Response to omalizumab using patient enrichment criteria from trials of novel biologics in asthma

Background: Recent efficacy studies of asthma biologics have included highly enriched patient populations. Using a similar approach, we examined factors that predict response to omalizumab to facilitate selection of patients most likely to derive the greatest clinical benefit from therapy. Methods: Data from two phase III clinical trials of omalizumab in patients with allergic asthma were examined. Differences in rates of asthma exacerbations between omalizumab and placebo groups during the 16-week inhaled corticosteroid (ICS) dose-stable phase were evaluated with respect to baseline blood eosinophil counts (eosinophils <300/L [low] vs 300/L [high]) and baseline markers of asthma severity (emergency asthma treatment in prior year, asthma hospitalization in prior year, forced expiratory volume in 1second [FEV1; FEV1 <65% vs 65% predicted], inhaled beclomethasone dipropionate dose [<600 vs 600g/day], and long-acting beta-agonist [LABA] use [yes/no]). Results: Adults/adolescents (N=1071) were randomized to receive either omalizumab (n=542) or placebo (n=529). In the 16-week ICS dose-stable phase, rates of exacerbations requiring 3days of systemic corticosteroid treatment were 0.066 and 0.147 with omalizumab and placebo, respectively, representing a relative rate reduction in omalizumab-treated patients of 55% (95% CI, 32%-70%; P=.002). For patients with eosinophils 300/L or with more severe asthma, this rate reduction was significantly more pronounced. Conclusion: In patients with allergic asthma, baseline blood eosinophil levels and/or clinical markers of asthma severity predict response to omalizumab.