First Line Therapy for High Risk Acute GVHD

Inclusion Criteria: 1. diagnosed with hematological diseases. 2. Have undergone first allogeneic hematopoietic stem cell transplantation (allo-HSCT) from any donor source using bone marrow, peripheral blood stem cells, or cord blood for hematologic malignancies. 3. new onset of grade II\~IV aGVHD or intermediate or high risk aGVHD (based on ST2, REG3a, other experimental objects) within 100 days post-transplantation. Exclusion Criteria: 1. recipients of second allogeneic stem cell transplant. 2. acute GVHD induced by donor lymphocyte infusion, interferon. 3. received first line aGVHD treatment before enrollment. 4. overlap GVHD syndrome. 5. pregnant or breast-feeding women. 6. absolute neutrophil count (ANC) \<0.5×10e9/L or platelet count (PLT) \< 20×10e9/L 7. Serum creatinine \> 2.0 mg/dL or creatinine clearance \< 40 mL/min measured or calculated by Cockroft-Gault equation. 8. uncontrolled infection 9. human immunodeficiency virus infection 10. active hepatitis b virus, hepatitis C virus infection and need antivirus treatment. 11. Subjects with evidence of relapsed primary disease, or subjects who have been treated for relapse after the allo-HSCT was performed, or graft rejection. 12. allergic history to Janus kinase inhibitors. 13. Severe organ dysfunction unrelated to underlying GVHD, including: Cholestatic disorders or unresolved veno-occlusive disease of the liver (defined as persistent bilirubin abnormalities not attributable to GVHD and ongoing organ dysfunction). Clinically significant or uncontrolled cardiac disease including unstable angina, acute myocardial infarction within 6 months from Day 1 of study drug administration, New York Heart Association Class III or IV congestive heart failure, circulatory collapse requiring vasopressor or inotropic support, or arrhythmia that requires therapy. Clinically significant respiratory disease that requires mechanical ventilation support or 50% oxygen. 14. Received Janus kinase inhibitor therapy after allo-HSCT for any indication. 15. Any condition that would, in the investigator's judgment, interfere with full participation in the study, including administration of study drug and attending required study visits; pose a significant risk to the subject; or interfere with interpretation of study data.