Use of a Thromboxane Receptor Antagonist in Pregnancy-Induced Hypertension and Related Conditions

This invention relates to a new medical use for [1R-[1.alpha.(Z),2.beta.,3.beta.,5.alpha.]]-(+)-7-[5-[[(1,1'-biphenyl)-4-y l]methoxy]-3-hydroxy-2-(1-piperidinyl)cyclopentyl]-4-heptenoic acid (hereinafter referred to as Compound A) or a physiologically acceptable salt, solvate or cyclodextrin complex thereof. In particular, it relates to the use of Compound A or a physiologically acceptable salt, solvate or cyclodextrin complex thereof in the therapy or prophylaxis of conditions associated with vasoconstriction and/or platelet aggregation in the uteroplacental circulation and/or excessive synthesis of thromboxane A.sub.2 in pregnant females.

Our UK Patent Specification 2097397 describes inter alia Compound A which is a potent thromboxane receptor blocker. We have stated therein that the compounds of the invention, including Compound A, inhibit thromboxane A.sub.2 and endoperoxide mediated aggregation of blood platelets and contraction of vascular smooth muscle and are thus of particular interest as anti-thrombotic agents.

We have now found that Compound A or a physiologically acceptable salt, solvate or cyclodextrin complex thereof is of use in the therapy or prophylaxis of conditions associated with vasoconstriction and/or platelet aggregation in the uteroplacental circulation and/or excessive synthesis of thromboxane A.sub.2 in pregnant females. Conditions which are covered by this pathophysiology include pregnancy-induced hypertension, preeclampsia, eclampsia and intrauterine growth retardation.

Thus according to one aspect of the present invention, we provide Compound A or a physiologically acceptable salt, solvate or cyclodextrin complex thereof for use in the manufacture of a medicament for the therapy or prophylaxis of conditions associated with vasoconstriction and/or platelet aggregation in the uteroplacental circulation and/or excessive synthesis of thromboxane A.sub.2 in a pregnant female subject.

It is preferable to employ Compound A or a physiologically acceptable salt solvate or cyclodextrin complex thereof in the form of a formulation. The present invention therefore also provides a composition for use in combatting conditions associated with vasoconstriction and/or platelet aggregation in the uteroplacental circulation and/or excessive synthesis of thromboxane A.sub.2 in pregnant females comprising Compound A or a physiologically acceptable salt, solvate or cyclodextrin complex thereof together, where desirable, with one or more carriers or excipients.

In a further aspect of the invention, we provide a method of treatment of a pregnant female subject for combatting conditions associated with vasoconstriction and/or platelet aggregation in the uteroplacental circulation and/or excessive synthesis of thromboxane A.sub.2 by therapy or prophylaxis which method comprises administering to the subject an effective amount of Compound A or a physiologically acceptable salt, solvate or cyclodextrin complex thereof.

It will, of course, be appreciated that the aforementioned pregnancy-induced hypertension preeclampsia and eclampsia are conditions which are not only deleterious to the female subject but which may also lead to growth retardation of the unborn foetus and even foetal loss. Contraction of umbilical vessels by thromboxane A.sub.2 may also lead to neonatal complications during parturition.

Compound A or a physiologically acceptable salt, solvate or cyclodextrin complex thereof may be used according to the present invention in various formulations for oral or parenteral administration. Suitable formulations for use according to the present invention are described in GB-B-2097397, GB-B-2127406 and UK Patent Application No. 8829793.

Suitable salts of Compound A include acid addition salts derived from inorganic and organic acids such as hydrochlorides, hyrobromides, sulphates, phosphates, maleates, tartrates, citrates, benzoates, 2-chlorobenzoates, p-toluenesulphonates, methanesulphonates salicylates, fumarates, lactates, hydroxynaphthalenecarboxylates (e.g. 1-hydroxy- or 3-hydroxy-2-naphthalenecarboxylates) or furoates or salts with suitable bases such as alkali metal (e.g. sodium and potassium), alkaline earth metal (e.g. calcium or magnesium), ammonium and substituted ammonium (e.g. dimethylammonium, triethylammonium, 2-hydroxyethyl dimethylammonium, piperazine, N,N-dimethylpiperazine, piperidine, ethylenediamine and choline) salts. A preferred salt of Compound A is the hydrochloride salt. Compound A and physiologically acceptable salts and solvates thereof are described in GB-B-2097397 and GB-B-2127406.

