Safety of Abatacept Versus Placebo in Rheumatoid Arthritis: Integrated Data Analysis of Nine Clinical Trials

Objective: To assess the safety of abatacept treatment in rheumatoid arthritis (RA) using integrated data from multiple clinical trials.

Methods: Data from nine double-blind, placebo-controlled studies of abatacept treatment (seven intravenous, two subcutaneous) in patients with RA were pooled, focusing on safety events in the double-blind treatment period of each study. Incidence rates (IRs) of adverse events (AEs) per 100 patient-years of exposure were calculated for abatacept- and placebo-treated patients. AEs in abatacept-treated patients were combined regardless of dose and formulation.

Results: In total, 2653 patients received abatacept and 1485 received placebo, with 2357 and 1254 patient-years of exposure, respectively. The mean (SD) durations of exposure in the abatacept and placebo groups were 10.8 (3.3) and 10.3 (3.5) months, respectively. The IRs (95% confidence interval [CI]) for serious AEs were 14.8 (13.3, 16.5) and 14.6 (12.5, 17.0) in the abatacept and placebo groups, respectively. Death occurred in 12 (0.5%) and 12 (0.8%) patients in the abatacept and placebo groups, respectively, and was most commonly caused by cardiac disorders. Malignancies were observed in 31 patients (1.2%) treated with abatacept (IR: 1.32 [95% CI: 0.90, 1.87]) versus 14 (0.9%; IR: 1.12 [0.61, 1.88]) who received placebo. Solid organ tumor was the most frequent malignancy reported in both groups (abatacept: 1.0%; IR: 1.11 [95% CI: 0.72, 1.62]; placebo: 0.8%; 0.96 [0.50, 1.67]).

Conclusion: In this integrated analysis, the IRs of safety events in the abatacept and placebo groups were similar with no new safety concerns identified.