A THROMBIN PREPARATION

Abstract: A thrombin preparation which has enhanced stability is disclosed. In addition to the thrombin, the preparation comprises a buffer in an amount sufficient to stabilise the thrombin and to buffer the preparation at a pH in the range of from 5.0 to 8.0. The preparation may also include saline and a polyol/polyalkylene polyol. A method for making the preparation is also disclosed.

Description: A THROMBIN PREPARATION Thrombin, a proteolytic enzyme, is essential for hemostasis. It is a principal reagent in the formation of blood clots via fibrin production. Due to its effectiveness as a clotting aid, thrombin and its preparations are useful during surgical procedures to control bleeding. While dry thrombin is available, liquid preparations are generally preferred due to handling and time considerations. From GB-A-2081090 there is known an aqueous thrombin preparation containing sodium chloride and 10-50% by weight of a straight chain 3 to 5 carbon fully hydroxylated polyol. The preparation may also contain an amino acid, preferably lysine, and/or polyethylene glycol. Until now, no highly stable liquid thrombin preparation which is both storage stable and ready for use during surgery has been available. This is because thrombin, when dissolved in water or saline, rapidly loses its activity due to denaturation and autolysis of the thrombin protein. It has been discovered that sterile, storage-stable thrombin preparations can be prepared by adding to thrombin, in a suitable medium, a stabilizing quantity of a buffer. Optionally, saline and one or more polyol stabilizers can also be employed. In a preferred embodiment, a solution containing 1000 U/ml (units per millilitre) Parke-Davis thrombin in 0.9% NaCl solution containing 25% (w/v) glycerol and 0.05 M sodium acetate buffer, pH 5.0, was prepared. This solution, after storage at room temperature for 39 days, had a clotting time of 14 seconds when measured on a fibrometer, which represents a retention of 70% of its original activity. A freshly prepared solution of the same composition had a clotting time of 10 seconds. The "unit" is a standard amount recognised in the art and relates to the quantity of blood which is clotted by the preparation. The thrombin preparations and methods of the invention have several advantages over conventional preparations and methods for assisting in blood clotting. Unlike powdered preparations, the use of the preparation of the instant invention requires no reconstitution before use. Thus, measuring, mixing, sterilizing, etc. of one or more components or containers are not necessary. The preparations of the present invention can be used with only minimal sterilization. Furthermore, the stability of the thrombin containing preparations is so high that the need for stock inventories and/or rotation of products is largely eliminated. Unlike most saline- or water-solutions of thrombin, which are stable for less than 1 week at 4°C, the instant preparations are designed to be stable at normal refrigeration temperatures (i.e., about 4°C) for 6 months or more. It is known that high concentrations of glycerol, sucrose, and other polyols can stabilize proteins in solution. In the case of thrombin, it is known that a glycerol concentration of 67% can greatly stabilize a 1000 u/ml thrombin solution. However, the use of high glycerol concentrations is not practical in the large scale manufacture of a sterile thrombin solution because of the high viscosity of such a preparation. According to a first aspect of the present invention, there is provided a stable thrombin preparation comprising thrombin and a buffer, in which the buffer is present in an amount sufficient to stabilise the thrombin and to maintain the preparation at a pH in the range of from 5.0 to 8.0. According to a second aspect of the present invention there is provided, a stable thrombin preparation in which the thrombin is stabilized by the presence of a quantity of buffer sufficient to stabilize the thrombin and maintain the preparation at a pH in the range of from 5.0 to 8.0. According to a third aspect of the present invention there is provided a haemostat for use as a wound dressing, the hemostat comprising a preparation in accordance with the first or second aspect of the present invention and a substrate. According to a fourth aspect of the present invention, there is provided a method of manufacturing a stabile thrombin preparation which method comprises, combining thrombin with a quantity of a buffer sufficient to stabilise the thrombin and to maintain the preparation at a pH in the range of from 5.0 to 8.0. The preparations made in accordance with the present invention must contain, in a liquid medium, thrombin and one or more buffers. They may contain saline, polyols and other substances conventionally employed in thrombin preparations. While the term "preparations" is employed, it should be noted that all types of formulations in which thrombin is substantially solubilized, or in a highly dispersed form, and is present in combination with one or more