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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
88
Time to Loss of Response in the Epworth Sleepiness Scale (ESS) Score During the Up to 4-Week RW Period
The ESS provides individuals with 8 different situations of daily life and asks them how likely they are to fall asleep in those situations (scored 0 to 3) and to try to imagine their likelihood of dozing even if they have not actually been in the identical situation; the scores are summed to give an overall score of 0 to 24. Higher scores indicate stronger subjective daytime sleepiness, and scores below 10 are considered to be within normal range.
Time frame: Up to 4-week RW period
Change From the End of the OL Treatment Period to Week 2 of the RW Period on the Maintenance of Wakefulness Test (MWT)
The MWT evaluates a person's ability to remain awake under soporific conditions for a defined period of time. Because there is no biological measure of wakefulness, wakefulness is measured indirectly by the inability or delayed tendency to fall asleep. This tendency to fall asleep is measured via electroencephalography (EEG)-derived sleep latency in the MWT. The MWT consists of four 40-minute sessions. Sleep latency in each wake trial will be recorded. Participants will be required to stay awake in between the 4 sessions.
Time frame: From the end of the OL treatment period (Week 16) to Week 2 of the RW period (Week 18)
Weekly Cataplexy Rate (WCR) at Week 2 of the RW Period
Time frame: Week 2 of the RW period
Change from the End of the OL Treatment Period to Week 2 of the RW Period in Mean Number of Lapses on the Psychomotor Vigilance Test (PVT)
The PVT is a simple reaction performance task with a duration of 10 minutes that aims to measure sustained attention.
Time frame: From the end of the OL treatment period (Week 16) to Week 2 of the RW period (Week 18)
Number of Participants Reporting Much or Very Much Worse in Patient Global Impression of Change (PGI-C) Score at Week 2 of the RW Period
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The PGI-C is a participant self-rated scale to assess improvement in daytime sleepiness and overall narcolepsy symptoms. It measures change due to treatment relative to baseline on a 7-point scale ranging from a score of 1 ("very much improved") to score of 7 ("very much worse").
Time frame: Week 2 of the RW period
Change from the End of the OL Treatment Period to Week 2 of the RW Period in Narcolepsy Severity Scale for Clinical Trials (NSS-CT) Total Score
The NSS-CT is a 15-item self-administered questionnaire assesses the severity and consequences of the 5 major narcolepsy symptoms such as daytime sleepiness, cataplexy, hallucinations, sleep paralysis, and disturbed night-time sleep (DNS) with a total score range of 0 to 57 (sum of 6 items that assess symptoms severity are rated using a six-point Likert scale \[0-5\] and 9 items that describe the symptom effect on daily life are rated using a four-point Likert scale \[0-3\]. Higher total scores mean a worse outcome.
Time frame: From the end of the OL treatment period (Week 16) to Week 2 of the RW period (Week 18)
Change from the End of the OL Treatment Period to Week 2 of the RW Period in Functional Impacts of Narcolepsy Instrument (FINI) Domain Scores
The FINI measures the functional impacts of narcolepsy across 6 domains. Each domain is scored from 0 to 4, where 0 indicates the best health and 4 the worst.
Time frame: From the end of the OL treatment period (Week 16) to Week 2 of the RW period (Week 18)
Change from the End of the OL Treatment Period to Week 2 of the RW Period in Number of Correct Responses on the International Digit Symbol Substitution Test-symbols (iDSST-s)
The iDSST-s is a processing speed test that is based on the pre-existing pencil and paper version of the Digit Symbol Substitution Test. The participants are presented with a legend that defines 9 symbols, with each symbol corresponding to a digit from 1 to 9. The participant is then presented with a conveyer belt in the middle of the screen that displays a series of empty boxes labelled with a number. The participant must select the symbol that corresponds to the number of a given highlighted box from symbol options presented at the bottom of the screen. The participant must try to place as many correct symbols in the boxes as possible over the duration of the test.
Time frame: From the end of the OL treatment period (Week 16) to Week 2 of the RW period (Week 18)
Number of Participants With At Least One Treatment-Emergent Adverse Event (TEAE)
An adverse event (AE) is any untoward medical occurrence in a clinical investigation participant administered a pharmaceutical product. A TEAE is defined as any event emerging or manifesting at or after the initiation of treatment with a study intervention or medicinal product or any existing event that worsens in either intensity or frequency following exposure to the study intervention or medicinal product.
Time frame: From Screening to End of study (approximately 31 weeks)