Enhanced potency of recombinant factor VIIa with increased affinity to activated platelets

Abstract

Background: Recombinant factor VIIa (rFVIIa) enhances thrombin generation in a platelet-dependent manner; however, rFVIIa binds activated platelets with relatively low affinity. Triggering receptor expressed on myeloid cells (TREM)-like transcript (TLT)-1 is expressed exclusively on activated platelets.Objective: To enhance the potency of rFVIIa via binding TLT-1.Methods: Recombinant FVIIa was conjugated to a TLT-1 binding Fab. In vitro potency of this platelet-targeted rFVIIa (PT-rFVIIa) was evaluated using factor X activation assays and by measuring viscoelastic changes in whole blood. In vivo potency was evaluated using a tail vein transection model in F8 −/− mice expressing human TLT-1.Results: PT-rFVIIa and rFVIIa had similar dissociation constant values for tissue factor binding and similar tissue factor-dependent factor X activation. However, PT-rFVIIa had increased catalytic efficiency on TLT-1-loaded vesicles and activated platelets.The in vitro potency in normal human blood with antibody-induced hemophilia A was dependent on assay conditions used; with maximally activated platelets, the half maximal effective concentration for clot time for PT-rFVIIa was 49-fold lower compared with rFVIIa. In the murine bleeding model, a 53-fold lower half maximal effective concentration was observed for blood loss for PT-rFVIIa, supporting the relevance of the assay conditions with maximally activated platelets. In vitro analysis of blood from subjects with hemophilia A confirmed the data obtained with normal blood. Conclusions:Increasing the affinity of rFVIIa to activated platelets resulted in approximately 50-fold increased potency both in vitro and in the mouse model. The correlation of in vivo with in vitro data using maximally activated platelets supports that these assay conditions are relevant when evaluating platelet-targeted hemostatic concepts.

Acquired Hemophilia Successfully Treated with Recombinant Factor Ⅶa: A Case Report

“…Recombinant factor VIIa (rFVIIa) is a medication used to treat bleeding episodes in people with hemophilia who also have inhibitory antibodies to factor VIII (FVIII) or IX (11). At concentrations of 20 nmol/L or greater, rFVIIa improves the production of thrombin on activated platelets (11).…”

“…Recombinant factor VIIa (rFVIIa) is a medication used to treat bleeding episodes in people with hemophilia who also have inhibitory antibodies to factor VIII (FVIII) or IX (11). At concentrations of 20 nmol/L or greater, rFVIIa improves the production of thrombin on activated platelets (11). The binding of rFVIIa to activated platelets relies on the Gla-domain of rFVIIa and involves negatively charged phospholipids on the activated platelets along with proteins such as GPIb/IX/V and/or endothelial protein C receptor (11).…”

“…At concentrations of 20 nmol/L or greater, rFVIIa improves the production of thrombin on activated platelets (11). The binding of rFVIIa to activated platelets relies on the Gla-domain of rFVIIa and involves negatively charged phospholipids on the activated platelets along with proteins such as GPIb/IX/V and/or endothelial protein C receptor (11). rFVIIa is a bypassing agent and is categorized as the rst-line therapy of bleeding in AHA.…”

A clinical case of the successful use of recombinant activated VII coagulation factor in a newborn with sepsis

“…В клинической практике rFVIIa зарегистрирован и используется для лечения кровотечений у больных с ингибиторной формой гемофилии А и В [7][8][9]. В настоящее время препарат нашел широкое применение у пациентов хирургического, акушерскогинекологического профиля, так как он продемонстрировал эффективность в лечении массивных кровотечений и жизнеугрожающих состояний [10,11].…”