Lemborexant in Delayed Sleep Phase Syndrome

Eligibility Criteria

• 1. 18 years of age or older.
• 2. Diagnosed with delayed sleep phase syndrome (DSPS) meaning that:
• 1. Sleep is delayed by two hours or more beyond what is considered an acceptable or conventional bedtime for the subject (their desired bedtime).
• 2. Subjects not able to fall asleep if trying to sleep before the later bedtime;
• 3. This is interfering with their wishes/having social impact.
• 3. Concomitant medications will be allowed, though dosages will be required to remain fixed throughout participation in the study.
• 4. The participant also needs to be willing and able to comply with all aspects of the protocol.
• 1. Clinically significant depression (PHQ-9 score of 10 or more), anxiety disorder (GAD-7 score of 10 or more), substance use disorder, any other sleep disorder (assessed by the Alliance Sleep Questionnaire- ASQ), or any medical disorder/therapy that could interfere with the trial (this will be verified through interview and analysis of the ASQ).
• 2. Use of medications with significant effects on sleep-wake function (insomnia therapies, stimulants)- unless they are discontinued at least 5 half-lives prior to study participation. Non-sedative antidepressants or SSRI will be allowed if at a stable dose in the absence of concomitant severe depression or severe anxiety.
• 3. Use of CYP3A inhibitors and CYP3A inducers, at least 1 week (or five half-lives, whichever is longer) prior to the first day of the baseline phase.
• 4. Pregnancy (verified by urine pregnancy test on visits 1, 2, and 3) or plan to become pregnant in the next 3 months or currently breastfeeding.
• 5. Shift workers or subjects working unusual hours.
• 6. Any risk of suicide within 6 months of screening period or throughout the trial (accessed by the Investigator and by the C-SSRS questionnaire).
• 7. Transmeridian travel across more than 3 time zones 4 weeks prior to the screening phase.
• 8. Transmeridian travel across more than 2 time zones during this trial (including the screening phase).
• 9. Having a positive drug test or being unwilling to refrain from using illegal drugs or marijuana during this trial.
• 10. Any clinically abnormal symptom or organ impairment found by medical history at Screening or Baseline and physical examinations, vital signs, ECG findings, or laboratory test results that require medical treatment.
• 11. Impaired liver function (values for enzymes aspartate transaminase (AST) and alanine transaminase (ALT) \> 1.5 times the Upper Limit of Normal).
• 12. Known to be human immunodeficiency virus positive.
• 13. Has a QT interval corrected using Fridericia's formula interval (QTcF interval) \>450 ms demonstrated on repeated ECGs (repeated only if initial ECG showed corrected QT interval (QTc) \>450 ms) at Screening or Baseline.