This study looks at how well and safely a medicine called HBS-301 helps adults (18 years or older) with idiopathic hypersomnia (IH), a condition causing too much daytime sleepiness, trouble waking up, and tiredness. In this study, HBS-301 will be compared to a placebo (a substance with no actual medicine) to see if it works better at treating these symptoms.

Before participants start, they must have a confirmed IH diagnosis. During the study, they will be in a randomized (assigned by chance), double-blind (neither participants nor researchers know who gets the medicine or placebo), placebo-controlled setup.

• Study Length: Screening/Baseline (up to 28 days), Treatment (8 weeks), optional Extension (1 year).
• Participants: About 248 adults with IH.
• Visits: Regular visits during the study, including follow-ups.

To join, participants need stable medication use and, if they have conditions like sleep apnea, must use treatments consistently. People with sleepiness due to other medical issues or certain health problems cannot join.