The purpose of this clinical trial is to evaluate the long-term efficacy and safety of low-dose oral corticosteroids combined with cyclophosphamide therapy and low-dose corticosteroids monotherapy, on a background of maximal RAS inhibitor therapy, for IgA nephropathy with stage 3 or 4 chronic kidney disease.

Inclusion Criteria:

• Biopsy-proven IgA nephropathy;
• Proteinuria ≥1.0g/day while receiving maximum tolerated dose of RAS blockade;
• Estimated glomerular filtration rate 15-60 ml/min/1.73/m2.

Exclusion Criteria:

• Indication or contraindication for immunosuppressive therapy with corticosteroids
• Use of corticosteroids and other immunosuppressive drugs within the last 1 year
• Current unstable kidney function for other reasons
• Under 18 years old
• Patients with secondary IgAN
• Patients who are unlikely to comply with the study protocol in the view of the treating physician