A Study of Pitolisant in Patients With Prader-Willi Syndrome

Inclusion Criteria: * Genetically confirmed diagnosis of PWS * Excessive daytime sleepiness * Has a consistent parent/caregiver (preferably the same person throughout the study) who is willing and able to complete the required study assessments. * In the opinion of the Investigator, the patient/parent(s)/caregiver(s)/legal guardian(s) are capable of understanding and complying with the requirements of the protocol and administration of oral study drug. Exclusion Criteria: * Has a diagnosis of sleep apnea (OSA, CSA) that is not adequately controlled * Has a diagnosis of hypersomnia due to another sleep/medical disorder * Participation in an interventional research study involving another investigational medication, device, or behavioral treatment within 30 days or 5 half-lives (whichever is longer) of the investigational medication prior to Screening