Thrombolytic agents

Abstract: Thrombolytic agents suited for oral administration comprise a proteolytic enzyme of the subtilisin family, such as subtilisin BPN′, subtilisin Carlsberg, subtilisin amylosacchariticus, produced by microorganisms belonging to genus Bacillus , such as Bacillus subtilis , Bacillus licheniformis or Bacillus amyloliquefaciens .

Description: This invention relates to thrombolytic agents for oral administration, which contains as an active ingredient a proteolytic enzyme of the subtilisin family produced by Bacillus amyloliquefaciens or Bacillus licheniformis . A thrombus is closely associated with various diseases, such as peripheral arteriovenous thrombosis, pulmonary embolism, myocardial infarction, coronary embolism, cerebral embolism and retinal arteriovenous thrombolism, and presents a grave problem as an pathogenic factor. For the treatment of thrombotic diseases, at present, fibrinolytic therapy has been often employed mainly with use of streptokinase (hereinafter referred to briefly as "SK") in Western Europe and United States of America and urokinase (hereinafter referred to briefly as "UK") in Japan. Recently, it has become known that plasminogen activator, as obtained from the cells of melanoma, one of the human malignant tumors, possesses the same amino acid sequence as the enzyme called the tissue plasminogen activator (hereinafter referred to briefly as "TPA") being produced into the blood by the human angioendothelial cells. The said TPA, with its stronger affinity than UK for fibrin being attributed to the formation of thrombi, is considered to be highly effective against thrombotic diseases, and clinical application studies have already been completed with TPA that is produced not only by the human melanoma cells but also by microorganisms through genetic engineering. Such TPA has been put on the market in the United States of America, whereas such product is still in the stage of clinical trials, with investigation being under way on modified TPA having part of the amino acid sequence changed. Such kinds of TPA are needed for clinical trials in larger quantities than initially anticipated, and are now encountering difficulties for example forcibly increased prices in relation to limited production amounts. SK is a kind of foreign matter to the human body, and when repeatedly given humans through intravenous injection, incurs the risk of causing a variety of allergic reactions. Since UK and TPA both show half-lives in the living body as short as 30 min or less after intravenous injection and are inhibited by different inhibitors in the blood, resulting in loss of their activities, such sophisticated techniques as infusion of large maintenance doses are required. However, large-dose administration of these drugs brings about the risk of enhanced tendency toward bleeding as a side effect. Once, there was developed a fibrinolytic enzyme for oral administration, or UK for oral administration. Oral administration of enteric coated capsules containing the UK was observed to cause endogenous plasminogen activator to be released into the blood (Robbins et al., "Urokinase", Basic on Clinical Aspects, pp. 265 (1982). Published by Academic Press). In practice, such oral UK preparations once were put into clinical trials and were confirmed to be effective (Abe et al., "blood and Vessel", 12 , 342 (1981)). However, they have never been brought into clinical use, because UK was already commercially available in the form of intravenous preparation and has found pertinent application, while the oral UK preparations had to be administered at fairly greater doses, resulting in difficulties encountered in securing larger production amounts. This invention is intended to overcome such problems and also to provide a thrombolytic agent for oral administration that can be made available at a comparatively cheap price in larger quantities. UK and TPA, as put heretofore into clinical use for the fibrinolytic therapy are known to act as an enzyme capable of dissolving fibrin plates, and such a fact has led to the utilization of these enzymes as a pharmaceutical. The present inventors as well have conducted intensive research so far on UK and a variety of microbial cultivation products and in the course of this, noticed that proteolytic enzymes such as subtilisin Carlsberg and subtilisin amylosacchariticus produced by Bacillus licheniformis and Bacillus amyloliquefaciens , respectively, can develop fibrinolytic activity in the screening test (the fibrin plate method) for fibrin-clot dissolving activity. The research, followed by further investigation, has led the present inventors to the finding that the proteolytic enzymes derived from said Bacillus microorganisms, can demonstrate fibrinolytic activity even in the absence of plasminogen, whereas UK needs plasminogen to elicit its fibrinolytic activity. The above-described enzymes produced by said Bacillus microorganisms, which the present invention is concerned with, are already known as proteolytic enzymes, but have been found by the