Pharmacokinetics of Novel Erythropoiesis Stimulating Protein Compared with Epoetin Alfa in Dialysis Patients

Abstract. Novel erythropoiesis stimulating protein (NESP) is a hyperglycosylated analogue of recombinant human erythropoietin (Epoetin) which has an increased terminal half-life in animal models. The aim of this study was to extend these observations to humans. Using a double-blind, randomized, cross-over design, the single-dose pharmacokinetics of Epoetin alfa (100 U/kg) and an equivalent peptide mass of NESP were compared following intravenous bolus in 11 stable peritoneal dialysis patients. This was followed by an open-label study to determine the single-dose pharmacokinetics of an equivalent peptide mass of NESP by subcutaneous injection in six of these patients. The mean terminal half-life for intravenous NESP was threefold longer than for intravenous Epoetin (25.3 versus 8.5 h), a difference of 16.8 h (95% confidence interval, 9.4 to 24.2 h, P = 0.0008). The area under the serum concentration—time curve was significantly greater for NESP (291.0 ± 7.6 ng · h per ml versus 131.9 ± 8.3 ng · h per ml; mean ± SEM; P < 0.0005), and clearance was significantly lower (1.6 ± 0.3 ml/h per kg versus 4.0 ± 0.3 ml/h per kg; mean ± SEM; P < 0.0005). The volume of distribution was similar for NESP and Epoetin (52.4 ± 2.0 ml/kg versus 48.7 ± 2.1 ml/kg; mean ± SEM). The mean terminal half-life for subcutaneous NESP was 48.8 h. The peak concentration of subcutaneous NESP was approximately 10% of that following intravenous administration, and bioavailability was approximately 37% by the subcutaneous route. The longer half-life of NESP is likely to confer a clinical advantage over Epoetin by allowing less frequent dosing in patients treated for anemia.