ENHANCE-1 was a 24-week (+48-wk subset), multi-center, randomized, double-blind, placebo-controlled trial to evaluate nebulized ensifentrine-3mg twice-daily (randomized 5:3) in subjects 40-80 years with symptomatic moderate-to-severe COPD (post-bronchodilator FEV1 30?70% predicted, FEV1/FVC ratio <0.7, >2mMRC), and smoking history >10 pack-years. Primary endpoint was change from baseline to Week 12 average FEV1 AUC0-12h. Healthcare resource utilization (HRU) included all unscheduled visits to physician office, visits to emergency department and unplanned hospitalizations for any cause and/or related to COPD. Exacerbation rate and time to first event were assessed. 760 subjects were randomized and treated. Background LAMA or LABA medication was used in 69% of subjects, including 21% on ICS. Results: The primary endpoint was met. At 24 weeks, the ensifentrine group had fewer unscheduled physician?s office visits (6.5% vs 10.6%) and emergency room attendance resulting in hospital admission (3.6% vs 4.9%) vs placebo. Ensifentrine reduced moderate/severe exacerbation rate (36%, p=0.050) and instant risk, as assessed by time to first exacerbation (38%, p=0.038) vs placebo. Ensifentrine reduced moderate exacerbation rate (RR=0.59 [95% CI 0.36, 0.97], p=0.036) and instant risk (HR=0.57 [0.35, 0.93], p=0.025) vs placebo. Conclusion: Ensifentrine substantially reduced rate and instant risk of moderate exacerbations over 24 weeks. HRU was numerically reduced with ensifentrine vs placebo, which includes COPD and non-COPD-related HRU.