This study is testing how well a medicine called belumosudil works for adults with a lung problem called Chronic Lung Allograft Dysfunction (CLAD). CLAD happens in some people after a lung transplant. The study is double-blind, meaning neither the doctors nor participants know who is getting the actual medicine or a placebo (a pill with no medicine). It involves participants who are 18 or older and at least one year post lung transplant. All participants will continue taking a medicine called azithromycin, which helps with CLAD.

Key Points:

• The study lasts up to 31 weeks or up to 57 weeks if the participant continues in the extended part of the study.
• There are 10 to 16 visits, depending on study participation length.
• Open to those who have been on azithromycin for at least 8 weeks.

This study is not for people whose lung problem is due to reasons other than CLAD, like other lung issues or rejections. Participants can’t have had other treatments for CLAD recently. This study is conducted in multiple countries and centers.