Background: 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.Methods: 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.Results: Of the 1,756 patients randomized, 1,740 patients were included in the intent-to-treat population (mean age 64.2 years, 74.1...