RecruitingPhase 2Drug trialA Study of Belumosudil in People at Risk of Developing Graft-Versus-Host Disease After a Stem Cell TransplantThe purpose of this study is to find out whether adding belumosudil to a usual approach for reducing the risk of graft-versus-host disease (GVHD) may be an effective GVHD prevention approach for people with blood cancer who have a stem cell transplant. The investigators will also look at the safety of the study approach.