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

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.