Medicaments for the treatment of restenosis and arterial sclerosis

Abstract: A medicament for the treatment and/or prophylaxis of restenosis and arterial sclerosis after percutaneous transluminal angioplasty, characterized in that the medicament contains batroxobin as an effective component.

Description: The present invention relates to "the use of batroxobin for the preperation of drugs for the treatment" and/or prophylaxis of restenosis and arterial sclerosis after percutaneous transluminal angioplasty. It has been considered that intima pachymenia in the wall of blood vessel after the percutaneous transluminal angioplasty which has been extended as a method for treating of arteriosclerotic intima pachymenia, myocardial infarction and angina pectoris is caused by endotherial injury of blood vessel, and it has been reported that intima pachymenia will be formed in such a process that smooth muscle cell wanders from the media of the blood vessel and repeats its proliferation in the intima. However, this phenomenon has hardly been elucidated physiologically and pharmacologically. Although it is known that platelet-derived growth factor (PDGF) accelerates smooth muscle cell migration and proliferation, there are no reports confirming that only this factor is directly involved in arteriosclerotic intima pachymenia or re-pachymenia after percutaneous transluminal angioplasty. Thus, there is a need for a medicament and a method for treating intima pachymenia in the wall of blood vessels after the percutaneous transluminal angioplasty which has been extended as a method for treating of arteriosclerotic intima pachymenia, myocardial infarction and angina pectoris. According to recent reports, the number of the percutaneous transluminal angioplasty conducted in Japan, for example PTCA (percutaneous transluminal coronary angioplasty) is reported to be about 35,000, and the incidence of restenosis caused by intima pachymenia in the wall of blood vessels after the percutaneous transluminal angioplasty ranges from 20% to 50%. Hence, it is very important to develop a medicament for the treatment and/or prophylaxis of the restenosis. The present invention is based on various studies to develop a medicament for the treatment and/or prophylaxis of intima pachymenia in the wall of blood vessels by the use of an animal model. As a result, it was found out that intima pachymenia in the wall of blood vessels can remarkably be inhibited by administering an effective amount of batroxobin. It is an object of the present invention to provide an effective medicament for the treatment and/or prophylaxis of intima pachymenia in the wall of blood vessels after percutaneous transluminal angioplasty which has been extended as a method for treating of arteriosclerotic intima pachymenia, myocardial infarction and angina pectoris. The present invention provides a medicament for the treatment and/or prophylaxis of restenosis and arterial sclerosis after percutaneous transluminal angioplasty containing batroxobin as an effective component. Since batroxobin exhibits species-specificity to mammals, it is preferable to use optionally batroxobin together with heparin in mammals of which the plasma fibrinogen concentration does not significantly decrease upon administration of batroxobin. Batroxobin used in the present invention is a thrombin-like enzyme derived from snake (Bothrops atrox moojeni) venom and and is commercially available as a batroxobin formulation from Tobishi Pharmaceutical Co., Ltd. It was hitherto not known that batroxobin as employed in the present invention inhibits intima pachymenia in the wall of blood vessels. The Overall primary structure of the amino acids of batroxobin employed in the present invention has already been determined [N. Itoh et al., J. Biol. Chem. 262 (7) 3132-3135, 1987]. Batroxobin is a kind of serine protease like thrombin and has a molecular weight close to that of thrombin. They decompose fibrinogen to release fibrinopeptide A. However, they are different from each other in that thrombin releases also fibrinopeptide B but batroxobin does not; and thrombin acts to various blood coagulation factors but batroxobin does not act to blood coagulation factors excepting fibrinogen. Batroxobin employed in the present invention is used as an inhibitor for intima pachymenia in the wall of blood vessels, as an anti-arteriosclerosis agent and as a medicament for the treatment and/or prophylaxis of restenosis after percutaneous transluminal angioplasty by inhibiting intima pachymenia in the wall of blood vessels. The dosage of batroxobin employed in the present invention is dependent on symptoms and conditions to be treated. In general, the dosage is in the range of from 1 to 20 batroxobin units (hereinafter, abbreviated as BU) per adult per day, although the dosage outside the above range can be used depending on the symptoms and condition. Batroxobin may be suitably diluted and administered in the form of drip or injection, intravenously or topically. The batroxobin unit described herein is a unit representing the enzymatic activity of batroxobin. The activity inducing coagulation of plasma within 19.0±0.2 seconds when 0.1 ml of a batroxobin solution is added to 0.3 ml of standard human plasma containing citric acid at a temperature of 37°C is defined as 2 BU. The present invention will hereunder be described in more detail with reference to the following Examples. [Example] The components