A Study of ANX009 in Adult Participants With Lupus Nephritis

Key Inclusion Criteria: * Participants who have a diagnosis of SLE according to European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) 2019 Criteria * Has a history of International Society of Nephrology/Renal Pathology Society (ISN/RPS) Class III or IV with or without Class V glomerulonephritis on renal biopsy within 24 months prior to screening or as performed during screening. * Has proteinuria level between ≥0.5 to 3.0 grams (g)/g/day assessed via urine protein to creatine ratio (UPCR) during screening. * Has evidence of classical complement activation at screening * Has a history of receiving one or more standard therapies for LN Key Exclusion Criteria: * Has a history of ISN/RPS Class VI or isolated Class V (without co-existent/predominant Class III or IV glomerulonephritis) glomerulonephritis on renal biopsy. * Has severe kidney disease defined as eGFR of \<30 milliliters (mL)/minute/1.73 square meter (m\^2) or end-stage renal disease (ESRD) requiring dialysis or kidney transplantation. * Has a concurrent systemic autoimmune disease that may confound study assessments other than SLE, LN, or cutaneous lupus erythematosus. NOTE: Other inclusion and/or exclusion criteria may apply.