A Study of TAK-861 for the Treatment of Selected Central Hypersomnia Conditions

The drug being tested in this trial is called TAK-861. TAK-861 is being tested to treat people who have narcolepsy type 1 (NT1). This trial will look at the safety of TAK-861 along with improvement in narcolepsy symptoms, including excessive daytime sleepiness (EDS) and number of cataplexy episodes. This trial was initiated in parallel with the parent phase 2 trials, TAK-861-2001 (NCT05687903) and TAK-861-2002 (NCT05687916), which included participants with NT1 and narcolepsy type 2 (NT2), respectively. This long-term extension (LTE) trial enrolled participants with both diagnoses from the two phase 2 trials. As the TAK-861-2002 trial did not meet prespecified criteria, all participants with NT2 were discontinued, and moving forward this extension study only includes participants with NT1 who previously completed a parent trial. Parent trials include all TAK-861 phase 3 trials in addition to the phase 2 trial participants from TAK-861-2001. The trial will enroll up to 500 participants. All participants in the trial will receive TAK-861. Participants who were previously on a placebo dose will be assigned to one of the TAK-861 doses randomly. This multi-center trial will be conducted worldwide. Study period is approximately 5 years or until the study is stopped at the sponsor's discretion, or the product is approved and launched. 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 the last dose of trial intervention.