Time Commitment - This is a multicenter, phase III prevention trial. Investigational drug is BAN2401 versus placebo given intravenously. The study lasts 216 weeks (approximately four years). Amyloid PET scan will be completed at screening to determine levels of amyloid in the brain and participants will be informed of the amyloid findings.

Location - All visits will be held in the General Clinical Research Center at Boston University Chobanian & Avedisian School of Medicine.

Eligibility -

1. Adults ages 55-80 inclusive with no memory problems but who may have an increased risk of memory loss associated with Alzheimer’s disease (AD) e.g. due to age or a history of AD in a first degree relative

2. Must be able to safely have MRI and PET scans

3. Must have a close friend or relative who can serve as a study partner

4. Must be willing to learn of the PET scan amyloid status report

5. Must be able to come to the clinic to receive study drug (transport support will be provided if needed)

Time Commitment - This is a 24-month, phase II/III, randomized clinical trial, funded by a grant from the National Institute on Aging (NIA). The investigational drug is extended release metformin versus placebo. Participants will be assessed every six months for a total of five visits.

Location - All visits will be held in the General Clinical Research Center at Boston University Chobanian & Avedisian School of Medicine.

Eligibility -

1. Adults aged 55-90 years with amnestic mild cognitive impairment

2. Must have a study partner to come to all appointments or be available by telephone at follow-up visits

3. Must be able to come to the clinic to receive study drug (transport support will be provided if needed)

Time Commitment - In person visits every 4 weeks for 3 years

Location - On site at Boston University Medical Center or over 70 centers across the United States, Canada, and Australia.

Eligibility -

1. Women and men 65-85 years old with normal thinking and memory abilities

2. Study partner able to answer questions about your memory once a year required