Dose conversion from recombinant human erythropoietin to darbepoetin alfa: recommendations from clinical studies

Recombinant human erythropoietin (r-HuEPO, epoetin alfa), is an established and effective treatment for anemia associated with both chronic kidney disease (CKD) and cancer and has improved the management of anemia over alternatives such as transfusion. Darbepoetin alfa is a new erythropoietic agent with a 3-fold longer half-life and increased in vivo potency relative to r-HuEPO. These properties allow patients to be treated with longer dosing intervals than with r-HuEPO. Relative potency between r-HuEPO and darbepoetin alfa is not a fixed relationship but is dependent on several factors. Clinical study results suggest that greater relative potency differences are seen between r-HuEPO and darbepoetin alfa when the dosing intervals are longer and when r-HuEPO dose requirements are higher. Although 200 U of r-HuEPO contains the same peptide mass as 1 microg of darbepoetin alfa, a fixed ratio of 200:1 does not necessarily predict an appropriate dose conversion between the two drugs across the entire spectrum of dose ranges. When converting patients with CKD from r-HuEPO to darbepoetin alfa, dosing should be based on relevant clinical data. Appropriate guidance for conversion of patients with CKD from r-HuEPO to darbepoetin alfa is provided in the approved United States package insert for darbepoetin alfa. In patients who are prescribed darbepoetin alfa, either by conversion from r-HuEPO or as de novo treatment, therapy should begin according to recommendations in the package insert, after which, doses should be titrated individually according to each patient's hemoglobin response. Dosing data from oncology clinical studies, although not necessarily applicable to CKD, indicate similar potency ratios between r-HuEPO and darbepoetin alfa, and in addition affirm the finding that, as the interval between doses of darbepoetin alfa is increased, hemoglobin response is maintained.