To evaluate abatacept therapy in patients with non–life‐threatening systemic lupus erythematosus (SLE) and polyarthritis, discoid lesions, or pleuritis and/or pericarditis.

In a 12‐month, multicenter, exploratory, phase IIb randomized, double‐blind, placebo‐controlled trial, SLE patients with polyarthritis, discoid lesions, or pleuritis and/or pericarditis were randomized at a ratio of 2:1 to receive abatacept (∼10 mg/kg of body weight) or placebo. Prednisone (30 mg/day or equivalent) was given for 1 month, and then the dosage was tapered. The primary end point was the proportion of patients with new flare (adjudicated) according to a score of A/B on the British Isles Lupus Assessment Group (BILAG) index after the start of the steroid taper.

A total of 118 patients were randomized to receive abatacept and 57 to receive placebo. The baseline characteristics were similar in the 2 groups. The proportion of new BILAG A/B flares over 12 months was 79.7% (95% confidence interval [95% CI] 72.4, 86.9) in the abatacept group and 82.5% (95% CI 72.6, 92.3) in the placebo group (treatment difference −3.5 [95% CI −15.3, 8.3]). Other prespecified flare end points were not met. In post hoc analyses, the proportions of abatacept‐treated and placebo‐treated patients with a BILAG A flare were 40.7% (95% CI 31.8, 49.5) versus 54.4% (95% CI 41.5, 67.3), and the proportions with physician‐assessed flare were 63.6% (95% CI 54.9, 72.2) and 82.5% (95% CI 72.6, 92.3), respectively; treatment differences were greatest in the polyarthritis group. Prespecified exploratory patient‐reported outcomes (Short Form 36 health survey, sleep problems, fatigue) demonstrated a treatment effect with abatacept. The frequency of adverse events (AEs) was comparable in the abatacept and placebo groups (90.9% versus 91.5%), but serious AEs (SAEs) were higher in the abatacept group (19.8 versus 6.8%). Most SAEs were single, disease‐related events occurring during the first 6 months of the study (including the steroid taper period).

Although the primary/secondary end points were not met in this study, improvements in certain exploratory measures suggest some abatacept efficacy in patients with non–life‐threatening manifestations of SLE. The increased rate of SAEs requires further assessment.