We enrolled patients aged 12–70 years with Alport syndrome diagnosed histologically (by electron microscopy) or genetically by a documented mutation in disease-associated genes, including COL4A3, COL4A4, or COL4A5. Genetic testing was conducted as part of the trial by an independent vendor (Machaon Diagnostics, Oakland, CA, USA) unless patients provided documentation of prior genetic or histological diagnosis for eligibility. Patients had eGFR between 30 and 90 mL/min/1.73 m2 (inclusive) and urinary albumin to creatinine ratio (UACR) ≤3,500 mg/g. Patients with macroalbuminuria (UACR of 301–3,500 mg/g) were to comprise no >40% of enrolled trial participants. Patients were to have received maximally tolerated labeled doses of an angiotensin-converting enzyme inhibitor (ACEi) and/or angiotensin receptor blocker (ARB), unless medically contraindicated. Patients with clinically significant cardiovascular disease or serum B-type natriuretic peptide concentrations >200 pg/mL during screening were not eligible for the study. Patients with uncontrolled diabetes and/or hypertension were also excluded.