| E.1 Medical condition or disease under investigation | 
| E.1.1 | Medical condition(s) being investigated | 
| Epileptic Encephalopathies: Dravet Syndrome, Lennox Gastaut Syndrome, CDKL5 Deficiency Disorder, and Chromosome 15 Duplication Syndrome |  | 
| E.1.1.1 | Medical condition in easily understood language | 
| Epileptic Encephalopathies: Dravet Syndrome, Lennox Gastaut Syndrome, CDKL5 Deficiency Disorder, and Chromosome 15 Duplication Syndrome |  | 
| E.1.1.2 | Therapeutic area | Diseases [C] - Nervous System Diseases [C10] | 
| MedDRA Classification | 
| E.1.2 Medical condition or disease under investigation | 
| 
| E.1.2 | Version | 20.0 |  
| E.1.2 | Level | LLT |  
| E.1.2 | Classification code | 10073682 |  
| E.1.2 | Term | Dravet syndrome |  
| E.1.2 | System Organ Class | 10010331 - Congenital, familial and genetic disorders |  | 
| E.1.2 Medical condition or disease under investigation | 
| 
| E.1.2 | Version | 20.1 |  
| E.1.2 | Level | PT |  
| E.1.2 | Classification code | 10048816 |  
| E.1.2 | Term | Lennox-Gastaut syndrome |  
| E.1.2 | System Organ Class | 10029205 - Nervous system disorders |  | 
| E.1.2 Medical condition or disease under investigation | 
| 
| E.1.2 | Version | 22.1 |  
| E.1.2 | Level | PT |  
| E.1.2 | Classification code | 10083005 |  
| E.1.2 | Term | CDKL5 deficiency disorder |  
| E.1.2 | System Organ Class | 10010331 - Congenital, familial and genetic disorders |  | 
| E.1.2 Medical condition or disease under investigation | 
| 
| E.1.2 | Version | 23.0 |  
| E.1.2 | Level | LLT |  
| E.1.2 | Classification code | 10083952 |  
| E.1.2 | Term | Dup15q syndrome |  
| E.1.2 | System Organ Class | 10010331 - Congenital, familial and genetic disorders |  | 
| E.1.3 | Condition being studied is a rare disease | Yes | 
| E.2 Objective of the trial | 
| E.2.1 | Main objective of the trial | 
| The primary objective of this study is to investigate the effect of TAK-935 on the frequency of motor seizures for patients with Dup15q or CDD during the Maintenance Period. |  | 
| E.2.2 | Secondary objectives of the trial | 
| - To investigate the effect of TAK-935 on frequency of motor seizures for patients with Dup15q or CDD during the Treatment Period (Dose Optimization and Maintenance) - To investigate the proportion of patients considered as treatment responders for patients with Dup15q or CDD throughout the Maintenance Period; treatment responders are defined as those with: Reduction of 25, 50, 75, or 100% in motor seizures from baseline
 - To investigate the effect of TAK-935 on the frequency of motor seizures lasting > 5 minutes for patients with CDD throughout the Treatment Period
 - To investigate the effect of TAK-935 on the percent/frequency of seizure free days in patients with Dup15q or CDD during the Maintenance Period
 - To assess Clinical Global Impression of severity (CGI-S) and the Clinical Global Impression of change (CGI-C) provided by the Investigator, the Caregiver Global Impression of Change (Care GI-C)
 - To investigate the relationship between 24HC level and motor seizure frequency
 |  | 
| E.2.3 | Trial contains a sub-study | No | 
| E.3 | Principal inclusion criteria | 
| 1. Clinical diagnosis of Dup 15q or CDKL5 deficiency disorder. 2. Currently taking 1 to 6 antiepileptic drugs (AEDs) at a stable dose.
 |  | 
| E.4 | Principal exclusion criteria | 
| 1. Two or more episodes of convulsive status epilepticus per 3 months requiring hospitalization and intubation.
