The study is designed to investigate the efficacy, safety and tolerability of SB-742457 versus placebo in subjects with mild-to-moderate Alzheimer's disease. SB-742457 is an experimental treatment which increases the levels of certain chemicals in the brain that are often decreased in patients with Alzheimer's disease.

• Drug: Donepezil
  investigational drug
• Drug: Placebo
  comparator
  Other Names:

  • Placebo
  • SB-742457
  • Donepezil
• Drug: SB-742457
  investigational drug

• arm 2: Placebo Comparator
  Intervention: Drug: Placebo
• arm 1: Experimental
  Interventions:

  • Drug: Donepezil
  • Drug: SB-742457

Inclusion criteria:

• Subjects and their caregivers must provide informed consent prior to study entry.
• Subjects must have a clinical diagnosis of probable mild-to-moderate Alzheimer's disease with a documented 6-month history of AD symptoms
• Subjects must have a regular caregiver who is willing to attend visits, oversee the subject's compliance with the study and report on the subject's status.
• Female subjects of child-bearing potential must agree to pregnancy testing and approved form of birth control.

Exclusion criteria:

• Diagnosis of possible, probable or definite vascular dementia.
• History/evidence of any other CNS disorder that could be interpreted as a cause of dementia
• History of known or suspected seizures, loss of consciousness or significant head trauma
• Subjects with ECG, blood pressure and laboratory values outside of protocol criteria are excluded.
• Subjects with known photosensitivity
• Subjects with a history of previous exposure to SB-742457, taking agents for which there is a theoretical risk of interaction with SB-742457, or taking medication for Alzheimer's disease or centrally acting agents which might impact study outcomes may not participate.