The invention relates to certain novel compounds, to pharmaceutical compositions containing such compounds, to a process for the preparation of such compounds and to the use of such compounds as active therapeutic agents, particularly in the treatment of atrial or ventricular cardiac arrhythmias.

Anti-arrhythmic agents are classified according to their electrophysiological effects on the cardiac cell (Vaugham-Williams, 1970, 1989) : class I agents block the fast sodium current, class II agents are beta-adrenergic blockers, class III agents block potassium currents, class IV agents block the calcium current, and class V agents are specific sinus node inhibitors.

A majority of ventricular and atrial arrhythmias are related to reentrant circuit. The prolongation of myocardial refractoriness within or surrounding such a reentrant circuit is a potential mechanism for the management of cardiac arrhythmias. Because class III antiarrhythmic agents block cardiac potassium currents, they prolong the repolarisation process and increase refractoriness. Consequently class HI agents represent the most specific class to treat reentrant arrhythmias. However, due to their mechanism of action, i.e. a concentration dependent increase in the cardiac action potential duration, higher doses of class III antiarrhythmic agents may trigger arrhythmias. Such arrhythmias, called Torsade de Pointe generally represents the main adverse effect for all pure class III compound currently in development.

European Patent Application, Publication Number 0233762 discloses a class of compounds of formula A

fc

R— N-A-N-B — R ₄

(A) wherein: R and R4 are independently phenyl optionally substituted by one, two or three of halogen, trifluoromethyl, C1-.4 alkoxy, C1-.4 alkyl, cyano, hydroxy, nitro, NR5 Rg or O2SNR5 R6 wherein R5 and Rg are independently hydrogen or C -.5 alkyl or together are C3.6 polymethylene, or disubstituted at adjacent carbon atoms by Cι_2 alkylenedioxy and optionally further substituted by one of the above groups; R2' is selected from (CH2) _Z CN where z is zero or an integer from 1 to 4, C\_ γι alkyl,

C3.7 cycloalkyl, C3.7 cycloalkyl Cj_4 alkyl, phenyl Cj_4 alkyl, pyridyl, pyridyl C\_ 4 alkyl, COR7 ^* , COCJ^COR ', SO2 7', CO2R7', CONHR ₇ ' and CSNHR7', where

R7' is selected from C3.12 alkyl, C3.7 cycloalkyl, C3.7 cycloalkyl C1-.4 alkyl, phenyl and phenyl C _j _4 alkyl, any alkyl moiety in R7 optionally substituted by hydroxy or C1-.4 alkanoyloxy, any pyridyl or phenyl moiety in R2 optionally substituted as defined for Rj ^' and R4' and any cycloalkyl moiety in R2 optionally substituted by one or two C1-.4 alkyl groups; R3 ^* is hydrogen or C 1.4 alkyl; A ^* represents C2.5 alkylene; and B represents Cj_4 alkylene.

These compounds are stated to possess cardiovascular activity, in particular calcium antagonistic activity which indicates that they are of potential use in the treatment of angina pectoris. In WO 93/23024 certain of the compounds of formula (A) are disclosed as having both class III and class IN antiarrhythmic activity.

It has now been discovered that certain heterocyclic amides, structurally distinct from the compounds of formula (A), induce a self-limiting increase of the cardiac action potential duration, related to a dual blockade of cardiac potassium and calcium channels. Consequently, they have an improved pharmacological profile over pure class III anti-arrhythmic agents, in particular they are indicated to have low proarrhytmic potential and to restore the contractile function of the ischaemic myocardium. Accordingly, the invention relates to a compound of formula (I):

(I) or a salt thereof, or a solvate thereof, wherein

A and B each independently represents a C1-.4 n-alkylene group wherein each carbon is optionally substituted by a Cj.g alkyl group;

D represents CO, SO2, NH-CO or CH2CO; T represents hydrogen, alkyl, alkene or cycloalkyl; and

Het represents substituted or unsubstituted: furanyl, pyranyl, thienyl, thiazolyl, imidazolyl, triazolyl or the benzo fused equivalents of furanyl, pyranyl, thienyl, thiazolyl, imidazolyl or triazolyl, indolyl, oxoindolyl, indenyl, isoindenyl, indazolyl, indolizinyl, or benzofurazanyl; optional substituents for the moiety Het include 1 to 5 substituents selected from the list consisting of nitro, halogen, alkylsulfonamido, alkylamido, IH-imidazolyl, alkyl and haloalkyl;

R _j , R2 and R3 each independently represent H, alkyl, OH or alkoxy or, if attached to adjacent carbon atoms, any two of R\ , R2 or R3 together with the carbon atoms to which they are attached may form a fused heterocyclic ring of five to six atoms wherein one, two or three of the said atoms are oxygen or nitrogen; Z represents a bond, CH2, (CH2)2 or X-CH2-CH2 wherein X represents O or S; and Ar represents substituted or unsubstituted aryl, wherein the optional substituents are the above defined Rj, R2 and R3

Suitably, A represents (CH2)3-

Suitably, B represents CΗ2CH2. Suitably, D represents CO, SO2, NH-CO or CH2CO.

