Peters RT, Toby G, Lu Q, Liu T, Kulman JD, Low SC, Bitonti AJ, Pierce GF. Biochemical and functional characterization of a recombinant monomeric factor VIII-Fc fusion protein.
J Thromb Haemost 2013;
11:132-41. [PMID:
23205847 PMCID:
PMC3588154 DOI:
10.1111/jth.12076]
[Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Accepted: 11/06/2012] [Indexed: 11/29/2022]
Abstract
BACKGROUND
Hemophilia A results from a deficiency in factor VIII activity. Current treatment regimens require frequent dosing, owing to the short half-life of FVIII. A recombinant FVIII-Fc fusion protein (rFVIIIFc) was molecularly engineered to increase the half-life of FVIII, by 1.5-2-fold, in several preclinical animal models and humans.
OBJECTIVE
To perform a biochemical and functional in vitro characterization of rFVIIIFc, with existing FVIII products as comparators.
METHODS
rFVIIIFc was examined by utilizing a series of structural and analytic assays, including mass spectrometry following lysyl endopeptidase or thrombin digestion. rFVIIIFc activity was determined in both one-stage clotting (activated partial thromboplastin time) and chromogenic activity assays, in the context of the FXase complex with purified components, and in both in vitro and ex vivo rotational thromboelastometry (ROTEM) assays performed in whole blood.
RESULTS
rFVIIIFc contained the predicted primary structure and post-translational modifications, with an FVIII moiety that was similar to other recombinant FVIII products. The von Willebrand factor-binding and specific activity of rFVIIIFc were also found to be similar to those of other recombinant FVIII molecules. Both chromogenic and one-stage assays of rFVIIIFc gave similar results. Ex vivo ROTEM studies demonstrated that circulating rFVIIIFc activity was prolonged in mice with hemophilia A in comparison with B-domain-deleted or full-length FVIII. Clot parameters at early time points were similar to those for FVIII, whereas rFVIIIFc showed prolonged improvement of clot formation.
CONCLUSIONS
rFVIIIFc maintains normal FVIII interactions with other proteins necessary for its activity, with prolonged in vivo activity, owing to fusion with the Fc region of IgG(1) .
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