A Study to Find Out Whether BI 765423 Has an Effect on Lung Function in People With Idiopathic Pulmonary Fibrosis (IPF) With or Without Standard Treatment

Inclusion criteria

• 40 years of age or older at the time of informed consent signature.
• Signed and dated written informed consent in accordance with International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use - Good Clinical Practice (ICH-GCP) and local legislation prior to admission to the trial.
• Male or female patients. Male patients must not donate sperm while taking part in this study and for a specific period after the last dose of the IMP. Male patients with woman of childbearing potential (WOCBP) sexual partners must use contraception (male condom) to avoid exposure via seminal fluid during treatment and for a specific period after last drug intake. Women can only be included if they are of non-childbearing potential, defined as meeting at least one of the below conditions:

• Permanently surgically sterilised (hysterectomy, bilateral salpingectomy and/or bilateral oophorectomy)
• Postmenopausal, defined as no menses for 12 months without an alternative medical cause. In questionable cases wherein the menopausal status is uncertain and cannot be clearly determined, the following should be taken into consideration by the investigator:

• Women not using sex hormone medication such as hormone replacement therapy may be included if a blood sample confirms levels of follicle stimulating hormone (FSH) > 40 U/L and estradiol < 30 ng/L"
• Patients with a documented diagnosis of IPF prior to Visit 1, confirmed by the investigator as per the 2022 American Thoracic Society (ATS)/European Respiratory Society (ERS)/Japanese Respiratory Society (JRS)/Latin American Thoracic Association (ALAT) Guideline and, if available, surgical lung biopsy or transbronchial lung cryobiopsy histopathology report.
• Patients with a high-resolution computed tomography (HRCT) taken within 12 months of Visit 1 (or during the screening period, if not available) confirming "UIP" or "probable UIP" HRCT pattern consistent with the clinical diagnosis of IPF by central review (prior to Visit 2).

• Patients with an "indeterminate" HRCT finding are eligible if a clinical diagnosis of IPF can be confirmed based on an historical histopathology report of a surgical lung biopsy or cryobiopsy demonstrating a "UIP" or "Probable UIP" pattern or Multidisciplinary Discussion and Diagnosis as per ATS guidelines.
• Patients with an "alternative diagnosis" HRCT finding are eligible if a clinical diagnosis of IPF can be confirmed based on an historical histopathology report of a surgical lung biopsy or cryobiopsy demonstrating a "UIP" pattern Multidisciplinary Discussion and Diagnosis as per ATS guidelines.
• Patients with an extent of fibrosis ≥20% as per an HRCT of the chest performed within 12 months prior to Visit 1 or during the screening period (if not available) and confirmed by central review.
• Patients with a Forced vital capacity (FVC) ≥45% predicted at Visit 1. Predicted normal values will be calculated according to Global Lung Initiative (GLI).
• Patients with haemoglobin-corrected diffusing capacity of the lungs for carbon monoxide (DLCO) ≥20% predicted at Visit 1.

Further inclusion criteria apply.

Exclusion criteria

• Acute exacerbation of IPF within at least 12 weeks prior to Visit 1 and/or during the screening period (investigator-determined).
• Relevant airways obstruction (pre-bronchodilator forced expiratory volume in 1 second (FEV1)/FVC <0.7) at Visit 1.
• Lower respiratory tract infection requiring treatment within 4 weeks prior to Visit 1 and/or during the screening period.
• Significant PH defined by any of the following:

• Previous clinical or echocardiographic evidence of significant right heart failure according to investigator's judgement
• History of right heart catheterisation showing a cardiac index ≤2 L/min/m^²
• PH requiring parenteral therapy with prostanoids
• On nintedanib or pirfenidone treatment for less than 12 weeks prior Visit 1, planning to start nintedanib or pirfenidone within the first 12 weeks of investigational medicinal product (IMP) treatment or on combined nintedanib plus pirfenidone treatment. Newly diagnosed patients considered in need of SoC treatment during the next 12 weeks by the treating physician, who would be withheld SoC treatment only for the sake of participation in the trial, should also be excluded.
• Cardiovascular comorbidities including

• Severe hypertension (uncontrolled under treatment≥160/100 mmHg at multiple occasions) within 3 months of Visit 1
• Myocardial infarction, stroke, or transient ischemic attack within 6 months of Visit 1
• Unstable cardiac angina within 6 months of Visit 1
• Life expectancy for any concomitant disease other than IPF <2.5 years (investigator assessment).

Further exclusion criteria apply.