 2. Currently receiving a study drug or participated in a clinical study involving another
 investigational product in the previous month.
 |  | 
| E.5 End points | 
| E.5.1 | Primary end point(s) | 
| Percent change from Baseline in motor seizure frequency per 28 days during the Maintenance Period |  | 
| E.5.1.1 | Timepoint(s) of evaluation of this end point | 
| Maintenance Period: Weeks 9 to 20 |  | 
| E.5.2 | Secondary end point(s) | 
| - Percent Change From Baseline in Motor Seizure Frequency Per 28 Days During the Treatment Period - Percentage of Participants Considered as Treatment Responders During the Maintenance Period
 - Percent Change From Baseline in Frequency of Motor Seizures Longer Than 5 Minutes in Participants With CDD
 - Proportion of Motor Seizure-free Days in Participants During the Maintenance Period
 - Change From Baseline in Clinician's Global Impression of Severity (CGI-S) Responses of Investigator
 - Percentage of Participants With Clinical Global Impression of Change (CGI-C) Responses as Per the Investigator Reported Impression
 - Percentage of Participants With Care Clinical Global Impression of Change (CGI-C) Responses of Parent/Family
 - Change From Baseline of Plasma 24S-hydroxycholesterol (24HC) Levels
 - Change From Baseline in Seizure Frequency in Participants Treated With TAK-935 as an Adjunctive Therapy
 |  | 
| E.5.2.1 | Timepoint(s) of evaluation of this end point | 
| Secondary end points will be assessed throughout the study, Weeks 0 to 20 |  | 
| E.6 and E.7 Scope of the trial | 
| E.6 | Scope of the trial | 
| E.6.1 | Diagnosis | No | 
| E.6.2 | Prophylaxis | No | 
| E.6.3 | Therapy | Yes | 
| E.6.4 | Safety | Yes | 
| E.6.5 | Efficacy | No | 
| E.6.6 | Pharmacokinetic | No | 
| E.6.7 | Pharmacodynamic | No | 
| E.6.8 | Bioequivalence | No | 
| E.6.9 | Dose response | No | 
| E.6.10 | Pharmacogenetic | No | 
| E.6.11 | Pharmacogenomic | No | 
| E.6.12 | Pharmacoeconomic | No | 
| E.6.13 | Others | Yes | 
| E.6.13.1 | Other scope of the trial description |  | 
| E.7 | Trial type and phase | 
| E.7.1 | Human pharmacology (Phase I) | No | 
| E.7.1.1 | First administration to humans | No | 
| E.7.1.2 | Bioequivalence study | No | 
| E.7.1.3 | Other | No | 
| E.7.1.3.1 | Other trial type description |  | 
| E.7.2 | Therapeutic exploratory (Phase II) | Yes | 
| E.7.3 | Therapeutic confirmatory (Phase III) | No | 
| E.7.4 | Therapeutic use (Phase IV) | No | 
| E.8 Design of the trial | 
| E.8.1 | Controlled | No | 
| E.8.1.1 | Randomised | No | 
| E.8.1.2 | Open | Yes | 
| E.8.1.3 | Single blind | No | 
| E.8.1.4 | Double blind | No | 
| E.8.1.5 | Parallel group | No | 
| E.8.1.6 | Cross over | No | 
| E.8.1.7 | Other | No | 
| E.8.2 | Comparator of controlled trial | 
| E.8.2.1 | Other medicinal product(s) | No | 
| E.8.2.2 | Placebo | No | 
| E.8.2.3 | Other | No | 
| E.8.2.4 | Number of treatment arms in the trial | 1 | 
| E.8.3 | Will this trial be conducted at a single site globally? | No | 
| E.8.4 | Will this trial be conducted at multiple sites globally? | Yes | 
| E.8.6 Trial involving sites outside the EEA | 
| E.8.6.2 | Trial being conducted completely outside of the EEA | No | 
| E.8.6.3 | Specify the countries outside of the EEA in which trial sites are planned |  | 
| E.8.7 | Trial has a data monitoring committee | No | 
| E.8.8 | Definition of the end of the trial and justification where it is not the last
                        visit of the last subject undergoing the trial | 
| It has been defined as the last subject last visit |  | 
| E.8.9 Initial estimate of the duration of the trial | 
| E.8.9.2 | In all countries concerned by the trial years | 2 |