COPD is a major global cause of mortality and morbidity. PINNACLE-4 evaluated the efficacy and safety of GFF MDI (glycopyrrolate/formoterol fumarate metered dose inhaler) in patients from Asia, Europe, and the USA with moderate-to-very severe COPD.In this double-blind, placebo-controlled, Phase III study, patients were randomized to treatment with GFF MDI 18/9.6 μg, glycopyrrolate (GP) MDI 18 μg, formoterol fumarate (FF) MDI 9.6 μg, or placebo MDI (all twice daily) for 24 weeks. Lung function, patient-reported outcomes (symptoms and health-related quality of life), and safety were assessed.Of the 1,756 patients randomized, 1,740 patients were included in the intent-to-treat population (mean age 64.2 years, 74.1% male, and 40.2% Asian). GFF MDI significantly improved morning predose trough FEV1 at Week 24 (primary endpoint) vs placebo MDI, GP MDI, and FF MDI (least squares mean differences: 165, 59, and 72 mL, respectively; all P<0.0001). GFF MDI also significantly improved other lung function endpoints vs placebo MDI, GP MDI, and FF MDI and patient-reported outcomes vs placebo MDI and GP MDI. A larger proportion of patients treated with GFF MDI achieved the minimum clinically important difference in Transition Dyspnea Index score vs GP MDI and placebo MDI and in St George's Respiratory Questionnaire score vs placebo MDI. Adverse event rates were similar across treatment groups.These results demonstrated the efficacy of GFF MDI in patients with moderate-to-very severe COPD. GFF MDI was well tolerated, with a safety profile commensurate with long-acting bronchodilators.