GB2192132A - Pharmaceutical calcium antagonists containing dihydropyridine derivatives - Google Patents

Abstract

Pharmaceutical compositions for treatment of ischaemic vascular diseases comprise a haemorheologically active calcium antagonist of formula I, <IMAGE> and a pharmaceutically acceptable carrier, wherein R1 is H, C1-6 alkyl, alkenyl or alkinyl, cycloalkyl, phenylalkyl or phenylalkenyl, wherein the phenyl ring may be substituted by halogen, alkyl, hydroxy or alkoxy; R3 and R4 are as for R1, or may be alkoxy, alkenoxy or alkinoxy; R2 and R5 are each hydrogen or alkyl, R6 is H, halogen, alkyl, alkoxy,alkylsulphonyl or alkylthio, and X is oxygen or sulphur.

Description

SPECIFICATION Novel use of dihydropyridines Sandoz European Patent Specification No.000150 discloses and claims compounds offormula I,

wherein R1 is hydrogen, alkyl of 1 to 6 carbon atoms, alkenyl or alkinyl of 3 to 6 carbon atoms, cycloalkyl of 3 to 7 carbon atoms, cycloalkylalkyl of 4to 8 carbon atoms, phenylalkyl of 7 to 9 carbon atoms or phenylalkenyl of 9 to 12 carbon atoms, the phenyl ring being unsubstituted or mono-, di- ortrisubstituted independently by halogen, hydroxy or alkyl or alkoxy of 1 to 4 carbon atoms, R2 and R5 independently, are hydrogen or alkyl of 1 to 6 carbon atoms, R3 and R4, independently, are alkyl of 1 to 6 carbon atoms, alkenyl or alkyl of to 6 carbon atoms, cycloalkyl of 3to 7 carbon atoms, cycloalkylalkyl of 4to 8 carbon atoms, alkoxy of 1 to 6 carbon atoms, hydroxyalkoxyof 2 to 6 carbon atoms, alkoxyalkoxy of 3 to 6 carton atoms, hydroxyalkoxyalkoxy of 4to 8 carbon atoms, alkenyloxy oralkinyloxy of 3 to 6 carbon atoms, cycioalkyloxy of 3 to 7 carbon atoms or cycloalkylalkoxy of4 to 8 carbon atoms, Re is hydrogen, halogen, alkyl or alkoxy or alkylthio or alkylsulfonyl, each of 1 to 4 carbon atoms,trifluoromethyl, nitro or hydroxy, and Xisoxygenorsulphur.

The compounds are indicated to have pharmacological activity. In particular, they are indicated to lead to a dilation ofthe coronary vessels and to possess a favourable effect against Angina pectoris and therefore to be indicated for use in the treatment of coronary insufficiency.

Additionally the compounds are indicated to have antihypertensive activity and to be therefore indicated for use as antihypertensive agents.

Further, Sandoz Belgian Patent No.886259 discloses and claimsforthese compounds offormula I: - cerebral blood flow increasing activity, making the compounds indicated for use in the treatment of cerebrovascular insufficiency, including cerebrovascular accidents, cerebral vasospasms and acute cer ebrovascularinsufficiencysuch as stroke and - calcium-antagonistic activity, making the compounds indicated for use as spasmolytic agents, forthe treatment of spasms in smooth muscles, e.g. cholic.

Further, Sandoz Belgian Patent Specification No.894272 discloses and claims forthe compounds offormula I, an arteriovenous shunted blood flow reducing activity in the carotid area and a selective serotonininduced vasoconstriction inhibiting activity of the basiliar artery, making the compounds indicated for use for the treatment ofvascular headaches, including migraine and cluster headaches.

Further, Sandoz Belgian Patent Specification No.897821 discloses and claims for the compounds offor- mula Ian antiasthmatic activity making the compounds indicated for use for the treatment of asthma, especi- ally of exercise induced asthma.

The present invention relates to the use of a compound offormula I or its pharmaceutically acceptable acid addition salts forthe preparation of medicaments having haemorheological activity.

It has been found that compounds offormula I surprisingly exhibit a pronounced inhibitory effect own calcium-mediated loss of erythrocyte deformabil ity.