When Compound A is used according to the present invention in the form of a cyclodextrin complex, the complex conveniently contains a molar ratio of Compound A with cyclodextrin within the range 1:1 to 1:3.

The term "cyclodextrin" means herein an unsubstituted or substituted .alpha.-, .beta.- or .gamma.-cyclodextrin (or a hydrate thereof) or a mixture of two or three of them. Examples of suitable substituted cyclodextrins include sulphur-containing cyclodextrins, nitrogen-containing cyclodextrins, alkylated (e.g. methylated) cyclodextrins such as mono-, di- or trimethylated derivatives of a cyclodextrin (e.g. of .beta.-cyclodextrin) and hydroxyalkyl (e.g. hydroxypropyl) cyclodextrins such as hydroxypropyl .beta.-cyclodextrin and acylated derivatives thereof. Hydroxyalkyl (e.g. hydroxypropyl) cyclodextrins such as hydroxypropyl .beta.-cyclodextrin have been found to be particularly suitable.

A particularly preferred cyclodextrin complex of Compound A is the .beta.-cyclodextrin complex in which the molar ratio of Compound A with .beta.-cyclodextrin is about 1:1.

Cyclodextrin complexes of Compound A and pharmaceutical formulations containing them are described in our co-pending British Patent Application No. 8829793. The cyclodextrin complexes may be prepared by mixing Compound A or the hydrochloride salt thereof with the cyclodextrin in a suitable solvent such as water or an organic solvent which is miscible with water (e.g. an alcohol such as methanol). The reaction may take place at any temperature in the range from 0.degree. to 80.degree. C. However, the mixture is preferably kept at around room temperature and the desired complex obtained by concentrating the mixture under reduced pressure or by allowing the mixture to cool. The mixing ratio or organic solvent with water may be suitably varied according to the solubilities of the starting materials and products. Preferably 1 to 4 moles of cyclodextrin are used for each mole of Compound A or its hydrochloride salt.

Pharmaceutical formulations containing a cyclodextrin complex of Compound A may be prepared in conventional manner by mixing the complex with one or more pharmaceutical carriers or excipients, for example, according to the general methods described in GB-B-2097397 and GB-B-2127406.

When Compound A or a physiologically acceptable salt, solvate or cyclodextrin complex is to he administered as an aqueous formulation for, in particular, parenteral (e.g. intravenous) use, the composition may be prepared accordIng to the general methods described in GB-B-2097397 and GB-B-2127406. Alternatively, the aqueous compositions may be prepared by mixing Compound A or, more preferably, the hydrochloride salt thereof with cyclodextrin together with one or more pharmaceutical carriers or excipients for example as described in the Examples hereinafter. Preferably Compound A or its hydrochloride salt are dissolved in water and the remaining constituents are added thereto.

The molar ratio of Compound A or its hydrochloride salt with cyclodextrin in the aqueous composition is conveniently within the range 1:1 to 1:3.

Preferably the aqueous formulation comprises the hydrochloride salt of Compound A and .beta.-cyclodextrin (or a hydrate thereof) at about physiological pH wherein the formulation contains at least about 1.2 moles of .beta.-cyclodextrin (e.g. 1.2 to 2 moles) for every one mole of the hydrochloride salt of Compound A. Preferably the molar ratio will be about 1:1.4 (e.g. 1:1.28).

The precise dose of Compound A or a physiologically acceptable salt, solvate or cyclodextrin complex thereof to be administered will, of course, depend on a number of factors including, for example, the age and weight of the patient and the route of administration. An effective oral dose, however, in the case of Compound A or a physiologically acceptable salt solvate or cyclodextrin complex thereof is likely to be in the range from 0.05 to 20 mg/kg body weight of patient per day, preferably in the range from 0.05 to 5 mg/kg per day.

