IE65721B1

IE65721B1 - Thrombolytically acting combined preparation

Info

Publication number: IE65721B1
Application number: IE465490A
Authority: IE
Inventors: Peter Dr Donner; Wolf-Dieter Dr Schleuning
Original assignee: Schering Ag
Priority date: 1989-12-22
Filing date: 1990-12-21
Publication date: 1995-11-15
Also published as: ES2057365T3; NO922454D0; WO1991009618A1; KR927003092A; HU9202087D0; EP0436261A1; DK0436261T3; EP0436261B1; BR9007940A; NO922454L; IE904654A1; HUT65411A; ZA9010367B; AU647763B2; ATE89741T1; DE59001558D1; AU6969691A; CA2033140A1; DE3943241A1

Abstract

The invention concerns a preparation with thrombolytic action, consisting of a combination of the non-fibrin-binding form of the thrombolytic agent v-PA and a fibrin-binding plasminogen activator.

Description

The present invention relates to novel agents having a thrombolytic action.

Thromboses occur as a result of the formation of a blood clot in blood vessels. A differentiation is made between venous thromboses, including pulmonary embolisms, and arterial thromboses, including acute cardiac infarct.

Pulmonary embolism and cardiac infarct are life-threatening conditions that require immediate medical intervention.

Apart from various invasive methods, in recent years enzymatic thrombolysis using plasminogen activators has been used as a form of therapy for arterial and venous thromboses. These substances, called thrombolytic agents, convert plasminogen, the inactive proenzyme of the fibrinolysis system in the blood, into the active proteolytic enzyme plasmin. Plasmin in turn dissolves the fibrous material fibrin, a basic component of a blood clot, which results in the reopening of the closed vessels and reinstatement of the blood flow. Plasmin, however, is a relatively non-specific protease, that is to say, once formed in the blood it destroys proteolytically components in the blood that are indispensable for an intact haemostasis (e.g. fibrinogen), and as a result may induce serious risks of bleeding.

The first-generation thrombolytic agents, streptokinase and urokinase, are substances that, once injected into the circulation, systemically convert plasminogen into plasmin and induce a systemic proteolysis. Thrombolysis therapies using those substances are therefore frequently accompanied by complications of bleeding. The thendeveloped fibrin-specific thrombolysis, in which recombinant plasminogen activators of the tissue type, abbreviated to t-PA, are used, was intended to overcome that dilemma. t-PA has only a low affinity for plasminogen in the blood circulation. In the presence of the fibrous material fibrin, however, with which it reacts by way of specific binding sites, there is a manifold 5 increase in that affinity, resulting in the formation of plasmin at the thrombus surface. It was possible for that concept to be verified in vitro and in animal experiment investigations; clinical studies, however, showed that large amounts of t-PA are necessary to bring 10 about the rapid dissolution of a coronary thrombosis.

If, however, high doses of t-PA are infused in such a manner then, similarly to the case with streptokinase and urokinase, the result is a systemic proteolysis associated with a relative risk of bleeding. Nowadays, tPA is considered to have a relative specificity for fibrin; the reason for that is founded in an important property of t-PA: that molecule is a protease, which under favourable conditions (high enzyme concentration, long exposure time, high substrate concentration, optimum pH and ionic medium) converts plasminogen into plasmin even in the absence of fibrin. All those conditions are met by the current standard clinical therapy with t-PA.

In the search for more specific plasminogen activators that meet the criterium of fibrin specificity, a novel, natural, fibrinolytically active substance called v-Pa (also called DSPA, Desmodus Salivary Plasminogen Activator) (EP-A-0 383 417) was discovered.

The invention relates to a thrombolytical ly active agent consisting of one of the non-fibrin-binding low-molec30 ular-weight forms, DSPA B or DSPA /, with molecular * weights of 46,000 and 42,000 (EP-A-0 383 417), and a fibrin-binding plasminogen activator. t There come into consideration as fibrin-binding plasminogen activators, for example: prourokinase (scu-Pa), t-PA and the high-molecular-weight form of the thrombolytic agent v-PA (DSPA al and DSPA a2, EP-A-0 383 417) having a molecular weight of 52,000.

The thrombolytic active substance v-PA (DSPA) is a novel, naturally occurring plasminogen activator that dissolves blood clots in the human body and is therefore suitable for treating, for example, cardiac infarct (EP-A-0 383 417).

It is found in low concentrations in the saliva of all species of bats of the Desmodus spec, genus and is secreted by the cells of the salivary glands of that genus of animals. Bats of the genus Desmodus spec, include all types of bat of the American continent. The Desmodus genus of Middle America and Mexico has proved especially good.

The invention furthermore relates to medicaments based on the above-mentioned combinations of non-fibrin-binding and f ibrin-binding plasminogen activators and conventional excipients and carriers.

The fibrinolytic activity of v-PA (DSPA) is further strengthened by means of the above-described combination of fibrin-binding and non-fibrin-binding plasminogen activators compared with conventional plasminogen activators. The daily dose administered parenterally to humans is from 5 to 500 mg, preferably from 20 to 200 mg.

EXAMPLE Fibrinogen and plasminogen are caused to clot in a Petri dish by means of the addition of thrombin. There are stamped into the resulting layer of fibrin holes of 3 mm diameter into which v-PA is then introduced in various concentrations and combinations. Both molecular forms of the fibrin-specific plasminogen activator v-PA produce concentration-dependent lysed aureoles after incubation in a humid chamber at 37'c.

If the two different molecular forms of v-PA are then combined, the result is lysed aureoles that are distinctly larger than the lysed aureoles that would have been expected on the basis of a simple additive effect. By means of the combination of high- and low-molecularweight v-PA a synergistic effect on fibrinolysis is thus achieved in vitro. That synergistic effect is attributable to the fact that the low-molecular-weight form of v-PAf which lacks the finger domains, can as a result of its non-fibrin-binding property diffuse better into a fibrin clot, and thus disaggregate the clot as a result of its fibrinolytic activity. The high-molecular-weight fibrin-binding v-PA variant can then completely lyse the already disaggregated fibrin clot.

Assessments of the results of that fibrin plate test have shown that a clearly synergistic effect is achieved as a result of the combination of the two forms of v-PA (Berenbaum, M.C. Clin. exp. Immunol., 28 f 1-18, 1977).

Claims

CLAIMS:

1. Thrombolytically active agent consisting of a combination of one of the non-fibrin-binding forms of the thrombolytic agent v-PA, DSPA B or DSPA /, with molecular 5 weights of 46,000 and 42,000, and a fibrin-binding plasminogen activator, and also conventional excipients and carriers.

2. Thrombolytically active agent according to claim 1, characterised in that prourokinase (scu-PA), t-PA or the 10 high-molecular-weight forms of the thrombolytic agent v-PA (DSPA al and DSPA a2) having a molecular weight of 52,000 comprise the fibrin-binding plasminogen activator.

3. · A thrombolytically active agent substantially as hereinbefore described with reference to the Examples.