Particularly interesting compounds offormula I according to the invention are 4-(2,1 ,3-benzoxadiazol-4- yI)1 ,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylic acid diethyl ester, hereinafter referred to as KP 1,4 (2,1 ,3-benzoxadiazol-4-yl) 1 ,4dihydro-2,6-dimethyl-3-methoxycarbonyI-pyridine-5-carboxyIic acid isopropyl ester, hereinafter referred to as KP 2, or 4-(2,1 ,3-benzothiadiazol-4-yl )-2,6-dimethyl-1 ,4-dihydropyridin-3,5- dicarboxylic acid dimethylester, hereinafter referred to as KP 3, especially compound Kip 3.

This activity is shown by the following test results: A) Calcium-mediated red blood cell rigidification andfilterability The calcium ionophoreA23187, i.e.

is capable of selectively transporting divalentcations, especially calcium, across the red cell membrane.

A231 87 together with calcium ions are used as mediators to render normal erythrocytes rigid. The extentof shear stress activated hemolysis occurring as a result of cells passing through pores smaller than their mean cellular diameter at a given pressure provides an index of deformability. The percentage of hemolysis or inhibition thereof in the presence of rheoactive substances provides an index of deformability. Flunarizine and pentoxifylline are used as standards for purposes of comparison. Flunarizine inhibits calcium-induced erythrocyte shape changes as well as reduces the uptake of 45Ca. This is indirect evidence thatflunarizine normalizes or inhibits loss of deformability of calcium-stressed erythrocytes.

The dose response relationship between inhibition of hemolysis and flunarizine and KP 3 concentration is shown in the attached Figure 1. The substances are incubated at the indicated concentrations at37" C in the presence of 2.5 mM calcium ions and 5 x 10-7 M A231 87 for one hour. The effects of KP 3 are approximately 11 times greater than those offlunarizine (Table I).

The attached Figure 1 showsthe relationship between the logrithm. of concentrations of KP 3 (leftcurve) and flunarizine (right curve) (in the abszissa) and the percentage of inhibition of hemolysis (in the ordinate).

The cells are incubated for 1 hour in the presence of 5 x 10-7 M A231 87 and 2.5 mM calcium ions afterwhich they are filtered as described above. The results are normalized to 100 percent with respect to the degree of hemolysis observed in the absence of the substance under investigation. The points represent the mean +/ S.D. of at least3 separate experiments.

Table 1 KP3 Flunarizine -log IC50 against 2.5 mM 4.75 3.87 cacium ions (human red cells) -log IC50 isthe negative logarithm ofthat concentration of the antagonist (e.g. KP 3) which inhibits the responsetotheagonist,i.e. calcium ions, by 50%.

Pentoxifylline was found to be inactive up to the highest concentration tested, namely, 0.6 mM.

B) Ektacytometric studies The effects of KP 3 and flunarizine on calcium ion-stressed human erythrocytes were also tested using the ektacvtomerictechnique described originally by Bessis and Mohandas [Blood Cells 1 (1975) 307-31 31. The instrument used in these studies was builtbyTechnicon Instruments (Tarrytown, N.Y.) and employs an automatic image analysis system [W. Groneretal., Clin. Chem. 26 980)1435]. The ektacytometerconsists of a rotational viscometer and a helium-neon laser.A beam of light is passed through the blood cell suspension contained in the gap between the two cylinders of the viscometer. Underthe action of physiologically re- levantfluid shear stresses normal arythrocytes undergo deformation and align themselves parallel to the direction of flow. In the absence offlowthe diffraction pattern produced is circular and is transformed into an elliptical pattern underthe action of applied fluid shear stresses. The intensity of light is measured atfour points, two in the horizontal plane and two in the vertical plane. Aso-called "deformability index" (DI) can be derived which is a measure of the ellipticity of a uniformly deforming cell population.The Dl may be measured either as a continuous function of shear stress or at a constant shear stress as a continuing function of suspending medium conductivity (continuous gradientektacytometry, M.R. Clark et al., Blood [1983] 899910).

For comparison purposes the maximum deformability index reached, i.e. Dl(maX), is used to comparethe deformability of different samples and the influence of KP 3 and flunarizine on calcium-stressed erythrocytes.

Forthermore, osmotic deformability profiles are obtained for calcium-stressed human erythrocytes and the effects of KP 3 and flunarizine are compared.

The attached Figure 2 shows the influence of KP 3 on the ektacytometric deformability index (DI) of calcium ion-loaded erythrocytes (in the ordinate). The DI was recorded continuously as a function of shear stress and plotted as a percentage ofthe maximum DI obtained fora normal control population of human erythrocytes.

