Efficacy and Safety of 3 Doses of S47445 Versus Placebo in Patients With Alzheimer's Disease at Mild to Moderate Stages With Depressive Symptoms

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