CAMPATH (CAMPATH-1H, alemtuzumab, MabCAMPATH), is a lymphocyte-depleting humanized monoclonal antibody that was recently approved in the USA and Europe for the treatment of chronic lymphocytic leukemia (CLL). It targets CD52--a small glycosylphosphatidylinositol-anchored glycoprotein that is highly expressed on normal T- and B-lymphocytes and on a large proportion of lymphoid cell malignancies--but not on hematopoietic progenitor cells. CAMPATH was shown to be effective against CLL refractory to chemotherapy with an acceptable toxicity profile. CAMPATH is also active against T-cell prolymphocytic leukemia and has been extensively used to prevent graft-versus-host disease associated with bone marrow transplantation. CAMPATH is owned by ILEX Pharmaceuticals LP and distributed by Schering AG and its US affiliate Berlex Laboratories.