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Coagulation & its Disorders
A mutated factor X activatable by thrombin corrects bleedings in vivo in a rabbit model of antibody-induced hemophilia A
Ferrata Storti Foundation
Haematologica 2020 Volume 105(9):2335-2343
Toufik Abache,1 Alexandre Fontayne,1 Dominique Grenier,1 Emilie Jacque,1 Alain Longue,1 Anne-Sophie Dezetter,1 Béatrice Souilliart,2 Guillaume Chevreux,2 Damien Bataille,2 Sami Chtourou1 and Jean-Luc Plantier1
1LFB Biotechnologies, Direction de l’Innovation Thérapeutique, Loos and 2LFB Biotechnologies, Direction Générale du Développement, Les Ulis, France
ABSTRACT
Rendering coagulation factor X sensitive to thrombin was proposed as a strategy to bypass the need for factor VIII. In this study, this non- replacement strategy was evaluated in vitro and in vivo for its ability to correct factor VIII but also factor IX, X and XI deficiencies. A novel modified factor X, named actiten, was generated and produced in the HEK293F cell line. The molecule possesses the required post-translational modifications, partially maintaining its ability to be activated by RVV-X, factor VIIa/tissue factor, and factor VIIIa/factor IXa and acquires the ability to be activated by thrombin. The potency of the molecule was evaluated in plasma samples with deficiencies of the respective factors and in plasma samples from patients with hemophilia A, some of which contained inhibitors. Actiten dose-dependently corrected all the deficient plasmas that were assayed. It was able to normalize the thrombin generation at 20 μg/mL although the lag time was increased. It was then assayed in a rabbit antibody-induced model of hemophilia A in which, in contrast to recombinant wild-type factor X, it normalized the bleeding time and the loss of hemoglobin. No sign of throm- bogenicity was observed and the generation of activated factor X was con- trolled by the anticoagulation pathway in all the coagulation assays per- formed. These data indicate that actiten may be considered as a possible non-replacement factor to treat hemophilia, with the advantage of being a zymogen that corrects bleeding only when needed.
Introduction
Hemophilia results from a default of coagulation factor IX or VIII (FIX or FVIII). It is treated by prophylactic or on-demand infusions of the missing or deficient fac- tor.1 While offering a satisfying protection against bleeding, repeated infusions, required to maintain an active threshold of factor, are uncomfortable for patients being deleterious to the venous access, and bringing risks of infection and of devel- oping inhibitors against the substitutive factor.2 These drawbacks justify a contin- uous search for improvement of hemophilia treatments, in particular prolonging the product’s circulating half-life.3,4 This property is sought in order to maintain a higher threshold of coagulation, aiming to increase the treatment efficiency and compliance.5
With regards to hemophilia B, the fusion of FIX to an IgG1 Fc fragment or to albumin allowed a significant increase in FIX half-life, a less frequent administra- tion schedule and a higher product threshold.5-7 In contrast, there was a limited improvement for hemophilia A using therapeutics based on the FVIII backbone. Persistence in the circulation of these therapeutic compounds is driven by the half- life of the FVIII chaperone, von Willebrand factor (VWF), which is only 1.5-fold greater than that of FVIII. Thus, modifications to FVIII only moderately improve a patient’s exposure to the therapeutic protein.8
In recent years, a novel class of agents to treat hemophilia has emerged. These agents are based on non-replacement factors (NRF), i.e. they are independent of FVIII or FIX molecules. Some NRF diminish the level of anticoagulation, reinforcing
Correspondence:
JEAN-LUC PLANTIER
plantierj@lfb.fr
Received: February 18, 2019. Accepted: November 5, 2019. Pre-published: November 7, 2019.
doi:10.3324/haematol.2019.219865 ©2020 Ferrata Storti Foundation
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