WO1987006831A1

WO1987006831A1 - Composition and method for treating a thrombus and embolus

Info

Publication number: WO1987006831A1
Application number: PCT/US1986/001747
Authority: WO
Inventors: Robert L. Hunter; Alexander Duncan
Original assignee: Emory University
Priority date: 1986-05-15
Filing date: 1986-08-25
Publication date: 1987-11-19
Also published as: ZA873512B; AU6334586A; MX9206336A; MX9206335A

Abstract

Composition which provides a synergistic action in dissolving blood clots and reestablishing and maintaining blood flow through a thrombosed coronary vessel or other blood vessel. The clot-dissolving composition of the present invention is a solution containing an effective concentration of a proteolytic enzyme and an effective concentration of a surface active copolymer. The surface active copolymer is preferably an ethylene oxide-propylene oxide condensation product with the following general formula: HO(C2H4O)b(C3H6O)a(C2H4O)bH, wherein a is an integer such that the hydrophobe represented by (C3H6O) has a molecular weight of about 950 to 4000 and b is an integer such that the hydrophile portion represented by (C2H4O) constitutes from about 50 % to 90 % by weight of the compound. The proteolytic enzymes that can be used in the clot-dissolving composition of the present invention include, but are not limited to, streptokinase, urokinase, and tissue plasminogen activator.

Description

"Composition and Method for Treating a Thrombus and Embolus"

Technical Field

The present invention relates to a composition and method for treating a thrombus or embolus and, more particularly, to a composition comprising certain ethylene- oxide propylene oxide condensation products in combination with clot-dissolving enzymes. The composition is effective in dissolving clots that occlude blood vessels, restoring the flow of blood through damaged tissue .and preventing new clots from forming.

Background of the Invention

Each year about 550,000 Americans die from heart attacks. Even more - close to 700,000 - have heart attacks and live. While a heart attack victim may survive, part of his or her heart will almost certainly die. The death of heart muscle, called myocardial infarction, is due to coronary artery thrombosis in 70-90% of the cases. When a thrombosis, or blood clot, occludes one of the -arteries of the heart, it stops the flow of blood to the surrounding muscle which deprives it of oxygen and other nutrients. In the past, nothing coujd be done to reverse this process. The high technology devices in intensive care units mostly supported patients so they could live while a portion of their heart died.

Use of copolymers prepared by the condensation of ethylene oxide and propylene oxide to treat an embolus or a thrombus has been described (See U.S. Patent No. 3,641,240).

However, use of the copolymer -alone has little or no effect on a patient who has suffered a severe coronary infarction wherein a blood clot has formed in the coronary artery. Large clots in which the fibrin has undergone crosslinking are not effected by presence of the ethylene oxide/propylene oxide copolymers.

SUBSTITUTE SHEET It has been found that certain enzymes are able to open clogged arteries. The enzymes which have been used successfully include streptokinase, urokinase, tissue plasminogen activator produced from ceil cultures (tissue plasminogen activator) and tissue plasminogen activator produced by recombinant DNA technology (r-tissue plasminogen activator). These enzymes are most successful if administered shortly after the occlusion of the blood vessels before the heart tissue has sustained irreversible damage. In one study of 11,806 patients treated with intravenous streptokinase, an 18% improvement of survival was demonstrated. If the treatment was begun within one hour after the initial pain onset of the heart attack, the in-hospital mortality was reduced by 47%. (See The Lancet. Vol 8478, p 397-401, Feb. 22, 1986). It was demonstrated that early lysis of the thrombus resulted in salvage of a portion of heart tissue which would have otherwise have died. In studies using angiography to assess the patency of blood vessels, it was found that tissue plasminogen activator could completely open the vessels of 61% of the 129 patients versus 29% of controls who were not treated with the enzyme.

(See Verstraete, et al., The Lancet, Vol 8462, p 965-969), Nov. 2, 1985). Tissue plasminogen activator requires the addition of approximately 100 μl of Tween 80 per liter of solution to promote dispersion of the enzyme. (See Ko ninger, et al., Thrombos, Haemostas, (Stuttgart) Vol. 46(2), p 561-565

(1981).

