Protocol IM101042: A Phase IIB, Multi-Center, Randomized, Double-Blind, Placebo-Controlled Study to Evaluate the Efficacy and Safety of Abatacept vs. Placebo on a Background of Oral Glucocorticosteroids in the Treatment of Subjects with Systemic Lupus Erythematosus and the Prevention of Subsequent Lupus Flares.

INTERVENTION: Drug: Abatacept plus Prednisone or Prednisone equivalent for 12‐month period OR placebo plus Prednisone or Prednisone equivalent for 12‐month period. Study Design: Prevention, Randomized, Double‐Blind, Placebo Control, Single Group Assignment, Safety/Efficacy Study. CONDITION: Systemic Lupus Erythematosus (SLE). PRIMARY OUTCOME: The primary objective of this study will be to assess the proportion of subjects with new clinical flare of Systemic Lupus Erythematosus (British Isles Lupus Assessment Group (BILAG) "A" or "B") during the 1 year double‐blind treatment period. SECONDARY OUTCOME: 1. Assess proportion of subjects with a new clinical flare of SLE (BILAG A or B) 2. Evaluate the proportion of subjects who during the study experienced a BILAG A or B flare. INCLUSION CRITERIA: 1. Subjects must be diagnosed with SLE and be experiencing an active lupus flare in at least one of three organ systems: skin (discoid lesions), inflammation of the lining of the heart (pericarditis), or inflammation of the lining of the lung (pleuritis/pleurisy); or inflammation of more than 4 joints within 14 days of a screening visit. 2. Stable dose of prednisone (<30mg) for at least one month.