Inclusion Criteria:  Participants ≥ 2 months of age Diagnosis of aGVHD grade II-IV following allogeneic HSCT according to standard criteria (Harris, 2016). Diagnosis of SR-aGVHD according to Mohty (2020)  Meet one of the following criteria:  Participants who are Ruxolitinib-refractory, according to Mohty (2020) Participants who are not eligible for SOC therapy Participants who agree to receive ASC930 as a second-line therapy Karnofsky/Lansky Performance Status of at least 30 at the time of study entry Minor participants must be capable of giving written assent as appropriate per the applicable age (per local regulatory requirements).  Exclusion Criteria:  Diagnosis of active Hepatic Sinusoidal Obstruction Syndrome (SOS) Presence of an active uncontrolled infection Active treatment for a hyprecoagulation disorder Evidence of diffuse alveolar hemorrhage or other active pulmonary disease Evidence of encephalopathy as defined by a change in mental status since the onset of aGVHD Evidence of relapse of malignancy Receival of agents other than steroids for primary treatment of aGVHD Severe allergic history to cell-based products