Engineering of a membrane-triggered activity switch in coagulation factor VIIa.

Recombinant factor VIIa (FVIIa) variants with increased activity offer the promise to improve the treatment of bleeding episodes in patients with inhibitor-complicated hemophilia. Here, an approach was adopted to enhance the activity of FVIIa by selectively optimizing substrate turnover at the membrane surface. Under physiological conditions, endogenous FVIIa engages its cell-localized cofactor tissue factor (TF), which stimulates activity through membrane-dependent substrate recognition and allosteric effects.

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.

Prolonged half-life of glycoPEGylated rFVIIa variants compared to native rFVIIa.

Introduction: Bleeding episodes in haemophilia patients with inhibitors are primarily treated with by-passing agents such as recombinant activated FVII (rFVIIa). Prophylactic treatment with rFVIIa has been shown to significantly reduce the number of bleeding episodes as compared to conventional on-demand haemostatic therapy, and a reduced dosing frequency could present an improved treatment option in inhibitor patients.

Materials And Methods: A series of glycoPEGylated rFVIIa derivatives (5-40K PEG) has been produced and their effect and pharmocokinetics have been investigated in several animal species.