In patients with severe asthma with eosinophilia in reslizumab clinical trials, high peripheral blood eosinophil levels are associated with low FEV 1 reversibility

Background A post hoc analysis of two randomized, placebo–controlled, Phase 3 trials of intravenous reslizumab, an anti-interleukin-5 (IL-5) biologic for severe eosinophilic asthma. Methods Relationships between baseline blood eosinophil levels (EOS), forced expiratory volume in 1 s (FEV 1 ) reversibility to β 2 -agonists and treatment outcomes were assessed. Results Mean baseline FEV 1 reversibility was numerically lower among patients with high (≥ 400 cells/µL) versus low baseline EOS. Reslizumab produced clinically significant improvement in FEV 1 , exacerbation rates and patient-reported outcomes after 52 weeks, including in patients with high EOS and low FEV 1 reversibility (≤ 14%) to β 2 -agonists at baseline. Conclusions Clinical trial eligibility criteria stipulating minimum FEV 1 reversibility to β 2 -agonists of ≥ 12% might exclude patients who would benefit from treatment with anti-IL-5 biologics.