buffers are contemplated. In general liquid preparations are preferred, and solutions in which the thrombin is solubilized are highly preferred. When a liquid formulation is made, it is generally preferred that the or each solvent or other diluent employed be sufficiently miscible with thrombin such that production standards, e.g., uniformity of thrombin concentration from batch to batch, can be readily met. The thrombin employed is commercially available. A preferred thrombin is THROMBOSTAT R powder, marketed by PARKE-DAVIS. It contains, in addition to thrombin, 30% (w/w) glycine, 5.3% CaCl₂2H₂O and 5.5% NaCl. THROMBOSTAT R is supplied in vials containing 5000 units, 10000 units and 20000 units. Thrombin is known to be soluble in physiological saline - i.e., a solution containing 0.9% NaCl in water. However, saline solutions with higher concentrations are contemplated as useful herein. Furthermore, the replacement of all or part of the NaCl in such solutions with one or more other suitable salts is contemplated. Water is a preferred medium for the preparations of the invention. However, the use of one or more other diluents which do not adversely affect the solubility and/or stability of thrombin in the subject preparations can be employed. One such diluent is glycerol. Glycerol and other polyols, such as polyaklylene glycols and preferably polyethylene glycols, are typical ingredients in many commercial thrombin-based products. Other useful polyols include mannitol, sorbitol, sucrose, glucose, and the like. Mixtures are operable. The buffer employed in the preparations of the present invention is prepared in the final aqueous formulation, and before the formulation is mixed with the thrombin. For instance, in order to prepare a formulation buffered at pH 5.3 with acetate and containing 25% glycerol in 0.9% NaCl, the glycerol-containing saline is first prepared, and the required amount of acetic acid is added. The pH is then adjusted to 5.3 with a strong sodium hydroxide solution. Alternatively, the buffer can be prepared by adding sodium acetate and adjusting the pH with a strong acid, or, thirdly, the buffer can be prepared by adding acetic acid and sodium acetate in a mole ratio calculated to produce the desired pH. Suitable buffer systems are those whose aqueous solutions will maintain the pH of the final thrombin solution between 5.0 and 8.0, with a preferred pH range of 5.0 to 6.0 and a highly preferred range of 5.3 to 5.7. Useful buffer systems include acetate, succinate, bicarbonate, imidazole, TRIS, and zwitterionic buffers described by N.E. Good and S. Izawa, in Methods in Enzymol , 24 , Part B, 53 (1972): and W.F. Ferguson, K.I. Braunschweiger, W.R. Braunschweiger, J.R. Smith, J. McCormick, C.C. Wasmann, N.P. Jarvis, D.H. Bell and N.E. Good in Anal. Biochem , 104 , 300 (1980). Suitable reagents for use in the buffer systems include MES, ACES, BES, MOPS, TES, HEPES and the like. Phosphate can only be used when calcium ion is absent or in the presence of EDTA. Mixtures of such reagents can be employed. Useful buffer systems also include acetic acid-sodium acetate, acetic acid-potassium acetate, bicarbonate, succinate, imidazole, and TRIS salts. Sodium acetate/acetic acid is a preferred reagent. Mixtures are operable. The buffers will be present in the buffer solution, along with water and/or other suitable diluent, at total concentrations of from 0.01 M to 1 M , preferably from 0.02 to 0.2 M . The use of various other conventional additives, e.g., antioxidants, colourants, surfactants, and the like, is also contemplated. Lysine and/or other amino acids may be employed as optional ingredients. In general, the concentration ranges for the ingredients discussed above will be within the limits set out in Table 1. Percentages are based on total composition weight. Haemostatic materials, such as GELFOAM, SURGICAL, and AVICEL, which are presently used alone or in combination with thrombin powder or thrombin in saline, can be effectively used with the stabilized thrombin solution of the present invention. The stabilized solution can be absorbed onto the haemostatic agent and the wet pad can be packaged in a sterile manner. Antimicrobial or antibiotic agents can be incorporated into such pads, especially for use on burn patients, where prevention of infection is critical. In addition, surfactants and salts other than NaCl can be employed. When one or more of such additives are present, their concentrations are generally within the ranges set out in Table II. One type of bandage suitable in the preparation of coagulants in accordance with the invention is set forth in U.S. Patent 4,363,319. Production of Thrombin Preparations The thrombin formulations made in accordance with the present invention are made by conventional processing techniques. The use of particular devices for mixing, adding, etc. should not be regarded as a limitation. The order of addition of the ingredients is believed to be critical, and it is generally preferred that all the ingredients except thrombin be mixed first, and the pH adjusted to 