The First Human Cell Line Recombinant Factor VIII (Human-cl rhFVIII) - Functional Properties and Differences From Currently Available Recombinant Factor VIII Products.

Abstract 1298

Poster Board I-320

All current recombinant factor VIII products produced today are derived from the expression of FVIII in hamster cell lines. This is a report of the functional properties of a newly developed recombinant factor VIII concentrate produced in a human cell line. The possible advantage of using a human cell line for expression of recombinant factor VIII is that a human pattern of post-translational modifications (PTM), such as glycosylation, are obtained. These human like PTMs, may possibly lead to improved function and a reduced immunogenic product profile compared to recombinant factor VIII products from CHO or BHK cells that have hamster-specific PTM. Data are presented on the characteristics of the Human-cl rhFVIII, a B-domain-deleted factor VIII protein produced in HEK293F cells, and how they compare with those of other factor VIII products.

Human-cl rhFVIII is highly pure (>99.9% purity) with a high specific activity of 8000-11000 IU/mg protein, and a FVIII:C to FVIII:Ag ratio close to 1.0. This indicates that the entire factor VIII protein in the product is active. Human-cl rhFVIII showed no significant assay discrepancy between one-stage and chromogenic assay results. Because of the human glycosylation profile of the new Human-cl rhFVIII, there was an absence of the antigenic type of sialic acid, N-glycolylneuraminic acid as well as of antigenic Galα (1,3) Gal epitopes found in the non humane derived products. Another type of PTM of factor VIII is the sulfation of certain tyrosines that are crucial for the biological function e.g. the interaction with von Willebrand factor (vWF). Human-cl rhFVIII was found to be optimally sulfated when compared to endogenous human FVIII. In this context, it is of interest to note that Human cl-rhFVIII showed a 60% higher affinity in binding to vWF compared to other recombinant factor VIII products and the number of molecules in the product able to bind to vWF was significantly higher for Human-cl rhFVIII.

Interaction with thrombin and capacity to generate thrombin were shown to be similar to those of plasma-derived factor VIII. The sensitivity to be inactivated by activated protein C was similar to all currently licensed rhFVIII products. The important properties of Human cell line derived recombinant factor VIII may be very promising for its use in future treatment of Haemophilia A.