A Phase 3 Study of Inebilizumab in Participants With Primary Membranous Nephropathy

Inclusion Criteria: * Adults aged ≥18 years and \<80 years. * Able and willing to provide written informed consent. * Primary membranous nephropathy (PMN) confirmed by renal biopsy (performed during screening or within 5 years before screening), or biopsy exemption for participants with anti-PLA2R antibody ≥20 RU/mL at screening. * Participants with diabetes Hemoglobin A1c (HbA1c) \<7.5% require a renal biopsy report within 2 years before screening (or biopsy during screening) demonstrating PMN without diabetic nephropathy. * Urine protein-to-creatinine ratio (UPCR) ≥3.5 from a 24-hour urine collection at screening. * Receiving a maximally tolerated Angiotensin-Converting Enzyme (ACE) inhibitor or (Angiotensin II receptor blocker) ARB for ≥3 months before randomization with adequately controlled blood pressure (\<140/90 mmHg). Exclusion Criteria: * Secondary membranous nephropathy (e.g., due to autoimmune disease, infection, malignancy, or medications). * Estimated glomerular filtration rate (eGFR) \<40 mL/min/1.73 m\^2 , ≥30% decline in eGFR during the previous 24 weeks, need for dialysis, kidney replacement therapy, kidney transplant, or planned transplant during the study. * Recent thromboembolic event (within 3 months). * Active HIV, hepatitis B infection, Hepatitis B surface antigen (HBsAg) positive, active hepatitis C infection, uncontrolled diabetes (HbA1c ≥7.5%), active or inadequately treated tuberculosis, recurrent herpes zoster or opportunistic infections, clinically significant active infection, recurrent serious infections, or immunodeficiency disorders. * Clinically significant laboratory abnormalities, including severe anemia, neutropenia, thrombocytopenia, low Cluster of Differentiation (CD19+) B-cell count, hepatic dysfunction, or immunoglobulin G (IgG) \<400 mg/dL. * History of solid organ or cell transplantation or progressive multifocal leukoencephalopathy. * Recent treatment with prohibited therapies, including: B-cell-depleting biologics or other biologic immunomodulators, calcineurin inhibitors, alkylating agents within 3 months;( except history of resistance to calcineurin inhibitors); other immunosuppressive agents within 4 weeks; glucocorticoids within 1 month, or live or live-attenuated vaccines (within 4 weeks before randomization). Note: Other protocol-defined Inclusion/Exclusion criteria may apply.