Characterization of thrombin derived from human recombinant prothrombin.

Area of Science:

• Biochemistry
• Hematology
• Biotechnology

Background:

• Thrombin (FIIa) is central to hemostasis, regulating clot formation and platelet activation.
• Understanding the properties of recombinant human prothrombin (rhFII)-derived thrombin is crucial for its therapeutic application.
• Endogenous thrombin is formed via prothrombin (FII) cleavage during coagulation.

Purpose of the Study:

• To compare the enzymatic and hemostatic properties of thrombin derived from recombinant human prothrombin (rhFIIa) versus plasma-derived human FII (pdhFIIa).
• To assess the functional similarity of rhFIIa and pdhFIIa in various coagulation substrates and settings.
• To evaluate potential differences in substrate activation, enzyme kinetics, and inhibition by antithrombin.

Main Methods:

• Isolation of pure FIIa from rhFII and pdhFII following cleavage by recombinant ecarin.
• Development of analytical methods to compare FIIa activity against multiple substrates.
• Assessment of FIIa-mediated activation of FVIII, FXIII, protein C, platelet aggregation, and coagulation in plasma and whole blood.

Main Results:

• FIIa from rhFII and pdhFII demonstrated highly similar activation of FVIII, FXIII, protein C, platelet aggregation, and plasma/whole blood coagulation.
• Similar turnover rates and Michaelis constants (KM) were observed for the S-2366 substrate.
• rhFIIa showed ~25% greater efficacy in activating Factor V (FV) and significantly more efficient heparin-enhanced inhibition by antithrombin compared to pdhFIIa.

Conclusions:

• Thrombin derived from recombinant human prothrombin (rhFIIa) exhibits largely comparable enzymatic and hemostatic properties to plasma-derived thrombin (pdhFIIa).
• Observed differences in FV activation and antithrombin inhibition suggest distinct kinetic profiles but do not negate functional similarity.
• rhFIIa is expected to possess very similar activity and function to endogenous thrombin when administered to humans, supporting its therapeutic potential.