The enzymes used to lyse thrombi in vessels do so by activating fibrinolysis. Fibrin is the protein produced by polymerization of fibrinogen. It forms a gel which holds the thrombus together. The fibrin molecules which form clots gradually become cross-linked to make a more stable clot All three enzymes, urokinase, streptokinase and tissue plasminogen activator, have similar effects on fibrin; however, they have different toxicities. If the fribrinolysis mechanisms are activated in the vicinity of a clot, the clot is dissolved. If, however, they

«! ! IB .are activated systemically throughout the circulation, the body's capacity to stop bleeding or hemorrhage is markedly reduced. Streptokinase and urokinase tend to activate systemic fibrinolysis. Consequently, they have been most effective when injected directly into the affected blood vessel. Tissue plasminogen activator, in contrast, becomes effective only when it is actually attached to fibrin. This means its activity is largely localized to the immediate area of a clot and does not produce systemic fibrinolysis. It can be injected intravenously into the general circulation. It circulates harmlessly until it contacts the fibrin in a blood clot where it becomes activated and lyses the clot Tissue plasminogen activator is able to lyse a clot which is extensively cross-linked. This means it is possible to lyse clots which have been present for many hours. Tissue plasminogen activator also produces less risk of hemorrhage than the other enzymes. Even more effective enzyme b.ased thrombolytic drugs are being developed.

Remarkable as the new enzyme therapies are, they are subject to serious complications and are not effective in all patients. Clots in the anterior descending branch of the left coronary artery are much more readily lysed than those in other arteries. If the enzyme is not delivered by the blood stream directly to the thrombus, it has no effect. For various reasons, more blood passes by or trickles around thrombi in the left anterior defending coronary artery than in the other major arteries. In addition, the presence of collateral circulation which forms in response to compromised blood flow in the major arteries adversely affects the rate of reopening or recanalization of the thrombosed major arteries. It is thought the presence of many collateral vessels which allows blood to bypass the clot reduces the pressure gradient across the clot This in turn reduces the blood flow through the tiny openings which may persist in the clot, impedes the delivery of enzymes to the clot, and prevents it from being dissolved.

HEET Once the clot is dissolved, the factors which led to the formation of the thrombus persist. This produces a high incidence of re-thrombosis and further infarction in the hours and days following lysis of the clot Rethrombosis has been reported in between 3% and 30% of cases in which the initial treatment successfully lysed the clot. Anticoagulants are currently used to prevent the formation of new thrombi, but they tend to induce hemorrhage. There is a delicate balance between the amount of anticoagulation necessary to prevent re¬ thrombosis of the vessels and that which will produce serious hemorrhage.

Finally, dissolving the clot after irreversible damage has taken place has little effect The irreversible damage could be either to the heart muscle or vascular bed of the tissue supplied by the blood vessel. A major problem in widespread implementation of this new enzyme therapy is to find ways of identifying and treating the patients earlier in their disease and to find ways to make the treatment effective for a longer period of time after the initiation of thrombosis. Animal studies have provided a better understanding of the events which control blood flow and tissue death following coronary artery thrombosis. The heart has several blood vessels so much of the muscle receives blood from more than one vessel. Consequently, the tissue changes following a coronary thrombosis are divided into distinct zones.

The central zone of tissue becomes almost completely necrotic. This is surrounded by an area of severe ischemia. Outside this is an area of lesser ischemia called the marginal zone. Finally, there is a jeopardized zone which surrounds the entire area. In studies with baboons, the central necrotic area was not affected by recanalization of the vessel after several hours. However, muscle in the other zones which had undergone less severe damage during the ischemic period could be salvaged. A surprising finding was that lysing of the thrombus to produce a perfect arteriograph was insufficient to restore flow in the _._ majority of animals. (See Flameng, et al, J. Clin. Invest., Vol 75, p 84-90, 1985) Some further impediment to flow had developed in the area supplied by the vessel during the time that it was occluded. In further studies, it was demonstrated that

⁵ immediately after removing the obstruction to the vessel, the flow through the damaged tissue began at a high rate. However, within a short time the blood flow through the ischemic zone decreased and the tissue died. Consequently, the regional blood flow immediately after reperfusion is a poor predictor of the

¹⁰ salvage of myocardial tissue. If the blood flow through the damaged tissue remained near the normal levels, the s - uccess of tissue salvage was much greater. Hemorrhage occurred almost exclusively to the severely ischemic zone reflecting damage to the small blood vessels. The hemorrhage, however, remained

¹⁵ limited to the severely ischemic tissue and did not cause extension of the infarction or other serious complication. Therapies which could preserve the blood flow through the small blood vessels distal to the major area of thrombus -after reperfusion could be expected to markedly increase the salvage ⁰ of myocardial tissue.

