A Study to Evaluate the Efficacy and Safety of ABBV-8E12 in Subjects With Early Alzheimer's Disease

Inclusion Criteria:

- Subject who meets the National Institute on Aging and the Alzheimer's Association
(NIA-AA) clinical criteria for mild cognitive impairment or probable AD, and have:

- Clinical Dementia Rating (CDR)-Global Score of 0.5

- Mini-Mental State Examination (MMSE) score of 22 to 30, inclusive

- Repeatable Battery for the Assessment of Neuropsychological Status-Delayed Memory
Index (RBANS - DMI) score of 85 or lower

- Subject has a positive amyloid Positron Emission Tomography (PET) scan.

- Subject has a Modified Hachinski Ischemic Scale (MHIS) score of ≤ 4.

- The subject has an identified, reliable, study partner (e.g., family member).

- If using medications to treat symptoms related to AD, doses must be stable for at
least 12 weeks prior to randomization.

Exclusion Criteria:

- Subject has any contraindications or inability to tolerate brain magnetic resonance
imaging (MRI), PET scans or lumbar puncture.

- Subject has evidence of any other clinically significant neurological disorder other
than Early AD.

- In the opinion of the investigator, the subject has any clinically significant or
uncontrolled medical or psychiatric illness, or has had an infection requiring medical
intervention in the past 30 days.

- Subject has had a myocardial infarction, unstable angina, stroke, transient ischemic
attack or required intervention for any of these conditions within 6 months of
Screening.