A Phase 3 Efficacy and Safety Study of HBS-301 in Participants With Idiopathic Hypersomnia (IH)

Inclusion Criteria: * Has a current documented diagnosis of IH per the International Classification of Sleep Disorders, Third Edition (ICSD-3) or Text Revision (ICSD-3-TR) criteria with confirmatory polysomnogram (PSG) with multiple sleep latency test (MSLT; and if applicable, a 24-hour PSG report or an actigraphy report with sleep log) on file that led to the diagnosis and was completed within the last 10 years. * Has EDS. * Has moderate to very severe symptoms of IH. * If taking a permitted chronic concomitant medication or supplement, including nonprohibited antidepressants or wake-promoting agents, must be on a stable dose for at least 3 months prior to Screening and agree to continue at that stable dose for the Double-blind Treatment Period of the study. As-needed use of any treatment that could affect daytime sleepiness (including but not limited to stimulants, modafinil, and armodafinil) used on an as-needed basis is not permitted. Exclusion Criteria: * Has hypersomnia due to another medical disorder. * Has a history of pitolisant use within 5 half-lives prior to Screening. * Has a primary diagnosis of psychiatric illness, including depression, that is not well controlled. * Has a history of moderate or severe hepatic impairment. * Has a body surface area (BSA)-corrected estimated glomerular filtration rate (eGFR) \<60 mL/min. * Has a known history of long QT syndrome or any significant history of a serious abnormality of the electrocardiogram (ECG).