Thromb Haemost 2010; 104(02): 355-365
DOI: 10.1160/TH09-11-0792
Animal Models
Schattauer GmbH

FIX-Triple, a gain-of-function factor IX variant, improves haemostasis in mouse models without increased risk of thrombosis

Chung-Yang Kao
1   Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, Taiwan
,
Chia-Ni Lin
1   Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, Taiwan
,
I-Shing Yu
1   Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, Taiwan
,
Mi-Hua Tao
2   Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
,
Hua-Lin Wu
3   Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
,
Guey-Yueh Shi
3   Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
,
Yung-Li Yang
4   Department of Laboratory Medicine, National Taiwan University Hospital, Taipei, Taiwan
5   Department of Pediatrics, National Taiwan University Hospital, Taipei, Taiwan
,
Jau-Tsuen Kao
1   Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, Taiwan
4   Department of Laboratory Medicine, National Taiwan University Hospital, Taipei, Taiwan
,
Shu-Wha Lin
1   Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, Taiwan
4   Department of Laboratory Medicine, National Taiwan University Hospital, Taipei, Taiwan
› Author Affiliations

Financial support: This work was supported by grants from the National Science Council (NSC95–3112-B-002–017, NSC96–2752-B-002–011-PAE) and from the National Health Research Institutes (NHRI-EX97–9729BI) (to S.W.L.).
Further Information

Publication History

Received: 23 November 2019

Accepted after major revision: 01 April 2010

Publication Date:
24 November 2017 (online)

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Summary

Engineered recombinant factor IX (FIX) with augmented clotting activity may prove useful for replacement therapy, but it has not been studied for risk of thrombosis. We used three mouse models to evaluate thrombosis risk associated with the FIX variant FIX-Triple, which has a 13-fold higher specific activity than wild-type FIX (FIX-WT). Protein infusion of FIX-Triple into haemophilia B mice was not thrombogenic, even at a dose of 13-fold higher than FIX-WT. Gene knock-in to generate mice that constitutively produce FIX-WT or FIX-Triple protein revealed that all mice expressed equal antigen levels. FIX-Triple knock-in mice that exhibited 10-fold higher FIX clotting activity did not show hypercoagulation. Adeno-associated viral (AAV) delivery of the FIX gene into mice was used to mimic gene therapy. Haemophilia B and inbred C57Bl/6 mice injected with different doses of virus particles carrying FIX-WT or FIX-Triple and expressing up to a nearly 13-fold excess (1289% of normal) of FIX clotting activity did not show increased risk of thrombosis compared with untreated wild-type mice in a normal haemostatic state. When challenged with ferric chloride (FeCl3), the mesenteric venules of AAV-treated C57Bl/6 mice that gave a nearly five-fold excess (474%) of FIX clotting activity were not thrombotic; however, thrombosis became obvious in FeCl3-challenged mice expressing extremely high FIX clotting activities (976–1289%) achieved by AAV delivery of FIX-Triple. These studies suggest that FIX-Triple is not thrombogenic at therapeutic levels and is a potential therapeutic substitute for FIX-WT.