RecruitingPhase 3Drug trialA Trial of TAK-861 for the Treatment of Narcolepsy With CataplexyThe 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.