A Multicenter, Open-label, Pilot Study of TAK-935 (OV935) in Participants With 15Q Duplication Syndrome or Cyclin-Dependent Kinase-Like 5 (CDKL5) Deficiency Disorder (ARCADE STUDY)

The drug being tested in this study is called TAK-935 (OV935). TAK-935 is being tested to
treat people with 15q duplication syndrome or CDKL5 deficiency disorder. This study will
assess the effects of TAK-935 on seizure frequency, safety.

The study will enroll approximately 30 participants. Participants will be enrolled into 2
groups based on their diagnosis as: 15q duplication syndrome or CDKL5 deficiency disorder.

All participants will be asked to take TAK-935 tablets twice daily with or without food.

The study comprises of 2 periods: Screening/Baseline Period and Treatment Period (Dose
Optimization and Maintenance). The overall time to participate in this study approximately 30
weeks, including 4 to 6 weeks Screening/Baseline Period, 20 weeks Treatment Period, 2 weeks
Taper, and 2 weeks safety follow up period. Participants completing this study will have an
option to enroll in the open-label extension (OLE) study, under a separate protocol.

Inclusion Criteria:

1. Clinical diagnosis of 15q duplication syndrome or CDKL5 deficiency disorder

2. Currently taking 1 to 6 antiepileptic drugs (AEDs) at a stable dose

Exclusion Criteria:

1. One or more episodes of convulsive status epilepticus per week requiring
hospitalization and intubation

2. Currently receiving a study drug or participated in a clinical study involving another
investigational product in the previous month