The purpose of the trial is the analysis of safety and efficacy of the chymase inhibitor BAY1142524 at a dose of 25 mg BID in comparison to placebo using a 6 months treatment period in type II diabetic patients with a clinical diagnosis of diabetic kidney disease. BAY1142524 or placebo will be given on top of evidence-based standard of care for diabetic kidney disease. Primary objective is the analysis of first signs of efficacy as determined by favourable changes in urinary albumin creatinine ratio. Secondary objective is the analysis of safety and tolerability as evidenced by the incidence and severity of adverse events. 64 valid patients have to complete treatment with verum and 32 valid patients have to complete treatment with placebo.

Inclusion Criteria:

• Patients with Type 2 Diabetes Mellitus and a clinical diagnosis of diabetic kidney disease (DKD) (as judged by the investigator) who have finished their up-titration with an angiotensin receptor blocker (ARB) or an ACEI (angiotensin-converting enzyme inhibitor) to their maximum tolerated dose at least 3 months prior to the screening visit, whereby the maximum tolerated dose has to be at least as high as the minimal recommended dose of an ARB or ACEI according to local and/or international guidelines. Patients have to be treated with an ARB or ACEI, but not with both simultaneously, without any adjustments to this therapy for at least 4 weeks prior to the screening visit.
• UACR >50 mg/g and <3000 mg/g in 2 out of 3 consecutive morning void samples at the screening and the baseline visit
• estimated glomerular filtration rate (eGFR) ≥30 mL/min/1.73 m*2 and <90 mL/min/1.73 m*2 (Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI]) at the screening visit and the baseline visit

Exclusion Criteria:

• Non-DKD if it is the main diagnosis contributory to chronic kidney disease (CKD), as judged by the investigator
• Known bilateral clinical relevant renal artery stenosis (>75%)
• New York Heart Association (NYHA) Class IV
• Acute kidney injury or dialysis within the last 3 months before the screening visit
• Renal replacement therapy during study conduct
• Renal allograft in place or a scheduled kidney transplant during study conduct
• Stroke, transient ischemic cerebral attack, acute coronary syndrome, or hospitalization for heart failure in the last 3 months prior to screening visit
• Clinically relevant hepatic dysfunction
• Uncontrolled hypertension as evidenced by systolic blood pressure >160 mmHg, diastolic blood pressure >100 mmHg (mean of triplicate values at the screening or baseline visit)