Belumosudil With Ruxolitnib as Third Line Therapy for Chronic Graft Versus Host Disease (cGvHD)

Chronic graft-versus-host disease (cGvHD) is a serious condition that can happen after a stem cell or bone marrow transplant. The donor's immune cells attack the patient's body, causing inflammation, pain, and damage to organs like the skin, liver, or lungs. For patients with moderate to severe cGvHD who don't improve with or can't tolerate standard front line therapy with steroids, there's a significant unmet need. Steroid-refractory cGvHD is hard to treat, with limited effective options, often leading to ongoing symptoms and reduced quality of life. This Phase II study tests a new treatment combining two oral drugs, ruxolitinib and belumosudil, for these patients. Both drugs have helped cGvHD individually, but this trial explores if they work better together. Patients will begin on ruxolitinib (10 mg twice daily) and will continue for up to 48 weeks. Upon ruxolitinib treatment failure, patients will add belumosudil (200 mg once or twice daily, depending on other medications) in addition to ruxolitinib for 48 weeks (12 cycles) unless their condition worsens or side effects become intolerable. Follow-up visits occur 28 days and 6 months after treatment ends to check health status. The study is non-randomized (all get the same treatment) and open-label (patients and doctors know the drugs used). It aims to see if this combination better controls cGvHD in patients where steroids failed. This could offer hope for better symptom management and improved quality of life for those with limited treatment options.

Inclusion Criteria: 1. 18 years of age or older at the time of enrollment. 2. Has previously been diagnosed with moderate to severe cGvHD OR mild cGvHD with high-risk features (defined as platelet counts \< 100 x 109/L at screening). 3. Capable of providing informed consent. 4. Meets the criteria of steroid-refractory cGvHD after first line corticosteroids therapy at the time of enrollment, as follows: * Lack of response or disease progression after prednisone ≥1 mg/kg/day for ≥1 week OR * Disease persistence without improvement with prednisone \>0.5 mg/kg/day or 1 mg/kg/every other day for ≥4 weeks OR * Increase in prednisone dose to \>0.25 mg/kg/day after 2 unsuccessful attempts to taper the dose. 5. Taking a steroid dose at the time of enrollment that is \0.5 mg/kg/day of prednisone or equivalent corticosteroids at the time of enrollment. 4. Ongoing use of any of the following pharmaceutical agents, which cannot be discontinued prior to belumosudil treatment (PRN/as-needed use is permissible if it can be fully discontinued at least 7 days prior to enrollment and is not expected to resume during the study): * Strong CYP3A inducers * UGT1A1 substrates (e.g., raltegravir) * P-gp substrates (e.g., dabigatran) * OATP1B1/OATP1B3/BCRP substrates (e.g., rosuvastatin) 5. Has had prior treatment with a JAK inhibitor or ROCK2 inhibitor within 8 weeks of enrollment. Participants who received a JAK inhibitor for aGvHD are eligible only if they achieved CR or PR prior to screening. 6. Active uncontrolled bacterial, fungal, parasitic, or viral infection. Infections are considered controlled if appropriate therapy has been initiated and, at the time of screening, no signs of infection are present. 7. Active hepatitis B virus (HBV) or hepatitis C virus (HCV) infection that requires treatment, or is at risk for HBV reactivation (i.e., positive HBsAg) within 4 weeks of enrollment. Participants with negative HBsAg and positive total HBc antibody may be included if HBV DNA is undetectable at the time of screening. Participants who are positive for HCV antibody are eligible only if PCR is negative for HCV RNA. Participants whose immune status is unknown or uncertain must have results confirming immune status before enrollment. 8. Known active infection or history of human immunodeficiency virus (HIV). 9. Evidence of relapsed primary hematologic disease, or receipt of treatment for relapse after the allo-HCT was performed. Patients treated with Donor Lymphocyte Infusion (DLI) who have developed GvHD will not be excluded if the primary hematological disease has resolved. 10. Maintenance therapy for the primary hematologic disease started within 4 weeks before initiation of study treatment (Cycle 1 Day 1) or plans to start maintenance therapy after Day 1. 11. Participants on mechanical ventilation, requiring oxygen support or with a FEV1 \< 30%. 12. History or current diagnosis of cardiac disease indicating significant risk of safety for participation in the study, such as uncontrolled or significant cardiac disease, including any of the following: 1. Recent myocardial infarction (within 6 months of enrollment) 2. New York Heart Association Class III or IV congestive heart failure 3. Unstable angina (within 6 months of enrollment) 4. Clinically significant (symptomatic) cardiac arrhythmias (e.g. sustained ventricular tachycardia, and clinically significant second or third degree AV block without a pacemaker). 13. Uncontrolled hypertension, defined as blood pressure that remains above 130/80 mmHg in spite of concurrent use of at least three antihypertensive agents of different classes. 14. Patients with known active CNS disease (malignant involvement of CNS). 15. Patients with active acute GvHD grade III-IV. 16. History or other evidence of severe illness or any other conditions that would make the patient, in the opinion of the treating Investigator, unsuitable for the study (such as malabsorption syndromes, poorly controlled psychiatric disease or coronary artery disease). 17. Known hypersensitivity to belumosudil, ruxolitinib or any of their excipients 18. Patients unable to swallow oral medications 19. Female participants who are pregnant or breastfeeding