Leflunomide Plus Low Dose Corticosteroid in Immunoglobulin A (IgA) Nephropathy With Renal Insufficiency

IgA nephropathy is the most common primary glomerulonephritis in the world. Because of the poor treatment effect in advanced patients, it is still the main cause of maintenance dialysis. Current immunosuppressive therapy is still controversial, especially to those progressive IgA nephropathy with eGFR\<50ml/min. Leflunomide is widely used in the treatment of rheumatic diseases, such as rheumatoid arthritis and lupus nephritis, it's serum concentration will not be affected by renal function, and it also has antiviral effect. There are two randomized controlled trials and a retrospective study suggesting that leflunomide combined with glucocorticoids can effectively control urinary protein compared with glucocorticoids or conservative treatment, but these three studies are not specifically targeted at patients with estimated Glomerular Filtration Rate(eGFR) \< 50ml/min. Investigators will perform a prospective, open-label, randomized, controlled trial to evaluate the efficacy and safety of leflunomide and low dose glucocorticoids therapy in progressive IgA nephropathy with eGFR\<50ml/min

all the participants enrolled in the study will be randomly assigned in a 1:1 ratio, the experimental group will receive leflunomide + low dose glucocorticoids therapy on the basis of conservative treatment, while the control group receive conservative treatment only. Conservative treatment is defined as the treatment of delaying the progress of renal function, including low-protein diet supplemented with ketoacid therapy, Renin Angiotensin system (RAS) inhibitor, blood pressure control, lipid-regulating therapy and antiplatelet aggregation therapy. The course of treatment will last one year, then the leflunomide+glucocorticoids group will continue the conservative treatment. Participants will be follow-up at least 98 weeks.