A PROCESS FOR PASTEURIZATION OF AQUEOUS SOLUTIONS OF FACTOR VIII

Abstract: In a process for pasteurization of aqueous solutions of Factor VIII, the solution is heated to a temperature of 55-65 DEG C for a period of time of 5-15 hours in the presence of saccharide or a sugar alcohol as well as 1-4, preferably 1.5-2.5 IU of heparin per g of solution. The heparin has a stabilizing effect so that degradation of Factor VIII is avoided or limited.

Description: A process for pasteurization of aqueous solutions of Factor VIII The present invention concerns a process for pasteuri¬ zation of aqueous solutions of of coagulation Factor VIII, in particular human Factor VIII. The object of the invention is to remove or inactivate infectious virus which might be present in preparations containing the coagulation Factor VIII. A particular object of the in¬ vention is to carry out heat treatment of aqueous solu¬ tions of Factor VIII under conditions where any present viruses are inactivated with certainty, while obtaining high recovery of the therapeutic protein human coagula- tion Factor VIII. The human coagulation Factor VIII (hereinafter called Factor VIII), also called Antihemophilic Factor (AHF), forms part of the coagulation system of the blood. Fac- tor VIII must be present for coagulation to take place. Humans having completely or partly lost the ability to synthesize Factor VIII suffer from the disease Hemo¬ philia A, which is a congenital disease. The disease is characterized by frequent bleedings, in particular in the joints and in the musculature. It is thus necessary to substitute humans having Factor VIII deficiency with preparations containing Factor VIII. Such a substitution therapy of Hemophilia A pa- tients was initiated in Europe in 1965. This substitu¬ tion therapy has resulted in a considerable increase in the average duration of life of Hemophilia A patients. Thus, the average duration of life for Hemophilia A pa¬ tients in Sweden has increased from about 16 years in 1948 to about 56 years in 1978. Furthermore, the substi¬ tution therapy has caused a reduction in the number of disabling bleedings in Hemophilia A patients and thus improved the patients' ability to earn their living and their conditions of life. Preparations containing Factor VIII are prepared from human blood or blood plasma. Various processes for this production are known. For all these, the initial process is equivalent. Blood from donor may be tapped in a bag system containing anticoagulant. The anticoagulant may be citrate phosphate dextrose (CPD), acid citrate dex- trose (ACD) or heparin. The blood plasma is separated from the other components by centrifugation. This sepa¬ ration may also take place in the actual tapping of donor by so-called plasma pheresis. The blood plasma is stored in a frozen state. The frozen blood plasma is thawed, and so-called cryoprecipitation is carried out. The resulting cryoprecipitate contains Factor VIII and forms the starting point for the further production. This may be performed in a known manner using precipita- tion techniques for removing undesirable protein mate¬ rial. Precipitation of this protein material may for example take place by addition of ethanol (Mattock et al., European Patent Application No. 0 062 456, 1982), of polyethylene glycol (Sarno et al., European Patent Application No. 0 221 556, 1987) or glycine (Mitra et al., European Patent Application No. 0 126 789/ 1984). Other known processes for removing undesirable protein material from solutions containing Factor VIII comprise using chromatographic techniques (for example as descri- bed by Chavin et al., European Patent Application No. 0 104 356, 1984). It is moreover known that the use of blood plasma pro¬ duced with heparin as anticoagulant, so-called heparin- ized blood plasma, can increase the recovery of Factor VIII in the cryoprecipitate (Rock et al., European Patent Application No. 0 053 046, 1982). Heparin is a group of sulphated polysaccharides having a molecular weight from 5000 to 40000, typically from 15000 to 25000, and has an anticoagulating effect in