A Trial of TAK-861 for the Treatment of Narcolepsy With Cataplexy

A Double-blind, Placebo-Controlled, Randomized Withdrawal Trial to Evaluate the Efficacy and Safety of TAK-861 for the Treatment of Narcolepsy With Cataplexy (Narcolepsy Type 1)

The main aim of this study is to assess how effective TAK-861 is for treating narcolepsy type 1 and if this effect is maintained over time. Participants will take TAK-861 for a few months and if they meet certain criteria, they will be randomly assigned (by chance, like flipping a coin) to continue taking TAK-861 or take placebo (fake medicine) for up to 4 weeks to see if their narcolepsy symptoms return.

The drug being tested in this study is called TAK-861. This study will look at how effective TAK-861 is for the treatment of narcolepsy type 1 and how well this effect is maintained over time. This study also evaluates how safe TAK-861 is and what adverse events may be associated with taking the drug and stopping the drug in participants with NT1.

The study will enroll approximately 88 participants. All participants will take TAK-861 during the open-label (OL) treatment period. Participants who meet certain criteria at the end of the OL Treatment Period will be randomized to one of two treatment groups for the up to 4-week double-blind randomized withdrawal (RW) Period. Participants will be randomized to one of the following treatment groups during the Double-blind RW Period:

1. TAK-861 (same dose participant was taking at the end of the OL Treatment Period)
2. Placebo

The randomized withdrawal period may last up to 4 weeks. Participants whose NT1 symptoms get worse during the RW period and whose Epworth Sleepiness Scale score rises above a certain score will stop the treatment and be invited to continue in a separate long term extension study. Participants who choose not to take part in the extension study will be followed-up for 4 weeks after their last dose of study drug. This multi-center trial will be conducted globally.

Inclusion Criteria:

1. The participant has a body mass index (BMI) within the range 18 to 40 kilograms per square meter (kg/m^2).
2. The participant has an International Classification of Sleep Disorders, Third Edition (ICSD-3) or International Classification of Sleep Disorders, Third Edition, Text Revision (ICSD-3-TR) diagnosis of NT1.
3. The participant is positive for the human leukocyte antigen (HLA) genotype Major Histocompatibility Complex, Class II, DQ Beta 1 (HLA-DQB1*06:02) or results from radioimmunoassay indicate the participant's CSF OX/hypocretin-1 concentration is ≤110 pg/mL (or less than one-third of the mean values obtained in normal participants within the same standardized assay).

Exclusion Criteria:

1. The participant has a current medical disorder, other than narcolepsy with cataplexy, associated with EDS.
2. The participant a) has a history of myocardial infarction, b) has a history of clinically significant hepatic disease, thyroid disease, coronary artery disease, cardiac rhythm abnormality or heart failure, or c) has any medical condition (such as unstable cardiovascular, pulmonary, renal or gastrointestinal disease.
3. The participant has current or recent (within 6 months) gastrointestinal disease that is expected to influence the absorption of drugs.
4. The participant has a history of cancer in the past 5 years.
5. The participant has a clinically significant history of head injury or head trauma.
6. The participant has a history of epilepsy, seizure, or convulsion (except for a single febrile seizure in childhood).
7. The participant has a history of cerebral ischemia, transient ischemic attack (less than 5 years from screening), intracranial aneurysm, or arteriovenous malformation.