A Study of the Safety and Tolerability of ASP0777 in Subjects With Alzheimer's Disease (AD) Taking a Stable Dose of Donepezil

Inclusion Criteria:

- Subject has a Mini-Mental Status Exam score of 18-26

- Subject has a diagnosis of "probable" Alzheimer's Disease

- Subject has used donepezil for at least 3 months and has been on a stable dose for at
least 6 weeks prior to screening

- Subject has a reliable adult who is residing with him/her during the outpatient
portion of the study

- Subject is medically stable

- Subject has adequate cognitive, hearing, vision, and language skills

- Subject is able to ingest oral tablets

Exclusion Criteria:

- Subject has received any investigational product in another clinical study or
post-marketing clinical study within past 3 months

- Subject has any clinically significant abnormal laboratory tests

- Subject is a female who is pregnant, lactating or of childbearing potential who
refuses to use a form of contraception during the study

- Subject has a history of a drug allergy or intolerance to memantine or a related
compound

- Subject is currently using anti-dementia drugs (except for donepezil) or has used any
such drugs within the last 4 weeks

- Subject has a score of 2 on item 16 of Cornell Scale for Depression in Dementia (CSDD)
or has an overall CSDD score > 10

- Subject is using off-label medicines, non-medicinal compounds, or dietary aids/food
supplements to improve cognition that have not been at a stable dose for at least 4
weeks prior to Screening and/or are anticipated to change dosing regimen during the
study

- Subject has a history of drug or alcohol abuse within the past 12 months or subject
consumes > 1 drink of alcohol daily, or is unable to refrain from alcohol during the
study

- Subject is a current smoker or recently quit smoking (within the past 12 months)

- Subject has a clinically significant medical condition that is unstable or is likely
to become unstable during the course of the study

- Subject has history of seizures, other than febrile seizures during infancy

- Subject has history of repeated falls within past 6 months

- Subject has a major psychiatric illness or has received treatment for symptoms of a
major psychiatric illness within past 1 year. Mild psychiatric disorders are allowable