Interleukin-5 (IL-5), a mediator of eosinophil activity, is an important potential treatment target in patients with uncontrolled asthma. The efficacy of reslizumab, a humanized anti-human IL-5 monoclonal antibody, has been characterized in patients with blood eosinophils ≥400cells/μL. This study further characterizes the efficacy and safety of reslizumab in patients with poorly-controlled asthma, and those with eosinophils <400cells/μL.
Patients were randomized to intravenous reslizumab 3.0mg/kg or placebo once every 4 weeks for 16 weeks. Primary endpoint was the change in forced expiratory volume in 1 second (FEV1) from baseline to week 16. Secondary measures included Asthma Control Questionnaire-7 (ACQ-7) scores, use of short-acting beta-agonists (SABAs), and forced vital capacity (FVC).
492 patients received ≥1 dose of placebo (n=97) or reslizumab (n=395). In the overall population, mean FEV1 change from baseline to week 16 was not significantly different between reslizumab and placebo and no significant relationship was detected between baseline blood eosinophils and change in FEV1. In the subgroup of patients with baseline eosinophils <400cells/μL, patients treated with reslizumab showed no significant improvement in FEV1 compared with placebo. In the subgroup with eosinophils ≥400cells/μL, however, treatment with reslizumab was associated with much larger improvements in FEV1, ACQ-7, rescue SABA use and FVC compared with placebo. Reslizumab was well tolerated, with fewer overall adverse events compared with placebo (55% vs 73%).
Reslizumab was well tolerated in patients with inadequately controlled asthma. Clinically meaningful effects on lung function and symptom control were not seen in patients unselected for baseline eosinophils.