The Role of Alemtuzumab in Nonmyeloablative Hematopoietic Transplantation

Nonmyeloablative stem cell transplants provide a viable therapeutic option for older patients or patients with comorbid conditions, who were previously deemed to be ineligible for transplantation. Despite improvements in clinical outcomes, graft-versus-host disease (GVHD) remains a significant and potentially lethal complication. One approach by which GVHD has been managed is through introduction of new agents, such as alemtuzumab, into the conditioning regimen. Alemtuzumab is a humanized monoclonal antibody that targets the CD52 antigen, which is highly expressed on both B and T lymphocytes. By depleting T cells in both the donor and the recipient, alemtuzumab has been shown to prevent development of both acute and chronic GVHD, without inhibiting the benefits associated with the graft-versus-leukemia effect. Clinical trials have shown that alemtuzumab is able to decrease the incidence of acute and chronic GVHD without impairing engraftment. Furthermore, in chronic lymphocytic leukemia therapy, alemtuzumab has been shown to purge malignant cells from the host to allow for harvesting for the purpose of autologous transplantation. Despite results showing that alemtuzumab can play an important role in managing GVHD, little information is available regarding a standardized dosing schedule. Greater insight into alemtuzumab’s pharmacokinetic activity would assist in developing a schedule that can optimize alemtuzumab-mediated T-cell depletion to prevent GVHD, while retaining sufficient host T-cell activity to encourage the graft-versus-leukemia effect and prevent relapse.