In this large ‘real world’ analysis of patients who participated in a prospective registry trial (BMT CTN 1202), we simulated rATG exposures post-HCT using a validated population-PK model (Admiraal et al) [9]. A previously described post-HCT rATG exposure of <30 AUxday/mL correlated with higher OS, faster CD4 + IR and lower relapse probability, compared to higher post-HCT rATG exposures (30-55 and ≥55 AUxd/mL) and patients who did not receive ATG [7, 9, 14, 18, 19].