Key Inclusion Criteria:

• Age 55 to 85 years
• Mild-to-moderate AD dementia subjects, MMSE 14-24, CDR 1 or 2 at the Screening visit
• Clinical diagnosis of dementia, due probably to AD, by Revised National Institute on Aging-Alzheimer's Association criteria (McKhann, 2011)
• Reliable and capable support person/caregiver
• Treatment-free or receiving stable acetylcholinesterase inhibitor (AChEI) treatment, defined as:
  • Treatment-naïve, OR
  • Subjects who received continuous dosing for at least 6 months, and are on a stable, approved dose of an AChEI for at least 3 months before Screening OR
  • Subjects who received an AChEI in the past and discontinued, e.g., due to tolerability issues
  • For subjects who received high dose donepezil at 23 mg PO, or galantamine at 24 mg PO or patch, a 3-month drug-free period is required between the last dose received and Screening.

Key Exclusion Criteria:

• History of significant neurologic disease, other than AD, that may affect cognition, or concurrent with the onset of dementia
• History of unexplained loss of consciousness, and epileptic fits (unless febrile)
• Subject has atypical variant presentation of AD, if known from medical history, particularly non-amnestic AD
• History of brain MRI scan indicative of any other significant abnormality
• Hearing test result considered unacceptable for auditory ERP P300 assessment
• Diagnosis of severe major depressive disorder even without psychotic features
• Significant suicide risk
• History within 2 years of Screening, or current diagnosis of psychosis
• Myocardial infarction or unstable angina within the last 6 months
• Clinically significant (in the judgment of the investigator) cardiac arrhythmia (including atrial fibrillation), cardiomyopathy, or cardiac conduction defect (note: pacemaker is acceptable)
• Subject has either hypertension (supine diastolic blood pressure > 95 mmHg), or symptomatic hypotension in the judgment of the investigator
• Clinically significant ECG abnormality at Screening or Baseline
• Renal insufficiency (serum creatinine > 2.0 mg/dL)
• Hepatic impairment with alanine aminotransferase or aspartate aminotransferase > 2 times the upper limit of normal, or Child-Pugh class B and C
• Malignant tumor within 3 years before Screening
• Memantine (Namenda®) and combination product of donepezil and memantine product (Namzaric®) within 6 weeks prior to Screening
• The subject has received active amyloid or tau immunization at any time, or passive immunization within 12 months of Screening