5.0, before addition of thrombin-containing powder. EXAMPLES The following is an example of a preferred formulation. Sodium chloride, 0.9g, and glycerol, 25.0g, are dissolved in approximately 75ml of distilled, deionized water. To this solution is added 0.29 ml of glacial acetic acid. The mixture is diluted to approximately 90ml and the pH is adjusted to 5.0 with 5 N sodium hydroxide. The volume of the solution is then brought to exactly 100ml by addition of distilled, deionized water. To prepare, for example, a 1000 unit/ml thrombin solution, 20ml of buffered formula are added to a vial containing 20000 units of thrombin in THROMBOSTAT powder, or 10ml of buffered formula are added to a vial containing 10000 units of thrombin, or 5.0ml of buffered formula are added to 5000 units of thrombin. The thrombin solution is shaken gently or otherwise agitated to dissolve the THROMBOSTAT powder, and the solution is stored at 4°C until ready for use. Table III below shows levels of thrombin activity remaining in thrombin solutions after storage at various temperatures. It is clear that the presence of a buffer significantly enhances the storage stability of thrombin preparations. The thrombin activity levels were determined by measurement of clotting time on a BBL fibrometer. The source of fibrinogen was pooled human plasma diluted 1:1 with 0.9% saline. The thrombin solution was diluted 200-fold with 0.5% polyethylene glycol 8000 in imidazole buffered saline. Into a coagulation cup was added 0.2ml of diluted plasma. This was kept at 37°C for 3 minutes, and to this solution was added 0.1ml of diluted thrombin solution, which had also been kept at 37°C for 3 minutes. Clotting time was determined directly from the fibrometer reading. The number of thrombin units/ml remaining was determined from a standard curve of thrombin concentration vs. clotting time. The data Table IV show that, while unbuffered solutions containing glycerol in saline provide some stability to low levels of solubilized thrombin, high levels of solubilized thrombin cannot be sterilized. In contract, the degrees of stabilization of both low and high concentrations of thrombin in the buffered composition of the present invention are approximately the same, and are much greater than that provided by glycerol alone.

Claims: Claims for the following Contracting States : BE, CH, DE, FR, GB, IT, LI, LU, NL, SE A stable thrombin preparation comprising thrombin and a buffer, in which the buffer is present in an amount sufficient to stabilise the thrombin and to maintain the preparation at a pH in the range of from 5.0 to 8.0. A stable thrombin preparation in which the thrombin is stabilized by the presence of a quantity of buffer sufficient to stabilize the thrombin and maintain the preparation at a pH in the range of from 5.0 to 8.0. A preparation according to Claim 1 or 2, which is maintained at a pH in the range of from 5.0 to 6.0. A preparation according to Claim 3, which is maintained at a pH of approximately 5.3. A preparation according to any preceding claim, which further comprises saline and at least one polyhydroxy stabilizer. A preparation according to Claim 5, wherein the stabilizer is chosen from C₃₋₁₂ polyols, polyethylene polyols having molecular weights in the range of from 200 to 8000 and mixtures thereof. A preparation according to any preceding claim, wherein the buffer is an acetate buffer. A haemostat, for use as a wound dressing, comprising a preparation according to any preceding claim and a substrate. A method of manufacturing a stable thrombin preparation, which method comprises combining thrombin with a quantity of a buffer sufficient to stabilise the thrombin and to maintain the preparation at a pH in the range of from 5.0 to 8.0. A method according to Claim 9, wherein the preparation is maintained at a pH in the range of from 5.0 to 6.0, preferably at a pH of approximately 5.3. Claims for the following Contracting States : AT, ES, GR A method of manufacturing a stable thrombin preparation, which method comprises combining thrombin with a quantity of a buffer sufficient to stabilise the thrombin and to maintain the preparation at a pH in the range of from 5.0 to 8.0. A method according to Claim 1, wherein the preparation is maintained at a pH in the range of from 5.0 to 6.0, preferably at a pH of about 5.3. A method according to Claim 1 to 2, which further comprises combining the thrombin and buffer with saline and at least one polyhydroxy stabilizer. A method according to Claim 3, wherein the stabilizer is chosen from C₃₋₁₂ polyols, polyethylene polyols having molecular weights in the range of from 200 to 8000 and mixtures thereof. A method according to any preceding claim, wherein the buffer is an acetate buffer. A haemestat, for use as a wound dressing, comprising a preparation manufactured by a method according to any preceding claim and a substrate.

Inventors: FAWZI, MAHDI B., NESBITT, RUSSELL U., SILBERING, STEVEN B.
Applicants: WARNER-LAMBERT COMPANY
Application year: 1986
Main classification: A61K37
IPC codes: A61K38, A61K47, A61L26, A61P7