Trial of AD036 in Obstructive Sleep Apnea

Male participants between 25 to 65 years of age or female participants between 25 to 70 years of age. Key Inclusion Criteria: * AHI ≥ 20 based on screening polysomnography * Epworth Sleepiness Scale (ESS) score ≥ 4 for participants not using CPAP * Previous surgical treatment for OSA is allowed if ≥ 1 year prior to enrollment Key Exclusion Criteria: * Clinically significant craniofacial malformation. * Clinically significant cardiac disease (e.g., rhythm disturbances, coronary artery disease or cardiac failure) or hypertension requiring more than 2 medications for control. * Clinically significant neurological disorder, including epilepsy/convulsions. * Positive screen for drugs of abuse or substance use disorder as defined in DSM-V within 24 months prior to Screening Visit. * A significant illness or infection requiring medical treatment in the past 30 days. * Women who are pregnant or nursing. * History of using oral or nasal devices for the treatment of OSA may enroll as long as the devices are not used during participation in the study. * History of using devices to affect participant sleeping position for the treatment of OSA, e.g. to discourage supine sleeping position, may enroll as long as the devices are not used during participation in the study. * Treatment with strong cytochrome P450 3A4 (CYP3A4) inhibitors, strong cytochrome P450 2D6 (CYP2D6) inhibitors, or monoamine oxidase inhibitors (MAOI) within 14 days of the start of treatment, or concomitant with treatment. * Use of another investigational agent within 90 days or 5 half-lives, whichever is longer, prior to dosing. * ESS total score \> 18. * Central apnea index \> 5/hour on baseline PSG. * Periodic limb movement arousal index \>15/hour on baseline PSG. * Hepatic transaminases \>3X the upper limit of normal (ULN), total bilirubin \>2X ULN (unless confirmed Gilbert syndrome), serum creatinine \>2X ULN. * \<6 hours typical sleep duration. * Night- or shift-work sleep schedule. * Employment as a commercial driver or operator of heavy or hazardous equipment.