A study to test an oral medicine, belumosudil, in combination with corticosteroids in participants at least 12 years of age with newly diagnosed chronic graft versus host disease.

Primary Objective: Demonstrate the superiority of belumosudil in combination with prednisone vs placebo in combination with prednisone in Event-Free Survival (EFS) Secondary Objective:Demonstrate the superiority of belumosudil in combination with prednisone vs placebo incombination with prednisone in modified Lee Symptom Scale (mLSS) improvement,overall ,response rate (ORR) and in the rate of corticosteroid withdrawal