A Phase 3 interventional study of TAK-861 and Placebo in Narcolepsy Type 1 (NT1) and Narcolepsy With Cataplexy, sponsored by Takeda. Active, not recruiting at 25 sites in 7 countries. Open to participants aged 16 Years to 70 Years. Per ClinicalTrials.gov, last updated 2026-10-30.
Sponsored by Takeda · Phase 3, Interventional, and Treatment
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:
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.
157 studies on the registry are indexed under Narcolepsy; 37 are open to participants now.
This study's enrollment of 98 is above the median of 78 across 114 interventional studies indexed under Narcolepsy.
Browse Narcolepsy studies →Takeda is the lead sponsor of 1,026 studies on the registry; 89 are open to participants now.
Of its 178 completed or terminated interventional studies of FDA-regulated products, 154 (87%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
A “mini-stroke”: temporary stroke-like symptoms caused by reduced blood flow to part of the brain, spinal cord or eye, without signs of a new stroke on a scan.
Stroke symptoms need emergency care at once, even if they go away.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
TIA (transient ischaemic attack)
A “mini-stroke”: temporary stroke-like symptoms caused by reduced blood flow to part of the brain, spinal cord or eye, without signs of a new stroke on a scan.
Stroke symptoms need emergency care at once, even if they go away.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants on stable TAK 861 dose will receive the same dose of TAK-861 they were taking at the end of the OL treatment period, for up to 4 weeks in the double-blind RW period.
Drug: TAK-861
Participants will receive TAK-861 matching-placebo, for up to 4 weeks in the double-blind RW period.
Drug: Placebo
TAK-861 tablets
TAK-861-matching placebo tablets
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
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)
Plan to share: Yes — Takeda provides access to the de-identified individual participant data (IPD) for eligible studies to aid qualified researchers in addressing legitimate scientific objectives (Takeda's data sharing commitment is available on https://clinicaltrials.takeda.com/takedas-commitment?commitment=5). These IPDs will be provided in a secure research environment following approval of a data sharing request, and under the terms of a data sharing agreement.
Supporting information: Study protocol, Statistical analysis plan, Informed consent form, Clinical study report
Access criteria: IPD from eligible studies will be shared with qualified researchers according to the criteria and process described on https://vivli.org/ourmember/takeda/. For approved requests, the researchers will be provided access to anonymized data (to respect patient privacy in line with applicable laws and regulations) and with information necessary to address the research objectives under the terms of a data sharing agreement.
Data sharing details ↗ · vivli.org
Started Jan 2026 (actual). Primary completion is estimated for Dec 2026, 10 months after the start.
Of 14 phase 3 interventional studies under Narcolepsy, half reached primary completion within 30 months of starting (the median), counting those still running; a quarter within 21 and three quarters within 40. This study's planned 10 months is below that.
Since we started tracking on Sep 25, 2026, the dates moved once, on Oct 30, 2026: primary completion Oct 2026 → Dec 2026 and completion Oct 2026 → Dec 2026.
Earlier changes are on the record history on ClinicalTrials.gov ↗
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is active, not recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
Get an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
Studies of the drug tested here: Oveporexton