This study is open to adults between 18 and 65 years of age with a type of depression called major depressive disorder. The purpose of the study is to find out whether a medicine called BI 1569912 helps people with depression.

Participants are put into 4 groups randomly, which means by chance. Three of the 4 groups take different doses of BI 1569912 and 1 group takes placebo. Placebo tablets looks like BI 1569912 but do not contain any medicine. Participants take the tablets once a day for 6 weeks.

Participants are in the study for about 2.5 months. During this time, they visit the study site at least 7 times. At the visits, doctors and their staff ask participants about their depression symptoms. At the end of the study, the results are compared between the groups to see whether the treatment works. The doctors also regularly check the general health of participants and take note of any unwanted effects.

Inclusion criteria

• Male and female participants, 18 to 65 years of age, both inclusively at the time of consent
• Signed and dated written informed consent in accordance with International Council for Harmonisation-Good Clinical Practice (ICH-GCP) and local legislation prior to admission to the trial
• Women of childbearing potential (WOCBP) must be ready and able to use a highly effective method of birth control per ICH M3 (R2) that results in a low failure rate of less than 1% per year when used consistently and correctly plus one additional barrier method. A list of contraception methods meeting these criteria and instructions on the duration of use is provided in the participant information
• Established diagnosis of Major depressive disorder (MDD), single episode or recurrent, as confirmed at the time of screening by the Mini-International Neuropsychiatric Interview (MINI) with a duration of the current depressive episode ≥8 weeks AND ≤24 months at the time of randomisation
• Hamilton Depression Rating Scale-17 (HDRS-17) - Severity scale score ≥20
• Clinical Global Impression- Severity Scale (CGI-S) score ≥4

Exclusion criteria:

• Per Mini International Neuropsychiatric Interview (MINI), have ever met diagnostic criteria for schizophrenia, schizoaffective disorder, schizophreniform disorder, bipolar disorder, or delusional disorder
• Diagnosis with antisocial, paranoid, schizoid or schizotypal personality disorder, or MDD with psychotic features as per Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria, at the time of screening visit. Any other personality disorder at screening visit that significantly affects current psychiatric status and likely to impact trial participation, as per the judgement of investigator
• Diagnosis of any other mental disorder that was the primary focus of treatment within 6 months prior to screening (as per clinical discretion of the investigator)
• Treatment failure to 2 or more antidepressants in the current episode, defined as less than 50% response to treatments administered at an adequate dose and duration as evaluated by the Antidepressant treatment response questionnaire (ATRQ)
• History or presence (upon clinical examination) of seizure disorders or an increased risk of seizures (first degree relative with epilepsy), stroke, brain tumour, or any other major neurological illness that could impact participation in the trial
• A current or recent history of clinically significant suicidal ideation with intent within the past 3 months, corresponding to a score of 4 or 5 for ideation on the Columbia-Suicide Severity Rating Scale (C-SSRS) or a suicidal attempt within the past year, as indicated by the C-SSRS at screening visit
• Participants with a body mass index (weight [kg]/height [m]²) lower than 18 kg/m² or greater than 40 kg/m2 at screening
• Diagnosis of a moderate to severe substance related disorder as defined by DSM-5 criteria within 6 months prior to screening visit (with exception of caffeine and tobacco) Further exclusion criteria apply.

Once the criteria in section "Time Frame" are fulfilled, researchers can use the following link https://www.clinicalstudies.boehringer-ingelheim.com/msw/datasharing to request access to the clinical study documents regarding this study, and upon a signed "Document Sharing Agreement".

Furthermore, researchers can request access to the clinical study data, for this and other listed studies, after the submission of a research proposal and according to the terms outlined in the website.

One year after the approval has been granted by major Regulatory Authorities and after the primary manuscript has been accepted for publication, or after termination of the development program.

For study documents - upon signing of a 'Document Sharing Agreement'.

For study data - 1. after the submission and approval of the research proposal (checks will be performed by the sponsor and/or the independent review panel, including checking that the planned analysis does not compete with sponsor's publication plan); 2. and upon signing of a legal agreement.