The drug being tested in this study is called TAK-861. TAK-861 is being tested to treat people who have narcolepsy type 1 (NT1) and narcolepsy type 2 (NT2). This study will look at the safety of TAK-861 along with improvement in narcolepsy symptoms, including excessive daytime sleepiness (EDS) and number of cataplexy episodes.~The study will enroll up to 160 patients from controlled studies conducted with TAK-861. Participants will be assigned to one of the treatment groups according to the dose assigned to them in their parent study. Similarly, participants who were previously on a placebo dose will also be assigned to one of the treatment groups randomly. All participants in the study will receive TAK-861.~Participants with NT1 will receive the following dose from the parent study:~TAK-861 Dose 1~TAK-861 Dose 2~TAK-861 Dose 3~TAK-861 Dose 4 Participants with NT2 will receive either TAK-861 Dose 1 or TAK-861 Dose 2 from the parent study.~This multi-center trial will be conducted worldwide. The overall time to participate in this study is approximately 108 weeks. Participants will make multiple visits to the clinic (with some visits optionally conducted by home health), and will have a follow up assessment 4 weeks after last dose of study drug.
The main aim is to evaluate the safety and tolerability of TAK-861 on participants with type 1 and type 2 narcolepsy from previous parent studies, TAK-861-2001 (NCT05687903) and TAK-861-2002 (NCT05687916).