Continuing therapy is needed even after restoration of blood flow and salvage of damaged tissue. The arteriosclerosis that caused the original heart attack remains. American and European researchers have found that

25 arteriosclerosis still narrows the arteries in 70-80% of patients whose clots were dissolved by thrombolytic therapy. Many physicians believe this obstruction must be opened for long term benefits. Balloon angioplasty is a procedure whereby a catheter with a small balloon is inserted into the narrowed artery. The

30 balloon is inflated, compresses the atherosclerotic plaque against the vesel wall and dilates the artery. The effectiveness of this procedure is limited by the effects of ischemia produced by the balloon, by embolization of atheromatous material which lodges in distal vessels and by an increased tendency for immediate

35 thrombosis in the area damaged by the balloon. The balloon

SUBSTITUT tears the tissue exposing underlying collagen and lipid substances which induce formation of thrombi. What is needed is a means of rendering the surface of the dilated vessel less thrombogenic, improving the blood flow through the distal tissue and breaking the embolized material into smaller pieces which are less likely to produce embolic damage.

Finally, lipid material on the atherosclerotic wall contributes to the bulk of the plaque which narrows the lumen of the artery and produces a highly thrombogenic surface. What is needed is a method of extracting lipids from atherosclerotic plaques which leaves their surfaces less thrombogenic and reduces their bulk.

Thus, a composition is needed that includes a clot- dissolving activity and a substance or substances that will prevent a clot from reforming after the initial clot has been cleared. Such a composition would thereby protect the patient from a damage caused by the reformation of a clot

Summary of the Invention In accordance with the present invention, a composition is provided that is effective in dissolving blood clots and reestablishing and maintaining blood flow through thrombosed coronary or other blood vessels. The clot- dissolving composition of the present invention comprises an enzyme, such as streptokinase, urokinase, tissue plasminogen activator or other proteolytic enzyme, and a surface active copolymer. The surface active copolymer can be an ethylene oxide-propylene oxide condensation product with the following general formula:

HO(C H O) (C H O) (C H O) H ^x 2 4 V 3 6 V 2 4 'b wherein a is an integer such that the hydrophobe represented by (C3H6O) has a molecular weight of about 950 to 4000, preferably about 1750 to 3500, and b is an integer such that the hydrophile portion represented by (C2H4O) constitutes approximately 50% to 90% by weight of the compound.

The clot-dissolving composition of the present invention is usually administered by intravenous injection into a patient

The present invention provides a composition that can be administered to patients who have a blood clot occluding a blood vessel. The combination of proteolytic enzyme and surface active copolymer according to the present invention increases blood flow around a clot, rapidly dissolves a clot, and provides further protection to the patient.by preventing a new clot from forming.

Because the clot-dissolving composition of the present invention stabilizes the patient to a greater extent than treatments in the prior art, the administration of more invasive procedures, such as balloon angioplasty, can be delayed thereby permitting selection of conditions for the invasive treatment that are most favorable to the patient

Accordingly it is an object of the present invention to provide a combination of proteolytic enzymes with a surface active copolymer to produce a synergistic action in dissolving blood clots.

It is another object of the present invention to provide a composition that will reduce the need for anticoagulation in cardiac therapy and thereby lessen the danger of hemorrhage.

It is another object of the present invention to provide a composition that accelerates the dissolution of clots by freeing aggregated platelets and blocking further platelets from aggregating to the clot

It is yet another object of the present invention to provide a composition that can reduce the dose of proteolytic enzyme required to dissolve a clot and thereby reducing the incidence of complications.

