Efficacy and Safety Study of ABT-288 in Subjects With Mild-to-Moderate Alzheimer's Disease

1. Have voluntarily signed an informed consent. 2. Subject meets diagnostic criteria criteria for probable AD (Alzheimer's Disease). 3. Female subjects must be postmenopausal for at least 2 years or surgically sterile. 4. Male subjects must be surgically sterile, sexually inactive or using a barrier method of birth control. 5. Subject has an identified, reliable caregiver. 6. Subject has a CT or MRI scan within 36 months prior to randomization. 7. With the exception of a diagnosis of mild-to-moderate AD and the presence of stable medical conditions, the subject is generally in good health based on medical history, physical examination, vital signs, clinical lab tests and ECG

1. Subject is currently taking or has taken a medication for the treatment of AD or dementia with 60 days of Screening visit, or is participating in cognitive therapy for the treatment of AD or dementia. 2. Subject uses non-prescribed drugs of abuse or has a history of drug or alcohol abuse/dependence. 3. Subject has a history of any significant neurologic disease other than AD. 4. Subject has a history of intolerance or adverse reaction to donepezil that led to discontinuation. 5. Subject has received any investigation product within 6 weeks prior to study drug administration.