MBS-303

Primary objective (Phase I): To evaluate the safety and tolerability of MSC303 in patients with immune glomerular diseases, observe the dose-limiting toxicity (DLT) of MSC303, determine the maximum tolerated dose (MTD) in humans (if any), and determine the recommended Phase II dose (RP2D) for subsequent clinical studies. Primary objective (Phase II): To evaluate the proportion of patients with pMN who achieve overall remission (OR) at 24 weeks (W25D1 visit) after MSC303 treatment. To evaluate the change in urine protein/creatinine ratio (UPCR) in 24-hour urine relative to baseline at 24 weeks (W25D1 visit) after MSC303 treatment of patients with IgA nephropathy (logarithm-transformed ratio). To evaluate the proportion of subjects who are free from/not receiving dialysis treatment at 24 weeks after MSC303 treatment of anti-GBM nephritis. To evaluate the proportion of patients with LN who achieve complete renal remission at 24 weeks after MSC303 treatment.