present inventors to demonstrate novel action and to be utilized in new application fields, and the finding has culminated into the present invention. FR-A-2233038 discloses the use of proteolytic enzymes derived from Bacillus subtilis as thrombolytic agents for oral administration. Sumi et al (Experientia 43 (1987) 1110-1111) discloses the use of the proteolytic enzyme nattokinase as a fibrinolytic agent for oral administration. The enzyme is produced by Bacillus natto which, according to the ATCC Catalogue, is the same as Bacillus subtilis . Chemical Abstract 93:36887d discloses the fibrinolytic activity of an enzyme produced by Bacillus subtilis . The present invention is concerned with thrombolytic agents for oral administration which contain the proteolytic enzymes of the subtilisin family being produced by Bacillus licheniformis and Bacillus amyloliquefaciens . As the proteolytic enzyme there may be mentioned, for example, subtilisin Carlsberg and subtilisin amylosacchariticus. As subtilisin Carlsberg which has been made commercially available, there may be used either of the commercial product after being purified through gel-permeation chromatography or a culture product of Bacillus licheniformis after being purified through the procedure of A. V. Guntelberg et al. (Comp. Rend. Lab. Carlsberg, Ser. Chim., 29 , 36 (1954)), followed by purification by gel-permeation chromatography. With reference to subtilisin amyloliquefaciens, or an enzyme produced by Bacillus amylosacchariticus , there may be employed a cultivation product of Bacillus amylosacchariticus after being purified through the method of D. Tsuruta et al. (Agr. Biochem., 30 ., 1261 (1966)), followed by further purification by use of Butyl Sepharose gel-permeation chromatography. According to ATCC (American Type Culture Collection), Bacillus mesentericus is contained in the species Bacillus licheniformis , and Bacillus licheniformis in this invention includes Bacillus mesentericus . The enzymes as exemplified in the above are already known, with their characteristic properties being clarified; given in "Biochemical Data Book" edited by the Biochemical Society of Japan is the description that subtilisin Carlsberg has a molecular weight of 27.3 Kd and an isoelectric point of 9.4, while subtilisin amylosacchariticus exhibits a molecular weight of 27.5 Kd and an isoelectric point of 7.8. The purified enzymes having the said characteristic properties as obtained by the above procedures can be used in the form of dried or concentrated product through drying under reduced pressure or lyophilization. However, the proteolytic enzymes according to this invention are not of human origin, and unlike UK of human origin, their intravenous administration for fibrinolytic therapy possibly brings about antigen-antibody reactions and involves a highly grave risk. In view of these, the present inventors conducted a great diversity of investigation with the varied methods of administration for the proteins. Oral administration is the least burdening and troubling to patients but is generally considered not to permit proteins given orally to migrate into the blood. The present inventors also realized well the fact but, entirely contrary to their expectation, found that the proteolytic enzymes according to this invention, when given orally for the confirmation of this, give rise to intensification of fibrinolysis activation system in the blood. Although the mechanism of action for such enzymes cannot at present be explained completely, it cannot be denied that the post-administration intensification of the tissue plaminogen activator activation in the blood is related to the effects of the orally given proteolytic enzymes of this invention. The dosage amount can be varied according to the degree of purification of the enzymes of the present invention, whereupon it is most desirable to use the commercially available enzymes according to this invetion after being purified to such an extent as may possibly by administered to humans. The enzymes of this invention as employed in the assessment of the effect after oral adminstration were assayed for purity by means of casein hydrolysis capacity; namely, the peptides, formed by hydrolyzing casein with the enzyme at 37°C and pH 7.5, were allowed to produce a color with Folin's reagent, and the purity was determined through the coloration, whereby the amount of the enzyme showing the coloration corresponding to 1 micromol of tyrosine for the 1 min period was taken as a unit. Referring to the drawings, Fig. 1-1, Fig. 1-2 and Fig. 1-3 are graphs showing the time-course changes of the blood EFA, FDP and TPA levels in relation to a number of days elapsed after administration of subtilisin Carlsberg. It is desirable to administer the enzyme of this invention in the form of enteric-coated preparation, taking it into consideration to prevent decomposition of the enzyme before absorption. The enteric-coated preparation can be produced by known procedures, for example, by providing powders or granules containing the enzyme