Impact of peritransplant alemtuzumab levels on the risk of acute GVHD. Cumulative incidence curves of the incidences of (A) grades I-IV acute GVHD, (B) grades II-IV acute GVHD, and (C) grades III-IV acute GVHD stratified by alemtuzumab level of ≤0.15 vs ≥0.16 μg/mL on the day of graft infusion. (D) Cumulative incidence curves of the incidences of grades I-IV acute GVHD stratified by multiple alemtuzumab levels.