-v r- «T « « ! HEET It is a further object of the present invention to provide a composition that can promote blood flow through microvascuiar channels of tissue damaged by ischemia and reduce the amount of tissue which undergoes necrosis.

It is a further object of the present invention to provide a composition that will significantly reduce the risk of rethrombosis after treatment with clot-dissolving enzymes.

It is a further object of the present invention to provide a composition that will promote removal of lipids from atherosclerotic vessel walls and thereby lessen the incidence of rethrombosis.

It another object of the present invention to provide a composition that will reduce the risk of rethrombosis and thereby allow delay in administering balloon angioplasty or other invasive procedures for treatment of the compromised vessels.

It is a further object of the present invention to provide a composition to block the aggregation of platelets in blood vessels distal to the thrombosis and thereby limit extension of tissue damage.

It is yet another object of the present invention to provide a composition to improve blood flow through and around tissue with extensive necrosis of myocardial or other cells thereby retarding necrosis of myocardial tissue. It is a further object of the present invention to provide a combination of a thrombolytic enzyme, balloon angioplasty or other operative procedures and a surface active copolymer to produce an improved method of removing a thrombus and reducing obstructive conditions which promote rethrombosis.

These and other objects, features and advantages of the present invention will become apparent after a review of the following detailed description of the disclosed embodiment and the appended claims.

^■ ~ ^s ^~ Detailed Description of the Disclosed Embodiment

The present invention comprises a composition which provides a synergistic action in dissolving blood clots and reestablishing and maintaining blood flow through a thrombosed coronary vessel or other blood vessel. The clot- dissolving composition of the present invention is a solution containing an effective concentration of a proteolytic enzyme and an effective concentration of a surface active copolymer. The combination of the two components is surprisingly effective in dissolving blood clots that are blocking blood vessels. In addition, the clot-dissolving composition of the present invention is highly effective in preventing a blood clot from reforming and in maintaining blood flow through the blood vessel. The clot-dissolving composition of the present invention improves the flow of blood through narrow passages around clots and increases the delivery of the proteolytic enzyme to the clot. The present invention also speeds the rate of dissolution of the clot by the enzyme and increases the proportion of clots dissolved by promoting delivery of enzyme to clots which would not otherwise be exposed to sufficient enzyme for their dissolution. In addition, the clot-dissolving composition of the present invention reduces the dose of enzyme required for particular applications and thereby reduces the incidence of complications due to side effects caused by the enzymes.

The clot-dissolving composition of the present invention reduces the risk of immediate rethrombosis by accelerating the dissolution of clots and freeing aggregated platelets and blocking further platelets from aggregating to the clot or clot site. By reducing the risk of immediate rethrombosis, the clot-dissolving composition of the present invention will allow delay of balloon angioplasty or other invasive procedures for treatment of the compromised vessels which have become thrombosed. The delay will permit

SUDS^{τ ,} « 'T SHEET selection of conditions for invasive treatment most favorable to the patient

The terms "isotonic" or "isoosmotic" solution .are defined as solutions having the same osmotic pressure as blood. These terms are well know in the art Solutions which may be employed in the preparation of the clot-dissolving composition of the present invention include, but are not limited to, saline (a solution of sodium chloride, containing 8.5 to 9.5 grams of sodium chloride in 1000 cc of purified water), Ringer's solution, lactated Ringer's solution, Krebs-Ringer's solution, and various sugar solutions. All of these solutions are well known to one of ordinary skill in the art However, it is to be understood that the clot-dissolving composition of the present invention may be administered as a solution that is not isotonic.

The surface active copolymer is preferably an ethylene oxide-propylene oxide condensation product with the following general formula:

HO(C H O) (C H O) (C H O) H

^X 2 4 V 3 β V 2 4 'b wherein a is an integer such that the hydrophobe represented by (C3H6O) has a molecular weight of about 950 to 4000, preferably from 1750 to 3500, and b is an integer such that the hydrophile portion represented by (C2H4O) constitutes from about 50% to 90% by weight of the compound. These copolymers are sold under the general trademark of Pluronic® polyols and are available from the BASF Corporation (Parsippany, NJ).

