• Must have the ability to understand and sign a written informed consent form, which must be obtained prior to initiation of study assessments

• Adult male or female of ≥18 years of age, or as per country specific legally or nationally recognized adult age, who provides written informed consent prior to performing any study assessments

• Diagnosis of IgAN as demonstrated by renal biopsy conducted within 10 years

• Total urine protein excretion ≥0.75 g per 24-hour or urine protein-to-creatinine ratio (UPCR) ≥0.75 mg/mg based on a 24-hour urine sample

• eGFR ≥30 mL/min/1.73 m2 at screening, as per the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)

• On a stable prescribed regimen of RASi (angiotensin converting enzyme inhibitor or angiotensin II receptor blocker) for at least 8 weeks that is at the maximum labeled or tolerated dose at screening and from screening to study Day 1