Study Evaluating TheSafety And Efficacy Of PF-05212377 Or Placebo In Subjects With Alzheimer's Disease With Existing Neuropsychiatric Symptoms On Donepezil

• Drug: PF-05212377 (SAM-760)
  
  30 mg QD of PF-05212377 (SAM-760)
• Other: Placebo
  
  Placebo QD

• Experimental: 30 mg QD of PF-05212377
  
  Intervention: Drug: PF-05212377 (SAM-760)
• Placebo Comparator: Placebo
  
  Intervention: Other: Placebo

Inclusion Criteria:

• Clinical diagnosis of probable AD with supportive brain imaging documentation
• Have existing neuropsychiatric symptoms as defined by a score equal or greater than 10 on the NPI at screening, arising from item scores equal or greater than 2 (frequency X severity) on at least 2 domains.
• Has been on donepezil (stable dose of 5 mg or 10 mg) for at least four months, with no intent to change such for the duration of the study.

Exclusion Criteria:

• Demonstrate extreme agitation, physical aggression or violence to themselves, their caregiver, or others, and/or an inability to complete the ADAS-cog assessment at Screening.
• Have major structural brain disease other than Alzheimer's Disease
• Other severe acute or chronical medical or psychiatric condition or laboratory abnormality