Multiple Dose Study of Aducanumab (BIIB037) (Recombinant, Fully Human Anti-Aβ IgG1 mAb) in Participants With Prodromal or Mild Alzheimer's Disease

Key Inclusion Criteria:

   - Participants must be ambulatory.

   - Participants must meet the following core clinical criteria as determined by the
   Investigator:

Prodromal Alzheimer's Disease (AD) (all of the criteria must apply):

   - Mini Mental State Examination (MMSE) scores between 24-30 (inclusive)

   - a spontaneous memory complaint

   - objective memory loss defined as a free recall score of ≤27 on the Free and Cued
   Selective Reminding Test (FCSRT)

   - a global Clinical Dementia Rating Scale (CDR) score of 0.5

   - absence of significant levels of impairment in other cognitive domains

   - essentially preserved activities of daily living, and an absence of dementia. OR

Mild Alzheimer's Disease (AD) criteria (all criteria must apply):

   - Mini Mental State Examination (MMSE) scores between 20-26 (inclusive)

   - a global Clinical Dementia Rating Scale (CDR) of 0.5 or 1.0

   - meeting the National Institute on Aging-Alzheimer's Association core clinical criteria
   for probable AD.

   - Participants must have a positive florbetapir positron emission tomography (PET)
   amyloid scan.

   - Participants must consent to apolipoprotein E (ApoE) genotyping.

   - Apart from clinical diagnosis of Alzheimer's Disease (AD), participant must be in good
   health.

   - Must have a reliable informant or caregiver.

Key Exclusion Criteria:

   - Any medical or neurological condition (other than Alzheimer's Disease) that might be a
   contributing cause of the participant's cognitive impairment.

   - Have had a stroke or Transient Ischemic Attack (TIA) or unexplained loss of
   consciousness in the past 1 year.

   - Clinically significant psychiatric illness in past 6 months.

   - Seizure in the past 3 years.

   - Poorly controlled diabetes mellitus.

   - History of unstable angina, myocardial infarction, chronic heart failure, or clinical
   significant conduction abnormalities within 1 year prior to Screening.

   - Indication of impaired renal or liver function.

   - Have human immunodeficiency virus (HIV) infection.

   - Have a significant systematic illness or infection in past 30 days.

   - Brain MRI showing evidence of acute or sub-acute micro or macrohemorrhage, greater
   than 4 microhemorrhages, cortical infarct or greater than one 1 lunar infarct.

   - Any contraindications to brain MRI or positron emission tomography (PET) scans.

   - Negative positron emission tomography (PET) scan with any amyloid-targeting ligand
   within 48 weeks of Screening.

   - Clinically significant 12-lead electrocardiogram (ECG) abnormalities.

   - Alcohol or substance abuse in past 1 year.

   - Taking blood thinners (except for aspirin at a prophylactic dose or less)

   - Have changes in medications or doses of medication in past 4 weeks.

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.