Alemtuzumab in stem cell transplantation.

Alemtuzumab, otherwise called CAMPATH-1H, is a humanized monoclonal antibody directed against the CD52 antigen of lymphocytes. It is one of a family of CAMPATH-1 antibodies that have been used over the last 20 yr in stem cell transplantation for depletion of donor and recipient T-cells to prevent graft-versus-host disease and graft rejection. Clinical trials have been carried out by a cooperative group of physicians and the protocols have gradually evolved as different problems have been identified and overcome. T-cell depletion carries risks of reducing graft-versus-tumor effects and increasing susceptibility to virus reactivation, but offers significant benefits in terms of reduced mortality and morbidity from graft-versus-host disease (GVHD). Two protocols are currently favored: (1) simple addition of CAMPATH-1H to the stem cell infusion and (2) administration in vivo prior to the transplant--especially in the context of nonmyeloablative conditioning regimens. Both of these give excellent control of GVHD with minimal graft rejection. Contrary to earlier expectations, a short course of posttransplant cyclosporin A (CyA) appears to further reduce transplant-related mortality, mainly by a reduction in late deaths from infection. These results need to be consolidated by means of prospective clinical trials.