title: Darbepoetin alfa has a longer circulating half-life and greater in vivo potency than recombinant human erythropoietin.
abstract: OBJECTIVE
  Experiments on human erythropoietin (EPO) demonstrated that there is a direct relationship between the sialic acid-containing carbohydrate content of EPO, its circulating half-life, and in vivo bioactivity. This led to the hypothesis that an EPO analogue engineered to contain additional oligosaccharide chains would have enhanced biological activity. Darbepoetin alfa, a hyperglycosylated recombinant human EPO (rHuEPO) analogue with two extra carbohydrate chains, was designed and developed to test this hypothesis.
  
  
  METHODS
  Comparative pharmacokinetic and pharmacodynamic studies and biochemical analyses of darbepoetin alfa and rHuEPO were performed to define the consequences of the increased carbohydrate content.
  
  
  RESULTS
  Due to its increased sialic acid-containing carbohydrate content, darbepoetin alfa has a higher molecular weight, a greater negative charge, and a approximately fourfold lower EPO receptor binding activity than rHuEPO. It also has a threefold longer circulating half-life than rHuEPO in rats and dogs. In spite of its lower receptor binding, and perhaps counterintuitively, darbepoetin alfa is significantly more potent in vivo than rHuEPO. Due to the pharmacokinetic differences, the relative potency of the two molecules varies as a function of the dosing frequency. Darbepoetin alfa is 3.6-fold more potent than rHuEPO in increasing the hematocrit of normal mice when each is administered thrice weekly, but when the administration frequency is reduced to once weekly, darbepoetin alfa is approximately 13-fold to 14-fold more potent than rHuEPO.
  
  
  CONCLUSIONS
  Increasing the sialic acid-containing carbohydrate content beyond the maximum found in EPO leads to a molecule with a longer circulating half-life and thereby an increased in vivo potency that can be administered less frequently.
authors.affiliation: Amgen Inc., Thousand Oaks, Calif 91320, USA. joane@amgen.com
authors.forename: Joan C
authors.initials: JC
authors.lastname: Egrie
authors.forename: Erik
authors.initials: E
authors.lastname: Dwyer
authors.forename: Jeffrey K
authors.initials: JK
authors.lastname: Browne
authors.forename: Anna
authors.initials: A
authors.lastname: Hitz
authors.forename: Michele A
authors.initials: MA
authors.lastname: Lykos
mesh_terms: D000818:Animals; D002241:Carbohydrates / Q000032:analysis; D000068256:Darbepoetin alfa; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004563:Electrochemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004921:Erythropoietin / Q000031:analogs & derivatives* / Q000378:metabolism / Q000493:pharmacokinetics* / Q000494:pharmacology; D006207:Half-Life; D006400:Hematocrit; D006801:Humans; D007700:Kinetics; D008297:Male; D051379:Mice; D008970:Molecular Weight; D019158:N-Acetylneuraminic Acid / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017467:Receptors, Erythropoietin / Q000378:metabolism; D011994:Recombinant Proteins
chemical_list: D002241:Carbohydrates; D017467:Receptors, Erythropoietin; D011994:Recombinant Proteins; D004921:Erythropoietin; D000068256:Darbepoetin alfa; D019158:N-Acetylneuraminic Acid