The polymer blocks are formed by condensation of ethylene oxide and propylene oxide at elevated temperature and pressure in the presence of a basic catalyst. There is some statistical variation in the number of monomer units which combine to form a polymer chain in each copolymer. The molecular weights given are approximations of the average weight of copolymer molecule in each preparation. It is to be understood that the blocks of propylene oxide and ethylene oxide do not have to be pure. Small amounts of other materials can be admixed so long as the overall physical chemical properties are not substantially changed. A more detailed discussion of the preparation of these products is found in U.S. Patent No. 2,674,619.

Illustrative ethylene oxide-propylene oxide condensation products which may be employed in the preparation of the clot-dissolving composition of the present invention include, but are not limited to, the following copolymers:

1. A polyol with an average molecular weight of 4700 containing approximately 80% by weight ethylene oxide.

2. A polyol with an average molecular weight of 3400 containing approximately 50% by weight ethylene oxide.

3. A polyol with an average molecular weight of 7700 containing approximately 70% by weight ethylene oxide.

4. A polyol with an average molecular weight of 14,600 containing approximately 80% by weight ethylene oxide.

5. A polyol with an average molecular weight of 12,600 containing approximately 70% by weight ethylene oxide.

6. A polyol with an average molecular weight of 9500 containing approximately 90% by weight ethylene oxide. The preferred ethylene oxide-propylene oxide copolymer for use in the clot-dissolving composition of the present invention is a copolymer having the following formula

HO(C H O) (C H O) (C H O) H

^X 2 4 3 6 V 2 4 'b

SW S_. r τ v-*_t ^~ iJi i~ zr^~m wherein the molecular weight of the hydrophobe (C3H6O) is approximately 1750 and the total molecular weight of the compound is approximately 8400.

The concentration of copolymer in the clot- forming composition of the present invention can vary depending the total volume of solution needed in the particular circumstances. The total amount of block copolymer employed in the present invention will also vary depending on the size and type of thrombus or embolus, the particular copolymer employed, the particul.ar proteolytic enzyme employed, and the size and weight of the patient

The copolymer can be used over a wide range of concentrations with no adverse side effects. The copolymer is rapidly excreted intact; 90% of the copolymer administered is excreted within three hours. Because of the absence of toxicity and the rapid clearance from the body, the copolymer can be administered over a long period of time.

The the clot-dissolving composition of the present invention may be employed by admixing with blood in any standard manner. Preferably, however, the solutions are intravenously injected into the blood stream either as a bolus, slow drip or both. The solutions are generally admixed with the blood in a manner so as to maintain a substantially steady venous pressure. The proteolytic enzymes that can be used in the clot-dissolving composition of the present invention include, but are not limited to, streptokinase (available from Hoechst- Roussel under the trademark Streptase®), urokinase (available from Abbot Laboratories, North Chicago, II under the trademark Abbokinase®) and tissue plasminogen activator

(Genentech, South San Francisco, CA). Some of the proteolytic enzymes are only sparingly soluble in water and must therefore be emulsified with the surface active copolymer before administration to the patient

"U ^ πT' i^ S JΓPT Ide-ally, a bolus injection of the copolymer solution without the enzyme is administered before the present invention is administered. For example, a 3% solution of the copolymer in 5% isotonic dextrose is injected within a two minute period so that the blood concentration of copolymer is approximately 0.6 mg/ml. In addition, it can be advantageous to administer a solution of the copolymer by intravenous drip at a rate of about 25 mg/kg body weight/hour to obtain of blood concentration of the copolymer of approximately 0.6 mg ml for up to four days following the administration of the clot-dissolving composition of the present invention. This treatment will aid in preventing a clot from reforming.

Although the descriptions relate mostly to heart disease, it is to be understood that the clot-dissolving composition of the present invention is equally applicable to thrombosis in other parts of the body, such -as the brain, legs, lungs or gastrointestinal tract

The following specific examples will illustrate the invention as it applies in particular dissolving clots in blood vessels and to preventing clots from reforming. It will be appreciated that other examples will be apparent to those of ordinary skill in the art and that the invention is not limited to these specific illustrative examples.

