This study is looking at two medicines, **belumosudil** and **rituximab**, to see if they are safe and helpful for people with a condition called chronic Graft-Versus-Host Disease (**cGVHD**). cGVHD happens when donated stem cells attack the body. This is a Phase 2 study, which means it is checking how well these medicines work and if they are safe. It is called "open-label" because both the doctors and the patients know what treatment is being given.

To join the study, you must be having your first treatment for cGVHD with medicine that affects the immune system. You should have good blood health and not have used certain medicines for more than 10 days. People with certain infections or heart problems cannot join.

• The study involves taking belumosudil and rituximab.
• There will be multiple visits to the study center for check-ups.
• Participants should consider their health to see if they meet the criteria.