Drug – bio-affecting and body treating compositions – Enzyme or coenzyme containing – Hydrolases
Reexamination Certificate
2000-03-29
2003-11-18
Lo, Weilun (Department: 3761)
Drug, bio-affecting and body treating compositions
Enzyme or coenzyme containing
Hydrolases
C424S488000, C128SDIG008, C128SDIG008
Reexamination Certificate
active
06649162
ABSTRACT:
The invention is related to a hemostatic sponge based on collagen and thrombin and a method for producing such a sponge as well as a wound coverage containing said sponge and a kit for preparing the wound coverage.
Biological glues based on coagulation factors of human or animal origin have long been known. A method for producing tissue adhesives based on fibrinogen an factor XIII has been described in U.S. Pat. Nos. 4,362,567, 4,298,598 and 4,377,572. The tissue adhesives are usually applied together with a separate component containing thrombin, which is enzymatically acting on fibrinogen to form fibrin, and on factor XIII to form the active factor XII Ia, which cross-links the fibrin to obtain a stable fibrin clot.
When applied to a large hemorrhaging area the tissue adhesives are usually applied on a collagen sheet before covering the wound with the sheet.
In U.S. Pat. No. 4,600,574 a tissue adhesive based on collagen combined with fibrinogen and factor XIII is described. This material is provided in the lyophilized form, ready for use. The fibrinogen and factor XIII are combined with the collagen by impregnating the collageneous flat material with a solution comprising fibrinogen and factor XIII, and lyophilizing said material.
The tissue sealing collagenic surgical dressing according to EP 0 049 469 is similarly prepared by combining collagen and fibrinogen and optionally an antibiotic through lyophilization.
Hemostatic sponges which are composed of natural bovine collagen are commercially available, e.g. Colgen®(IMMUNO AG), as wound coverage for a bleeding site. These products act on the intrinsic and extrinsic hemostatic pathways without forming a glue, which makes them rather slow-acting. However, their solid structure gives them mechanical strength.
When collagen is combined with fibrinogen and thrombin, such as described in EP 0 059 265, the material has to be carefully prepared by avoiding any water content. In the presence of minute amounts of water fibrinogen will be converted to fibrin and the material will no more be suitable for tissue sealing. Therefore, such a material is usually provided in a lyophilized form hematically packed together with a desiccant.
When fibrinogen in a hemostatic-sponge is avoided thrombin or a precursor therefore can be absorbed on a porous structure of biologically absorbable collagen according to WO 90/13320. This material is having a total water content of below 50% w/w. It is prepared by injecting an aqueous solution of thrombin or a precursor therefore together with thrombin stabilizing agents into the solid material at several sites. The thrombin stabilizing agents are preferably amino acids, PEG or polysaccharides. The relatively high water content results from the injection of the thrombin solution into the collagen sponge. Although the sponge can be dried at elevated temperatures, the drying is only moderate because of the risk of denaturation of the thrombin and collagen.
Due to the application of thrombin by injection, the distribution of thrombin in the sponge is highly inhomogenous which reduces the reproducibility and reliability of the wound coverage.
A homogeneous mixture of dispersible or soluble collagen with thrombin is prepared according to U.S. Pat. No. 4,515,637. The solution is then freeze-dried and rendered free of moisture yielding a storage-stable product. Although the dry collageneous sponges have high mechanic strength they turned out to be rather inflexible and thus could break when used by the surgeon. However, the drying to an absolutely moisture-free product was seen as essential for avoiding stability problems with thrombin.
The alternative use of a hemostatic collagen paste composition comprising an aqueous solution of thrombin is described in EP 0 372 966. This paste is packed in a squeeze tube or syringe package. The paste is however difficult to use for stopping bleeding in a large hemorrhaging area. When material of human or animal origin is applied to a patient there is a risk of transmitting pathogenic substances originated from the source material. Thrombin is usually derived from human or animal blood plasma carrying the risk of transmitting blood-born viruses, such as AIDS-virus, hepatitis virus and parvoirus. Therefore, measures are taken to inactivate any virus potentially present in plasma fractions, such as thrombin preparations. EP 0 541 507 describes a method for producing a virus-safe thrombin preparation derived from a human blood plasma fraction.
Collagen is usually treated by beta- or gamma-irradiation besides pretreating the collageneous source material with high concentrations of alkaline. These are common measures for inactivating any virus or prion potentially present in the source material.
A commercially available product, TachoComb®, which is produced by a method according to EP 0 059 265 is treated by gamma-irradiation after packing the prepared sheet. It turned out, that the irradiation treatment destroys the nativity of the fibrinogen. Denatured fibrinogen is hardly clottable. Therefore, this material is less effective than an in situ prepared combination of collagen and a tissue adhesive based on fibrinogen, which components are provided as a kit which is easily treated for virus inactivation separately.
It is the object of the present invention to provide a ready for use compress sponge containing resorbable collagen material, which does not have the above described disadvantages, especially with regard to the flexibility and mechanic stability of the material.
There is provided, according to the invention, a hemostatic sponge based on collagen and an activator or proactivator of blood coagulation homogeneously distributed therein. This sponge is provided in a dry form, which could be air-dried or lyophilized. However, it still contains a water content of at least 2%, preferably in the range of 2 to 25%. It is especially preferred that the water content is in the range between 10 and 20% in order to improve the storage stability at elevated temperatures.
It surprisingly turned out that the definite water content makes the sponge flexible, though maintaining its physico-chemical structure and mechanical strength.
It is also important to have the thrombin or a precursor of thrombin evenly distributed in the material in order to prevent local instability or hypercoagulability of the material. Despite of the water content the thrombin activity is surprisingly stable, probably because of the intimate contact of thrombin and collagen in the homogeneous mixture.
Nevertheless, thrombin stabilizers preferably selected from the group consisting of a polyol, a polysaccharide, a polyalkylene glycol, amino acids or mixtures thereof might be used according to the invention. The exemplary use of sorbitol, glycerol, polyethylene glycol, polypropylene glycol, mono- or disaccharides such as glucose or saccharose or any sugar or sulfonated amino acid capable of stabilizing thrombin activity is preferred.
The sponge is provided as a storage stable solid product, which is useful even after a storage of 6 months, preferable 2 years or even more years at room temperature.
Thrombin or the precursor of thrombin is understood as a protein that has thrombin activity and that induces thrombin activity when it is contacted with blood or after application to the patient, respectively. Its activity is expressed as thrombin activity (NIH-Unit) or thrombin equivalent activity developing the corresponding NIH-Unit. In the following thrombin activity is understood to comprise both, the activity of thrombin or any equivalent activity. A protein with thrombin activity might be selected from the group consisting of alpha-thrombin, meizo-thrombin, a thrombin derivative or a recombinant thrombin. A suitable precursor is possibly selected from the group consisting of: prothrombin, factor Xa optionally together with phospholipids, factor IXa, activated prothrombin complex, FEIBA, any activator or a proactivator of the intrinsic or extrinsic coagulation, or mixtures thereof.
The hemostatic sponge according to t
Biering Wolfgang
Habison Georg
Mansour Hamza
Scheel Edgar
Schlag Guenther
Baxter Aktiengesellschaft
Heller Ehrman White & McAuliffe LLP
Lo Weilun
Truong Linh
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