Efficacy Study of MPC-7869 to Treat Patients With Alzheimer's

Inclusion Criteria: * Have had a diagnosis of probable Alzheimer's disease. * Men or women ages 55 years or greater and living in the community at the time of enrollment (i.e., not living in a rest home or nursing care facility). * Signed the subject Informed Consent Form and is willing and able to participate for the duration of the study. * Ability to read and understand English or Spanish to ensure compliance with cognitive testing and study visit procedures. * Female subjects must be surgically sterile or postmenopausal for \> 1 year. * Subjects currently taking approved medication for Alzheimer's disease for at least six months prior to day 1 may be enrolled. * Subjects must have a reliable caregiver who can read, understand and speak English or Spanish. Exclusion Criteria: * Current evidence of other causes of dementia. * History or evidence of, active malignancy, except for basal cell carcinoma or squamous cell carcinoma of the skin, within the 24 months prior to entry. Men with prostate cancer may be enrolled at the discretion of the sponsor. * Chronic or acute renal, hepatic or metabolic disorder. * Use of any investigational therapy within 30 days, or 5 half-lives, whichever is longer, and/or use of AD immunotherapy prior to screening. * Major surgery and related complications not resolved within 12 weeks prior to Day 1.