Pure red cell aplasia and anti-erythropoietin antibodies in patients treated with epoetin

Recombinant human erythropoietin (epoetin) was first used for the treatment of renal anaemia in 1986. During the first 10 years of its use, epoetin-induced antibodies were a rare complication and only three cases of patients with epoetin-induced antibodies associated with pure red cell aplasia (PRCA) were published. Since 1998, however, there has been a significant increase in the number of patients developing severe anaemia during the course of epoetin treatment due to neutralizing antibodies. Patients with PRCA present with an absolute resistance to epoetin therapy and then rapidly develop severe anaemia with a very low reticulocyte count ( < 10 000/mm(3)). Consequently, patients become dependent on blood transfusions to maintain an acceptable level of haemoglobin. By December 2002, approximately 142 patients worldwide had been diagnosed with antibody-positive PRCA after receiving epoetin. The vast majority of these patients had been treated with the Eprex(TM) /Erypo(TM) brand of epoetin alfa, but there were also some cases in which patients had been receiving epoetin beta (NeoRecormon(TM)). To date, there have been no cases of antibody-mediated PRCA reported with the sole use of darbepoetin alfa (Aranesp(R)). All patients with epoetin-induced anti-erythropoietin antibodies had received the drug subcutaneously (s.c.), and almost all had chronic kidney disease-related anaemia. To our knowledge, no patient treated exclusively by intravenous (i.v.) administration has developed anti-erythropoietin antibodies. The increase in reported cases coincides with the removal of human serum albumin from the ex-US formulation of epoetin alfa, in order to comply with new regulations from the European regulatory authorities. It has been proposed that the new formulation is less stable, allowing aggregates of erythropoietin molecules to form, which increases the probability of antibody formation. Treatment with epoetin must be discontinued if PRCA is suspected. Patients do not respond to an increase in dose. Furthermore, patients must not be switched to another form of erythropoietic therapy as the antibodies cross-react with all erythropoietic therapies available. In around 70% of cases, immunosuppressive regimens are effective in eliminating the antibodies; cessation of epoetin therapy without concomitant immunosurpression is rarely effective. Kidney transplantation seems to provide an immediate and effective cure.