Study to Evaluate the Safety, Tolerability, and Pharmacokinetics of ABT-957 in Subjects With Mild-to-Moderate Alzheimer's Disease on Stable Doses of Acetylcholinesterase Inhibitors

Inclusion Criteria:

- Meets the National Institute of Neurological and Communicative Disorders and
Stroke/Alzheimer's Disease and Related Disorders Association criteria for probable
Alzheimer's disease (AD);

- Has a Mini-Mental State Examination total score of 16 to 26;

- Has a Modified Hachinski Ischemia Scale score of ≤ 4;

- Is taking a stable dose of donepezil, galantamine or rivastigmine for at least 30
days;

- Has had a computerized tomography or magnetic resonance imaging. The scan must not
show evidence for an alternative etiology for dementia;

- With the exception of a diagnosis of mild-to-moderate AD and the presence of stable
medical conditions, is in general good health.

Exclusion Criteria:

- Positive screen for drugs of abuse, alcohol or cotinine;

- Females must not have positive results for pregnancy;

- Focal neurological signs on examination;

- Has a clinically significant abnormal value, in serum chemistry, hematology or
urinalysis;

- History of any significant neurologic disease other than AD;

- History of head trauma, motor vehicle accident, concussion.