Alemtuzumab (Campath 1H) in hairy cell leukaemia relapsing after rituximab treatment.

Monoclonal antibodies (mAbs) are gaining increasing importance in the course of nucleoside analogue refractory hairy cell leukaemia (HCL). On the one hand, there is the chimaeric anti-CD20 antibody rituximab, which has been in use in relapsed and refractory HCL for almost 5 years now with moderate activity. Very recently, two major studies examined and reviewed the use of this antibody – however, with diverging results. On the other hand, there are immunotoxins like BL22 (targeted against the CD 22 antigen) and LMB-2 (an anti-CD25 immunotoxin), with good response rates but remarkable toxicity and limited availability. Another chimaeric antibody that is used especially in unrelated and reduced intensity haematopoietic stem cell transplantation as well as chronic lymphocytic leukaemia is alemtuzumab (Campath 1H). Alemtuzumab is directed against CD52, a broad haematopoietic marker also expressed in B-cell neoplasias like HCL. To our knowledge, Campath 1H has not been administered in HCL before. We report on a patient with progressive anaemia and thrombocytopenia who was diagnosed with HCL in October 2000. The initial response to cladribine was only short-lasting; the patient was retreated with cladribine followed by a-interferon and finally underwent splenectomy. Various bone marrow biopsies as well as flow cytometric analyses initially and during the course of the disease confirmed the morphological and immunological diagnosis of a typical hairy cell leukaemia with simultaneous expression of CD103, CD25 and CD11c. In July 2002, progressive thrombocytopenia required treatment initiation with rituximab, which was administered four times on a weekly and thereafter three times