blood plasma. Even though heparin can increase the recovery of Factor VIII, heparin is not extensively used as anticoa¬ gulant because this prevents using a number of the other components of the blood for therapeutic purposes. Heparin has an anticoagulating effect in blood or blood plasma. Heparin per se partly inhibits thrombin, partly acts as a catalyzer in the formation of a thrombin - antithrombin III complex. Thrombin is one of the pro¬ teins which can cleave the Factor VIII molecule in frag¬ ments. Factor VIII is an important coagulation Factor in the coagulation system of the blood. Activation of Fac¬ tor VIII causes cleavage of the Factor VIII molecule in fragments. This activation is caused either by activated Factor X activated protein C or thrombin, of which the latter is the most important one. Thus, addition of he- parin affects the natural coagulation system and conse¬ quently stabilizes Factor VIII. Heparin does not affect the content of free calcium ions in blood or blood plasma containing Factor VIII. This is in contrast to citrate or citrate-containing anticoagu¬ lants such as citrate phosphate dextrose (CPD), where the present citrate acts as a chelate former and forms a complex with calcium. Since the presence of calcium is of importance for the stability of Factor VIII, the use of heparin as an anticoagulant may be instrumental in improving the stability of Factor VIII. Stabilization of Factor VIII with heparin in heparinized blood plasma thus takes place partly by inhibition of thrombin, which degrades Factor VIII, and partly by not changing the presence of calcium ions. Factor VIII preparations may be prepared from heparini- zed plasma having a high recovery of Factor VIII activi¬ ty in the cyroprecipitate (Smit-Sibinga et al., Lancet, ii, 449, 1981). The reason is partly that heparin stabi- lizes Factor VIII in the plasma, partly that heparin in¬ creases precipitation of Factor VIII by the cryoprecipi- tation. For a higher recovery of Factor VIII in the cryoprecipi- tate to be obtained, it is important that the plasma is heparinized during tapping of the donor. Later addition of heparin to blood plasma produced with citrate-con¬ taining anticoagulant does not result in an increased recovery of Factor VIII in the cryoprocipitate (Mikaels- son et al., Blood, Vol. 62, No. 5, 1983, p. 1006). Like¬ wise, addition of heparin during the production of pre¬ parations containing Factor VIII after or during redis- solution of the cryoprecipitate does not improve the recovery of Factor VIII. Thus, the effect of heparin depends upon addition of heparin in connection with tapping of the donor. On the other hand, addition of both heparin and calcium to citrate-containing blood plasma or fractions may result in an increased recovery of Factor VIII. A serious problem in the therapeutic use of preparations or fractions produced from human blood or blood plasma is that this blood or blood plasma may contain infec¬ tious virus. Examples of such infectious virus are Hepa- titis B Virus, Hepatitis non-A-non-B Virus and Human Immunodeficiency Virus. Transmission of infectious virus is known not only from the use of preparations contain¬ ing Factor VIII, but generally from the use of prepara¬ tions produced from human blood or blood plasma. Exa p- les of such preparations are coagulation Factor IX, coa¬ gulation Factor XIII, immunoglobulin, antithrombin III. Known are various processes for removing infectious virus from therapeutic preparations or solutions con¬ taining these produced from human blood or blood. Such a known process comprises heating for 10 hours at 60 °C of aqueous solutions containing therapeutic protein, which provides certainty against transfer of infectious virus when using preparations containing these plasma pro¬ teins. To avoid denaturation or other damage to the therapeutically active protein in the aqueous solution it is necessary, however, to add stabilizers during the heat treatment. Thus, salts of fatty acids or amino acid are added as stabilizers in a heat treatment for 10 hours at 60 °C of solutions containing human