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

Area of Science:

• Biochemistry
• Hematology
• Protein Engineering

Background:

• Hemophilia treatment relies on factor replacement therapies.
• Inhibitor development complicates hemophilia management, necessitating alternative strategies.
• Recombinant factor VIIa (FVIIa) shows promise but requires optimization for enhanced efficacy.

Purpose of the Study:

• To engineer a recombinant factor VIIa (FVIIa) variant with significantly increased procoagulant activity.
• To enhance FVIIa activity by optimizing substrate turnover on cell membrane surfaces.
• To develop a novel therapeutic agent for bleeding episodes in hemophilia patients with inhibitors.

Main Methods:

• Engineered a covalent complex between FVIIa and soluble tissue factor (sTF) using specific cystine bridges (FVIIa Q64C-sTF G109C).
• Introduced a FVIIa-M306D mutation to decouple sTF-mediated allosteric stimulation.
• Coexpressed and purified the engineered FVIIa-sTF complex.
• Assessed complex activity in vitro and in a mouse model of hemophilia A.

Main Results:

• The engineered FVIIa-sTF complex exhibited FVIIa-like activity in solution.
• The complex demonstrated a two to three orders-of-magnitude increase in activity on procoagulant membranes compared to native FVIIa.
• In a hemophilia A mouse model, the complex normalized hemostasis at a significantly lower dose (0.3 nmol/kg) than FVIIa (300 nmol/kg).

Conclusions:

• Engineered covalent FVIIa-sTF complexes represent a promising strategy for enhancing hemostasis.
• This approach significantly boosts FVIIa activity on procoagulant surfaces, offering a potent therapeutic for bleeding disorders.
• The developed complex shows potential for improved treatment of hemophilia, particularly in inhibitor patients.