Résumé : Background: Dual bronchodilation combining a long-acting β2-agonist (LABA) and a long-acting muscarinic antagonist (LAMA) is the preferred choice of treatment recommended by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2017 guidelines for the management of patients with moderate-to-severe chronic obstructive pulmonary disease (COPD). The once-daily (q.d.) fixed-dose combination (FDC) of LABA, indacaterol 110 μg and LAMA, glycopyrronium 50 μg (IND/GLY 110/50 μg q.d.) demonstrated superior improvements in lung function, dyspnoea and overall health status and better tolerability against LABA or LAMA monotherapies and combination of LABA and inhaled corticosteroid (ICS) in more than 11,000 patients with moderate-to-severe COPD in several randomised controlled clinical trials. Methods: The CRYSTAL study was the first, 12-week, randomised, open-label trial that evaluated the efficacy and safety of a direct switch from previous treatments to IND/GLY 110/50 μg q.d. on lung function and dyspnoea in patients with moderate COPD and a history of up to one exacerbation in the previous year. Patients were divided into 2 groups according to their background therapy and symptom scores and were randomised (3:1) to IND/GLY or to continue with their previous treatments. Results: The study included 4389 randomised patients, of whom 2160 were in groups switched to IND/GLY (intention-to-treat population). The effect of IND/GLY was superior to LABA + ICS on trough forced expiratory volume in 1 s (FEV1; treatment difference, Δ = +71 mL) and transition dyspnoea index (TDI; [Δ = 1.09 units]), and to LABA or LAMA on trough FEV1 (Δ = +101 mL) and a TDI (Δ = 1.26 units). Improvements in health status and lower rescue medication use were also observed with IND/GLY. The safety profile of the study medication was similar to that observed in previous studies. Conclusions: IND/GLY demonstrated superior improvements in lung function and dyspnoea after direct switch from previous treatments. Trial registration: ClinicalTrials.gov number: NCT01985334.