Vedolizumab, Anti-CD25 Antibody, Rapid Reduction of Glucocorticoids for SR-aGVHD With Gastrointestinal Involvement

Inclusion Criteria: * Clinical diagnosis of grade 3-4(according to MAGIC criteria) steroid-resistant acute graft-versus-host disease(progression after 3 days or lack of improvement after 5 days of systemic 1.5-2 mg/kg steroids) with gastrointestinal involvement. * Age 18-65. * ECOG score≤3. * Must be able to understand and willing to participate in the study and sign the informed consent. Exclusion Criteria: * Refractory/secondary graft-versus-host disease. * Severe complications such as myocardial infarction, chronic cardiac insufficiency, * hepatic failure, renal insufficiency, etc. * Clinically uncontrolled active infections. * Other Malignant tumors with progression. * Heart failure: EF\<30%, NYHA≥grade III. * Pregnant or lactating women. * Expected survival \<60 days. * Undergoing other drug clinical trials.