A Study to Test Different Doses of BI 1569912 in People With Depression Who Take Anti-depressive Medicine

Inclusion criteria:

1. Male and female participants, 18 to 65 years of age, both inclusively at the time ofconsent.

2. Signed and dated written informed consent in accordance with ICH-GCP and locallegislation prior to admission to the trial.

3. Women of childbearing potential (WOCBP) must be ready and able to use a highlyeffective method of birth control per ICH M3 (R2) that results in a low failure rateof less than 1% per year when used consistently and correctly plus one additionalbarrier method. A list of contraception methods meeting these criteria andinstructions on the duration of use is provided in the participant information andin the study protocol.

4. Established diagnosis of major depressive disorder (MDD), single episode orrecurrent, as confirmed at the time of screening by the mini-internationalneuropsychiatric interview (MINI) with a duration of current depressive episode ≥8weeks at the time of screening visit.

5. Hamilton Depression Rating Scale-17 (HDRS-17) - Severity scale score >17.

6. A documented ongoing monotherapy treatment of ≥6 weeks at the randomisation visit,with an selective serotonin reuptake inhibitor (SSRI) or serotonin andnorepinephrine reuptake inhibitor (SNRI) specified in the investigator site file (ISF) at adequate dose (at least minimum effective dose as per prescribinginformation).

• The participant must adhere to the screening visit dose of the backgroundSSRI/SNRI until the end of the trial. Participants should be on a stable dosefor at least 4 weeks prior to randomisation.

• Participants, who, in addition to their monotherapy with an SSRI/SNRI, aretaking additional low dose antidepressant medications for purposes other thantreating depressive symptoms, are not excluded. The dose must be less than thelowest dose indicated for MDD.

7. In the current episode, participants have shown insufficient treatment responsedefined by less than 50% response to a maximum of 4 antidepressant treatments ofadequate dose and treatment duration (according to Summary of ProductCharacteristics) as evaluated by the antidepressant treatment response questionnaire (ATRQ).

Exclusion criteria:

1. Per MINI, have ever met diagnostic criteria for schizophrenia, schizoaffectivedisorder, schizophreniform disorder, bipolar disorder, or delusional disorder.

2. Diagnosis with antisocial, paranoid, schizoid or schizotypal personality disorder,or MDD with psychotic features as per Diagnostic and Statistical Manual of MentalDisorders, Fifth Edition (DSM-5) criteria, at the time of screening visit. Any otherpersonality disorder at screening visit that significantly affects currentpsychiatric status and likely to impact trial participation, as per the judgement ofinvestigator.

3. Diagnosis of any other mental disorder that was the primary focus of treatmentwithin 6 months prior to screening (as per clinical discretion of the investigator).

4. History or presence (upon clinical examination) of seizure disorders or an increasedrisk of seizures (first degree relative with epilepsy), stroke, brain tumour or anyother major neurological illness that could impact participation in the trial.

5. A current or recent history of clinically significant suicidal ideation with intentwithin the past 3 months, corresponding to a score of 4 or 5 for ideation on theColumbia-suicide severity rating scale (C-SSRS) or a suicidal attempt within thepast year, as indicated by the C-SSRS at screening visit.

6. Participants with a body mass index (weight [kg]/height [m]²) lower than 18 kg/m² orgreater than 40 kg/m² at screening.

7. Diagnosis of a moderate to severe substance related disorder within 6 months priorto screening visit (with exception of caffeine and tobacco).

8. Positive drug screen (amphetamines, opiates, cocaine, barbiturates, phencyclidine)at screening or Visit 1A (if applicable). Participants with positive cannabis andbenzodiazepine drug tests can be included if the investigator confirms that there isno active substance related disorder. Further exclusion criteria apply.