A Study to Test the Effect of Different Doses of BI 685509 on Kidney Function in People With Diabetic Kidney Disease

Inclusion criteria

• Signed and dated written informed consent in accordance with International Council of Harmonisation-Good Clinical Practice (ICH-GCP) and local legislation prior to admission to the trial.
• Male or female patients aged ≥ 18 years at time of consent.
• eGFR (Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI] formula) ≥ 20 and < 90 mL/min/1.73 m2 at Visit 1 by central laboratory analysis. eGFR must remain ≥ 20 mL/min/1.73 m2 after Visit 1 up to the start of Visit 3, measured by central or any local laboratory analysis.
• Urine Albumin Creatinine Ratio (UACR) ≥ 200 and < 3,500 mg/g in spot urine (midstream urine sample) by central laboratory analysis at Visit 1.
• Treatment with the highest tolerated dose of either Angiotensin Converting Enzyme inhibitor (ACEi) or Angiotensin Receptor Blocker (ARB) (but not both together), and stable dose for ≥ 4 weeks before Visit 1 with no planned change of the therapy during the trial.
• If the patient is taking any of the following medications they should be on a stable dose at least 4 weeks prior to visit 1 until start of treatment, with no planned change of the therapy during the trial: anti-hypertensives, Non-steroidal anti-inflammatory drug(s) (NSAIDs), endothelin receptor antagonists, systemic steroids or Sodium-Glucose co-Transporter-2 (SGLT2) inhibitors.
• Patients with stable type 1 or type 2 diabetes mellitus, diagnosed before informed consent. Treatment (including SGLT2 inhibitor and/or Glucagon-Like Peptide 1 (GLP1) receptor agonist) should have been unchanged or changes deemed minor (according to investigator's judgement) within 4 weeks before Visit 1 and until start of trial treatment.
• Glycated Haemoglobin (HbA1c) < 10.0% at Visit 1 measured by the central laboratory.

Further inclusion criteria apply.

Exclusion criteria

• Treatment with Renin Angiotensin Aldosterone System (RAAS) interventions (apart from either ACEi or ARB), phosphodiesterase 5 inhibitors, non-specific phosphodiesterase inhibitors (such as dipyridamole and theophylline), NO donors including nitrates, sGC-stimulators/activators (other than trial treatment) or any other restricted medication (including OATP1B1/3 inhibitors, UGT inhibitors/inducers) as provided in the Investigator Site File (ISF) within 4 weeks prior to visit 1 and throughout screening and baseline run-in. Patients who must or wish to continue the intake of restricted medications or any drug considered likely to interfere with the safe conduct of the trial are also excluded.
• Any clinically relevant laboratory value from screening until start of trial treatment, which in the investigator's judgement puts the patient at additional risk.
• Biopsy or otherwise confirmed non-diabetic chronic kidney disease, or non-diabetic chronic kidney disease in the opinion of investigator, e.g., Autosomal Dominant Polycystic Kidney Disease (ADPKD), uncontrolled lupus nephritis. The presence of a hypertensive etiology does not need to be excluded unless it is evident this is the only cause for the Chronic Kidney Disease (CKD).
• Any immunosuppression therapy or immunotherapy in the last 3 months prior to visit 1 and throughout screening and baseline run-in (except prednisolone ≤10 mg or equivalent).
• Acute kidney injury (AKI) according to the Kidney Disease: Improving Global Outcomes (KDIGO) in the 30 days prior to Visit 1 until the start of trial treatment.
• Planned start of chronic renal replacement therapy during the trial or end stage renal disease before start of trial treatment.
• Known history of moderate or severe symptomatic orthostatic dysregulation as judged by the investigator before start of trial treatment.
• The patient has an active infection with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) (or is known to have a positive test) from screening until randomisation.

Further exclusion criteria apply.