This study aims to determine whether the Cogstate testing battery can detect improvements in cognitive function in participants with mild AD. The primary hypothesis is that for one of the Cogstate battery tests, One Card Learning (OCL), the standard deviation associated with the change from baseline in OCL measurements after 12 weeks of donepezil and placebo treatments is =<0.1

Inclusion Criteria:

• Meets listed criteria for a diagnosis of probable AD
• Has a clearly documented history either in medical records or from an informant of cognitive decline over at least 6 months
• Has a reliable partner/caregiver who is willing to provide input by participating in assessments
• Has results of a physical examination and clinical laboratory tests within normal or clinically acceptable limits
• Can communicate with trial staff acceptably, possesses the ability to respond verbally to questions, follow instructions, complete questionnaires, and adhere to visit schedules
• Can read at a 9th grade level or equivalent, and has an acceptable history of academic achievement and/or employment
• Has a magnetic resonance imaging (MRI) scan that rules out non-AD conditions contributing to cognitive dysfunction
• Capably performs the CogState screening battery
• Has adequate visual acuity and function
• Females are not of childbearing potential

Exclusion Criteria:

• Has ever received acetylcholinesterase inhibitors, memantine, or other symptomatic AD treatment including approved medical foods
• Has an uncontrolled, clinically significant medical condition or situation within 3 months prior to screening
• Has had major surgery within 3 months prior to screening
• Has tested positive for human immunodeficiency virus (HIV) or has evidence of an active hepatitis B infection
• Has a history of malignancy within the prior 5 years
• Is unwilling or ineligible to undergo an MRI scan
• Has a history of clinically important structural changes on screening MRI scan
• Has a clinically important history of stroke or a diagnosis of vascular dementia
• Has evidence of a clinically relevant non-AD neurological disorder
• Has a history of head trauma, or serious infectious disease affecting the brain within the prior 3-5 years
• Has evidence of a clinically relevant or unstable psychiatric disorder, excepting major depression in remission
• Has evidence of a current episode of major depression
• Has evidence of Type 4 or Type 5 Suicidal Ideation
• Has clinically significant vitamin B12 or folate deficiency in the 6 months prior to screening
• Is pregnant, attempting to become pregnant or is nursing children
• Has used any investigational drug or participated in any other clinical trial within the prior 30 days
• Has a history of alcoholism or drug dependency/abuse within the last 5 years
• Has a relative contraindication to donepezil including sick sinus syndrome, third degree heart block, active gastrointestinal (GI) bleeding, Zollinger-Ellison syndrome, uncontrolled peptic ulcer disease, or uncontrolled asthma

https://www.merck.com/clinical-trials/pdf/ProcedureAccessClinicalTrialData.pdf

Up to Week 18 (approximately up to 129 days)

All participants who received study medication.