Darbepoetin alfa: a novel erythropoiesis-stimulating protein

Darbepoetin alfa is a novel erythropoiesis-stimulating protein developed for the treatment of anemia. It is a hyperglycosylated analog of recombinant human erythropoietin with the same mechanism of action as erythropoietin, but with a three-fold longer terminal half-life after intravenous administration than recombinant human erythropoietin and the native hormone both in animal models and in humans. Clinical studies in patients with chronic renal failure either receiving or not receiving dialysis have shown that darbepoetin alfa is equivalent to recombinant human erythropoietin in terms of increases in hemoglobin concentration, percentage of patients achieving target hemoglobin concentration and average time to reach target hemoglobin concentration, although darbepoetin alfa is administered less frequently (once weekly or every other week). Clinical trials in cancer patients either receiving or not receiving chemotherapy have demonstrated that darbepoetin alfa is safe and effective in alleviating anemia at dose intervals of once every 1, 2 or 3 weeks, and results suggest that it may achieve greater and more rapid responses than recombinant human erythropoietin in cancer patients. Furthermore, an improvement in health-related quality of life has been observed in association with anemia correction using darbepoetin alfa therapy in these patients. Darbepoetin alfa has been approved for intravenous and subcutaneous administration by the European Commission and the FDA for the treatment of anemia in patients with chronic renal failure. Additionally, this product was recently approved by the FDA for the treatment of anemia in patients with nonmyeloid malignancies where anemia is due to the effect of concomitantly administered chemotherapy. The recommended starting dose in chronic renal failure patients is 0.45 microg/kg once weekly for both intravenous and subcutaneous administration, with subsequent titration based on the hemoglobin concentration. In cancer patients, the recommended starting dose is 2.25 microg/kg once weekly by subcutaneous injection and subsequent titration. The adverse event profile of darbepoetin alfa is similar to that of recombinant human erythropoietin in both settings. There are no reports of antibody formation associated with darbepoetin alfa in chronic renal failure patients, and three cases of antibody formation, with neutralizing activity in one of the cases, have been reported in cancer patients. However, no cases of antibody-mediated pure red cell aplasia have been reported. The longer half-life of darbepoetin alfa, together with a similar efficacy and safety profile, confers the clinical advantage over recombinant human erythropoietin of allowing a less frequent dosing (once weekly or every other week versus one to three times weekly in renal patients), thus reducing health-care utilization and probably improving patient compliance.