RecruitingPhase 4Drug trialStudy of Efficacy and Safety of Ruxolitinib in Patients With Grade II to IV Steroid-refractory Acute Graft vs. Host DiseaseThe purpose of this study is to assess the efficacy and safety of ruxolitinib therapy in Chinese adults and adolescents (≥ 12 years old) with Grade II-IV steroid-refractory acute graft versus host disease (SR-aGvHD).