title: Catalytic domain modification and viral gene delivery of activated factor VII confers hemostasis at reduced expression levels and vector doses in vivo.
abstract: Catalytic domain variants of activated factor VII (FVIIa) with enhanced hemostatic properties are highly attractive for the treatment of bleeding disorders via gene-based therapy. To explore this in a hemophilic mouse model, we characterized 2 variants of murine activated FVII (mFVIIa-VEAY and mFVIIa-DVQ) with modified catalytic domains, based on recombinant human FVIIa (rhFVIIa) variants. Using purified recombinant proteins, we showed that murine FVIIa (mFVIIa) and variants had comparable binding to human and murine tissue factor (TF) and exhibited similar extrinsic coagulant activity. In vitro in the absence of TF, the variants showed a 6- to 17-fold enhanced proteolytic and coagulant activity relative to mFVIIa, but increased inactivation by antithrombin. Gene delivery of mFVIIa-VEAY resulted in long-term, effective hemostasis at 5-fold lower expression levels relative to mFVIIa in hemophilia A mice or in hemophilia B mice with inhibitors to factor IX. However, expression of mFVIIa-VEAY at 14-fold higher than therapeutic levels resulted in a progressive mortality to 70% within 6 weeks after gene delivery. These results are the first demonstration of the hemostatic efficacy of continuous expression, in the presence or absence of inhibitors, of a high-activity gene-based FVIIa variant in an animal model of hemophilia.
authors.affiliation: Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA. margaritis@email.chop.edu [corrected]
authors.forename: Paris
authors.initials: P
authors.lastname: Margaritis
authors.forename: Elise
authors.initials: E
authors.lastname: Roy
authors.forename: Armida
authors.initials: A
authors.lastname: Faella
authors.forename: Harre D
authors.initials: HD
authors.lastname: Downey
authors.forename: Lacramioara
authors.initials: L
authors.lastname: Ivanciu
authors.forename: Giulia
authors.initials: G
authors.lastname: Pavani
authors.forename: Shangzhen
authors.initials: S
authors.lastname: Zhou
authors.forename: Ralph M
authors.initials: RM
authors.lastname: Bunte
authors.forename: Katherine A
authors.initials: KA
authors.lastname: High
mesh_terms: D000818:Animals; D020134:Catalytic Domain / Q000235:genetics*; D002460:Cell Line; D000229:Dependovirus / Q000235:genetics; D004195:Disease Models, Animal; D015942:Factor VIIa / Q000737:chemistry / Q000235:genetics*; D005786:Gene Expression Regulation; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods* / Q000401:mortality; D006467:Hemophilia A / Q000097:blood / Q000235:genetics / Q000628:therapy*; D006487:Hemostasis / Q000502:physiology*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D017434:Protein Structure, Tertiary
chemical_list: D015942:Factor VIIa