A Study to Evaluate Safety and Tolerability of IV or SC Dose of MEDI-545 in Patients With Systemic Lupus Erythematosus.

Inclusion Criteria: * Patients must have previously met ≥4 of the 11 revised ACR criteria * Have positive antinuclear antibody test (ANA) at ≥1:80 serum dilute in the past or at screening * Have at least 1 system with a score of A or 2 systems with a score of B on the BILAG index at screening, or have a SELENA-SLEDAI score ≥6 Exclusion Criteria: * Have received prednisone \>20 mg/day (or an equivalent dose of another oral corticosteroid) within 14 days before Visit 2 (Day 1) * Have received the following medications within 28 days before Visit 2 (Day 1): * Systemic cyclophosphamide at any dose * Cyclosporine at any dose * Tacrolimus at any dose * Thalidomide at any dose * Mycophenolate mofetil \>2 g/day * Methotrexate \>15 mg/week * Azathioprine \>2 mg/kg/day * Women who have a positive pregnancy test (serum hCG) at Visit 1