This study is open to people aged 18 to 65 who have post-traumatic stress disorder. The purpose of this study is to find out whether a medicine called BI 1358894 improves symptoms in people with post-traumatic stress disorder.

Participants are put into 2 groups randomly, which means by chance. Participants take BI 1358894 or placebo as tablets every day for 2 months. Placebo tablets look like BI 1358894 tablets but do not contain any medicine.

Participants are in the study for about 3 months. During this time, they visit the study site about 8 times and get about 4 phone calls from the trial staff. During the study, participants answer questions in interviews and complete questionnaires so the doctors can check whether their symptoms change.

The doctors also regularly check participants' health and take note of any unwanted effects.

Inclusion Criteria:

• Established diagnosis of Post-Traumatic Stress Disorder (PTSD) corresponding to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria
• Time since index event according to Life Events Checklist / Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) Criterion A at least 3 months before screening visit
• PTSD must be the clinically pre-dominant disorder, as per investigator´s judgement. Other comorbid psychiatric disorders are allowed, unless specifically excluded in the exclusion criteria
• A total severity score of ≥ 33 on the PTSD Checklist for DSM-5 (PCL-5) at the screening visit
• Moderate to severe PTSD confirmed by CAPS-5 range ≥ 30 confirmed at screening visit
• Male or female patients, 18 to 65 years of age, both inclusively at the time of informed consent
• Women who are of child-bearing potential (WOCBP) must be able and willing to use two methods of contraception, as confirmed by the investigator, which include one highly effective method of birth control per International Council on Harmonisation (ICH) M3 (R2) that result in a low failure rate of less than 1%, plus one additional barrier method
• Signed and dated written informed consent in accordance with International Council on Harmonisation - Good Clinical Practice (ICH-GCP) and local legislation prior to admission to the trial

Exclusion Criteria:

• Corresponding to DSM-5, had ever met diagnostic criteria for schizophrenia, schizoaffective disorder, schizophreniform disorder, bipolar disorder, delusional disorder, brief psychotic disorder or any other psychotic disorder as well as Major Depressive Disorder (MDD) with psychotic features as assessed by the Mini-International Neuropsychiatric Interview (MINI) at the time of screening
• Any psychiatric or non-psychiatric medical condition likely to negatively impact trial participation as per the judgement of the investigator
• Acute stress disorder or significant traumatic event within 3 months prior to the screening visit
• Use of stimulant medications within 3 months prior to the screening visit (Attention Deficit Hyperactivity Disorder (ADHD) diagnosis alone is not exclusionary)
• Severe traumatic brain injury (life-time) or moderate traumatic brain injury within the last 2 years prior to screening visit or 3 months for mild traumatic brain injury, based on the Ohio State University Traumatic Brain Injury (TBI) Identification Method Short Form. Or history of traumatic brain injury that would impact ability to complete trial assessments or procedures according to investigator.
• Current treatment with trauma focused therapy (i.e. Cognitive Processing Therapy (CPT), Prolonged Exposure Therapy (PE), Eye Movement Desensitization and Reprocessing (EMDR)). A psychotherapy in type, intensity and/or frequency other than trauma focused therapy is allowed if stable within the last 8 weeks prior to screening and not anticipated to change during the entire course of the trial. Long-term psychotherapy is permitted as long as patients are not in an exposure phase during the trial.
• Diagnosis of a current moderate or severe alcohol use disorder according to MINI within 3 months prior to screening visit (mild alcohol use disorder (AUD) and patients in early remission = criterion not met for between 3 & 12 months are allowed) Further exclusion criteria apply

After the study is completed and the primary manuscript is accepted for publishing, researchers can use this following link https://www.mystudywindow.com/msw/datasharing to request access to the clinical study documents regarding this study, and upon a signed "Document Sharing Agreement".

Also, Researchers can use the following link https://www.mystudywindow.com/msw/datasharing to find information in order to 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.

The data shared are the raw clinical study data sets.

After all regulatory activities are completed in the US and EU for the product and indication, and after the primary manuscript has been accepted for publication.

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 both the independent review panel and the sponsor, including checking that the planned analysis does not compete with sponsor's publication plan); 2. and upon signing of a 'Data Sharing Agreement'.