albumin or protein concen¬ trate (Gellis et al, J. Clin. Invest., 27, 239, (1948)). The use of this process for treating human albumin or protein concentrate has entailed that no infectious virus has been transferred using these preparations since this process was introduced in 1948. In this pro¬ cess, there are np or only insignificant losses of the therapeutic plasma protein albumin. Solutions containing plasminogen may be stabilized with the amino acid lysin under a heat treatment at 60 °C for 10 hours (Baumgarten et al, USA Patent No. 3 227 626, 1966). According to the patent this process destroys present hepatitis virus. Solutions containing the coagulation Factor XIII may be heated to 60 °C for 10 hours in the presence of amino acid, monosaccharide or sugar alcohol (Fukushima, Patent No. Sho 51-134878, 1976). A loss of Factor XIII activity of about 50% has been reported for this process. Further, solutions containing the proteinase inhibitor Antithrombin III may be stabilized with salts of citric acids before heating for 10 hours at 60 °C (Holleman et al., Thromb. & Haemo., 38, 201, (1977)). The loss of the therapeutic protein Antithrombin III amounts to about 30% in this process. Various processes for stabilizing Factor VIII by heat treatment in aqueous solutions are known. A process for stabilizing Factor VIII by heat treatment for 10 hours at 60 °C with a polyol has been described (US Patent No. 4 440 697, 1984). This process comprises adding for example saccharose, optionally together with the amino acid glycine, in an amount so that after ad¬ dition the solution contains 62% w/w saccharose or is saturated with saccharose. A similar process for stabilizing Factor VIII likewise by heat treatment for 10 hours at 60 °C has been de¬ scribed using sugar alcohol or disaccharide (European Patent Application No. 0 117 064, 1984). This process comprises adding for example 66% w/w saccharose or sor- bitol as a stabilizer during the heat treatment. A process using a combination of either a neutral amino acid, a saccharide or a sugar alcohol and the salt of a carboxylic acid having from 3 to 10 carbon atoms for stabilizing Factor VIII by heat treatment at 60 °C for 10 hours is known (European Patent Application No. 0 077 879, 1983). Human albumin may be added as a further sta- bilizer. This process comprises adding for example 25% w/v glycine and 20% w/v sodium caprylate as a stabiliz¬ er. Further, known is a process for heat treatment of Factor VIII for 10 hours at 60 °C with simultaneous reduction of a contaminating fibrinogen content (DE Offenlegungs- schrift No. 29 16 711, 1980). The stabilizer is a sac- charide or sugar alcohol in combination with a high con¬ centration of amino acid. The present amino acid causes the fibrinogen in the Factor VIII solution to be preci¬ pitated. This process comprises adding for example 50% w/w saccharose and 2 M glycine to the Factor VIII solu¬ tion during the heat treatment. Finally, it is known from UK 2 172 000 to perform heat treatment for 10 hours at 60 °C of a solution contain- ing, in addition to Factor VIII, residual amounts of heparin or other sulfated polysaccharide which has not been removed completely in the previous purification steps. In these previous tests, the presence of such residual amounts of heparin were found to have no in- fluence on the yield or recovery of Factor VIII after the heat treatment (see p. 4, 1. 6-7 in the description of UK 2 172 000) . It is characteristic of the previously known processes for stabilizing Factor VIII in aqueous solutions with heat treatment at 60 °C for 10 hours that the recovery of Factor VIII after the heat treatment is low. Thus, the examples in the patent specifications mentioned above report recovery of Factor VIII after heat treat- ment for 10 hours at 60 °C as stated in the following table. Description of process Per cent recovery F VIII activity US Pat. No. 4 440 679, example 1 A 63 US Pat. No. 4 440 679, example 1 B 61 EP Appl. No. 0 077 870, table 1 40 - 70 EP Appl. No. 0 117 064, example 1 58 EP Appl. No. 0 117 064, example 2 56 EP Appl. No. 0 117 064, example 3 58 EP Appl. No. 0 117 064, example 4 57 DE Off. No. 29 16 711, example 2 52 The low recovery of Factor VIII in the previously known processes constitutes a severe drawback of these. Since preparations of fractions containing Factor VIII are produced from human blood or blood plasma originating from donors, this material is a highly limited raw material. Thus, in Denmark about 20 million IU of Factor VIII (1987) are used per year, corresponding to tapping of about 400,000 donors. 