This study is designed to compare the safety and efficacy of Mycocep Capsules (Mycophenolate Mofetil) and a marketed Azathioprine formulation, Imuran Azathioprine Tablets, in the maintenance therapy of lupus nephritis.

This study is designed to compare the two different doses of Mycocep Capsules (1.0g/day & 1.5g/day) and Imuran Azathioprine Tablets (2mg/kg/day), all in combination with low-dose prednisolone (≤10mg/day) as maintenance treatment for lupus nephritis.

Inclusion Criteria:

• Diagnosis of lupus nephritis.
• Currently receiving maintenance therapy with Azathioprine, Mycophenolate Mofetil, Mycophenolate Sodium, or Cyclosporine for lupus nephritis for at least 3 months prior to randomization.
• Stable use of low dose (≤10mg/day) oral prednisolone for lupus nephritis for at least 3 months prior to randomization.

Exclusion Criteria:

• Untreated, not in need of immunosuppressive treatment (in addition to corticosteroids), currently receiving induction therapy, or not responding to Azathioprine, Mycophenolate Mofetil or Mycophenolate Sodium as induction or maintenance therapy for lupus nephritis.
• Currently receiving or anticipated to receive cyclophosphamide or IV pulse of corticosteroids.
• Currently receiving continuous dialysis starting more than 2 weeks before randomization, and/or with an anticipated duration of more than 8 weeks.
• Previous kidney transplant or planned transplant.
• Presence of life threatening complications such as cerebral lupus or severe infection.
• Presence of liver dysfunction.
• Presence of COPD or asthma requiring oral steroids.
• Presence of bone marrow insufficiency or pure red cell aplasia unrelated to active systemic lupus erythematosus.
• Presence of persistent hematuria or pyuria for causes other than lupus nephritis.