with enteric coating or filling them into enteric-coated capsules. With reference to the amount of the enzyme being contained in such pharmaceutical preparation, a wide range of selection can be allowed (from 0.02 to 2 g per human adult), and the enzyme is desirably administered at a daily dose of 0.05 to 1 g, as divided once to three times. Described below are the experiment examples and examples to illustrate this invention more specifically. Experiment Example 1 Fibrinolytic activity by the fibrin plate method (T. Astrup and S. Mullertz, Archs. Biochem. Biophys., 40 , 346-351 (1952)): Subtilisin BPN′ (type XXVII) manufactured by Sigma Co., subtilisin Carlsberg (type VIII) and subtilisin amylosacchariticus as obtained by the procedure described in Example 1 were dissolved in deionized water, individually, to prepare their respective, aqueous solutions of 100, 50 and 25 µg/ml concentrations. Each of the sample solutions was placed on a fibrin plate and warmed for 18 hours at 37°C, followed by measurement of the dissolved area (mm²) of the fibrin membrane. In this experiment, two kinds of the fibrin plates were prepared and used; namely, one was fibrinogen type I of bovine origin manufactured by Dai-Ichi Kagaku Yakuhin Co. of Japan, Tokyo, which was used as a standard plate (+Plg) and the other was fibrinogen type II of bovine origin manufactured by the same company, which was utilized as a plasminogen-free plate (-Plg), while thrombin used was of bovine origin manufactured by Mochida Pharmaceutical Co. of Japan. In this experiment, urokinase (produced by our own company) and plasmin (supplied by Sigman Co.) were employed as a control enzyme. The results are shown in Table 1, which indicates evidently that the proteolytic enzymes of the subtilisin family exhibit fibrinolytic activity, thereby leading to the finding that such proteolytic enzymes demonstrate fibrinolytic activity without the need of mediating the activation of plasminogen to plasmin. The mode of action as shown by the enzymes of this invention is evidently different from the one of UK, but display the same tendency as plasmin; nonetheless, it is obvious that the enzymes of this invention differ in mode of action from plasmin, as well. The evaluation results, as tabulated in Table 1, are based on the test procedure of utilizing fibrin clots attributed to the thrombus formation in the living body which were prepared experimentally in the laboratory, and prove that the proteolytic enzymes of the subtilisin family develop proteolytic activity. Example 1 Subtilisin Carlsberg (produced by Sigma Co.) was subjected several times to gel-permeation chromatography on a column (5 cm° x 90 cm) of Sephadex G-100 equilibrated with 0.05 M phosphate buffer of pH 7.0 containing 1 % of sodium chloride, and elution was performed with the same buffer to give the purified enzyme having a specific activity of 17 U/mg. The thus purified enzyme was filled in 0.5 g portions into enteric-coated capsules to conduct the application experiment; the enteric-coated capsules were given to five human adults orally at the daily dose of 3 capsules, as divided three times, for the period of 4 days, and blood samples were drawn from each of the adult volunteers in time-course manner to determine changes in blood fibrinolytic activity. The whole blood clot lysis times (hereinafter referred to briefly as "WBCLT") were measured in accordance with the procedure of Chochan et al. [I. S. Chochan et al.: Thrombo. Diathes. Haemorrh. (Stuttg), 33 , 226-229 (1975)], according to which 0.2 ml of the blood sample was admixed with 1.7 ml of 0.12 M sodium acetate (pH 7.4) and 0.1 ml of thrombin solution (50 units, thrombin used was as produced by Mochida Pharmaceuticals Co. of Japan), followed by measurement of the length of time required for the dissolution of fibrin clots formed at 37°C; the fibrinolysis activity (EFA) of the eurogloburin fraction was determined with use of the method of Kluft et al. [C. Kluft et al.: Progress in Chemical Fibrinolysis and Thrombolysis, 2 , 57-65, J. F. Dabidson et al. (ed), Reven Press, New York (1976)]; namely, a precipitate (eurogloburin fraction) formed by adjusting to pH 5.9 a blood sample diluted 10 fold with distilled water was dissolved in EDTA buffer, and 0.03 ml of the solution was placed on the standard fibrin plate (T. Astrup and S. Mullertz, Archs. Biochem. Biophys., 40 ., 346-351 (1952)), followed by measurement of the dissolved area (mm²) of the fibrin membrane 18 hours later, wherein fibrinogen used for the preparation of the standard fibrin plate was of bovine origin (as produced by Dai-Ichi Kagaku Yakuhin Co. of Japan) and thrombin used was of bovine origin (as manufactured by Mochida Pharmaceuticals Co. of Japan). Fibrin and fibrinogen degradation products (hereinafter referred to briefly as "FDP") were determined by use of the latex coagulation method based on the FDPL test of Teikoku Hormone Mnfg. Co. of Japan; a sample serum was diluted 1 to 32 fold with a diluent for the sample as specified in the attached instructions for use, and 