This study is for adults aged 18 to 65 who have major depressive disorder (MDD) and have not had success with past depression treatments. The aim is to see if a new medicine, BI 1569912, can help. Participants will continue using their regular depression medicine during the study. They will be randomly assigned to one of four groups: three groups will receive different doses of BI 1569912, and one group will receive a placebo (a pill that looks like BI 1569912 but contains no medicine). The study lasts for about 2 to 4.5 months, with visits to the study site at least six times. Doctors will ask about symptoms and check health regularly.

• Study Length: 2 to 4.5 months with at least 6 visits.
• Participation: Random assignment to medication or placebo.
• Eligibility: Must have MDD and continue regular depression treatment.