Inclusion Criteria:

• SLE as defined by meeting at least 4 of the 11 classification criteria of the American College of Rheumatology for the classification of Systemic Lupus Erythematosus, either sequentially or coincident. The 4 criteria need not be present at study entry
• Renal Biopsy within 12 months of randomization (Day 1) indicating active proliferative lupus glomerulonephritis ISN/RPS 2003 classification Class III or IV [excluding Class III (C), IV-S (C) and IV-g (C)] or WHO 1982 Classification Class III or IV (excluding Class IIIc, IVd).
• Active renal disease at the screening visit, as defined by: urinary protein/creatinine ratio ≥0.5 AND an active urinary sediment as defined by at least one of the following 3 criteria: i) >5 RBC/hpf OR ii) >5 WBC/hpf (with no evidence of a urinary tract infection) OR iii) cylindruria AND
• A Stable serum creatine ≤3 mg/dL

Exclusion Criteria:

• Subjects with a rise in serum creatine of ≥1 mg/dL within 1 month prior to the screening visit
• Subjects with drug-induced SLE, as opposed to idiopathic SLE
• Subjects with severe, unstable and/or progressive CNS lupus
• Subjects with autoimmune disease other than SLE as their main diagnosis (e.g.; RA, MS)
• Subjects who have received treatment with cyclophosphamide within 3 months of randomization (Day 1).
• Subjects who have received treatment with rituximab < 6 months prior to the screening visit