title: A new drug form of blood coagulation factor IX: red blood cell-entrapped factor IX.
abstract: BACKGROUND
  Deficiency of factor IX causes hemophilia B, and primary treatment for hemophilia B is based on recurrent infusions of deficient factor IX. Frequent infusions of foreign protein diminish patients' quality of life, and increase the risk of development of immune reaction. We entrapped factor IX into erythrocytes-carriers (pharmacocytes) to prolong the drug's circulation life time, and to prevent immune response to the drug.
  
  
  METHODS
  Factor IX was biotynilated by standard method and then loaded aseptically into volunteers' erythrocytes with our gentle procedure of stepwise dialysis. The comparison of pharmacokinetics for free and autologous erythrocytes-entrapped biotinylated factor IX (FIXbiot) was done. Concentrations of factor IXbiot in plasma and lysates of erythrocytes were quantitatively assessed with a sandwich ELISA.
  
  
  RESULTS
  Stepwise dialysis method allowed stable loading of factor IXbiot into erythrocytes. Elimination of the loaded erythrocytes followed the first-order kinetics. The mean half-time of elimination for free FIXbiot was 8.8±5.6 hours, and for RBC-entrapped factor IXbiot 73.9±16.0 hours. Elimination of FIXbiot from plasma did not follow the first order kinetics because this factor concentration depended not only on the rate of its elimination, but also on the rate of factor appearance in plasma as a result of pharmackocytes' degradation. A rough estimate of the feasibility of the approach was done.
  
  
  CONCLUSIONS
  The life time of the erythrocyte-based form of FIXbiot in the circulation is significantly (5-10 times) prolonged compared with its free form, suggesting that this form has potential clinical applications.
authors.affiliation: National Research Center for Hematology, Russian Academy of Medical Sciences, Moscow, Russia. sinaurid@list.ru
authors.forename: Elena Ivanovna
authors.initials: EI
authors.lastname: Sinauridze
authors.forename: Tatyana Alekseevna
authors.initials: TA
authors.lastname: Vuimo
authors.forename: Elena Viktorovna
authors.initials: EV
authors.lastname: Kulikova
authors.forename: Igor Igorevich
authors.initials: II
authors.lastname: Shmyrev
authors.forename: Fazoil Inoyatovich
authors.initials: FI
authors.lastname: Ataullakhanov
mesh_terms: D000328:Adult; D019921:Biotinylation; D004337:Drug Carriers; D004912:Erythrocytes; D005164:Factor IX / Q000032:analysis / Q000493:pharmacokinetics / Q000627:therapeutic use; D005240:Feasibility Studies; D005260:Female; D002836:Hemophilia B / Q000097:blood / Q000188:drug therapy / Q000628:therapy; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D013678:Technology, Pharmaceutical; D055815:Young Adult
chemical_list: D004337:Drug Carriers; D005164:Factor IX