The purpose of this study is to assess the tolerability of HBS-201 when starting at a therapeutic dose in adult participants with narcolepsy.

This is a Phase 1b, open-label, multicenter study to assess the tolerability of HBS-201 when starting at a therapeutic dose in adult participants with narcolepsy. Therapeutic dose range is defined as 17.8 milligram (mg) to 35.6 mg based on the FDA-approved prescribing information for WAKIX.

The study will consist of an up to 30-day Screening/Baseline Period, a 2-week Open-Label Period, and a 30-day Safety Follow-up Period.

Inclusion Criteria:

1. Has a current documented diagnosis of narcolepsy type 1 or narcolepsy type 2 per International Classification of Sleep Disorders, 3rd Edition (ICSD-3) criteria.

Exclusion Criteria:

1. Has hypersomnolence due to another medical disorder.
2. Is currently taking or has taken WAKIX (pitolisant).
3. Has participated in an interventional research study involving another investigational medication, device, or behavioral treatment within 30 days or within 5 half-lives of the investigational medication prior to Screening.
4. Based on the judgment of the Investigator, is unsuitable for the study for any reason, including but not limited to unstable or uncontrolled medical conditions (including psychiatric and neurological conditions) or a medical condition that might interfere with the conduct of the study, confound interpretation of study results, pose a health risk to the participant, or compromise the integrity of the study.