A Study of Cizutamig in Patients With Immunoglobulin A Nephropathy

Inclusion Criteria: * 18 to 75 years of age at the time of signing the informed consent form (ICF). * Biopsy-confirmed IgAN as specified in the protocol. * 24-hour urine protein excretion ≥1.0 g/day or 24-hour urine protein to creatinine ratio (uPCR) ≥0.75 g/g . * Inadequate response to ≥1 of the therapies defined in the protocol. * eGFR \>30 mL/min/1.73m2. Exclusion Criteria: * Inadequate clinical laboratory parameters at Screening. * Receipt of or inability to discontinue any of the following excluded therapies as specified in the protocol. * Receipt of live vaccine within 4 weeks prior to Screening. * MEST-C score of T2 from the Oxford IgAN classification schema. If MEST-scoring was not performed, the presence of \>50% tubular atrophy/interstitial fibrosis is exclusionary. * Rapidly progressing glomerulonephritis with eGFR reduction ≥50% within 12 weeks of Screening. * Secondary IgAN (eg, chronic liver disease, celiac disease, HIV). * History of IgA vasculitis. * Presence of any concomitant autoimmune disease . * History of progressive multifocal leukoencephalopathy. * History of primary immunodeficiency or a hereditary deficiency of the complement system. * Central nervous system (CNS) disease . * Presence of 1 or more significant concurrent medical conditions per investigator judgment. * Diagnosis or history of malignant disease within 5 years prior to Screening. * Tonsillectomy within 24 weeks prior to Screening.