Kit for measuring the thrombin generation in a sample of a patient's blood or plasma

a thrombin generation and kit technology, applied in the field of kits for measuring can solve the problems of no direct monitoring of the drug substance for either treatment regime, no response, and patients with haemophilia a who develop inhibitors, and achieve the same sensitivity in the generation of thrombin, simple and efficient assay, fast and reproducible

Inactive Publication Date: 2005-10-06
BAXTER INT INC +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0010] Surprisingly, it has been found that a lyophilized TF / PL-complex and a lyophilized mixture containing a thrombin-substrate and CaCl2 provide a simple, efficient, fast and reproducible assay system for measuring the thrombin generation in a sample. The kit of the present invention provides at least a lyophilized TF / PL-complex and a lyophilized mixture containing a thrombin-substrate and CaCl2 in easy resolvable lyophilized form, whereby only the addition of a sample to be tested is necessary. The lyophilized TF / PL-complex and said lyophilized mixture containing a thrombin-substrate and CaCl2 of the claimed kit can also be immobilized onto a support, such as the inner surface of a vial or the well of a microtiter-plate, whereby the thrombin generation assay is brought to an assay format known from conventional ELISAs, thus, making it a very convenient type of assay. The kit of the present invention provides at least the same sensitivity in the thrombin generation assay than prior art assays using frozen components. Therefore, the thrombin generation assay performed with the kit of the present invention allows a rapid diagnosis of the overall activity status of the haemostatic system of a patient. Further, it is possible to detect treatment-dependent changes in the thrombin generation kinetics, for example after administration of bypassing therapeutics to a patient, whereby it is possible to optimize the treatment intervals and doses of therapeutics helping to avoid thrombotic complications due to overdosing.

Problems solved by technology

However, Haemophilia A patients who develop inhibitors to factor VIII during replacement therapy consequently fail to respond to the above-mentioned therapy and are treated with preparations containing activated coagulation factors (so-called bypassing agents) to achieve haemostasis independently of factor VIII through bypassing mechanisms.
No direct monitoring of the drug substance is possible for either treatment regime because the activated components of the bypassing agents interact immediately with proteins of the haemostatic system to induce activation of the clotting cascade.
All existing assays measure surrogate markers, which are of limited value for the assessment of the efficacy of the bypassing agent because the specificity and sensitivity depend on the specific assay conditions and because these assays do not give any information on the overall activity status of the haemostatic system.
Currently there is no routine test that quantitatively assesses the thrombin formation capacity of a plasma sample.
There have also been other reports of such assays being used for assessing the efficacy of factor VIII-bypassing agents but, because of their technical complexity, the assays have not disseminated into routine use.
All the known prior art assays have the disadvantage that components can only be partially dosed before using the assay.
Therefore, a lot of preparation steps are necessary to use these assays thereby making the assays uncomfortable and susceptible to mistakes during handling.
Moreover, these assays are time-consuming.

Method used

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  • Kit for measuring the thrombin generation in a sample of a patient's blood or plasma
  • Kit for measuring the thrombin generation in a sample of a patient's blood or plasma
  • Kit for measuring the thrombin generation in a sample of a patient's blood or plasma

Examples

Experimental program
Comparison scheme
Effect test

example 1

Preparation of a Frozen and a Lyophilized TF / PL-Complex

[0048] A tissue factor having phospholipid vesicles (TF / PL-complex) is prepared by using a recombinant full-length TF (American Diagnostica Inc. Greenwich, Conn., U.S.A.) and synthetic PLs (Avanti Polar Lipids, Alabaster, Ala., U.S.A.). The preparation comprises the following steps:

[0049] Phospholipid vesicles composed of 1,2-Dioleyl-sn-glycero-3-phosphocholine (DOPC), 1-Palmitoyl-2-oleyl-sn-glycero-3-phosphoserine (POPS) and 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) (Avanti Polar Lipids, Alabaster, Ala.) are prepared by the extrusion method of Hope et al. (Hope M J, Bally M B, Webb G, Cullis P R: “Production of large unilamellar vesicles by a rapid extrusion procedure. Characterization of size distribution, trapped volume and ability to maintain a membrane potential.” Biochim Biophys Acta 812:55, 1985) using an extrusion device of Lipex Biomembranes, Inc. (Vancouver, Canada) equipped with two stacked polycarbonate ...

