The purpose of this trial is to assess the efficacy and safety of S47445 versus placebo in patients with Alzheimer's disease at mild to moderate stages with depressive symptoms. An optional 28-week extension period will be performed to evaluate safety/tolerance and efficacy of S47445 in co-administration with donepezil.

Inclusion Criteria:

• Out-patients
• Able to perform neuropsychological tests
• Have a responsible informant
• DSM-IV-TR criteria for Dementia of the Alzheimer's Disease Type
• Mini mental State Examination (MMSE) = 15-24 both inclusive
• National Institute of Mental Health (NIMH) provisional criteria for depression in AD (NIMH-dAD)
• Cornell Scale for Depression in Dementia total score > or = 8
• Patients who have never been treated with AD treatments or patients who have stopped AD treatment whatever the reason
• Patients either not currently treated with an antidepressant or patients being treated with an antidepressant at the recommended dose for at least 8 weeks without clinical efficacy, who can stop this treatment according to the investigator's opinion.

Exclusion Criteria:

• Patients not able to read or write
• Patients having participated in a study testing disease modifying therapy for AD, or in another study with administration of investigational drug or device within the previous 3 months prior to selection visit
• Depressive symptoms that, in investigator's judgment, are clearly due to a medical condition other than AD, or are a direct result of non-mood related dementia symptoms
• History of epilepsy or solitary seizure
• Medical history of Major Depressive Disorder more than 3 years before onset of the disease, treated with antidepressive drugs or electroconvulsive therapy
• Severe or unstable disease of any type that could interfere with safety and efficacy assessments
• Alcohol abuse or drug abuse or addiction, as judged by the clinician (excluding nicotine)
• Clinically relevant lactose intolerance
• Antidepressant treatment not stopped for at least 3 weeks before inclusion
• Significant worsening of depressive symptoms or high suicidal risk according to investigator's judgment
• For optional extension phase: medically instable Chronic Obstructive Pulmonary Disease and asthma, known hypersensitivity to donepezil hydrochloride or piperidine derivatives

Researchers can ask for a study protocol, patient-level and/or study-level clinical trial data including clinical study reports (CSRs).

They can ask all interventional clinical studies:

• submitted for new medicines and new indications approved after 1 January 2014 in the European Economic Area (EEA) or the United States (US).
• Where Servier or an affiliate are the Marketing Authorization Holders (MAH). The date of the first Marketing Authorization of the new medicine (or the new indication) in one of the EEA Member States will be considered within this scope.

After Marketing Authorisation in EEA or US if the study is used for the approval.

Researchers should register on Servier Data Portal and fill in the research proposal form. This form in four parts should be fully documented. The Research Proposal Form will not be reviewed until all mandatory fields are completed.