Inclusion Criteria:

• Male / female outpatients.
• Age > 50 years at screening.
• Dementia of Alzheimer’s Type (DSM-IV 290.0) according to DSM-IV criteria, Probable AD according to NINCDS-ADRDA criteria, Mini-Mental State Examination score > 12 and < 26.
• Untreated or treated for a minimum of 6 months before randomization with a stable dose of the cholinesterase inhibitors
• Generally healthy and ambulatory or ambulatory-aided (i.e., walker or cane).
• Presence of a reliable caregiver.
• Patient, identified caregiver and, if applicable, patient surrogate (primary relative, legal guardian, medical proxy) have given their informed written consent and are capable of following study procedures

Exclusion Criteria:

• Any cause of dementia not due to Alzheimer’s disease, Delusions, delirium, psychosis, depression, or other significant psychiatric disorder.
• Treatment with any registered or putative cognitive enhancer or disease modifier other than donepezil, rivastigmine or galantamine.
• Females who are pregnant or breast-feeding. Females of child bearing potential (premenopausal female biologically capable of becoming pregnant) must have a confirmed negative serum b–HCG pregnancy test at the screening visit, and must use an acceptable method of birth control.
• Severe or unstable cardiovascular, respiratory, renal, hematological, endocrinological, neurological or other somatic disease.
• Use of CYP3A4 strong inhibitors
• Evidence (detected by history, physical examination and / or laboratory / ECG tests) of any clinically significant or unstable medical disorder that could interfere with the subject's participation in the clinical trial; interfere with the absorption, metabolism or excretion of the study medication; or interfere with the evaluation of the study drug. Alterations of laboratory tests or ECG findings of potential clinical significance.