example 2

Thrombin Generation Triggered with Frozen or Lyophilized TF / PL-Complex in Various Plasma Samples

[0052] The thrombin generation is triggered by a TF / PL-complex, prepared as described above containing 18 pM TF and 3.2 μM PL, wherein the PL is composed of a ratio of 80% by weight DOPC and 20% by weight POPS. The lyophilized TF / PL-complex is dissolved in water for injection (to a final concentration of 18 pM TF and 3.2 μM PL) and 10 μL of this aqueous solution is added to 50 μL of 1 mM thrombin substrate Z-Gly-Gly-Arg-AMC (Bachem AG, Bubendorf, Switzerland) premixed with 15 mM CaCl2. For comparison 10 μL of a frozen TF / PL-complex (18 pM TF and 3.2 μM PL) is mixed with 50 μL of the above mentioned thrombin-substrate. The addition of 40 μL plasma sample starts the reaction. The components are incubated at 37° C.

[0053] The thrombin-substrate is cleaved by the generated thrombin and a fluorophore-containing moiety is released. The increase of the fluorescence intensity, which is proportio...

example 3

Comparison of the Thrombin Generation Triggering Effect of Frozen and Lyophilized TF / PL-Complexes with Various Compositions

[0057] The TF / PL-complexes are prepared as described in Example 1, but composed of various phospholipids in a concentration of 3.2 μM with 18 pM or 89 pM TF. The TF / PL-complexes are frozen in aliquots or lyophilized without sucrose with the lyophilization cycle described in Example 1.

TABLE 2Composition of TF / PL-complexesPL compositionPL concentrationTF concentration(weight ratio)(μM)(pM)PC:PS80 / 203.218PC:PS60 / 403.218PC:PS95 / 5 3.218PC:PS:PE78 / 17 / 5 3.218PC:PS:PE60 / 20 / 203.218PC:PS80 / 203.289PC:PS60 / 403.289PC:PS95 / 5 3.289PC:PS:PE78 / 17 / 5 3.289PC:PS:PE60 / 20 / 203.289

PC: 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC)

PS: 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphoserine (POPS)

PE: 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE)

[0058] Thrombin generation curves are measured as described above. The most characteristic parameter, the peak thrombin, i.e. the maximum t...

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Abstract

The invention provides a kit for measuring the thrombin generation in a sample of a patient's blood or plasma, or in a sample of clotting factors. The kit contains lyophilized tissue factor/phospholipid-complex and a lyophilized mixture containing a thrombin-substrate and CaCl2. The invention also provides processes for preparing the reagents for the kit. The kit can be used in a method for measuring the thrombin generation in a sample, wherein it is possible to detect changes in thrombin generation kinetics, for example after administration of inhibitor bypassing agents to a patient who has developed inhibitors to an exogenous clotting factor such as Factor VIII.

Description

FIELD OF INVENTION [0001] The present invention relates to a kit for measuring the thrombin generation in a sample of a patient's blood or plasma, or in a sample of clotting factors. The invention also relates to processes for preparing reagents for the kit. BACKGROUND OF THE INVENTION [0002] Haemophilia A is a hereditary blood coagulation (clotting) disorder. It is caused by a deficient activity of the plasma protein factor VIII, which affects the clotting property of blood. The standard treatment for Haemophilia A patients is the infusion of factor VIII concentrates to replace the defective clotting factor. However, Haemophilia A patients who develop inhibitors to factor VIII during replacement therapy consequently fail to respond to the above-mentioned therapy and are treated with preparations containing activated coagulation factors (so-called bypassing agents) to achieve haemostasis independently of factor VIII through bypassing mechanisms. Both activated prothrombin complex co...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C12Q1/56G01N33/86
CPCC12Q1/56A61K31/66G01N2333/745G01N33/86
Inventor VARADI, KATALINTURECEK, PETERKEIL, BRIGITTEPEYRER-HEIMSTAETT, SYLVIASCHWARZ, HANS-PETER
Owner BAXTER INT INC
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