Prophylaxis or treatment of thromboses and inhibition of platelet aggregation in human blood

A method for the prophylaxis or treatment of thromboses in humans which comprises administering to a human in need thereof a therapeutically effective amount of a compound of the formula (II) ##STR1## or a pharmaceutically acceptable acid addition salt thereof, wherein R is 1-piperidyl or 1-pyrrolidyl. Compounds of the formula (II) are also useful for the inhibition of platelet aggregation in vitro or in vivo.

This invention relates to antithrombotic compositions and in particular to 
compositions comprising as active ingredient one or more compounds 
selected from a small class of benzisothiazolones. 
Arterial thrombosis develops initially from the aggregation of blood 
platelets within the artery. This aggregate may eventually lead to the 
formation of fibrin and the formation of a consolidated occlusive 
thrombus. The most widely used therapy for thrombosis is the use of 
anti-coagulant agents, which influence blood clotting, However, although 
effective in venous thrombosis, where the thrombus is formed mainly of 
fibrin, anti-coagulant therapy has no effect on platelet aggregation and 
has therefore limited effectiveness in arterial thrombosis. It is now 
accepted that anti-coagulant drugs have little to offer in the treatment 
of arterial thrombosis. 
With the increasing recognition of the primary role of platelets in 
thrombosis, attention had turned to drugs which are capable of inhibiting 
the aggregation of platelets. 
U.S. Pat. Specification No. 3,227,715 discloses a class of 
benzisothiazolones of the formula (I): 
##STR2## 
wherein A represents a lower alkylene of 2 to 4 carbon atoms, R.sub.1 and 
R.sub.2 are hydrogen or halogen, R.sub.3 and R.sub.4 represent hydrogen, 
lower alkyl, cycloalkyl, hydroxyalkyl of 2 to 4 carbon atoms or 
alkoxyalkyl of 2 to 4 carbon atoms, and R.sub.3 and R.sub.4 together with 
the nitrogen atom on which they are substituted stand for an unsubstituted 
or lower alkyl substituted heterocyclic ring having from 5 to 6 atoms in 
the ring; as being useful for the therapy of inflammatory processes. 
It has now been found that two of the benzisothiazolones disclosed in that 
patent have exceptional activity as inhibitors of platelet aggregation and 
are therefore useful for the prophylaxis and treatment of thrombosis. 
U.S. Pat. No. 3,227,715 does not suggest any antithrombotic activity for 
any of the compounds described therein.

