Pharmacological Intervention for Symptomatic Mild Sleep Disordered Breathing

Inclusion Criteria at Enrollment: * Between 25 to 70 years of age, inclusive * SRQ at screening ≥ 4 (at least mild impact of snoring) * ESS at screening ≤ 12 (absence of sleepiness) * BMI between 18.5 and 40 kg/m2, inclusive. * Use of specified contraceptive methods if appropriate Inclusion Criteria for First Study Phase (Run-in Period): * AHI ≥5-10, or AHI 0-\<5 if either: * Snoring frequency (100dB snoring for \>10% of sleep) by tracheal microphone, or * Flow limitation frequency (\>50% obstruction for \>10% of sleep). * PGI-S that improves by at least 1 point during AD036 run-in period Inclusion Criteria for Randomization: • PGI-S that improves by at least 1 point during AD036 run-in period. Exclusion Criteria: Participants are excluded from the study if any of the following criteria apply: * History of narcolepsy * 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. * History of schizophrenia, schizoaffective disorder or bipolar disorder * History of attempted suicide or suicidal ideation within 1 year prior to screening, or current suicidal ideation. * History of clinically significant constipation, gastric retention, or urinary retention. * Positive screen for drugs of abuse or substance use disorder * A significant illness or infection requiring medical treatment in the past 30 days. * Clinically significant cognitive dysfunction. * Untreated narrow angle glaucoma. * Women who are pregnant or nursing. * History of using oral or nasal devices for the treatment of OSA or snoring; 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 or snoring, e.g. to discourage supine sleeping position; may enroll as long as the devices are not used during participation in the study. * History of oxygen therapy (last 12 months). * Use of medications from the list of disallowed concomitant medications during study participation. * MAOIs or other drugs that affect monoamine concentrations (e.g., rasagiline) \[MAOIs are contraindicated for use with atomoxetine\] * Selective Serotonin Reuptake Inhibitors (e.g., paroxetine) * Selective Norepinephrine Reuptake Inhibitors (e.g., duloxetine) * Norepinephrine Reuptake Inhibitors (e.g., reboxetine) * Alpha-1 antagonists (e.g., tamsulosin) * Tricyclic antidepressants (e.g., desipramine) * Centrally acting antihypertensives (e.g. clonidine, alpha-methyl-DOPA) * CYP2D6 inhibitors * Strong CYP3A4 inhibitors (e.g., ketoconazole) * Benzodiazepines and other anxiolytics or sedatives * Nonbenzodiazepine hypnotics * Opioids * Muscle relaxants * Pressor agents * Drugs with clinically significant cardiac QT-interval prolonging effects * Drugs known to lower seizure threshold (e.g., chloroquine) * Amphetamines * Antiepileptics * Antiemetics * Modafinil or armodafinil * Beta2 agonists, (e.g., albuterol) * Antipsychotics * Anticholinergics and anticholinesterase inhibitors, including drugs with substantial anticholinergic side effects, (e.g., first generation antihistamines) * Sedating antihistamines * Pseudoephedrine, phenylephrine, oxymetazoline * Nicotine replacement products * Most drugs for Parkinson's, Alzheimer's, Huntington's, Amyotrophic Lateral Sclerosis, or drugs for other neurodegenerative diseases * 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 30 days or 5 half-lives prior to dosing, whichever is longer. * \<5 hours typical sleep duration. * Smoking more than 10 cigarettes or 2 cigars per day. * Unwilling to use specified contraception. * Unwilling to limit alcohol consumption to no greater than 2 units/day or less for men, or 1 unit/day for women, not to be consumed within 3 hours of bedtime. * Unwilling to limit caffeinated beverage intake (e.g., coffee, cola, tea) to 400 mg/day or less of caffeine (approximately 4 cups of coffee); caffeine not to be used within 3 hours of bedtime. * Any condition that in the investigator's opinion would present an unreasonable risk to the participant, or which would interfere with their participation in the study or confound study interpretation. * Participant considered by the investigator, for any reason, an unsuitable candidate to receive AD036 or unable or unlikely to understand or comply with the dosing schedule or study evaluations.