As can be seen, the calcium-mediated reduction in DI is inhibited by KP3.

The attached Figure 2 shows the improvement of erythrocyte deformability by KP 3. The maximum ektacyt ometric deformability index (DI)(max) of normal cells is 100%. Human erythrocytes are incubated for 1 hour in the presence of 2.5 mM calcium ions and 2.5 x 10-7 ionophore A231 87 and the respective logarithm of con centrations of KP 3 (in the abszissa). Dl(maX) is measured at a shear stress of 255 dynes x cm-2. The points representthe mean +/-S.E.M. of 2 to 6 experiments.

These osmotic gradient ektacytometry data on calcium-loaded red cells suggest both reduced membrane flexibility as well as a concomitant reduction in surface area to volume ratio and cell water content. At low concentrations KP 3 primarily inhibits the loss of membrane flexibility whereas at higher concentrations both the loss of cell waterand membraneflexibility are normalized. The osmolarity at which the deformability reaches a hypotonic minimum is essentially unaffected by calcium stress or treatment with KP 3. As the osmolarity at which the hypotonic minimum occurs is linearly correlated with 50% hemolysis in a con ventional osmoticfragility assay the data suggest that neither the calcium stress nor KP 3 affect red cell osmotic fragility.

In the above tests similar results were obtained when KP 3 was replaced by KP 1 and KP 2.

Itthus appearsthatcompounds of formula I inhibitthe calcium-mediated rigidification of erythrocytes ata concentration offrom about 1 0- M to about 1 10-4M M as demonstrated in both the red cell filtration model and by ektacytometry. As shown above compounds of formula I are approximately 1 Otimes moreefficacious than flunarizine. Pentoxifylline is inactive.

C) Further, although no pathophysiological animal models existfortesting rheoactive substances, evidence that KP 1, KP 2 and KP 3 also act on red cell deformability in vivo is provided by its effects on the postischaemic CNS recovery after complete, biphasic ischaemia induced in the isolated perfused rat head [P.

Gygax et al., Brain andlleartlnfarctll, Springer-Verlag Berlin Heidelberg (1979) 293-305]. It has been fond that if red cells which have prolonged micropore filtration times are utilized in the perfusion medium the EEG activity rapidly declines and becomes isoelectric.

The above test results show that compounds offormula I have beneficial therapeutic effects in subjects suffering from ischaemicvascular diseases when these are associated with calcium-mediated loss of erythrocyte deformability, particularly peripheral and cerebral vascular diseases.

The compounds offormula I are therefore indicated for use as a hemotheological agents, in particularto improve microcirculation, especially in the prophylaxis and treatment of ischaemic vascular diseases when these are associated with a loss of erythrocyte defo rmability, e.g.:: - in peripheral vascular ischaemia, e.g. in intermittent claudication; - in Angina pectoris; - in retinal microcirculatory disturbances, e.g. reversible visual field deficits, e.g. reversible vasospastic scotoma; - as an adjunt in the treatment of myocardial infarction; - in cerebral vascular ischaemia, including stroke and transient ischaemic attack; - in sickel cell anemia; - as an adjunct in the treatment of diabetes mellitus; - as an adjunct in the treatment of senile dementia; - as an erythtocyte-protective agent, e.g. after implantation of artificial heartvalves;; - in Morbus Raynaud and - in Atherosclerosis obliterans when these conditions are associated with a calcium-mediated loss of erythrocyte deformability, Preferred are the uses in peripheral and cerebral vascular ischaemia, especially intermittant claudication, in Morbus Raynaud, Atheroclerosis obliterans and sickel cell anemia.

The compounds offormula I may thus be administered in similar mannerto known standards, for example asflunarizine and/orpentoxifylline.

The suitable daily dosage will depend on a number of factors such as its relative potency of activity. It is indicated that the compounds of formula I may be administered at similar or lower dosages than conventionally employed forfiunarizine and pentoxifylline.

