Reslizumab for inadequately controlled asthma with elevated blood eosinophil counts: results from two multicentre, parallel, double-blind, randomised, placebo-controlled, phase 3 trials

Background Elevated numbers of blood eosinophils are a risk factor for asthma exacerbations. Reslizumab is a humanised anti-interleukin 5 monoclonal antibody that disrupts eosinophil maturation and promotes programmed cell death. We aimed to assess the efficacy and safety of reslizumab in patients with inadequately controlled, moderateto-severe asthma. Methods We did two duplicate, multicentre, double-blind, parallel-group, randomised, placebo-controlled phase 3 trials. Both trials enrolled patients with asthma aged 12-75 years (from 128 clinical research centres in study land 104 centres in study 2) from Asia, Australia, North America, South America, South Africa, and Europe, whose asthma was inadequately controlled by medium-to-high doses of inhaled corticosteroid based therapy and who had blood eosinophils of 400 cells per mu L or higher and one or more exacerbations in the previous year. Patients were randomly assigned (1:1) to receive either intravenous reslizumab (3.0 mg/kg) or placebo every 4 weeks for 1 year by computerised central randomisation. Patients and investigators were masked to treatment assignment during the study. Each patient received a specific volume of study drug (reslizumab or matching placebo) on the basis of the patient's body weight and randomly assigned treatment group. Additionally, the sponsor's clinical personnel involved in the study were masked to the study drug identity until the database was locked for analysis and the treatment assignment revealed. The primary outcome was the annual frequency of clinical asthma exacerbations and was analysed by intention to treat. We assessed safety outcomes in the patients who had received one or more dose of the drug. The trials have been completed and are registered with ClinicalTrials.gov, numbers NCT01287039 (study 1) and NCT01285323 (study 2). Findings Study 1 was done between April 12,2011, and March 3,2014 and study 2 between March 22,2011, and April 9,2014. Of 2597 patients screened, 953 were randomly assigned to receive either reslizumab (n=477 [245 in study 1 and 232 in study 2]) or placebo (n=476 [244 and 232]). In both studies, patients receiving reslizumab had a significant reduction in the frequency of asthma exacerbations (study 1: rate ratio [RR] 0.50 [95% CI 0.37-0.67]; study 2: 0.41 [0.28-0.59]; both p<0.0001) compared with those receiving placebo. Common adverse events on reslizumab were similar to placebo. The most common adverse events were worsening asthma symptoms (127 [52%] for placebo and 97 [40%] for reslizumab in study 1; 119 [51%] for placebo and 67 [29%] for reslizumab for study 2), upper respiratory tract infections (32 [13%] and 39 [16%]; 16 [7%] and eight [3%]), and nasopharyngitis (33 [14%] and 28 [11%]; 56 [24%] and 45 [19%]). Two patients in the reslizumab group had anaphylactic reactions; both responded to standard treatment at the study centre and resolved, and the patients were withdrawn from the study. Interpretation These results support the use of reslizumab in patients with asthma and elevated blood eosinophil counts who are inadequately controlled on inhaled corticosteroid-based therapy.