Comparative Study to Test Safety and Efficacy of Neurotrophic and Cholinergic Treatment of Alzheimer's Disease

Inclusion criteria * Diagnosis of probable AD (Diagnostic and Statistical Manual of Mental Disorders, 4th revision \[DSM-IV\], National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association \[NINCDS-ADRDA\]) * Mini-Mental-State-Examination (MMSE) of 12-25, inclusive * Modified Hachinski score ≤4 * Computed tomography (CT) or magnetic resonance imaging (MRI) scan within 12 months prior to screening without evidence of infection, infarction, or other focal lesions and without clinical symptoms suggestive of intervening neurological disease. Patients who have had a single, clinically silent lacunar infarct are eligible provided the lacunar infarct is not felt to be responsible for the patient's symptoms, is \<1 centimeter (cm) maximal diameter in any dimension, is not present in hippocampus of either hemisphere, head of the left caudate, or the dorsomedial region of the left thalamus. Subjects with scans showing atrophy, ventricular enlargement or mild to moderate white matter changes (involving up to approximately 25% of hemispheric white matter) are eligible if the study is otherwise normal. * Hamilton Depression Scale score of ≤15 * Adequate visual and auditory acuity to allow neuropsychological testing * Ability to attempt all sections of the Alzheimer's Disease Assessment Scale Cognitive Subpart (extended version)(ADAS-cog+) * Good general health without additional diseases expected to interfere with the study * Normal B12, folic acid, venereal disease research laboratory (VDRL), and thyroid-stimulating hormone (TSH) or without any clinically significant laboratory abnormalities that would be expected to interfere with the study * Electrocardiogram (ECG) and chest x-ray (if clinically necessary per Investigator) without clinically significant laboratory abnormalities that would be expected to interfere with the study * Patient is not institutionalized * Patient is not pregnant, lactating, or of childbearing potential * Sufficient language skills to complete all testing without assistance of a language interpreter * Responsible caregiver being present during administration of study drug, monitor the patient's compliance with study procedures and adverse events, and accompany the patient to all clinic visits * Written informed consent obtained from the patient and caregiver prior to entry into the study Exclusion criteria * Any clinically significant laboratory abnormalities on the battery of screening tests * Patients who in the past have not tolerated treatment with 10 mg Aricept or treatment with a corresponding dose of another cholinesterase inhibitor * Severe psychotic features, depression, agitation or behavioral problems within the last three months that could lead to difficulty complying with the protocol * Any significant systemic illness or unstable medical condition that could lead to difficulty complying with the protocol * Patients who in the Investigator's opinion would not comply with study procedures * Any significant neurological disease other than Alzheimer's Disease, within the past five years, or with residual effects * Delusional symptoms are often characteristic of Alzheimer's Disease, but patients with symptoms so pronounced that they warrant an alternative diagnosis are excluded * History of alcohol or substance abuse or dependence within the past two years (DSM-IV) * History of schizophrenia (DSM-IV) * Patients with a history of systemic cancer within the past two years are excluded * History of myocardial infarction in the past year or unstable or severe cardiovascular disease, including uncontrolled hypertension * Uncontrolled insulin-requiring diabetes or non-insulin dependent diabetes mellitus (Haemoglobin A1c \[HBA1c\] \> 10.0) * Use of: * systemic corticosteroids for more than one week within three months prior to Baseline (BL) * Anti-Parkinsonian agents within two months prior to baseline (BL) * Approved or investigational Cholinesterase Inhibitors within 30 days or five half-lives, whichever is longer, prior to BL * Memantine or other N-methyl-D-aspartic acid (NMDA) antagonists within 30 days or five half-lives, whichever is longer, prior to BL * Treatment with high potency neuroleptics or narcotic analgesics within four weeks prior to BL * Cimetidine within four weeks prior to BL * Sedatives more frequently than two times per week for sleep within four weeks prior to BL