A Study to Find Out Whether BI 1015550 Improves Lung Function in People With Progressive Fibrosing Interstitial Lung Diseases (PF-ILDs)

This study is open to adults with Progressive Fibrosing Interstitial Lung Diseases (PF-ILDs). People who have a form of PF-ILD other than Idiopathic Pulmonary Fibrosis (IPF) can join the study. If they already take nintedanib, they can continue treatment throughout the study. The purpose of this study is to find out whether a medicine called BI 1015550 helps people with PF-ILD. Participants are put into 3 groups randomly, which means by chance. Participants in 2 groups take different doses of BI 1015550 as tablets twice a day. Participants in the placebo group take placebo tablets twice a day. Placebo tablets look like BI 1015550 tablets but do not contain any medicine. Participants are in the study for up to two and a half years. During the first year, they visit the study site 10 times. Afterwards, they visit the study site every 3 months. The doctors regularly test participants' lung function. The results of the lung function tests are compared between the groups. The doctors also regularly check participants' health and take note of any unwanted effects.