A Study to Learn More About How Well the Study Treatment Finerenone Works, How Safe it is, How it Moves Into, Through, and Out of the Body, and the Effects it Has on the Body When Taken With an ACE Inhibitor or Angiotensin Receptor Blocker in Children With Chronic Kidney Disease and Proteinuria

Inclusion Criteria

• •Participants must be 6 months to \<18 years old 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 1-3 (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 2 and 3 or
• •* UPCR ≥ 1.0 g/g for patients \< 2 years of age or ≥ 2 years of age and with CKD stage 1
• •Participants must have stable kidney function between screening and D0 defined as:
• •* For participants with a creatinine of \> 0.8 mg/dL at screening: no increase or decrease in eGFR by ≥ 20% at D0
• •* For participants with a creatinine of ≤ 0.8 mg/dL at screening: no increase or decrease in creatinine ≥ 0.15 mg/dL at D0.
• •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