For the above-mentioned hemorheological usesthe dosage will of course vary depending on the mode of administration and therapy desired. However, in genqral a daily dosage of compounds offormula I offrom about 0.25 mg/kg to about 5 mglkg animal body weight is satisfactory, conveniently given in divided doses 2 to 4times a day or as part of q sustained release form. In the case of man the total daily dosage of compounds offormula I is in the range of from about 10 mg to about 300 mg, preferably about 50 mg to about 300 mg, and dosage forms suitable for oral ornon-oral administration comprise from about 2.5 mg to about 300 mg ofthe compounds admixed with a solid or liquid pharmacqutical carrier of diluent.

Conveniently compounds of formula I are administered in the form or a pharmaceutical composition comprising the compounds offormula I in free base form or in pharmaceutically acceptable acid addition salt form, in association with a pharmaceutical carrier or diluent. Such compositions are known and may be formulated in conventional manner so as to be, for example, a solution or a tablet A convenient salt may be the hydrochloride.

The present invention also provides a pharmaceutipal composition for the above use comprising compounds offormula I in association with a pharmaceutcal carrier or diluent. Such compositions may be in the form of, for examplq, a solution or a tablet. Oral administration is preferred.

Claims (7)

1. Use of a compound offormula I

wherein R1 is hydrogen, alkyl of 1 to 6 carbon atoms, alkenyl or alkyl of 3to 6 carbon atoms, cycloalkyl of 3to7 carbon atoms, cycloalkylalkyl of 4to 8 carbon atoms, phenylalkyl of 7 to 9 carbon atoms or phenylalkenyl of9 to 12 carbon atoms, the phenyl ring being unsubstituted or mono-, di- ortrisubstituted independently by halogen, hydroxy or alkyl or alkoxy of 1 to 4 carbon atoms, R2 and R5 independently, are hydrogen or alkyl of 1 to 6 carbon atoms, R3 and R4, independently, are alkyl of 1 to 6 carbon atoms, alkenyl or alkinyl of 3to 6 carbon atoms,cycloalkyl of 3 to 7 carbon atoms, cycloalkylalkyl of 4to 8 carbon atoms, alkoxy of 1 to 6 carbon atoms, hydroxyalkoxy of 2 to 6 carbon atoms, alkoxyalkoxy of3 to 6 carbon atoms, hydroxyalkoxyalkoxy of 4to 8 carbon atoms, alkenyloxy or alkinyloxy of 3to 6 carbon atoms, cycloalkyloxy of 3 to 7 carbon atoms or cycloalkylalkoxy of4 to 8 carbon atoms, R5 is hydrogen, halogen, alkyl or alkoxy or alkylthio or alkylsulfonyl, each of 1 to 4 carbon atoms,trifluoromethyl, nitro or hydroxy, and Xis oxygen or sulphur or a pharmaceutically acceptable acid addition salt of a basic compound of the above formula for the prepara- tion of medicaments having haemorheological activity.

2. Use according to claim 1 characterized in that the medicaments having haemorheological activity can be used in the prophylaxis or treatment of ischaemicvascular diseases associated with calcium-mediated loss of erythrocyte deformability.

3. Use according to claim 1 or 2 wherein the compound offormula I is selected from 4-(2,1 3- benzoxadiazol-4-yl)-1,4-dihydro-2,6-dimethyl-pyridine-3,5-dicarboxylic acid diethyl ester, 4-(2,1 ,3- benzoxadiazol-4-yI)-1 ,4-dihydro-2,6-dimethyl-3-methoxycarbonyl-pyridine-5-carboxylic acid isopropyl ester of 4-(2,1 ,3-benzothiadiazol-4-yl)-2,6-dimethyl-1 ,4-dihydro-pyridine-3,5-dicarboxylic acid dimethylester or a pharmaceutically acceptable acid addition salt of a basic compound thereof.

4. Use according to claim 1,2 or 3 wherein the daily dose of a compound offormula I or a pharmaceutically acceptable acid additon salt of a basic compound offormula I is from 1 Oto 300 mg.

5. Use according to any preceding claim wherein the compound offormula I or a pharmaceuticallyac ceptable saltof a basic compound offormula I is administered in unit dosage form containing frnm 2.5 to 300 mg of compound offormula I or a pharmaceutically acceptable salt of a basic compound offormula

6. Use according to claim 1 or 2 substantially as herein before described with reference to any one ofthe examples.

7. A pharmaceutical composition useful forthe prophyllactic use against or treatment of ischaemic vascular diseases containing compounds offormula I according to claim 1 or a pharmaceutically acceptable salt of a basic compound offormula I in association with a pharmaceutical carrier or diluent.