Functional Characterization of a Recombinant FVIIa Drug Candidate

Abstract 4653

Human coagulation factor VII (FVII) is a vitamin-K-dependent protein with a molecular weight of 50 kDa. Activation of FVII occurs by cleavage of the arginine 152 – isoleucine 153 peptide bond resulting in two disulfide-linked peptide chains. The therapeutic utility of rFVIIa is based on its capacity to trigger hemostasis independently from factor VIII and factor IX and thus even in the presence of factor VIII or factor IX inhibitors.

Baxter has developed a recombinant FVIIa (rFVIIa) that is synthesized by a genetically engineered Chinese hamster ovary (CHO) cell line. No materials of human or animal origin are employed in the manufacture, purification, or formulation of the final product, thus reducing the risk of transmission of adventitious agents. The growth medium is a chemically defined medium, and the downstream process does not use monoclonal antibodies for the purification of rFVIIa.

The rFVIIa drug candidate was functionally characterized in vitro and its features were compared with those of a commercially available rFVIIa. The overall hemostatic potency of rFVIIa was assessed by its FVIII bypassing activity in a human FVIII-deficient plasma with high-titer inhibitor by measuring the kinetics of thrombin generation and fibrin formation. The thrombin-generating capacity of the rFVIIa drug candidate was similar to that of commercial rFVIIa. The time and rate of fibrin formation was measured by thromboelastography, where a dose-dependent normalization of the impaired clotting times and fibrin formation was observed. A similar FXa-generating potency was found for rFVIIa and commercial rFVIIa when measured on the surface of TF-expressing fibroblasts, suggesting a full capability to bind to TF-bearing cells and trigger hemostasis on their surfaces. rFVIIa could be inactivated by anti-thrombin III-heparin in solution with relipidated TF with no relevant difference to the comparator product. TF pathway inhibitor effectively inhibited FXa generation in a cell-based activity assay, with a similar IC50 for rFVIIa and the comparator.

In summary, the functional characteristics of the rFVIIa drug candidate were very similar to those of commercially available rFVIIa.