The concentration of Compound A or the hydrochloride salt thereof in the aforementioned aqueous formulations suitable for parenteral administration, in particular for administration by injection (e.g. Intravenously), is conveniently within the range 0.1-10 mg/ml, e.g. 0.1-5 mg/ml, expressed as the free base. Preferably, the concentration is 2 mg/ml expressed as the free base when the aqueous formulation is administered by intravenous injection. If desired, a higher concentration may be used and the solution may be diluted prior to use with, for example, an isotonic saline solution or dextrose or mannitol solution. Conveniently, solutions suitable for injection are presented in an appropriate dose volume (e.g. 1-100 ml). Dilutions suitable for continuous infusion may have a concentration of Compound A or its hydrochloride salt of 0.01-0.2 mg/ml expressed as the free base. The solution for continuous infusion may be presented in this form, for example in packs of 50-100 ml, or may be presented in more concentrated forms for subsequent dilution before use with, for example, an isotonic saline solution or dextrose or mannitol solution. Alternatively small volumes of a more concentrated solution (e.g. 0.1-5 mg/ml) may be utilised for continuous infusion conveniently administered at a rate of 0.5 to 9.9 ml/h.

The aforementioned aqueous formulations may also be adapted for oral administration (e.g. as a capsule, syrup or solution). The preparation of suitable formulations for oral use will be within the knowledge of persons skilled in the art and may generally follow the procedures described in GB-B-2097397, GB-B-2127406 and in the Examples hereinafter.

The following examples are provIded in illustration of the present invention and should not be construed in any way as constituting a limitation thereof.

The hydrochloride salt of Compound A was dissolved in 35 ml water suitable for injection and the .beta.-cyclodextrin was added. This solution was titrated to pH 7 with 0.02 M sodium hydroxide solution and then adjusted to volume with water suitable for injection.

The solution may then be sterilised by filtration and filled into vials or ampoules.

The hydrochloride salt of Compound A was dissolved in approximately 25 ml water suitable for injection. The .beta.-cyclodextrin was dissolved therein and the resulting solution was titrated to pH 6 with 0.02 M sodium hydroxide solution and the phosphate buffer added. The sodium chloride was added to the solution and the pH adjusted to pH 7 with sodium hydroxide. The solution was made up to volume with water suitable for injection. A sample of this solution was filled into a glass vial which was sealed with a rubber plug and metal overseal. This was then autoclaved.

The hydrochloride salt of Compound A was dissolved in approximately 25 ml water suitable for injection and the hydroxypropyl-.beta.-cyclodextrin was added. The mannitol was then added and the solution titrated to pH 6 with 0.02 M sodium hydroxide solution. The phosphate buffer solution was added and the solution adjusted to volume with water suitable for injection. The solution was then filtered and filled into glass vials which were sealed with rubber plugs and metal overseals. These were then autoclaved.

The hydrochloride salt of Compound A was dissolved in approximately 25 ml water suitable for injection. The .beta.-cyclodextrin and mannitol were dissolved therein and the solution titrated to pH 6 with 0.02 M sodium hydroxide solution. The sodium acid phosphate and anhydrous disodium phosphate were dissolved in water suitable for injection. This solution was added to the bulk solution which was made up to volume with water suitable for injection. The solution was filtered and filled into glass ampoules which were sealed and then autoclaved.

The hydrochloride salt of Compound A was dissolved in approximately 25 ml water suitable for injection and the cyclodextrin(s) was (were) added. The mannitol was then added and the solution titrated to pH 6 with 0.02 M sodium hydroxide solution. The phosphate buffer solution was added and the solution was adjusted to volume with water suitable for injection. The solution was then filtered and filled into glass vials which were sealed with rubber plugs and metal overseals.

Dissolve the sucrose in a minimum quantity of water. Add the hydrochloride salt of Compound A and then the .beta.-cyclodextrin with stirring; adjust the pH to 4.5 with citric acid. With continued stirring add a solution of the hydroxybenzoate and lastly the flavour. Adjust almost to volume with water and stir. Check the pH and adjust to 4.5 with citric acid if necessary. Make up to volume with water.