ABSTRACT: Background:Current pharmacological therapies for COPD improve quality of life and symptoms and reduce exacerbations. Given the progressive nature of COPD, it is arguably more important to understand whether the available therapies are able to delay clinical deterioration; the concept of "clinically important deterioration" (CID) has therefore been developed. We evaluated the efficacy of the single-inhaler triple combination beclometasone dipropionate, formoterol fumarate, and glycopyrronium (BDP/FF/G), using data from three large 1-year studies. Methods:The studies compared BDP/FF/G to BDP/FF (TRILOGY), tiotropium (TRINITY), and indacaterol/glycopyrronium (IND/GLY; TRIBUTE). All studies recruited patients with symptomatic COPD, FEV1 <50%, and an exacerbation history. We measured the time to first CID and to sustained CID, an endpoint combining FEV1, St George's Respiratory Questionnaire (SGRQ), moderate-to-severe exacerbations, and death. The time to first CID was based on the first occurrence of any of the following: a decrease of ?100 mL from baseline in FEV1, an increase of ?4 units from baseline in SGRQ total score, the occurrence of a moderate/severe COPD exacerbation, or death. The time to sustained CID was defined as: a CID in FEV1 and/or SGRQ total score maintained at all subsequent visits, an exacerbation, or death. Results:Extrafine BDP/FF/G significantly extended the time to first CID vs BDP/FF (HR 0.61, P<0.001), tiotropium (0.72, P<0.001), and IND/GLY (0.82, P<0.001), and significantly extended the time to sustained CID vs BDP/FF (HR 0.64, P<0.001) and tiotropium (0.80, P<0.001), with a numerical extension vs IND/GLY. Conclusion:In patients with symptomatic COPD, FEV1 <50%, and an exacerbation history, extrafine BDP/FF/G delayed disease deterioration compared with BDP/FF, tiotropium, and IND/GLY. Trial registration:The studies are registered in ClinicalTrials.gov: TRILOGY, NCT01917331; TRINITY, NCT01911364; TRIBUTE, NCT02579850.