title: Glycoengineered factor IX variants with improved pharmacokinetics and subcutaneous efficacy.
abstract: BACKGROUND
  The rapid clearance of factor IX (FIX) necessitates frequent intravenous administration to achieve effective prophylaxis for patients with hemophilia B. Subcutaneous administration would be a preferred route of administration but is limited by bioavailability.
  
  
  OBJECTIVE
  To improve the pharmacokinetics (PK) and bioavailability of FIX, a screen was performed to identify positions for the introduction of novel glycosylation sites with maximal effect on PK and maintenance of coagulation activity.
  
  
  METHODS
  Two hundred fifty-one variants, each containing one additional N-linked glycosylation site, were screened in vitro, and the PK profiles of selected variants mapping to spatially distinct regions of FIX were evaluated in mice. Optimal variants were combined, and their PK and efficacy were determined in mice with hemophilia B.
  
  
  RESULTS
  Variants that mapped to spatially distinct regions of the FIX structure exhibited different degrees of improved PK and enabled selection of optimized sites while minimizing the loss of FIX activity. Combining the most effective N-glycan sites in the same FIX molecule resulted in further improvements in PK. An optimized variant containing three novel N-glycan sites (at amino acids 103, 151, and 228), and the activity enhancing 338A variant had double the specific activity of wild-type FIX, exhibited 4.5-fold reduced clearance and 2.4-fold increased subcutaneous bioavailability, and was efficacious at a fivefold lower mass dose than wild-type FIX after subcutaneous injection in a bleeding model in mice with hemophilia B.
  
  
  CONCLUSIONS
  Glycoengineering was used to significantly improve the subcutaneous PK and efficacy of FIX and may have advantages for subcutaneous dosing.
authors.affiliation: Biologics Research, Bayer Healthcare Pharmaceuticals, San Francisco, CA, USA.
authors.forename: A R
authors.initials: AR
authors.lastname: Brooks
authors.forename: D
authors.initials: D
authors.lastname: Sim
authors.forename: U
authors.initials: U
authors.lastname: Gritzan
authors.forename: C
authors.initials: C
authors.lastname: Patel
authors.forename: E
authors.initials: E
authors.lastname: Blasko
authors.forename: R I
authors.initials: RI
authors.lastname: Feldman
authors.forename: L
authors.initials: L
authors.lastname: Tang
authors.forename: E
authors.initials: E
authors.lastname: Ho
authors.forename: X-Y
authors.initials: XY
authors.lastname: Zhao
authors.forename: H
authors.initials: H
authors.lastname: Apeler
authors.forename: J E
authors.initials: JE
authors.lastname: Murphy
mesh_terms: D000818:Animals; D001682:Biological Availability; D004195:Disease Models, Animal; D005164:Factor IX / Q000008:administration & dosage / Q000235:genetics / Q000493:pharmacokinetics* / Q000627:therapeutic use; D006031:Glycosylation; D057809:HEK293 Cells; D002836:Hemophilia B / Q000188:drug therapy; D006801:Humans; D007279:Injections, Subcutaneous; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D015202:Protein Engineering
chemical_list: D005164:Factor IX
keywords: coagulation factor IX; glycosylation; hemophilia B; injections; pharmacokinetics; subcutaneous