Inclusion Criteria:
- Ages 50-85 years.
- Diagnosis of either MCI due to AD or mild AD dementia.
- MMSE 20-30 (inclusive).
- Amyloid PET scan of the brain or CSF biomarkers consistent with AD.
- Neuroimaging (MRI) obtained during screening consistent with the clinical diagnosis of Alzheimer's disease, as based on central read.
Exclusion Criteria:
- Screening MRI of the brain indicative of significant abnormality.
- Clinically significant abnormalities in screening laboratory tests.
- Clinical or laboratory findings consistent with:
- Other primary degenerative dementia, (dementia with Lewy bodies, fronto-temporal dementia, Huntington's disease, Creutzfeldt-Jakob Disease, Down syndrome, etc.).
- Other neurodegenerative condition (Parkinson's disease, amyotrophic lateral sclerosis, etc.).
- Other infectious, metabolic or systemic diseases affecting the central nervous system (syphilis, present hypothyroidism, present vitamin B12, other laboratory values etc.)
- A participant known to be actively infected with hepatitis B or hepatitis C at screening. History of acute/chronic hepatitis B or C and/or carriers of hepatitis B (seropositive for hepatitis B surface antigen [HbsAg] or anti-hepatitis C [HCV] antibody). Participants who have evidence of resolved hepatitis infection (e.g., HCV RNA negative) may be considered following discussion with the Medical Monitor.
- A current DSM-V diagnosis of active major depression or GDS > 6, schizophrenia, or bipolar disorder.