0.07 ml of the diluted solution was admixed with 0.04 ml of latex reagent and stirred on a slide plate, followed by observation for coagulation 2 min later (for example, when coagulation took place with a two-fold diluted solution of the serum, the FDP concentration was taken as 1 µg/ml, and in the case of occurrence of coagulation with a 4-fold diluted solution, the FDP concentration as 2 µg/ml). The plasma TPA activity was expressed in terms of an amount of produced antigen as determined against the human melanoma TPA (ng/ml) in accordance with the method of Bergsdorf (N. Bergsdorf et al.: Thromb. Haemostats., 500 , 740-744 (1983)) while using the ELISA kit manufactured by Blopool Co. of U.S.A.). The measurement results are shown graphically in Fig. 1. The enzyme did not produce any appreciable change in WBCLT. Example 2 A cultivation product of Bacillus amyloliquefaciens was purified by use of the method of D. Tsuruta et al. as stated herein and further treated for purification through gel permeation column chromatography (5 cm° x 90 cm) on Butyl Sepharose (400 ml) and Sephadex G-100 under the same chromatographic conditions as described in Example 1 to give 10 g of purified subtilisin amylosacchariticus. The administration experiment was conducted in the same manner as mentioned in Example 1 using three enteric-coated capsules containing 0.05 g of the purified enzyme, as divided three times, for the period of 8 consecutive days. Their measurements as taken in the time-course manner are shown in Table 2, which indicates that subtilisin amylosacchariticus, when administered orally, also produced an effect on the fibrinolytic system nearly identical to the case with subtilisin Carlsberg of Example 1. Example 3 Each of adult mongrel dogs (male weighing from 10 to 16 kg), which had had artificial thrombus formed through injecting 0.4 ml of 5 % bovine fibrinogen and 0.2 ml of 50 units/ml bovine thrombin into the lateral saphena vein according to the procedure of K. Sasaki et al. (Life Science, 27 , 1659-1665 (1980)), were given orally four enteric-coated capsules containing purified subtilisin Carlsberg as obtained in Example 1 (250 mg/capsule) at once which were prepared by the same procedure as described in Example 1, and after the capsules migrated into the intestinum duodenum, blood samples were drawn in time-course manner to measure the eurogloburin lysis time (ELT) in accordance with the previously mentioned procedure of K. Sasaki et al. and also to conduct X-ray angiography by injecting Angiograf in (produced by Scherring Co. of West Germany) into the main artery of the inguinal region at a rate of 4 ml/2 sec. The results are shown in Table 3, which indicates that the control group (N=3) receiving the capsules not containing the test drug produced no change (p 0.5) in ELT over the period of 0.5 to 12 hours after administration and was observed not to cause any lysis of the artificial thrombus for the period of not less than 18 hours after its formation, whereas the group treated through administration of the test drug showed shortened lengths of ELT (or intensified lysis activity) over the period of 0.5 to 6 hours after administration. In the group treated with the test drug, the artificial thrombus was observed in every case to undergo lysis within 5 hours after its formation. The above findings led to the confirmation that subtilisin Carlsberg possesses thrombus lyzing activity.

Claims: An oral pharmaceutical composition comprising a proteolytic enzyme belonging to the subtilisin family and obtained from Bacillus amyloliquefaciens or Bacillus licheniformis and a pharmaceutically acceptable carrier. A composition as claimed in Claim 1, wherein the composition is in the form of a tablet or capsule. A composition as claimed in Claim 1 or Claim 2, wherein the composition is in the form of an enteric-coated preparation. A composition as claimed in any one of the preceding claims, wherein said enzyme is subtilisin amylosacchariticus or subtilisin Carlsberg. A composition as claimed in any one of the preceding claims, wherein the composition is in the form of dosage units each containing 0.02 to 2 g of said enzyme. A composition as claimed in Claim 5, wherein said dosage units each contain 0.05 to 1 g of said enzyme. The use of a proteolytic enzyme belonging to the subtilisin family and obtained from Bacillus amyloliquefaciens or Bacillus licheniformis in the manufacture of a medicament for use in the prevention or treatment of thrombotic disease. The use of subtilisin amylosacchariticus or subtilisin Carlsberg in the manufacture of a medicament for use in the prevention or treatment of thrombotic disease. A use as claimed in Claim 7 or Claim 8, wherein the medicament is for oral administration.

Inventors: HIRATANI HAJIME, KATO KAZUO, NAKANISHI KOICHIRO, HIRATANI, HAJIME, KATO, KAZUO, NAKANISHI, KOICHIRO
Applicants: JAPAN CHEM RES, NIHON CHEMICAL RESEARCH KABUSHIKI KAISHA ALSO KNOWN AS JCR PHARMACEUTICALS CO., LTD
Application year: 1990
Main classification: A61K37
IPC codes: A61K38, A61K9, A61P7