Who may be eligible to participate? • Individuals 60-75 years of age who are cognitively normal. • Participants must have a reliable study partner: a spouse, relative, or friend who knows the participant well and sees him or her often, who will attend some study visits, and who will provide information about the participant during the study. Genetic Disclosure Prior to screening, research participants will meet with a genetic counselor to learn their APOE4 genotype status. Screening, which may be spaced out over multiple visits, will determine eligibility. It includes: • a physical/neruological exam • medical history • medication review • electrocardiogram (ECG) • collection of blood and urine • tests of memory and thinking • brain MRI/PET scan Study Activity • This study is comprised of 23 visits over the course of 60 months at the Perelman Center for Advanced Medicine at the Hospital of the University of Pennsylvania. • Participants will receive the study drug six times in the first year and four times in each year after. • Visits can include cognitive testing, blood work, physical and neurological exams, MRI scans and PET scans. Participants will be reimbursed for time and travel.