A Study of TAK-994 in Adults With Narcolepsy

A Dose-Blind Extension Study With Double-blind, Placebo-Controlled, Randomized Withdrawal Period to Evaluate the Safety and Explore the Pharmacokinetics and Pharmacodynamics of TAK-994 in Adults With Narcolepsy With Cataplexy (Narcolepsy Type 1)

Adults with narcolepsy who have completed the TAK-994-1501 study will be able to take part in this study.

The main aim of this study is to check if participants have side effects from TAK-994.

Participants will take one of 3 different TAK-994 dose for 8 weeks.

Then, half the participants will continue with their dose of TAK-994 and half will take a placebo. In this study, a placebo will look like a TAK-994 tablet but will not have any medicine in it. Participants will take TAK-994 or placebo for 4 weeks.

Participants will visit the clinic for a final check-up 2 weeks after their last dose of TAK-994 or placebo.

The study doctors will check for side effects from TAK-994 and placebo throughout the study.

Participants will continue to record any narcolepsy symptoms as they did in Part B of the TAK 994-1501 study.

The drug being tested in the study is called TAK-994. TAK-994, is being tested to treat participants with NT1. Participants who completed Part B of TAK-994-1501(NCT04096560) will be eligible for enrollment in this study.

This study will enroll approximately 112 patients to receive one of three different TAK 994 dose for 8 weeks (active drug extension period). Participants will be randomly assigned to one of these different TAK 994 doses which will remain undisclosed to the participant and study doctor during the study (unless there is an urgent medical need).

Following the 8-week Active Drug Extension Period, participants will continue into a 4-week Double-blind Randomized Withdrawal Period and will receive TAK-994 or Placebo.

Participants randomized to TAK-994 will continue to receive the same dose as before.

This multi-center trial will be conducted worldwide. The duration of treatment in this study is 12 weeks plus a 2 week safety follow up period. Participants will visit the clinic 10 times after the first dosing.

Inclusion Criteria:

1. Participant with a diagnosis of Narcolepsy Type 1 (NT1) who has completed TAK-994-1501 Part B before enrollment (which will occur immediately following the final TAK-994-1501 assessments), and for whom the investigator has no clinical objection they be enrolled.

Exclusion Criteria:

1. Participant has a clinically significant moderate or severe ongoing AE related to the study drug from the prior study.