Impact of anti-T-lymphocyte globulin dosing on graft versus host disease in matched sibling peripheral blood stem cell transplantation

Anti-T-lymphocyte globulin (ATLG) is commonly administered to reduce graft-versus-host disease (GVHD) in allogeneic stem cell transplantation (allo-SCT). However, the optimal ATLG dose in matched-sibling-donor (MSD) peripheral blood stem-cell transplantation (PBSCT) remains uncertain. We compared two ATLG doses (15 mg/kg vs. 30 mg/kg) in the MSD-PBSCT setting to assess allo-SCT outcomes. In this single-center retrospective study, we included 165 consecutive patients with hematologic malignancies who underwent MSD-PBSCT. Of these, 71 received 15 mg/kg ATLG (ATLG-15), and 94 received 30 mg/kg ATLG (ATLG-30). ATLG-15 was associated with earlier leukocyte (median 11 vs. 12 days, p = 0.004) and platelet engraftment (median 12 vs. 15 days, p = 0.0002). Moderate/severe chronic GVHD at 2 years was significantly higher with ATLG-15 (43% vs. 28%, p = 0.045), with no difference in OS, PFS, NRM, or CIR. In multivariable analysis, ATLG-30 was associated with improved GRFS (HR 0.47, p = 0.02). After propensity score matching, GRFS and all-grade cGVHD remained significantly better with ATLG-30 (p = 0.047), with a trend toward reduced moderate/severe cGVHD (p = 0.067). In AML/MDS patients not receiving TBI (n = 108), moderate/severe cGVHD remained lower with ATLG-30 (19% vs. 38%, p = 0.039). Our study suggests that ATLG-30 in MSD-PBSCT reduces moderate/severe cGVHD and improves GRFS.