Example I

For treating a patient weighing about 180 lbs with a pulmonary embolism, reconstitute 500 mg of urokinase (Abbokinase, Abbot Laboratories, North Chicago, 111) in 105 mis of sterile water. To the urokinase solution add 90 ml of an 0.9% sodium chloride solution containing 6 grams of an ethylene oxide-propylene oxide copolymer with the following general formula:

HO(C H OHC H O) (C H O) H ^x 2 4 3 β V 2 4 'b

• j o π J ^{~ ~}- ^~. Υ wherein the molecular weight of the hydrophobe (C3H6O) is approximately 1750 and the total molecular weight of the compound is approximately 8400. The urokinase and the copolymer are thoroughly mixed to form a homogeneous solution. The final volume of the solution is 195 ml.

Administer the clot-dissolving composition of the present invention by means of a constant infusion pump that is capable of delivering a total volume of 195 ml. A priming dose of the clot-dissolving composition of the present invention is administered at a rate of 90 ml/hour over a period of 10 minutes. This is followed by a continuous infusion of the present invention at a rate of 15 ml /hour for 12 hours. Since some of the present invention will remain in the tubing at the end of an infusion pump delivery cycle, the remaining solution is flushed out of the tube by administering a solution of 0.9% sodium chloride at a rate of 15 l/hour.

Example II

For treating a patient with a coronary artery thrombi, reconstitute 75 mg of urokinase (Abbokinase, Abbot Laboratories, North Chicago, 111) in 15.6 mis of sterile water. To the urokinase solution add 300 ml of 5% dextrose solution containing 15 grams of an ethylene oxide-propylene oxide copolymer with the following general formula:

HO(C H O) (C H O) (C H O) H

¹ 2 4 V 3 β V 2 4 'b wherein the molecular weight of the hydrophobe (C3H6O) is approximately 1750 and the total molecular weight of the compound is approximately 8400. The urokinase and the copolymer are thoroughly mixed to form a homogeneous solution. The solution is then diluted with 5% dextrose to a final volume of 500 ml.

The solution comprising the present invention is infused into the occluded artery at a rate of 4 ml per minute for - periods up to 2 hours. To determine response to the solution of the clot-dissolving composition of the present invention, periodic angiography is performed.

⁵ Example III

For treating a patient weighing about 180 lbs with a pulmonary embolism, reconstitute 500 mg of urokinase (Abbokinase, Abbot Laboratories, North Chicago, 111) in 105 ¹ ° mis of sterile water. To the urokinase solution add 90 ml of an

0.9% sodium chloride solution containing 6.0 grams of an ethylene oxide-propylene oxide copolymer with the following general formula:

HO(C H O) (C H O) (C H O) H

15 ^X 2 4 V 3 β V 2 4 'b wherein the molecular weight of the hydrophobe (C3H.5O) is approximately 1750 and the total molecular weight of the compound is approximately 8400. The urokinase and the copolymer are thoroughly mixed to form a homogeneous

2_Q solution. The solution is then diluted with 0.9% sodium chloride to a final volume of 195 ml.

Administer 137 ml of a 5% isotonic dextrose solution with 3% wt/vol ethylene oxide-propylene oxide copolymer dissolved therein to the patient over a 2 minute

₂₅ period. This gives a blood concentration of copolymer of approximately 0.6 mg/ml (assuming blood is 8% of body weight)

The clot-dissolving composition of the present invention is then immediately administered by means of a constant infusion pump that is capable of delivering a total

30 volume of 195 ml. A priming dose of the present invention is administered at a rate of 90 ml/hour over a period of 10 minutes. This is followed by a continuous infusion of the present invention at a rate of 15 ml /hour for 12 hours. Since some of the present invention will remain in the tubing at the end of an infusion pump delivery cycle, the remaining solution is flushed out of the tube by administering a solution of 0.9% sodium chloride containing 3.0% copolymer at a rate of 15 ml/hour.

After the clot is dissolved, a solution of the copolymer is administered by intravenous drip at a rate of about 25 mg/kg body weight hour to maintain a blood concentration of the copolymer of approximately 0.6 mg/ml. The administration of the copolymer solution is continued for four days following the administration of the clot-dissolving composition of the present invention.

It should be understood, of course, that the foregoing relates only to a preferred embodiment of the present invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.