1 Iϋ (international unit) of Fac¬ tor VIII corresponds to the Factor VIII activity of 1 ml of normal plasma. At the same time, the costs of produc¬ ing these preparations are very high, and the recovery of Factor VIII activity low, which causes Factor VIII to be a very costly protein. Thus, the price of 1 Iϋ of Factor VIII in a highly purified Factor VIII preparation is about Dkr. 4 in Denmark. The annual consumption of Factor VIII in Denmark corresponds to about Dkr. 80 mil¬ lion. It is thus of great importance that the recovery of Factor VIII is high. The present invention concerns a process of the type defined in the introductory portion of claim 1 and is characterized by the subject-matter defined in the cha¬ racterizing portion of the claim. This process prevents transmission of infectious virus when using the prepara¬ tion and also gives a high recovery of Factor VIII. The process comprises adding to the solution of Factor VIII heparin as a stabilizer in combination with a sac¬ charide or sugar alcohol, and the heat treatment is carried out in a manner known per se, preferably for 10 hours at 60 °C. This provides a surprisingly improved recovery of Factor VIII. When adding heparin as a stabilizer in combination with a saccharide or sugar alcohol in a heat treatment for 10 hours at 60 °C of an aqueous solution containing citrate and Factor VIII, it is only the effect of inhibition of thrombin which is important. This effect may be intensi¬ fied by bonding heparin to von Willebrand Factor. Owing to the present citrate there is no increase in the cal- cium level with consequent stabilization of Factor VIII. The effect of adding heparin in a heat treatment may thus be ascribed to an impact on the natural coagulation system with consequent stabilization of Factor VIII. This is in contrast to the previously known additions in a heat treatment for 10 hours at 60 °C of an aqueous so¬ lution containing Factor VIII. Saccharides, sugar alco¬ hol, amino acids or salts of organic acids have a stabi- lizing effect in that these stabilizers influence the hydration degree or charge difference of the protein. The process in the heat treatment for 10 hours at 60 °C of an aqueous solution containing Factor VIII with hepa- rin as a stabilizer in combination with a saccharide or sugar alcohol may be performed on any fraction or prepa¬ rations containing Factor VIII. A saccharide or sugar alcohol is added to citrate solu¬ tions containing Factor VIII. Addition of saccharose is a preferred embodiment. Stabilization of Factor VIII increases with increased addition of saccharide or or sugar alcohol. Thus, from 20 w/w % to saturation may be addead. The preferred embodiment is addition of saccha¬ rose corresponding to 60 w/w %. Saturation of a solution containing Factor VIII with saccharide or sugar alcohol causes partly handling difficulties owing to the high viscosity, partly stabilization of the infectious virus. Heparin may be added before or after addition of saccha¬ ride or sugar alcohol corresponding to from 1.0 to 4.0 Iϋ (international units) of heparin per g of solution after addition of saccharide or sugar alcohol. Addition corresponding to from 1.5 to 2.5 Iϋ of heparin per g of solution is a preferred embodiment. Addition of too large amounts of heparin causes precipi- tation of Factor VIII. This precipitation may be detect¬ ed by measuring the cloudiness of the solution. It has thus been found that an increase in the cloudiness of the solution may be detected by addition of 4.0 Iϋ of heparin per g of solution. It applies to precipitation of proteins that chemical