A factor VIIIa-mimetic bispecific antibody, Mim8, ameliorates bleeding upon severe vascular challenge in hemophilia A mice.

Hemophilia A is a bleeding disorder resulting from deficient factor VIII (FVIII), which normally functions as a cofactor to activated factor IX (FIXa) that facilitates activation of factor X (FX). To mimic this property in a bispecific antibody format, a screening was conducted to identify functional pairs of anti-FIXa and anti-FX antibodies, followed by optimization of functional and biophysical properties. The resulting bispecific antibody (Mim8) assembled efficiently with FIXa and FX on membranes, and supported activation with an apparent equilibrium dissociation constant of 16 nM.

Thrombin generation potential in the presence of concizumab and rFVIIa, APCC, rFVIII, or rFIX: In vitro and ex vivo analyses.

Background: The anti-tissue factor plasma inhibitor monoclonal antibody concizumab is under clinical investigation for subcutaneous prophylaxis of hemophilia A/B (HA/HB) with or without inhibitors. Breakthrough bleeds while on concizumab prophylaxis may be treated with bypassing agents (recombinant activated factor VIIa [rFVIIa] and activated prothrombin complex concentrate [APCC]), or with factor VIII (FVIII) or factor IX (FIX).

Objectives: To evaluate the effect of combining concizumab with rFVIIa, APCC, rFVIII, and rFIX on thrombin generation (TG) potential.

Measurement of plasma and platelet tissue factor pathway inhibitor, factor V and Protein S in people with haemophilia.

Introduction: Tissue factor pathway inhibitor (TFPI) is a naturally occurring anticoagulant found in plasma, where it circulates bound to lipoproteins, factor V (FV) or Protein S (PS), and in platelets. Therapeutic agents targeting TFPI are under development for the treatment of haemophilia A and haemophilia B.

Aim: To begin to understand how TFPI, FV and PS interact to modulate haemophilia bleeding.

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

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.

Administration of recombinant FVIIa (rFVIIa) to concizumab-dosed monkeys is safe, and concizumab does not affect the potency of rFVIIa in hemophilic rabbits.

Essentials Hemophilia patients on concizumab prophylaxis may need rFVIIa to treat breakthrough bleeds. Effect and safety of concizumab + rFVIIa were tested in vitro and in vivo. Concizumab + rFVIIa had no additive effects on bleeding in hemophilic rabbits.

Correlates of plasma and platelet tissue factor pathway inhibitor, factor V, and Protein S.

Background: Plasma Tissue Factor Pathway Inhibitor (TFPI) circulates bound to factor V (fV) and Protein S (PS). Estrogen therapy decreases plasma TFPI and PS. TFPI, fV, and PS circulate within platelets, and are released upon activation to modulate thrombus formation.

TFPIα interacts with FVa and FXa to inhibit prothrombinase during the initiation of coagulation.

Tissue factor pathway inhibitor α (TFPIα) inhibits prothrombinase, the thrombin-generating complex of factor Xa (FXa) and factor Va (FVa), during the initiation of coagulation. This inhibition requires binding of a conserved basic region within TFPIα to a conserved acidic region in FXa-activated and platelet-released FVa. In this study, the contribution of interactions between TFPIα and the FXa active site and FVa heavy chain to prothrombinase inhibition were examined to further define the inhibitory biochemistry.

Inhibitory effects of LDL-associated tissue factor pathway inhibitor.

Introduction: Tissue factor pathway inhibitor (TFPI) is present in plasma as full-length free TFPI (TFPIα) and as C-terminally degraded forms mainly associated with low-density lipoprotein particles (LDL-TFPI). Addition of TFPIα to plasma induces a prolongation of the clotting time when tested in a diluted prothrombin time (dPT) assay, whereas no prolongation is observed with LDL-TFPI or truncated recombinant TFPI (TFPI 1-161). The aim was to further characterize kinetic properties of purified LDL-TFPI in thrombin generation and chromogenic activity assays.

Pharmacokinetics of an anti-TFPI monoclonal antibody (concizumab) blocking the TFPI interaction with the active site of FXa in Cynomolgus monkeys after iv and sc administration.

Introduction: Concizumab (mAb 2021) is a monoclonal IgG4 antibody (mAb) that binds to the Kunitz-type protease inhibitor (KPI) 2 domain of TFPI thereby blocking the interaction of this domain with the active site of FXa. The objective of the present study was to characterize the pharmacokinetics of concizumab in Cynomolgus monkeys after intravenous (iv) and subcutaneous (sc) administration.

Methods: Data from two studies were included in the modelling, all in all data from 52 monkeys distributed into 9 groups.

Target-mediated clearance and bio-distribution of a monoclonal antibody against the Kunitz-type protease inhibitor 2 domain of Tissue Factor Pathway Inhibitor.

Introduction: A humanised monoclonal antibody, concizumab, that binds with high affinity to the Kunitz-type protease inhibitor (KPI) 2 domain of human tissue factor pathway inhibitor (TFPI) is in clinical development. It promotes coagulation by neutralising the inhibitory function of TFPI and may provide a subcutaneous prophylaxis option for patients with haemophilia. We aimed to study biodistribution and pharmacokinetics (PK) of concizumab.

A novel B-domain O-glycoPEGylated FVIII (N8-GP) demonstrates full efficacy and prolonged effect in hemophilic mice models.

Frequent infusions of intravenous factor VIII (FVIII) are required to prevent bleeding associated with hemophilia A. To reduce the treatment burden, recombinant FVIII with a longer half-life was developed without changing the protein structure. FVIII-polyethylene glycol (PEG) conjugates were prepared using an enzymatic process coupling PEG (ranging from 10 to 80 kDa) selectively to a unique O-linked glycan in the FVIII B-domain.

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

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).

Rat liver sinusoidal endothelial cells (LSECs) express functional low density lipoprotein receptor-related protein-1 (LRP-1).

Background & Aims: The low density lipoprotein receptor-related protein-1 (LRP-1) is a large, multifunctional endocytic receptor from the LDL receptor family, highly expressed in liver parenchymal cells (PCs), neurons, activated astrocytes, and fibroblasts. The aim of the study was to investigate if liver sinusoidal endothelial cells (LSECs), highly specialized scavenger cells, express LRP-1.

Methods: To address this question, experiments were performed in vivo and in vitro to determine if receptor associated protein (RAP) and trypsin-activated α(2)-macroglobulin (α(2)M∗) were endocytosed in LSECs.

Regulation of thrombin generation by TFPI in plasma without and with heparin.

The purpose of this study was to investigate the impact of recombinant glycosylated TFPI (rg-TFPI) from BHK cells, nonglycosylated TFPI (r-TFPI) from Escherichia coli, and truncated TFPI (1-161) on thrombin generation (TG) in plasma treated with and without heparin in vitro and ex vivo. Fasting plasma samples were collected from 6 healthy persons. TG was assessed by the calibrated automated thrombography (CAT) method.