Anti-T lymphocyte Globulin plus Posttransplant Cyclophosphamide 25 mg/kg versus Posttransplant Cyclophosphamide 50 mg/kg in Patients with Acute Leukemias

In this study, we aimed to compare the engraftment days, graft-versus-host disease (GVHD) development, relapse and overall survival rates in patients using myeloablative/reduced intensity conditioning regimens with posttransplant cyclophosphamide (PTCy) 25 mg/kg x2 with Anti-T lymphocyte Globulin (ATLG) (n = 29) and PTCy 50 mg/kg x2 doses (n = 41) in patients with acute leukemias. Matched related, matched unrelated, 1 mismatched unrelated, and haploidentical donors were selected for the patients. Platelet (median 11 vs 17 days) and neutrophil (median 14 vs 15 days) engraftment times were shorter in ATLG+ PTCy25 treated patients (both p < 0.05); veno-occlusive disease rates, graft failure and poor graft functions were similar between the two approaches (all p > 0.05); cumulative incidences of grade II-IV aGVHD at +100 days, grade III-IV aGVHD at +100 days, and grade II-IV cGVHD at 1-year were comparable between ATLG+PTCy25 and PTCy50 groups (all p > 0.05). Cumulative incidences of relapse and non-relapse mortality at 1-year were similar in two cohorts (both p > 0.05). PTCy50 was associated with a statistically significant benefit in terms of GVHD-free/relapse-free survival (GRFS) at 1-year (p = 0.03). Median GRFS was 115 (95% CI: 42–214) days and 248 (95% CI: 151-not reached) days, respectively [HR was 0.51 (0.28–0.95), p = 0.03; GRFS at 1-year was 20.7% vs 44.3%, respectively]. However, the groups were comparable in terms of PFS and OS. Median PFS was 332 days (95% CI: 182 days-not reached) for ATLG+PTCy25 group. It was not reached (95% CI: 210 days-not reached) for the patients who received PTCy50. Median OS was not reached in either ATLG+PTCy25 (95% CI: 191 days-not reached) or PTCy50 groups (Log rank = 0.42). Our study showed that lowering PTCy dose with ATLG seems to accelerate platelet and neutrophil engraftment rates; confers similar survival and relapse rates, similar acute and chronic GVHD frequency despite increased GRFS at 1-year.