Introduction and Objectives The Phase III ATTAIN study investigated the effect of two twice daily doses of aclidinium bromide, a second-generation, long-acting muscarinic antagonist with low systemic activity, in patients with moderate to severe chronic obstructive pulmonary disease (COPD).

Methods In this 24-week, double-blind study, patients were randomised (1:1:1) to receive aclidinium (200 μg, 400 μg) or placebo, twice daily. The primary endpoint was change from baseline in trough forced expiratory volume in 1 second (FEV₁) at Week 24. Other study assessments at 24 weeks included: change from baseline in peak FEV₁; percentage of patients achieving a clinically meaningful improvement in St George's Respiratory Questionnaire total score and Transition Dyspnoea Index; COPD symptoms as assessed by the EXACT Respiratory Symptoms score; exacerbation rate based on two definitions (healthcare resource utilisation and EXAcerbations of Chronic pulmonary disease Tool). Adverse events (AEs), clinical laboratory measures, vital signs and ECGs were also assessed.

Results A total of 819 patients were included in intention-to-treat (ITT) and safety populations. At Week 24, aclidinium 200 μg and 400 μg significantly improved trough FEV₁ from baseline compared with placebo (by 99 ml and 128 ml, respectively; both p<0.0001). Aclidinium was significantly superior to placebo at Week 24 for all other study assessments (Abstract P255 table 1). Aclidinium was well tolerated and the incidence of anticholinergic AEs was low and similar to placebo. Changes in laboratory tests, vital signs and ECGs were similar between all groups.

Conclusion Aclidinium 200 μg and 400 μg twice daily provided clinically meaningful improvements in bronchodilation, health status, symptoms, breathlessness and exacerbation rate. Aclidinium was well tolerated with a similar safety profile for both doses; the incidence of AEs was similar to placebo.