ABSTRACT: The clinical efficacy and safety of a mometasone furoate/formoterol fumarate (MF/F) fixed-dose combination formulation administered via a metered-dose inhaler was investigated in patients with moderate to very severe chronic obstructive pulmonary disease (COPD).Two 52-week, multicenter, double-blind, placebo-controlled trials with identical study designs were conducted in current or ex-smokers (aged ?40 years), and pooled study results are presented herein. Subjects (n = 2251) were randomized to 26 weeks of twice-daily treatment with MF/F 400/10 ?g, MF/F 200/10 ?g, MF 400 ?g, F 10 ?g, or placebo. After the 26-week treatment period, placebo subjects completed the trial and 75% of subjects on active treatment entered a 26-week safety extension. Coprimary efficacy variables were mean changes in forced expiratory volume in one second (FEV(1)), area under the curve from 0 to 12 hours postdose (AUC(0-12 h)), and morning predose/trough FEV(1) from baseline to the week 13 endpoint. Key secondary efficacy variables were St George's Respiratory Questionnaire scores, symptom-free nights, time-to-first exacerbation, and partly stable COPD at the week 26 endpoint.In the 26-week treatment period, significantly greater increases in FEV(1) AUC(0-12 h) occurred with MF/F 400/10 versus MF 400 and placebo at the week 13 and week 26 endpoints (P ? 0.032). These increases were over three-fold greater with MF/F 400/10 than with MF 400. Also, significantly greater increases in morning predose/trough FEV(1) occurred with MF/F 400/10 versus F 10 and placebo at the week 13 endpoint (P < 0.05). The increase was four-fold greater with MF/F 400/10 than with F 10. All active treatment groups achieved minimum clinically important differences from baseline (>4 units) in St George's Respiratory Questionnaire scores at week 26. Symptom-free nights increased by ?14% in the MF/F 400/10, MF 400, and F 10 groups (P ? 0.033 versus placebo). The incidence of exacerbations was lower in the MF/F groups (?33.3%) than it was in the MF, formoterol, and placebo groups (?33.8%) over the 26-week treatment period. The incidence of adverse events was similar in the active-treated and placebo-treated subjects across 26 weeks of treatment. Over the 1-year study period, there were no notable differences in the incidence or types of adverse events between the MF/F 400/10 and MF/F 200/10 groups compared with the MF or formoterol groups. Differences in rates of individual treatment-emergent adverse events were <3% between treatment groups. Rates of pneumonia were low (?2%) across all treatment groups.Patients treated with MF/F demonstrated significant improvements in lung function, health status, and exacerbation rates. Although significant improvements were seen with both doses, a trend showing a dose-response effect was observed in the lung function measurements.