Modified factor VIII

Details Modified factor VIII Modified factor VIII

2001-09-19

2004-08-03

Wax, Robert A. (Department: 1653)

Chemistry: natural resins or derivatives; peptides or proteins;

Proteins, i.e., more than 100 amino acid residues

Blood proteins or globulins, e.g., proteoglycans, platelet...

C435S069100, C435S069600, C435S013000, C435S007100, C435S183000, C514S002600, C514S012200, C514S802000, C514S834000, C530S380000, C530S381000, C930S010000, C930S100000

Reexamination Certificate

active

06770744

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to a modified mammalian factor VIII having amino acid substitutions which reduce its immunogenicity and/or antigenicity as compared to the proteins from which they were derived or other factor VIII preparations such as human factor VIII.
BACKGROUND OF THE INVENTION
Blood clotting begins when platelets adhere to the cut wall of an injured blood vessel at a lesion site. Subsequently, in a cascade of enzymatically regulated reactions, soluble fibrinogen molecules are converted by the enzyme thrombin to insoluble strands of fibrin that hold the platelets together in a thrombus. At each step in the cascade, a protein precursor is converted to a protease that cleaves the next protein precursor in the series. Co-factors are required at most of the steps.
Factor VIII circulates as an inactive precursor in blood, bound tightly and non-covalently to von Willebrand factor. Factor VIII is proteolytically activated by thrombin or factor Xa, which dissociates it from von Willebrand factor and activates its procoagulant function in the cascade. In its active form, the protein factor VIIIa is a cofactor that increases the catalytic efficiency of factor IXa toward factor X activation by several orders of magnitude.
People with deficiencies in factor VIII or antibodies against factor VIII who are not treated with factor VIII suffer uncontrolled internal bleeding that may cause a range of serious symptoms, from inflammatory reactions in joints to early death. Severe hemophiliacs, who number about 10,000 in the United States, can be treated with infusion of human factor VIII, which will restore the blood's normal clotting ability if administered with sufficient frequency and concentration. The classical definition of factor VIII is that substance present in normal blood plasma that corrects the clotting defect in plasma derived from individuals with hemophilia A.
The development of antibodies (“inhibitors” or “inhibitory antibodies”) that inhibit the activity of factor VIII is a serious complication in the management of patients with hemophilia. Autoantibodies develop in approximately 20% of patients with hemophilia A in response to therapeutic infusions of factor VIII. In previously untreated patients with hemophilia A who develop inhibitors, the inhibitors usually develops within one year of treatment. Additionally, autoantibodies that inactivate factor VIII occasionally develop in individuals with previously normal factor VIII levels. Inhibitory antibodies (inhibitors) to factor VIII (fVIII) either develop as alloantibodies in hemophilia A patients following fVIII infusions or as autoantibodies in nonhemophiliacs (Hoyer, L. W. and D. Scandella, 1994, “Factor VIII inhibitors: structure and function in autoantibody and hemophilia A patients,”
Semin.Hematol.
31:1-5). Antibodies to epitopes in the A2, ap-A3, and C2 domains within the A1-A2-B-ap-A3-C1-C2 fVIII molecule are responsible for all anticoagulant activity in most inhibitor plasmas (Prescott, R. et al., 1997, “The inhibitory antibody response is more complex in hemophilia A patients than in most nonhemophiliacs with fVIII autoantibodies,”
Blood
89:3663-3671; Barrow, R. T. et al., 2000, “Reduction of the antigenicity of factor VIII toward complex inhibitory plasmas using multiply-substituted hybrid human/porcine factor VIII molecules,”
Blood
95:557-561). The 18-kDa C2 domain, defined as residues Ser2173-Tyr2332 in single chain human fVIII, contains a phospholipid membrane-binding site that is necessary for the normal procoagulant function of fVIII. Human C2-specific anti-fVIII antibodies inhibit this interaction (Arai, M. et al., 1989, “Molecular basis offactor-VIII inhibition by human antibodies—antibodies that bind to the factor-VIII light chain prevent the interaction of factor-VIII with phospholipid,”
J. Clin. Invest.
