BI 425809 in Patients With Cognitive Impairment Due to Alzheimer's Disease.

Inclusion criteria: * Patients with early signs of dementia of Alzheimer Type * Male and female patients with an age of at least 55 years * Concomitant use of acetylcholinesterase inhibitors (AChEIs) is allowed but not required. Patients who are currently taking AChEIs are eligible as long as they have been using a stable dose for at least 3 months prior to screening and no change is foreseen for the duration of the study. This dose must be consistent with the product label in the concerned country. Patients who are not currently taking AChEIs but have taken them in the past are also eligible if AChEIs were stopped at least 3 months prior to screening. * Patients must have at least 6 years of formal education and fluency in the test language as verbally confirmed by the patient and documented by the study investigator. * Patients must have a reliable study partner (per investigator judgement, for instance a family member, partner etc., guardian) * Further inclusion criteria apply Exclusion criteria: * Cognitive impairment or dementia with any etiology other than Alzheimer's Dementia (AD) * Substantial concomitant cerebrovascular disease (defined by a history of a stroke / intracranial haemorrhagia) temporally related to the onset of worsening of cognitive impairment per investigator judgement * Medical history or diagnosis of any of symptomatic and unstable/uncontrolled conditions per investigator judgement * Patients receiving prescribed drugs for treatment of dementia of Alzheimer Type (other than Acetylcholine Esterase Inhibitors) at screening or within 3 months prior to screening * Previous participation in investigational drug studies of dementia of Alzheimer's Type within three months prior to screening. Patients having received any active treatment in studies targeting disease modification of AD are excluded. Previous participation in studies with non-prescription medications, vitamins or other nutritional formulations is allowed. * Clinically significant uncompensated hearing loss in the judgment of the investigator. Use of hearing aids is allowed. * Further exclusion criteria apply