A Study to Test How Well Different Doses of BI 3804379 Are Tolerated by Healthy People and Patients With Metabolic Dysfunction-associated Steatohepatitis (MASH)

Inclusion criteria for Part A and Part B: 1. Healthy male or female (of non-child-bearing potential) participants according to the assessment of the investigator, as based on a complete medical history including a physical examination, vital signs (blood pressure (BP), pulse rate (PR), respiratory rate (RR), temperature (TEMP)), 12-lead electrocardiogram (ECG), and clinical laboratory tests 2. Age of 18 to 65 years (inclusive) 3. Body mass index (BMI) of 18.5 to 30.0 kg/m2 (inclusive) 4. Signed and dated written informed consent in accordance with ICH Harmonized Guideline for Good Clinical Practice (ICH-GCP) and local legislation prior to admission to the trial Further inclusion criteria apply Inclusion criteria for Part C: 1\. Male or female patients with advanced liver fibrosis due to MASH, aged between 18 and 70 years (inclusive) Further inclusion criteria apply Exclusion criteria for Part A and Part B: 1. Any finding in the medical examination (including BP, PR or ECG) deviating from normal and assessed as clinically relevant by the investigator. 2. Repeated measurement of systolic BP outside the range of 90 to 140 millimetre of mercury (mmHg), diastolic BP outside the range of 45 to 90 mmHg, or PR outside the range of 45 to 100 beats per minute (bpm). 3. Any laboratory value outside the reference range that the investigator considers to be of clinical relevance. 4. Gastrointestinal, hepatic, renal, respiratory, cardiovascular, metabolic, immunological or hormonal disorders that the investigator considers to be of clinical relevance. Further exclusion criteria apply Exclusion criteria for Part C: 1. Type 1 diabetes or uncontrolled type 2 diabetes (e.g., hemoglobin A1C (HbA1c) ≥10%, recent major treatment changes, or severe hypoglycemia). 2. Significant weight loss (≥10%) between diagnosis and screening. 3. Relevant surgery after diagnosis or planned during the study period. 4. Evidence of clinically significant or unstable disease increasing risk to the participant. 5. Severe renal impairment (estimated glomerular filtration rate (eGFR) \<30 mL/min/1.73 m²). 6. Uncontrolled hypertension or significant cardiovascular disease (e.g., recent myocardial infarction, stroke, or heart failure New York Heart Association (NYHA) class III/IV). 7. Clinically relevant ECG abnormalities, including QT interval corrected for heart rate (QTc) prolongation or risk factors for Torsade de Pointes. 8. Participation in another clinical trial or exposure to an investigational drug within 60 days prior to study treatment. Further exclusion criteria apply