Hemostatic effect of a monoclonal antibody mAb 2021 blocking the interaction between FXa and TFPI in a rabbit hemophilia model

Abstract

<jats:title>Abstract</jats:title><jats:p>Hemophilia is treated by IV replacement therapy with Factor VIII (FVIII) or Factor IX (FIX), either on demand to resolve bleeding, or as prophylaxis. Improved treatment may be provided by drugs designed for subcutaneous and less frequent administration with a reduced risk of inhibitor formation. Tissue factor pathway inhibitor (TFPI) down-regulates the initiation of coagulation by inhibition of Factor VIIa (FVIIa)/tissue factor/Factor Xa (FVIIa/TF/FXa). Blockage of TFPI inhibition may facilitate thrombin generation in a hemophilic setting. A high-affinity (KD = 25pM) mAb, mAb 2021, against TFPI was investigated. Binding of mAb 2021 to TFPI effectively prevented inhibition of FVIIa/TF/FXa and improved clot formation in hemophilia blood and plasma. The binding epitope on the Kunitz-type protease inhibitor domain 2 of TFPI was mapped by crystallography, and showed an extensive overlap with the FXa contact region highlighting a structural basis for its mechanism of action. In a rabbit hemophilia model, an intravenous or subcutaneous dose significantly reduced cuticle bleeding. mAb 2021 showed an effect comparable with that of rFVIIa. Cuticle bleeding in the model was reduced for at least 7 days by a single intravenous dose of mAb 2021. This study suggests that neutralization of TFPI by mAb 2021 may constitute a novel treatment option in hemophilia.</jats:p>

Concizumab, an anti‐tissue factor pathway inhibitor antibody, induces increased thrombin generation in plasma from haemophilia patients and healthy subjects measured by the thrombin generation assay

“…In preclinical studies, concizumab concentrationdependently shortened clot time under haemophilialike conditions in plasma and whole blood [7]. Furthermore, in a rabbit haemophilia model, concizumab administered intravenously (i.v.)…”

“…Furthermore, in a rabbit haemophilia model, concizumab administered intravenously (i.v.) or s.c. reduced cuticle bleeding with similar efficacy to recombinant FVIIa [7]. In the first-in-human phase I trial (explorer TM 1), i.v.…”

“…Although the functional TFPI assay used in explorer TM 1 provides valuable information about the pharmacodynamic profile of concizumab, it is specific for the ability of TFPI to inhibit FXa [7] and may not capture the entire physiological function of TFPI. The thrombin generation assay (TGA) is a global haemostatic assay that provides a more complete picture of the coagulation process [8,9].…”

Catalytically inactive Gla-domainless factor Xa binds to TFPI and restores ex vivo coagulation in hemophilia plasma

“…2,3 Indeed, when the intrinsic tenase pathway leading to factor Xa (FXa) activation is blocked due to FVIII or FIX deficiency, a small amount of FXa can be generated by the extrinsic tenase (FVIIa/tissue factor), but it is immediately neutralized by binding of TFPI through its Kunitz 2 (K2) domain while the Kunitz 1 (K1) domain of TFPI subsequently binds to FVIIa, inhibiting the tenase. 4,5 Our team has postulated an original anti-TFPI strategy, Gla-domainless factor Xa (GD-FXa), deprived of its membrane binding domain, and we have validated the proof of concept of this approach.…”

Correcting the hemophilic imbalance

“…Recent reports have suggested the value of reducing the functions of anticoagulant pathways to correct the deficiency in procoagulant pathways that causes hemophilia. Experimental studies of administration of monoclonal antibodies to TFPI 5,6 have demonstrated improved hemostasis in animal models of hemophilia.…”