Belumosudil is an oral tablet taken by mouth. It works by blocking a protein that helps control the immune system, which can reduce the harmful immune activity that causes chronic graft‑versus‑host disease (cGVHD). In this study it is the new treatment being tested to see if it works better than the other medicines that patients may already be using.

Sirolimus is a pill that suppresses the immune system by stopping certain immune cells from growing. Doctors often use it to prevent organ rejection after a transplant. In the trial it is one of the existing medicines that could be chosen as part of the best available therapy for cGVHD.

Ibrutinib is an oral drug that blocks a signaling pathway important for certain immune cells and cancer cells. It is approved for some blood cancers and for chronic graft‑versus‑host disease. In this study it may be used as a comparator option for patients who need additional therapy.

Everolimus is a tablet that reduces activity of the immune system by inhibiting a key growth‑regulating protein. It is used to prevent organ rejection and to treat some cancers. Here it can be selected as part of the standard treatments against cGVHD.

Imatinib is a pill that blocks a specific enzyme involved in the growth of certain abnormal cells. It is best known for treating chronic myeloid leukemia but is also used for some forms of cGVHD. In the trial it may be one of the medicines offered as best available therapy.

Rituximab is given by infusion into a vein. It is an antibody that targets a protein on B‑cells, a type of immune cell, leading to their removal. It is used for various autoimmune diseases and some cancers. In this study it can be chosen as a treatment option for cGVHD.

Carfilzomib is an intravenous medication that blocks a protein‑degrading system inside cells, which can reduce abnormal immune activity. It is approved for multiple myeloma and may be used for severe cGVHD. It is listed as a possible comparator therapy.

Pentostatin is a pill that interferes with DNA synthesis in certain immune cells, helping to lower excessive immune responses. It is sometimes used in the treatment of blood cancers and severe immune disorders. In this trial it may be part of the best available therapy options.

Methotrexate is an oral medication that slows down the growth of rapidly dividing cells, including overactive immune cells. It is widely used for cancers, rheumatoid arthritis, and some transplant‑related conditions. It can be selected as a standard therapy for cGVHD in the study.

Bortezomib is given by injection and works by blocking a protein‑degradation pathway in cells, which can reduce harmful immune activity. It is approved for multiple myeloma and sometimes used for severe cGVHD. It is one of the comparator drugs in the trial.

Ixazomib is an oral tablet that also blocks the same protein‑degradation system as bortezomib, helping to control abnormal immune responses. It is used for certain blood cancers and may be chosen as a therapy for cGVHD in the study.

Mycophenolate mofetil (often called mycophenolic acid) is taken by mouth and works by stopping the growth of certain immune cells, thereby dampening the immune response. It is commonly used to prevent organ rejection and to treat autoimmune conditions. In this trial it can be part of the best available therapy for cGVHD.

Chronic graft‑versus‑host disease – Chronic graft‑versus‑host disease is an immune‑mediated condition that can develop after an allogeneic stem cell transplant, when donor immune cells recognize the recipient’s tissues as foreign. It typically appears three months or more after transplantation and may involve the skin, liver, eyes, mouth, lungs, gastrointestinal tract, and other organs. The disease often starts with mild symptoms such as rash or dry eyes, and over time can become more extensive, affecting multiple organ systems. In some people, the inflammation and fibrosis progress gradually, leading to functional impairment of the involved organs. The severity can fluctuate, with periods of worsening followed by partial improvement.