors, and independence. Scores are from a 5-point Likert scale and then are transformed to a scale of 0 to 100. Possible scores range from 0-100, with higher scores indicating better quality of life. | Baseline up to Week 16 | 
| CGI-I Seizure Intensity and Duration Score | The CGI-I seizure Intensity and duration instrument is used by the parent/caregiver to rate improvement in intensity and/or duration of the most impactful seizures from the first assessment. The participant's symptoms will be rated on 7-point scale as follows: 1 (very much improved), 2 (much improved), 3 (minimally improved), 4 (no change), 5 (minimally worse), 6 (much worse), and 7 (very much worse). Higher score will indicate worse symptoms. | Baseline up to Week 16 | 
| Percent Change From Baseline in Frequency of all Seizures per 28 Days During the Maintenance Period | Seizure frequency per 28 days is defined as total number of seizures reported during the period divided by number of days during the period seizures were assessed multiplied by 28. Percent change from Baseline is defined as (frequency of seizures per 28 days during Maintenance Period - frequency of seizures per 28 days at Baseline) divided by the frequency of seizures per 28 days at Baseline multiplied by 100. | Baseline up to Week 16 | 
| Percent Change From Baseline in Frequency of all Seizures per 28 Days During the Full Treatment Period | Seizure frequency per 28 days is defined as total number of seizures reported during the period divided by number of days during the period seizures were assessed multiplied by 28. Percent change from Baseline is defined as (frequency of seizures per 28 days during Treatment Period - frequency of seizures per 28 days at Baseline) divided by the frequency of seizures per 28 days at Baseline multiplied by 100. | Baseline up to Week 16 | 
| Percent Change From Baseline in Convulsive Seizure Frequency per 28 days During the Maintenance Period | Convulsive seizure frequency per 28 days is defined as total number of convulsive seizures reported during the period divided by number of days during the period seizures were assessed multiplied by 28. Percent change from Baseline is defined as (frequency of seizures per 28 days during Maintenance Period - frequency of seizures per 28 days at Baseline) divided by frequency of seizures per 28 days at Baseline multiplied by 100. | Baseline up to Week 16 | 
| Change from Baseline in Percentage of Convulsive Seizure-free Days | Convulsive seizure-free days will be defined as number of days a participant remained convulsive seizure free after initiation of the treatment. | Baseline up to Week 16 | 
| Longest Convulsive Seizure-free Interval. | Longest convulsive seizure-free interval will be defined as the longest time period that the participant remained convulsive seizure free after initiation of the treatment. | Baseline up to Week 16 | 
| Number of Days When Rescue Antiseizure Medication (ASM) is Used |  | Baseline up to Week 16 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Drug Therapy