The study will consist of a Screening Period, an 11-week Double-Blind Treatment Phase (including a 3-week Titration Period and an 8-week Stable Dose Period), and an optional Open Label Extension (OLE) Phase. The OLE Phase will be multi-year in duration and will continue until either pitolisant is approved for patients with PWS or the Sponsor elects to terminate the study.~Approximately 60 patients ages 6 to 65 years who meet all eligibility criteria will be randomized at the Baseline Visit in a 1:1:1 ratio to low dose pitolisant, high dose pitolisant, or matching placebo. In the Double-Blind Treatment Phase, patients will be titrated to their randomized stable dose of study drug during the 3-week Titration Period.~After completion of the 3-week Titration Period, patients will continue to take study drug at their randomized stable dose once daily in the morning upon wakening for an additional 8 weeks of blinded treatment (Stable Dose Period). The duration of the Double-Blind Treatment Phase will be 11 weeks.~Following the 11-week Double-Blind Treatment Phase, eligible patients will be given the opportunity to participate in an optional OLE Phase. During the OLE Phase, all eligible patients will receive treatment with open-label pitolisant and will undergo titration during a 3-week Titration Period to a maximum target dose based on their age. At the end of the 3-week Titration Period, patients will continue to take their target dose of pitolisant once daily in the morning upon wakening until the end of the study.
The primary objective of this study is to evaluate the safety and efficacy of pitolisant compared with placebo in treating excessive daytime sleepiness (EDS) in patients with Prader Willi syndrome (PWS) ages 6 to 65 years.