and physical conditions in the solution, such as for example protein concentration, protein composition, conductivity, pH or salt concentra¬ tion, influence the degree of precipitation. Changes in for example protein concentration or protein composition may thus cause changes in the heparin concentration which gives the highest recovery of Factor VIII without the protein solution beginning to precipitate. To obtain a maximum yield, the pH value must be adjusted in the solution to a physiological level. Thus, the pH value should be between 6.0 and 7.0 with from 6.2 to 7.0 as a preferred process. Addition of CaCl2 in limited amounts may cause stabili¬ zation of Factor VIII during the heat treatment. In the present process, from 0 to 150 mmols of CaCl2'per g of ready solution are used. Removal of saccharide or sugar alcohol from the solution containing Factor VIII after the heat treatment can take place by dialysis or precipitation of Factor VIII from the solution. Determination of Factor VIII activity can be performed either by a 2-step assay or a 1-step assay. It is known that 1-step and 2-step assays may result in various de¬ terminations of the Factor VIII activity in a given sample. It is moreover known that repeated measurements with the same assay on the same sample may give rise to great variations in the determination of Factor VIII activity. It is also known that the results of the de¬ termination of Factor VIII activity can depend upon other present proteins or other components in the given sample. Determination of Factor VIII activity in a 2-step assay is performed by means of a chromogenic substrate method (KABI Coatest Factor VIII), the original method in test tubes at 37 °C having been modified for execution in microtiter plate with reduced reagent use at room tem¬ perature. 50 microlitres of sample or standard are used, which, following mixing with 50 microlitres of phospho- lipid, Factor IXa and Factor X, are warmed for 10 minu¬ tes. After addition of 25 microliters of 25 m CaCl2, incubation is effected for 15 minutes, and then 50 microlitres of substrate are added. After an additional 20 minutes' incubation the reaction is stopped by addition of 50 microlitres of 1 M citric acid. The colour development is read at 405 nm with re- ference at 492 nm. Determination of Factor VIII activity in 1-step assay is performed by means of the APTT method (Activated Partial Thromboplastin Time). 100 microlitres of sample or stan¬ dard are pipetted in the cuvettes, and then 100 micro- litres of deficient plasma are added (Factor VIII de¬ ficient plasma. General Diagnostic). 100 microlitres of APTT-reagent (General Diagnostic) are added, and the solution is thermostated at 37 °C for 5 minutes. After addition of 100 microlitres of 0.03 M CaCl2, the time until coagulation of the solution is measured. For quantitative determinations, calibration curves are prepared, based on dilution series of an internal stan¬ dard calibrated against WHO standard (3rd Int. Standard of F VIII, Human Plasma, 3.9 Iϋ/ml). 2-step assay, as stated here, has a lower detection limit (about 10 times) than 1-step assay. In connection with addition of heparin it is an advantage to use 2-step assay since any heparin effect on the assay can more easily be destroyed by dilution. Determination of cloudiness is performed by measuring the extinction at 400 nm. Thus, tests have shown that addition of heparin corre¬ sponding to a concentration of from 1.0 to 4.0 Iϋ of heparin per g of solution containing Factor VIII stabi- lized with a saccharide or sugar alcohol during the heat treatment results in an increase in Factor VIII re¬ covery. The process of the invention is illustrated by the fol- lowing examples. Example 1 14 ml of citrate solution (0.53 g of sodium citrate/- litre) containing 1680 Iϋ Factor VIII) are distributed in 7 tubes so that each tube contains 2 ml of solution. To each tube are added 3 g of saccharose which is caused to dissolve. Heparin solution (500 Iϋ/ml) is additional¬ ly added to each tube so that the individual tube con¬ tains a heparin amount as stated in