Ability of Serum IgE Concentration to Predict Exacerbation Risk and Benralizumab Efficacy for Patients with Severe Eosinophilic Asthma

INTRODUCTION: For patients with eosinophilic asthma with allergic characteristics, understanding the key drivers of exacerbations is important to identify optimal treatment strategies. Benralizumab is an interleukin-5 receptor alpha–directed cytolytic monoclonal antibody that significantly reduces exacerbation frequency for patients with severe, uncontrolled eosinophilic asthma. We evaluated the predictive value of baseline blood eosinophil counts vs. serum immunoglobulin E (IgE) concentrations on exacerbation risk and the association of these variables with benralizumab treatment effect. METHODS: Analyses were performed with data pooled from the phase III SIROCCO and CALIMA benralizumab trials. Crude annual asthma exacerbation rates (AERs) were determined for placebo as a function of baseline blood eosinophil counts and serum IgE concentrations with prespecified blood eosinophil count categories (< 150, ≥ 150 to < 300, ≥ 300 to < 450, ≥ 450 cells/µL) and IgE concentration quartiles (< 62.0, ≥ 62.0 to < 176.2, ≥ 176.2 to < 453.4, and ≥ 453.4 kU/L). We compared AERs for patients receiving benralizumab 30 mg every 8 weeks (first three doses every 4 weeks) vs. placebo for overlapping baseline blood eosinophil count categories and serum IgE concentration quartiles via a regression approach and by continuously using locally weighted regression smoothing analysis. RESULTS: Exacerbation risk for patients with severe asthma receiving placebo increased with increasing baseline blood eosinophil counts but not with increasing serum IgE concentrations. Addition of baseline atopy status did not influence the relationship between IgE concentrations and exacerbation risk for patients receiving placebo. Patients with blood eosinophil counts ≥ 300 cells/µL had consistent decreases in exacerbation risk with benralizumab relative to placebo across all serum IgE concentration quartiles. CONCLUSION: Baseline blood eosinophil counts, but not serum IgE concentrations, are an important predictor of exacerbation risk. Patients with severe eosinophilic asthma treated with benralizumab had consistent reductions in exacerbation risk, regardless of IgE concentrations. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov: SIROCCO, NCT01928771; CALIMA, NCT01914757. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s12325-019-01191-2) contains supplementary material, which is available to authorized users.