The study is testing a medicine called povetacicept for adults with a kidney problem known as Immunoglobulin A Nephropathy (IgAN). The goal is to see if povetacicept helps reduce the amount of protein in the urine and keeps the kidneys working well. Some people in the study will get a placebo, which looks like the medicine but doesn't have any medicine in it. To join, you must have been diagnosed with IgAN, and your kidneys must filter at least 30 milliliters per minute (eGFR ≥ 30 mL/min). You also need to take certain blood pressure medicines like ACE inhibitors or ARBs. If you have taken other treatments that affect the immune system recently, you cannot join. The study will have specific rules on who can and cannot participate.

• The study involves taking a new medicine or a placebo to see its effects on kidney function.
• Participants should be diagnosed with IgAN and meet certain health criteria.
• Recent use of immune-affecting treatments may exclude participation.