the table below, and about 48 Iϋ of Factor VIII of ready solution. The tubes are sealed and heat treated for 10 hours at 60 °C. Fac¬ tor VII is determined by 1-step assay, and the cloudi¬ ness of the solution is determined as the extinction at 400 nm. Iϋ heparin added Per cent recovery E 400 per g solution Factor VIII activity 0.0 70 0.35 0.3 70 0.34 0.5 71 0.35 1.0 87 0.35 2.0 91 0.37 4.0 93 0.40 8.0 85 0.63 Example 2 20 ml of citrate solution (0.53 g of sodium citrate/- litre) containing 6000 Iϋ Factor VIII are distributed in 10 tubes, so that each tube contains 2 ml of solution. To each tube are added 3 g of saccharose which is caused to dissolve. Heparin solution (500 Iϋ/ml) is additional¬ ly added to each tube, so that the individual tube con- tains a heparin amount as stated in the table below, and about 120 Iϋ of Factor VIII per g of ready solution. The tubes are sealed and heat treated for 10 hours at 60 °C. Factor VIII is determined by 2-step assay. Iϋ heparin added Per cent recovery of per g solution Factor VIII activity 0.0 66 1.0 86 1.5 81 2.0 91 2.5 87 Example 3 8 ml of citrate solution (0.53 g of sodium citrate/- litre) containing about 5000 Iϋ of Factor VIII are di¬ stributed in 4 tubes, so that each tube contains 2 ml of solution. To each tube are added 3 g of saccharose which is caused to dissolve. Heparin solution (500 Iϋ/ml) is additionally added to 2 tubes, so that the tube contains a heparin amount of 2.0 ID per g of solution. The tubes are sealed and heat treated for 10 hours at 60 °C. The test is repeated on different sample material, a total of 5 times. The Factor VIII content varied in these tests from 220 to 260 Iϋ per g of ready solution. Factor VIII is determined by 2-step assay. Test IU heparin per Per cent recovery of Per cent g solution Factor VIII activity improvement 1 0 40 0 40 Average 42 2 71 2 81 Average 76 2 0 51 0 55 Average 53 81 2 86 2 87 Average 87 63 3 0 55 0 60 Average 58 2 85 2 89 Average 87 51 4 0 71 0 71 Average 71 2 83 2 84 Average 84 18 5 0 59 0 66 Average 63 2 84 2 85 Average 85 35 Average improvement for all tests is 50%, Example 4 2 ml of citrate solution (0.53 g of sodium citrate/- litre) containing 600 IU of Factor VIII are mixed with 3 g of saccharose which is caused to dissolve. Heparin so¬ lution (500 Iϋ/ml) and calcium chloride (10 ~2 M) are ad¬ ditionally added, so that the tube contains a heparin amount of 2.0 Iϋ, 100 mmols calcium chloride and 120 Iϋ Factor VIII per g of solution. The tube is sealed and heat treated for 10 hours at 60 °C. Factor VIII is de¬ termined by 2-step assay. Recovery of Factor VIII was 88 %.

Claims: P a t e n t c l a i m s 1. A process for pasteurization of aqueous solutions of Factor VIII by heating to a temperature of 55-65 °C for a period of time of 5-15 hours in the presence of a sac¬ charide or a sugar alcohol, c h a r a c t e r i z e d by adding to the solution 1-4 Iϋ of heparin per g of ready solution followed by heat treatment. 2. A process according to claim 1, c h a r a c t e r i ¬ z e d in that the added heparin amount constitutes 1.5- 2.5 Iϋ per g of ready solution. 3. A process according to claim 1 or 2, c h a r a c t e¬ r i z e d in that the pH value is maintained at 6.2-7.0 during the heat treatment. 4. A process according to any of claims 1-3, c h a - r a c t e r i z e d in that the Factor VIII content is maintained between 10 and 300 IU per g of ready solu¬ tion. 5. A process according to any of chaims 1-4, c h a - r a c t e r i z e d in that the amount of saccharide or sugar alcohol constitutes 50-65% w/w calculated' on the ready solution. 6. A process according to claim 5, c h a r a c t e r i - z e d in that the saccharide is saccharose. 7. A process according to any of claims 1-6, c h a ¬ r a c t e r i z e d by performing the heat treatment in the presence of CaCl2 in an amount not exceeding 150 mmols per g of ready solution.

Inventors: KIHL JESPER, NORDFANG OLE, NYRUP ALLAN, KIHL, JESPER, NORDFANG, OLE, NYRUP, ALLAN
Applicants: NORDISK GENTOFTE, NORDISK GENTOFTE A/S
Application year: 1989
Main classification: A61L2
IPC codes: A61K38, A61L2