Response to Omalizumab Observed Over Wide Range of Blood Eosinophil Levels

RATIONALE: Inclusion criteria for efficacy studies of asthma biologics have resulted in highly enriched patient populations. Applying comparable methods, we examined response to omalizumab using different baseline blood eosinophil cutpoints to facilitate selection of patients most likely to derive the greatest clinical benefit from therapy.

METHODS: This post hoc analysis included patients with moderate or severe persistent allergic asthma from the 16-week inhaled corticosteroid dose-stable phase of two phase III clinical trials of omalizumab. For this analysis, asthma exacerbations were defined as the number of events requiring ≥3 days of systemic corticosteroids. Asthma exacerbation rates for omalizumab versus placebo were evaluated with respect to baseline blood eosinophil counts using a wide range of cutpoints (≥0, 100, 200, 300, 400/μL) to define subgroups. P-values and 95% confidence intervals (CI) for comparisons of exacerbation rates were calculated using unadjusted negative binomial models.

RESULTS: A total of N=1071 adults/adolescents (≥12 years) were randomized to receive either omalizumab (n = 542) or placebo (n = 529). The overall relative exacerbation rate reduction for omalizumab versus placebo was 57% (95% CI, 34–71%; P < 0.001). Exacerbation rate reductions were significant across a wide range of eosinophil levels (≥0: 56% (95%CI 33%, 71%; p=0.0002), ≥100: 57% (95%CI 33%, 72%; p=0.0002), ≥200: 55% (95%CI 25%, 73%; p=0.002), ≥300: 67% (95%CI 36%, 84%; p=0.001), ≥ 400: 74% (95%CI 40%, 88%; p=0.001).

CONCLUSIONS: In patients with moderate or severe persistent allergic asthma, response to omalizumab is observed across a wide range of eosinophil levels.