Accordingly, the present invention provides a process for inhibiting 
platelet aggregation which comprises the addition to human blood in vitro 
or in vivo of a compound of formula (II), or a pharmaceutically acceptable 
acid addition salt thereof: 
##STR3## 
wherein R is 1-piperidyl or 1-pyrrolidyl. 
Suitable acid addition salts include inorganic salts such as sulphates, 
nitrate, phosphate, and borate, hydrohalides e.g., hydrochloride, 
hydrobromide, and hydroiodide, and organic acid addition salts such as 
acetate, oxalate, tartrate, maleate, citrate, succinate, benzoate, 
ascorbate, methanesulphonate, and p-toluenesulphonate. 
Preferred salts are the hydrochloride and hydrobromide. 
For in vivo applications this invention therefore provides a method of 
prophylaxis or treatment of thrombosis in humans which comprises 
administration to humans of a compound of formula (II) or a 
pharmaceutically acceptable acid addition salt thereof. 
The compounds are generally administered to the patient in the form of a 
composition formulated for administration by any route, although an oral 
administration is preferred. The compositions may be in the form of 
tablets, capsules, powders, granules, lozenges, or liquid preparations, 
such as oral or sterile parenteral solutions or suspensions. 
Tablets and capsules for oral administration may be in unit dose 
presentation form, and may contain conventional excipients such as binding 
agents, for example syrup, acacia, gelatin, sorbitol, tragacanth, or 
polyvinyl-pyrollidone; fillers, for example lactose, sugar, maize-starch, 
calcium phosphate, sorbitol, or glycine; tabletting lubricants for example 
magnesium stearate, talc, polyethylene glycol, or silica; disintegrants, 
for example potato starch; or acceptable wetting agents such as sodium 
lauryl sulphate. The tablets may be coated according to methods well known 
in normal pharmaceutical practice. Oral liquid preparations may be in the 
form of, for example, aqueous or oily suspensions, solutions, emulsions, 
syrups, or elixirs, or may be presented as a dry product for 
reconstitution with water or other suitable vehicle before use. Such 
liquid preparations may contain conventional additives such as suspending 
agents, for example sorbitol, syrup, methyl cellulose, glucose syrup, 
gelatin, hydroxyethylcellulose, carboxymethyl cellulose, aluminium 
stearate gel or hydrogenated edible fats, emulsifying agents, for example 
lecithin, sorbitan monooleate or acacia; non-aqueous vehicles (which may 
include edible oils) for example almond oil, fractionated coconut oil, 
oily esters, such as glycerine, propylene glycol, or ethyl alcohol; 
preservatives for example methyl or propyl p-hydroxybenzoate, or sorbic 
acid, and if desired conventional flavouring or colouring agents. The 
compound may also if desired be incorporated in a foodstuff, for example 
in the form of a biscuit. 
For parenteral administration, fluid unit dosage forms are prepared 
utilizing the compound and a sterile vehicle, water being preferred. The 
compound, depending on the vehicle and concentration used, can be either 
suspended or dissolved in the vehicle. In preparing solutions the compound 
can be dissolved in water for injection and filter sterilised before 
filling into suitable vials or ampoules and sealing. Advantageously, 
adjuvants such as local anesthetic, preservative and buffering agents can 
be dissolved in the vehicle. To enhance the stability, the composition can 
be frozen after filling into the vial and the water removed under vacuum. 
The dry lyophilized powder is then sealed in the vial and an accompanying 
vial of water for injection is supplied to reconstitute the liquid prior 
to use. Parenteral suspensions are prepared in substantially the same 
manner except the compound is suspended in the vehicle instead of being 
dissolved and sterilization cannot be accomplished by filtration. The 
compound can be sterilised by exposure to ethylene oxide before suspending 
in the sterile vehicle. Advantageously, a surfactant or wetting agent is 
included in the composition to facilitate uniform distribution of the 
compound. 
The compositions may contain from 0.1% to 99% by weight preferably from 
10-60% by weight, of the active material, depending on the method of 
administration. Where the compositions comprise dosage units, each unit 
will preferably contain from 1-500 mg, of the active ingredients. 
The dosage employed for adult treatment will of course depend on the dose 
response characteristics of the particular active ingredient, and also on 
the blood volume and condition of the patient, but will normally be in the 
range of 0.01 to 30 mg/kg/day depending on the route and frequency of 
administration. The preferred dose is 10 to 500 mg, orally 1 to 3 times a 
day for an adult human. The method of the invention is useful to prevent 
clot formation for example after surgery to prevent postoperative 
thrombosis; in geriatric patients to prevent transient cerebral ischemic 
attacks; and long-term prophylaxis following myocardial infarcts and 
strokes. 
The in vitro aspect of this invention comprises the addition of a compound 
(II) or a pharmaceutically acceptable salt thereof to whole blood or 
platelet rich concentrates and has applications in the storage of whole 
blood in blood banks, and whole blood to be used in heart-lung machines, 
or to be circulated through organs, e.g. heart and kidneys, which have 
been removed from a cadaver and prior to transplant. 
The dosage for such an addition is preferably from 0.01 to 5 micrograms/ml 
of whole blood. 
The compounds of formula (II) may be prepared as described in U.S. Pat. No. 
3,227,715. 
Biological Data 
Two compounds of formula (II) were tested for their ability to inhibit 
platelet aggregation in the guinea pig ex vivo as follows: 
METHOD 
Male guinea pig weighing 250-300 g were orally dosed 1% methyl cellulose (5 
ml/kg) in which the compound under test was suspended. Control animals 
were given methyl cellulose alone. Two hours later, each animal was killed 
and 4.5 ml blood drawn from the inferior vena cava into 0.5 ml trisodium 
citrate dihydrate. Platelet-rich-plasma (PRP) was prepared from each blood 
sample by centrifugation at 450 g for 5 min. The platelet concentration in 
each sample of PRP was adjusted with autologous platelet-poor-plasma 
measured turbidometrically (G.V.R. Born, 1962, Nature, 194, 927-929) at 
37.degree. using a Bryston aggregometer coupled to a pen-recorder. The 
concentration of collagen producing approximately 50% maximal aggregation 
and the concentration of ADP producing first-phase aggregation were 
compared in PRP samples from control and drug treated animals. Results are 
summarised in Table 1 together with some known anti-aggregant compounds 
for comparison. 
In Table 1 the dose ratio represents the ratio of the concentration of 
aggregating agent to cause aggregation in PRP from drug-treated animals to 
the concentration of aggregating agent to cause aggregation in PRP from 
control animals. 
The results are shown in Table 1. 
TABLE 1 
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Dose, P.O. 
Dose Ratio 
Compound tested 
(mmol/kg) Collagen ADP 
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2-[.beta.-(1-piperidyl)- 
ethyl]-1,2,-benz- 
isothiazol-3-one 
0.15 &gt;18.2* 8.3* 
0.08 6.7* 1.4* 
2-[.beta.-(1-pyrrolidinyl)- 
ethyl]-1,2-benz- 
isothiazol-3-one 
0.15 13.9* 1.9 
6.6* 1.3 
0.08 
7.5* 1.5* 
Sulfinpyrazone 
0.3 2.1* 1.2 
Aspirin 0.15 2.2* 1.3 
4-(4-morpholinyl)- 
0.15 3.0* 1.3 
2-(1-piperazinyl)- 
thieno [3,2-d]pyrim- 
idine dihydrochlor- 
ide. 
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