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 last approximately one year for each patient or until the Sponsor elects to terminate the study.~Approximately 78 patients ages 18 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. Patients will first undergo a 3-week Titration Period to a maximum target dose, after which they will continue to take their dose of pitolisant once daily in the morning upon wakening until the end of the study. The patient's dose of pitolisant may be adjusted during the OLE phase.
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 Myotonic Dystrophy Type 1 ages 18 to 65 years.~The secondary objectives of this study are to assess the impact of pitolisant on fatigue, cognitive function and the burden of disease along with assessing the long-term safety and effectiveness of pitolisant in patients with Myotonic Dystrophy Type 1 ages 18 to 65 years.