This study tests the safety of **felzartamab** for people with **Lupus Nephritis (LN)**, a kidney disease caused by **Systemic Lupus Erythematosus (SLE)**, an autoimmune condition where the immune system attacks healthy tissue. Participants must have specific criteria, like certain kidney test results and a history of not responding well to other treatments. A **renal biopsy**, a procedure to collect kidney tissue for testing, must have been done recently. People who are very sick, such as those needing dialysis or with severe kidney damage, cannot participate.

• The study sponsor is HI-Bio, A Biogen Company.
• Participants must have tried other treatments without success.
• Not suitable for those needing dialysis or with severe kidney damage.