Safety of belimumab in adult patients with systemic lupus erythematosus: Results of a large integrated analysis of controlled clinical trial data

OBJECTIVES: Systemic lupus erythematosus (SLE) is a chronic, autoimmune disease that affects multiple organ systems. Belimumab, a targeted human monoclonal antibody, binds to and inhibits soluble B-lymphocyte stimulator. The safety and efficacy of belimumab has consistently been demonstrated in multiple clinical trials for the treatment of patients with active SLE. Integration of these data provides an additional opportunity to explore the safety of belimumab in a larger and more diverse population. This post hoc pooled analysis of clinical studies evaluated the safety profile of belimumab versus placebo in adults with SLE. METHODS: This was a pooled post hoc analysis of 52-week safety data from one Phase 2 and five Phase 3 belimumab trials in adult patients with SLE. Patients received ≥1 dose of placebo or belimumab (1, 4, or 10 mg/kg intravenous or 200 mg subcutaneous), plus standard therapy. Outcomes included the incidence of adverse events (AEs), serious AEs (SAEs), severe AEs, AEs of special interest (AESI), and mortality. RESULTS: Across 4170 patients (placebo: N = 1355; belimumab: N = 2815), baseline demographics, disease characteristics, and treatment exposure were similar for placebo and belimumab. Most patients (placebo: 76.6%; belimumab: 81.0%) completed the protocol Week 52 visit. Overall, incidence of AEs, SAEs, severe AEs, AESI, and mortality were similar between groups. In both groups, the most commonly reported SAEs by system organ class were infections and infestations (placebo: 5.9%; belimumab: 5.4%) and renal and urinary disorders (placebo: 2.2%; belimumab: 1.7%). Additionally, a greater proportion of patients experienced AESI with belimumab versus placebo for post-infusion/injection systemic reactions (placebo: 8.1%; belimumab: 10.2%). Mortality rates were similar between groups (placebo: 0.4%; belimumab: 0.6%). CONCLUSIONS: These results are consistent with those of the individual studies, BASE, BLISS-LN, and long-term extension studies, making belimumab one of the most studied SLE treatments for safety. Collectively, this evidence continues to support a positive benefit–risk profile of belimumab in the treatment of adult patients with SLE.