Claims

1. A clot-dissolving composition comprising: a solution with an effective .amount of a proteolytic enzyme; and an effective amount of a surface active copolymer with the following formula:

HO(C H O) (C H O) (C H O) H 2 4 3 β V 2 4 b wherein a is an integer such that the hydrophobe represented by (C3H6O) has a molecular weight of about 950 to 4000, and b is an integer such that the hydrophile portion represented by

(C2H4O) constitutes about 50% to 90% by weight of the compound.

2. The clot-dissolving composition of Claim 1 wherein said proteolytic enzyme is tissue plasminogen activator.

3. The clot-dissolving composition of Claim 1 wherein said proteolytic enzyme is streptokinase.

4. The clot-dissolving composition of Claim 1 wherein said proteolytic enzyme is urokinase.

5. The clot-dissolving composition of Claim 1 wherein said surface active copolymer has the following formula:

HO(C H O) (C H O) (C H O) H

2 4 V 3 6 Λ 2 4 'b wherein the molecular weight of the hydrophobe (C3H6O) is approximately 1750 and the total molecular weight of the compound is approximately 8400.

6. The clot-dissolving composition of Claim 1 wherein said solution is an isotonic solution.

7. A method for dissolving clots in blood vessels comprising injecting into a body a clot dissolving composition, said composition comprising a solution with an effective amount of a proteolytic enzyme; and an effective amount of a surface active copolymer of the following formula:

HO(C H O) (C H O) (C H O) H 2 4 V 3 6 V 2 4 'b wherein a is an integer such that the hydrophobe represented by ((C3H6O) has a molecular weight of about 950 to 4000, preferably from 1750 to 4000, and b is an integer such that the hydrophile portion represented by (C2H4O) constitutes from about 50% to 90% by weight of the compound.

8. The method of Claim 7 wherein said proteolytic enzyme is tissue plasminogen activator.

9. The method of Claim 7 wherein said proteolytic enzyme is streptokinase.

10. The method of Claim 7 wherein said proteolytic enzyme is urokinase.

11. The clot-dissolving composition of Claim 7 wherein said surface active copolymer has the following formula:

HO(C H O) (C H O) (C H O) H

^X 2 4 V 3 6 V 2 4 'b wherein the molecular weight of the hydrophobe

(C3H6O) is approximately 1750 and the total molecular weight of the compound is approximately 8400.

12. The method of Claim 7 wherein said solution is isotonic.

13. The method of Claim 7 wherein said clot- dissolving composition is used in conjunction with balloon angioplasty.

-

14. A method for dissolving clots in blood vessels comprising the steps of: injecting into a body a solution of a surface active copolymer of the following formula:

HO(C H O) (C H O) (C H O) H

^V 2 4 V 3 6 V 2 4 'b wherein a is an integer such that the hydrophobe represented by ((C3H6O) has a molecular weight of from 950 to 4000,

₁₀ preferably from 1750 to 4000, and b is an integer such that the hydrophile portion represented by (C2H4O) constitutes from about 50% to 90% by weight of the compound, so that the blood concentration in the body is between approximately 0.4 mg/ml and 2 mg mi; 5 then injecting into the body a solution with an effective amount of a proteolytic enzyme and an effective amount of said surface active copolymer; and then injecting into the body an solution of the surface active copolymer at a rate so that the blood ₂₀ concentration of the copolymer is maintained between approximately 0.4 and 2 mg/ml of blood for between approximately 4 hours to 144 hours.

15. The method of Claim 14 wherein said proteolytic

25 enzyme is tissue plasminogen activator.

16. The method of Claim 14 wherein said proteolytic enzyme is streptokinase.

17. The method of Claim 14 wherein said proteolytic

30 enzyme is urokinase.

35

18. The clot-dissolving composition of Claim 14 wherein said surface active copolymer has the following formula:

HO(C H O) (C H 0) (C H O) H . ^x 2 4 V 3 β V 2 4 'b wherein the molecular weight of the hydrophobe (C3H6O) is approximately 1750 and the tot molecular weight of the compound is approximately 8400.

19. The method of Claim 14 wherein said solution is isotonic.