Key Inclusion Criteria:  Meets National Institute on Aging and Alzheimer's Association Research Framework criteria for individuals in clinical Stage 4 or 5 of the Alzheimer's continuum. Evidence for AD pathophysiology, confirmed prior to screening MMSE score ≥ 16 and ≤ 27 at screening. Clinical Dementia Rating - Global Score must be 0.5, 1 or 2. If receiving background AD medications, the dosing regimen must be stable for at least 12 weeks prior to randomization. The subject has been a non-smoker for at least 3 years. Availability of a study partner Individuals who have participated in a clinical study with an investigational drug targeting the underlying AD process may be permitted to participate in this study.  Key Exclusion Criteria:  A neurologic condition other than AD that significantly contributes to the subject's dementia. Any current primary psychiatric diagnosis other than AD if it is likely to confound cognitive assessment or ability to comply with study procedures Geriatric Depression Scale (15-item) score > 8 Suicidal ideation during the past 3 months or suicidal behavior during the past 12 months Alcohol or substance use disorder within 2 years of screening MRI presence of cerebral vascular or other significant pathology History of transient ischemic attack or stroke within 12 months of screening Seizure within 12 months of screening. Severe head trauma or head trauma considered likely to be contributing to the subject's cognitive impairment. Sleep apnea that is considered likely to be contributing to the subject's cognitive impairment. Insufficiently controlled diabetes mellitus or hypertension Body mass index < 18.5 or > 35.0. History or diagnosis of clinically significant cardiac disease Prescribed aducanumab. COVID-19 infection within 3 months of screening. If no history of a prior COVID-19 infection, subject must be fully vaccinated for COVID-19 at least 2 weeks prior to randomization.