Inclusion Criteria:

   1. Is able to provide voluntary, informed consent.

   2. Completed the Double-Blind Randomized Withdrawal Phase (EOT/Visit 5) from the
   HBS-101-CL-010 study.

   3. A patient who is a female of child-bearing potential must have a negative urine
   pregnancy test at the Screening Visit. A patient who is a female of child-bearing
   potential must agree to remain abstinent or use an effective method of non-hormonal
   contraception to prevent pregnancy for the duration of the study and for 21 days after
   final dose of study drug.

   4. Must have a negative result on urine drug screen at the Screening Visit, except for
   medications that are prescribed by a healthcare provider for medical conditions.

   5. In the opinion of the Investigator, the patient is capable of understanding and
   complying with the protocol and administration of oral study drug.

Exclusion Criteria:

   1. Does not agree to discontinue any prohibited medication or substances listed in the
   protocol.

   2. Is currently breastfeeding or planning to breastfeed over the course of the study.
   Lactating women must agree not to breastfeed for the duration of the study and for 21
   days after final dose of study drug.

   3. Participation in an interventional research study with an investigational medication
   or device, other than pitolisant, for the duration of the study.

   4. Has a diagnosis of end-stage renal disease (ESRD; estimated glomerular filtration rate
   [eGFR] of <15 mL/minute/1.73 m2) or severe hepatic impairment (Child-Pugh C).

   5. Is receiving or is unable to discontinue a medication known to prolong the QT
   interval.

   6. Has a significant risk of committing suicide or suicidality based on history; routine
   psychiatric examination; Investigator's judgment; or who has an answer of "yes" on any
   question other than questions 1 to 3 or "yes" on any question in the suicidal behavior
   section of the C-SSRS, Since Last Visit.

   7. Based on the judgment of the Investigator, is unsuitable for the study for any reason,
   including but not limited to an unstable or uncontrolled medical condition or one that
   might interfere with the conduct of the study, confound interpretation of study
   results, pose a health risk to the patient, or compromise the integrity of the study.