Suitably, T represents CH3

Suitably, one or two of Rj, R2 and R3 represents alkoxy, for example methoxy, the remaining member(s) being H.

Suitably, Het includes furanyl and thienyl. Suitably Het is sustituted by 1,2 or 3 substituents, favourably 1.

An example of a substitutent for Het is a nitro group.

Examples of Het are 4-nitro-2-thiophenyl, 5-nitro-2-furanyl and 5- benzofurazanyl.

As used herein, unless indicated to the contrary, the term "alkyl" includes straight or branched chain alkyl groups having from 1 to 12, favourably 1 to 6, carbon atoms and shall include such alkyl groups when forming part of other groups such as alkoxy or arylalkyl groups.

As used herein, unless indicated to the contrary, the term "alkenyl" includes straight or branched chain alkylene groups having from 2 to 12, favourably 2 to 6, carbon atoms and one or more double bonds.

As used herein, unless indicated to the contrary, the term "aryl" includes phenyl and naphthyl, preferably phenyl.

As used herein, unless indicated to the contrary, the term "cycloalkyl" includes C3-8 preferably C4.6 cycloalkyl groups. As used herein "halogen" includes fluorine, chlorine or bromine.

As used herein, the term "cardiac arrhythmia" relates to any variation from the normal rhythm of heart beat, including, without limitation, sinus arrhythmia, premature heartbeat, heartblock, fibrillation, flutter, tachycardia, paroxysmal tachycardia and premature ventricular contractions. The compounds of formula (I) may possess chiral carbon atoms and therefore may exist in more than one stereoisomeric form. The invention extends to any of the stereoisometric forms, including enantiomers of the compounds of formula (I) and to mixtures thereof, including racemates. The different stereoisomeric forms may be

separated or resolved one from the other by conventional methods or any given isomer may be obtained by conventional stereospecific or asymmetric syntheses.

The pharmaceutically acceptable salts of the compounds of formula (I) include acid addition salts with pharmaceutically acceptable mineral acids such as hydrochloric, hydrobromic, boric, phosphoric, sulphuric and pharmaceutically acceptable organic acids such as acetic, tartaric, maleic, citric, succinic, benzoic, ascorbic, methanesulphonic, a-keto-glutaric, a-glycerophosphoric, and glucose- 1- phosphoric acids. Preferably the acid addition salt is a hydrochloride.

Pharmaceutically acceptable salts also include quaternary salts. Examples of quaternary salts include such compounds quatemised by compounds such as R ^z -T-** wherein R ^z is C\.- alkyl, phenyl-Cj_6 alkyl or C5.7 cycloalkyl, and T is a radical corresponding to an anion of an acid. Suitable examples of R ^z include methyl, ethyl and n- and iso- propyl; and benzyl and phenethyl. Suitably T*-- includes halide such as chloride, bromide and iodide. Pharmaceutically acceptable salts also include pharmaceutically acceptable N- oxides, and the invention extends to these.

The compounds of the formula (I) and their salts may also form solvates, especially pharmaceutically acceptable solvates, such as hydrates, and the invention extends to these, and especially to the pharmaceutically acceptable solvates. The salts of the compounds of the formula (I) which are not pharmaceutically acceptable may be useful as intermediates in the preparation of pharmceutically acceptable salts of compounds of formula (I) or the compounds of the formula (I) themselves, and as such form an aspect of the present invention.

A compound of formula (I) or a salt thereof, or a solvate thereof, may be prepared by reacting a compound of formula (II):

(ID wherein A, B, T, Z, R\, R2, R3 and Ar are as defined in relation to formula (I) with a compound of formula (III);

Het-X (III) wherein Het is as defined in relation to formula (I) and:

(a) for compounds of formula (I) wherein D is CO or SO2, X represents CO.Lj or

SO2. 1 respectively wherein L] is a leaving group or atom such as a halogen atom; or

(b) for compounds of formula (I) wherein D is NH.CO, X is N=C=O; and thereafter, if required, carrying out one or more of the following optional steps: (i) converting a compound of formula (I) into a further compound of formula (I); (ii) preparing a salt of the compound of formula (I) and/or a solvate thereof. The reaction conditions for the reaction between compounds of formulae (II) and (III) are conventional conditions appropriate to the nature of the reagent used, generally however the reaction may be carried out in an inert solvent, such as methylene chloride, at any suitable temperature providing a convenient rate of formation of the desired product, generally at an ambient to elevated temperature, conveniently at the reflux temperature of the solvent and preferably in the presence of a base such as triethylamine.

