Inclusion Criteria:  Participants must be 6 months to <18 years at the time when the informed consent/assent is signed  Participants must have a clinical diagnosis of chronic kidney disease (CKD) at screening which is defined as  CKD stages I-III (eGFR ≥30 mL/min/1.73m^2) for children ≥1 year to <18 years of age or a serum creatinine ≤ 0.40 mg/dL for infants 6 months to < 1 year of age and  severely increased proteinuria as defined by  Urinary protein-to-creatinine ratio (UPCR) of ≥ 0.50 g/g in participants ≥ 2 years with CKD stage II and III or UPCR ≥ 1.0 g/g for patients < 2 years of age or ≥ 2 years of age and with CKD stage I Treated with an angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) at optimized doses defined as maximally tolerable doses within the recommended dose range according to guidelines on blood pressure management, unchanged for at least 30 days prior to screening K+ ≤5.0 mmol/L for children ≥2 years of age at both screening and D0, and ≤5.3 mmol/L for children <2 years of age at both screening and D0  Exclusion Criteria:  Planned urological surgery expected to influence renal function Children with hemolytic uremic syndrome (HUS) diagnosed ≤6 months prior to screening Patients with nephrotic syndrome receiving albumin infusions within the last 6 months prior to screening Scheduled renal transplant within the next 6 months Renal allograft in place Bilateral renal artery stenosis Acute kidney injury requiring dialysis within 6 months prior to screening Systemic hypertension stage 2 in children ≥1 year of age defined according to institutional guidelines on blood pressure management at screening or randomization Systolic blood pressure (SBP) above 110 mmHg in infants 6 months to <1 year of age at screening or randomization Systemic hypotension defined as a systolic blood pressure below the 5th percentile for age, sex and height at either screening or randomization but no lower than 80 mmHg (although for some participants the 5th percentile of SBP is < 80 mmHg they must be excluded if their SBP is <80 mmHg) Participants using rituximab, cyclophosphamide, abatacept, or intravenous glucocorticoids, within <6 months prior to screening for any reason