The Role of Alemtuzumab Compared to Antitymocyte Globulin in Non-Myeloablative Stem Cell Transplantation; Especially for the Prevention of GVHD and Immune Recovery.

Alemtuzumab is an anti-CD52 antibody, and has been used for lymphoid malignancies or as a member of non-myeloablative conditioning regimen in allogeneic transplantation. Especially, in non-myeloablative stem cell transplantation (NST), it has been reported that alemtuzumab is effective for graft-versus-host disease (GVHD), but the immune reconstruction after transplantation is delayed. In this study, we comparatively evaluated the efficacy of alemtuzumab for non-myeloablative conditioning, GVHD prophylaxis, and immune recovery in NST for hematologic diseases. We have compared the results in 28 recipients of a sibling or unrelated NST enrolled. The recipients were divided into 2 groups according to the use of alemtuzumab. In group A (n=21), the conditioning regimen was a combination of fludarabine, cyclophosphamide (or busulfan) and antithymocyte globulin (ATG), and group B (n=7) received fludarabine, cyclophosphamide (or busulfan), and alemtuzumab instead of ATG. GVHD prophylaxis was by cyclosporin A or FK506 plus methotrexate. There were no significant differences in the graft engraftment and period of granulocyte colony-stimulating factor infusion. Patients receiving alemtuzumab had a significantly lower incidence of acute GVHD (stage 2 or more) (14.3% versus 38.1%, P=0.03) and chronic GVHD (14.3% versus 52.4%, P=0.005). The relapse rate after transplantation was 28.6% (6 patients) in group A and 14.3 (1 patients) in group B (P=0.04). Flow cytometric analysis of peripheral mononuclear cells for evaluation of immune recovery showed that T-cell and NK-cell recovery were delayed in both groups. However, T-cell and NK-cell recovery after transplantation occurred earlier in patients received alemtuzumab. No significant differences were observed in disease-free or overall survival between two groups. In conclusion, alemtuzumab can be recommended for immune suppression in NST, with successful control over acute/chronic GVHD and inducing relatively earlier immune recovery after transplantation.