Comparison of GvHD prophylaxis regimens based on in vivo T-cell depletion (ATG vs. alemtuzumab) in patients with AML undergoing allo-HCT from unrelated donors with intermediate transplant conditioning intensity protocols: a registry study on behalf of the EBMT acute leukemia working party.

Allogeneic hematopoietic cell transplantation is a potentially curative therapy for acute myeloid leukemia (AML), but its success is limited by graft-versus-host disease (GvHD). Optimal in vivo T-cell depletion strategies for GvHD prophylaxis given with conditioning regimens remain under investigation. We compared antithymocyte globulin (ATG) and alemtuzumab as GvHD prophylaxis in adult AML patients in complete remission (CR1/CR2) undergoing allogeneic cell transplantation from unrelated-donors conditioned with intermediate-intensity regimens. From the EBMT registry, 1545 patients were identified (710 ATG; 835 alemtuzumab). Patients receiving ATG were slightly older and had higher comorbidity scores, but groups were otherwise comparable. At 3 years, ATG was associated with superior overall survival (58.3% vs. 50.4%, p = 0.03) and leukemia-free survival (52.1% vs. 45.7%, p = 0.014). ATG recipients also demonstrated significantly lower relapse incidence (21.9% vs. 28.1%, p = 0.006), while non-relapse mortality remained similar between groups (26% vs. 26.3%, p = 0.46). Although ATG was associated with a higher incidence of acute GvHD, chronic GvHD rates did not differ significantly. In summary, for AML patients in complete remission receiving intermediate-intensity conditioning, ATG improved long-term survival and reduced relapse risk compared with alemtuzumab, despite increased acute GvHD. These findings support ATG as an effective GvHD prophylactic option in this setting.