LEEP (Losartan Effects on Emphysema Progression) was a clinical trial for adults over the age of 40 who have mild to severe Chronic Obstructive Pulmonary Disease (COPD). The purpose of this study was to learn how a medicine called losartan may help people who have COPD with emphysema, which is defined as lung tissue damage created over time. Participants were followed for 1 year. LEEP was sponsored by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH). The LEEP study has been completed.