A Phase 3 Randomized, Double-Blind, Placebo-Controlled Study to Evaluate the Efficacy and Safety of BMS-188667 (Abatacept) or Placebo on a Background of Mycophenolate Mofetil and Corticosteroids in the Treatment of Subjects With Active Class III or IV Lupus Nephritis

Inclusion Criteria:

- Systemic Lupus Erythematosus (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 coincidentally

- Urine protein creatinine ratio (UPCR) ≥ 1.0 at Screening

- Biopsy within 12 months prior to screening visit indicating active proliferative
lupus glomerulonephritis International Society of Nephrology (ISN)/ Renal Pathology
Society (RPS) 2003 classification Class III or IV [excluding Class III (C), IV-S (C)
and IV-G (C)] or World Health Organization (WHO) 1982 Classification Class III or IV
(excluding IIIc, IVd)

- Evidence of active disease within 3 months of Screening, based on at least one of the
following:

- Renal Flare

- UPCR > 3 at Screening

- Active urine sediment, defined as at least one of the following:

- ≥ 5 red blood cells (RBC) per high power field (hpf)

- ≥ 5 white blood cells (WBC) per hpf

- Presence of cellular casts

- Biopsy within 3 months prior to screening visit indicating active proliferative
lupus glomerulonephritis

- Serum creatinine ≤ 3 mg/dL (ie, ≤ 265 micromol/L)

Exclusion Criteria:

- Subjects with drug-induced SLE, as opposed to idiopathic SLE

- Subjects with autoimmune disease other than SLE as their main diagnosis [eg;
Rheumatoid Arthritis (RA), Multiple Sclerosis (MS)]

- Current symptoms of severe, progressive, or uncontrolled non-SLE related renal,
hepatic, hematological, gastrointestinal, pulmonary, cardiac, neurological, or
cerebral disease, or other concomitant medical conditions that, in the opinion of the
Investigator, might place the subject at unacceptable risk for participation in this
study

- Active Central nervous system (CNS) lupus [British Isles Lupus Assessment Group
(BILAG) A or B)] with the exception of fatigue or mild stable cognitive dysfunction
[screening Magnetic Resonating Imaging (MRI) or other imaging of the brain is not
required to rule-out CNS disease in subjects who have no clinical features suggesting
active CNS disease]

- Subjects who are diagnosed as end-stage renal disease

- Subjects with persistent non-lupus related pyuria or hematuria (eg, hemorrhagic
cystitis)

- Subjects with a degree of tubulo-interstitial changes that suggests a significant and
irreversible decrease in renal function