Safety Study of AMG 811 in Subjects With Systemic Lupus Erythematosus With and Without Glomerulonephritis

Inclusion Criteria: * Men and women, between the ages of 18 and 70 years of age; * Body mass index from 18 to 40 kg/m2 \[Body Weight (kg)/Height2 (m2)\] at screening; * Diagnosis of SLE at least 6 months before randomization, including a positive antinuclear antibodies (ANA) during screening; if screening ANA is negative, documented historical ANA with a titer of at least 1:80 will be acceptable; * Any concurrent SLE pharmacologic regimen (including mycophenolate mofetil, azathioprine, leflunomide, methotrexate, and anti-malarials) must be stable for at least 30 days before randomization; * Prednisone ≤ 20 mg/day (or equivalent) is permitted; one increase or one decrease of ≤ 5 mg/day prednisone equivalent will be allowed within 30 days before randomization; Additional inclusion criteria for Part B: \- Active SLE with GN with no other apparent cause, defined by the following: Renal biopsy evidence (within 18 months) of nephritis using the WHO or International Society of Nephrology (ISN)/Renal Pathology Society (RPS) classification of SLE with GN (Class III or IV); Urine protein/creatinine ratio (UP/Cr) \> 1 or 24 hour urine protein \> 1g after at least 12 weeks of treatment with mycophenolate mofetil (at least 1.5 grams/day) or azathioprine (at least 100 mg orally per day); Superimposed membranous changes are allowed for those with Class III or Class IV SLE with GN; \- Prednisone ≤ 20 mg/day (or equivalent) at the time of randomization. Exclusion Criteria: * Any disorde…