Antithymocyte globulin (ATG) was shown to reduce the incidence of grade 2 to 4 acute graft-vs-host disease (GVHD) in patients who received matched-sibling donor transplantations (MSDT) for hematologic malignancies, according to the results of a prospective study published in the Journal of Clinical Oncology.
The study authors explained that ATG has been linked to lower rates of GVHD in patients receiving unrelated donor transplantations or haploidentical donor transplantations, but that efficacy in patients receiving MSDT has been unclear.
In this randomized controlled, open-label study (ClinicalTrials.gov Identifier: NCT01856803), conducted at 23 transplantation centers in China, 263 patients had received human leukocyte antigen-matched stem cell transplants from siblings. The patients were randomly assigned into a treatment group that received ATG (132 patients) or a control group (131 patients) that was not given ATG. All patients received cyclosporine, methotrexate, and mycophenolate mofetil. The primary endpoint of the study was the rate of acute GVHD of grades 2 to 4.
At 100 days, the group receiving ATG showed a cumulative incidence of grade 2 to 4 acute GVHD of 13.7%, while the control group had a cumulative incidence of 27.0% (P =.007). The cumulative incidence of grade 3 to 4 acute GVHD was lower with ATG than for the control group, but the rates for this comparison did not significantly differ (P =.151).
The 2-year incidence of overall chronic GVHD was 27.9% for the ATG group and 52.5% for the control group (P <.001). The 2-year incidence of extensive GVHD was also lower in the ATG group compared with the control group (8.5% vs 23.2%, respectively; P =.029).
The rate of 3-year GVHD relapse-free survival was also superior for patients in the ATG group compared with patients in the control group (38.7% vs 24.5%, respectively; P =.003). In addition, at 2 years, fewer patients remained on immunosuppressant therapy in the ATG group than in the control group (84.8% vs 57.4%, respectively; P =.001).
The authors reported that multiple other endpoints showed no significant differences between the groups, including 3-year rates of nonrelapse mortality, cumulative incidence of relapse, overall survival, and leukemia-free survival. Reactivations of cytomegalovirus or Epstein-Barr viral infections also did not significantly differ between groups.
The study authors determined that including ATG as a component of GVHD prophylaxis therapy can significantly lower the risk of grade 2 to 4 acute GVHD in patients given MSDT and without increasing the risk of relapse or nonrelapse mortality.
Chang Y, Wu D, Lai Y, et al. Antithymocyte globulin for matched sibling donor transplantation in patients with hematologic malignancies: a multicenter, open-label, randomized controlled study [published online July 10, 2020]. J Clin Oncol. doi: 10.1200/JCO.20.00150