83:1978-1984). Consistent with this, phospholipid protects fVIII from inactivation by fVIII inhibitors (Arai et al., supra; Barrowcliffe, T. W. et al., 1983, “Binding to phospholipid protects factor VIII from inactivation by human antibodies,”
J. Lab. Clin. Med.
101:34-43). The C2 domain also contains part of the von Willebrand factor (vWf) binding site (Saenko, E. L. et al., 1994, “A role for the C2 domain of factor binding to von Willebrand factor.
J. Biol. Chem.
269:11601-11605; Saenko, E. L. and Scandella, D., 1997, “The acidic region of the factor VIII light chain and the C2 domain together form the high affinity binding site for von Willebrand factor,”
J. Biol. Chem.
272:18007-18014). Some inhibitors may act by interfering with this interaction (Shima, M. et al., 1995, “Common inhibitory effects of human anti-C2 domain inhibitor alloantibodies on factor VIII binding to von Willebrand factor,”
Br. J. Haematol.
91:714-721; Saenko, E. L. et al., 1996, “Slowed release of thrombin-cleaved factor VIII from von Willebrand factor by a monoclonal and human antibody is a novel mechanism for factor VIII inhibition,”
J. Biol. Chem.
271:27424-27431; Gilles, J G. et al., 1999, “Some factor VIII (FVIII) inhibitors recognize a FVIII epitope(s) that is present only on FVIII-vWf complexes,”
Thromb. Haemost.
82:40-45).
Patients can be managed by increasing the dose of factor VIII provided the inhibitor titer is low enough. However, often the inhibitor titer is so high that it cannot be overwhelmed by factor VIII. An alternative strategy is to bypass the need for factor VIII during normal hemostasis using factor IX complex preparations (for example, KONYNE®, Proplex®) or recombinant human factor VIIIa. Additionally, since porcine factor VIII usually has substantially less reactivity with inhibitors than human factor VIII, a partially purified porcine factor VIII preparation (HYATE:C®) is used. Many patients who have developed inhibitory antibodies to human factor VIII have been successfully treated with porcine factor VIII and have tolerated such treatment for long periods of time. However, administration of porcine factor VIII is not a complete solution because inhibitors may develop to porcine factor VIII after one or more infusions.
Several preparations of human plasma-derived factor VIII of varying degrees of purity are available commercially for the treatment of hemophilia A. These include a partially-purified factor VIII derived from the pooled blood of many donors that is heat- and detergent-treated for viruses but contain a significant level of antigenic proteins; a monoclonal antibody-purified factor VIII that has lower levels of antigenic impurities and viral contamination; and recombinant human factor VIII, clinical trials for which are underway. Unfortunately, human factor VIII is unstable at physiologic concentrations and pH, is present in blood at an extremely low concentration (0.2 &mgr;g/ml plasma), and has low specific clotting activity.
Hemophiliacs require daily replacement offactor VIII to prevent bleeding and the resulting deforming hemophilic arthropathy. However, supplies have been inadequate and problems in therapeutic use occur due to difficulty in isolation and purification, immunogenicity, and the necessity of removing the AIDS and hepatitis infectivity risk. The use of recombinant human factor VIII or partially-purified porcine factor VIII will not resolve all the problems.
The problems associated with the commonly used, commercially available, plasma-derived factor VIII have stimulated significant interest in the development of a better factor VIII product. There is a need for a more potent factor VIII molecule so that more units of clotting activity can be delivered per molecule; a factor VIII molecule that is stable at a selected pH and physiologic concentration; a factor VIII molecule that is less apt to cause production of inhibitory antibodies; and a factor VIII molecule that evades immune detection in patients who have already acquired antibodies to human factor VIII.
U.S. Pat. No. 6,180,371 to Lollar describes amino acid substitutions in the A2 domain of human factor VIII which alter the antigenicity of the resulting fac

Affiliated with

Also associated with

Rating

Modified factor VIII does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Modified factor VIII, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Modified factor VIII will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3357250