Dupilumab is a fully human anti-interleukin-4 receptor α monoclonal antibody that blocks both interleukin-4 and interleukin-13 signaling. Its effectiveness in reducing oral glucocorticoid use in patients with severe asthma while maintaining asthma control is unknown. We randomly assigned 210 patients with oral glucocorticoid-treated asthma to receive add-on dupilumab (at a dose of 300 mg) or placebo every 2 weeks for 24 weeks. After a glucocorticoid dose-adjustment period before randomization, glucocorticoid doses were adjusted in a downward trend from week 4 to week 20 and then maintained at a stable dose for 4 weeks. The primary end point was the percentage reduction in the glucocorticoid dose at week 24. Key secondary end points were the proportion of patients at week 24 with a reduction of at least 50% in the glucocorticoid dose and the proportion of patients with a reduction to a glucocorticoid dose of less than 5 mg per day. Severe exacerbation rates and the forced expiratory volume in 1 second (FEV ) before bronchodilator use were also assessed. The percentage change in the glucocorticoid dose was -70.1% in the dupilumab group, as compared with -41.9% in the placebo group (P<0.001); 80% versus 50% of the patients had a dose reduction of at least 50%, 69% versus 33% had a dose reduction to less than 5 mg per day, and 48% versus 25% completely discontinued oral glucocorticoid use. Despite reductions in the glucocorticoid dose, in the overall population, dupilumab treatment resulted in a severe exacerbation rate that was 59% (95% confidence interval CI, 37 to 74) lower than that in the placebo group and resulted in an FEV that was 0.22 liters (95% CI, 0.09 to 0.34) higher. Injection-site reactions were more common with dupilumab than with placebo (9% vs. 4%). Transient blood eosinophilia was observed in more patients in the dupilumab group than in the placebo group (14% vs. 1%). In patients with glucocorticoid-dependent severe asthma, dupilumab treatment reduced oral glucocorticoid use while decreasing the rate of severe exacerbations and increasing the FEV . Transient eosinophilia was observed in approximately 1 in 7 dupilumab-treated patients. (Funded by Sanofi and Regeneron Pharmaceuticals; LIBERTY ASTHMA VENTURE ClinicalTrials.gov number, NCT02528214 .).