A Study to Assess the Effects of Zigakibart on IgA Nephropathy.

This is an open-label multicenter study where participants are randomized into one of two groups, where the only difference between the groups is the on-treatment biopsy time point, end of the first year of treatment (Group A) or at the end of the second year of treatment (Group B).

The total study duration for each participant may be up to 125 weeks, including the maximum screening period (8 weeks), the treatment period (104 weeks), and the safety follow up period (13 weeks).

Inclusion criteria

• Primary IgAN, confirmed by kidney biopsy, within 5 years prior to Screening
• eGFR ≥45 mL/min/1.73 m2, based on the 2021 CKD-EPI equation, at Screening
• Persistent proteinuria, defined as either

• Total Urine Protein ≥0.5 g/day or UPCR ≥0.5 g/g in a 24-hour urine collection, at Screening, despite maximally tolerated dose or poorly tolerated supportive therapy or
• IgAN diagnosis <6 months prior to Screening with Total Urine Protein >1.5 g/day or UPCR >1.5 g/g in a 24-hour urine collection, at the time of clinical presentation or diagnosis
• Body weight ≥45 kg and body mass index (BMI) ≤35.0 kg/m2, at Screening

Exclusion criteria

• Secondary forms of IgAN, as determined by the Investigator, diagnosis of IgA vasculitis, or any other nephropathy or chronic urinary tract disorder
• Total IgG <6.0 g/L at screening
• Any chronic urinary tract disorder, including but not limited to retention, incontinence, and/or recurrent urinary tract infections
• An average systolic blood pressure >150 mmHg or average diastolic blood pressure >90 mmHg based on three measurements at Screening
• Treatment with complement pathway inhibitors, mycophenolic acids, systemic calcineurin inhibitors or corticosteroids, immunosuppressive or immunomodulatory agents within 12 months prior to screening
• Acute kidney injury (AKI), defined by AKI network criteria, within 4 weeks prior to screening
• Current treatment with anti-APRIL monoclonal antibodies or dual APRIL/BAFF inhibitors or past treatment of the same at any time for >3 consecutive months prior to screening
• Planned initiation of, or recently (within 24 weeks) initiated, treatment with glucagon-like peptide-1 agonists at screening

Other protocol-defined inclusion/exclusion criteria may apply.