A Study of YKST02 in Participants With Primary IgA Nephropathy

The goal of this clinical trial is to evaluate the safety and tolerability of YKST02 and to explore its potential to treat adults with primary IgA nephropathy (IgAN). The study will also assess how the drug moves through the body and how it affects the immune system. The main questions it aims to answer are: * Is YKST02 safe and well tolerated? * Does YKST02 reduce protein levels in the urine? * How does YKST02 behave in the body (pharmacokinetics, PK)? * How does YKST02 affect the immune system (pharmacodynamics, PD)? Participants are adults with IgAN who have persistent proteinuria despite standard treatment. Participants will: * Receive YKST02 by intravenous (IV) infusion * Be monitored after each dose for safety * Attend clinic visits for safety assessments and laboratory tests * Provide blood and urine samples during the study and follow-up period