and their contents in 1 ml of batroxobin formulation [a thrombin-like enzyme derived from snake (Bothrops atrox moojeni) venom] are as follows: batroxobin (main component) 10 BU chlorobutanol (preservative) 3 mg gelatin hydrolyzate (stabilizer) 0.1 mg sodium chloride (isotonic agent) 9 mg distilled water for injection to 1 ml [Test] Common iliac arteries of high cholesteric rabbits to which a diet containing 2% of cholesterol was loaded for a month were used as a model of restenosis. The experiment was carried out using a heparin group with seven male rabbits and a group receiving the batroxobin combined with heparin also comprising seven male rabbits, weighing between 2.5 kg and 3 kg, respectively. This model has been frequently used whereby many observations have been obtained and hence is suitable as a model of restenosis after percutaneous transluminal angioplasty of arterial sclerosis. More specifically, a catheter sheath was inserted into the femoral artery of the rabbit and then the common iliac artery was injured by advancing a balloon catheter through the catheter sheath to the common iliac artery. After the common iliac artery was injured, the balloon catheter was further advanced to the bifurcation of the aorta. After 2ml of saline was locally injected through the sheath while occluding a proximal portion by inflating the balloon catheter, the blood perfusion was restarted. This is referred to as a control side. On the other hand, similarly, 2ml of saline containing heparin (25 U/kg) or a mixed solution of batroxobin formulation (1 BU/kg) and heparin (25 U/kg), that is, 2ml of saline in which batroxobin and heparin were mixed at a weight ratio of 1:100 was locally injected into the injured common iliac artery and after retaining the state for 3 minutes, the blood perfusion was restarted. This is referred to as a drug administered side. The observation by angioscope and angioscopic visualization after one hour showed the presence of occlusive thrombus or mural thrombus in the control side of all animals but did not show the presence of occlusive thrombus on the drug administered side. Post-operatively, the percent luminal obstruction (%) of both the control side and the drug administered side were compared by continuing the load of high cholesterol for one month. That is, the effects for preventing stenosis by local administration of batroxobin was evaluated by angioscopic visualization after one month from vasucular injury to compare the percent luminal obstruction (%) caused by intima pachymenia. The control side to which only saline was administrated showed a higher percent luminal obstruction (%) by angioscopic visualization after one month and the formation of stenosis in the common iliac artery by loading high cholesterol. The drug administrated side to which batroxobin and heparin were administered showed remarkably reduced percent luminal obstruction (%) as compared with the group to which only heparin was administered (P < 0.05). The results are shown in the following table. Percent luminal obstruction (%) Control side Drug administered side Heparin group 73 ± 17 34 ± 31 (n=7, p < 0.01) Batroxobin + heparin group 59 ± 39 5 ± 5 (n=7, P < 0.05) The percent luminal obstruction (%) was calculated by the following equation: Percent luminal obstruction (%) = 100× [( 1 + 2 )/2 - 3 ]/[( 1 + 2 )/2] 1 ○ : Inner diameter of blood vessel near stenosis (proximal portion) 2 ○ : Inner diameter of blood vessel near stenosis (distal portion) 3 ○ : Minimum inner diameter of blood vessel on stenosis. As shown in the results, the combination of batroxobin and heparin prevent restenosis. However, the use of heparin is not alway necessary. The defibrinogenating action of batroxobin to plasma fibrinogen in rabbit is significantly lower than that of human-fibrinogen ("Medicine and Pharmacy", Mitsuoki Ohba et al., Vol. 14, No. 4, p. 1061-1071, 1985.10, Shizen Kagakusha, Tokyo, Japan). Therefore, heparin was used with batroxobin in the test for preventing reocclusion caused by early forming of thrombus by platelet. An acute toxicity test for batroxobin was conducted by intravenous administration to mice, rats, rabbits and dogs. The LD 50 values (BU/kg) were found as follows: LD 50 value (BU/kg) mice (ddY strain) 192 ~ 210 rats (Wistar strain) 105 ~ 110 rabbits (NW species) > 300 dogs (hybrid) 190 ~ 208 Batroxobin used in the present invention prevents thrombus formation, inhibits intima pachymenia in the wall of blood vessels and is effective for the treatment and/or prophylaxis of restenosis and arterial sclerosis after percutaneous transluminal angioplasty. Whereas particular embodiments of the invention have been described above for purposes of illustration, it will be appreciated by those skilled in the art that numerous variations of the details may be made without departing from the invention as described in the appended claims.

Claims: The use of batroxobin for the preparation of drugs for the treatment and/or prophylaxis of restenosis and arterial sclerosis after percutaneous transluminal angioplasty. The use of claim 1, wherein heparin is used in combination with batroxobin. The use of claim 2, wherein batroxobin and heparin are mixed at the weight ratio of 1:100.

Inventors: TOMARU TAKANOBU, TOMARU, TAKANOBU
Applicants: TOBISHI PHARMACEUTICAL CO, TOBISHI PHARMACEUTICAL CO., LTD.
Application year: 1995
Main classification: C07K14
IPC codes: A61K35, A61P9, A61K38, A61K31, C12N9