Compounds of formula (II) are known compounds or they may be obtained by procedures analogous to those used to prepare known compounds, for example as described in EP 0 233 762. The compounds of formulae (III) are known commercially available compounds or they may be obtained by procedures analogous to those used to prepare known compounds, for example compounds of formula (III) wherein L* represents CO.X may be prepared according to methods described in Organic Synthesis, Coll. Vol. I page 394 or Organic Synthesis, Coll. Vol. Ill, page 29, compounds of formula (III) wherein L ^*** represents SO2.X may be prepared according to methods described in Organic Synthesis, Coll. Vol. VIII, page 104 and for compounds of formula (III) wherein h\ represents N=C=O according to methods described in Organic Synthesis, Coll. Vol. Ill, page 846.

It will be appreciated that in any of the abovementioned reactions any reactive group in the substrate molecule may be protected, according to conventional chemical practice.

Suitable protecting groups in any of the abovementioned reactions are those used conventionally in the art. The methods of formation and removal of such protecting groups are those conventional methods appropriate to the molecule being protected.

As mentioned above the compounds of the invention are indicated as having useful therapeutic properties: The present invention accordingly provides a compound of formula (I), or a pharmaceutically acceptable salt thereof and/or a pharmaceutically acceptable solvate thereof, for use as an active therapeutic substance. More particularly, the present invention provides a compound of formula (I), or a pharmaceutically acceptable salt thereof and/or a pharmaceutically acceptable solvate thereof, for use in the treatment of and/or prophylaxis of arrhythmia, especially cardiac arrhythmia such as ventricular arrhythmia, and also ischeamic rhythm disorders.

A compound of formula (I), or a pharmaceutically acceptable salt thereof and/or a pharmaceutically acceptable solvate thereof, may be administered ≤i ≤g or, preferably, as a pharmaceutical composition also comprising a pharmaceutically acceptable carrier. Accordingly, the present invention also provides a pharmaceutical composition comprising a compound of the general formula (I), or a pharmaceutically acceptable salt thereof, or a pharmaceutically acceptable solvate thereof, and a pharmaceutically acceptable carrier thereof.

A compound of formula (I) or a pharmaceutically acceptable salt thereof and/or a pharmaceutically acceptable solvate thereof is normally administered in unit dosage form.

An amount effective to treat the disorder hereinbefore described depends upon such factors as the efficacy of a compound of formula (I) , the particular nature of the pharmaceutically acceptable salt or pharmaceutically acceptable solvate chosen, the nature and severity of the disorders being treated and the weight of the mammal.

However, a unit dose will normally contain 1 to 50 mg for example 2 to 15 mg, of the compound of the invention.

Unit doses will normally be administered once or more than once a day, for example 2, 3, 4, 5 or 6 times a day, more usually 2 to 4 times a day, such that the total daily dose is normally in the range, for a 70 kg adult of 1 to 300 mg, more usually 4 to 100 mg, for example 10 to 60mg, that is in the range of approximately 0.02 to 5 mg/kg/day, more usually 0.1 to 2 mg kg/day, for example 0.1 to 0.5 mg/kg/day.

In such treatment, the compound may be administered by any suitable route, e.g. by the oral, parenteral or topical routes. For such use, the compound will normally be employed in the form of a pharmaceutical composition in association with a human or veterinary pharmaceutical carrier, diluent and/or excipient, although the exact form of the composition will naturally depend on the mode of administration.

Compositions are prepared by admixture and are suitably adapted for oral, parenteral or topical administration, and as such may be in the form of tablets, capsules, oral liquid preparations, powders, granules, lozenges, pastilles, reconstitutable powders, injectable and infusable solutions or suspensions, suppositories and transdermal devices. Orally administrable compositions are preferred, in particular shaped oral compositions, since they are more convenient for general use.

Tablets and capsules for oral administration are usually presented in a unit dose, and contain conventional excipients such as binding agents, fillers, diluents, tabletting agents, lubricants, disintegrants, colourants, flavourings, and wetting agents. The tablets may be coated according to well known methods in the art.

Suitable fillers for use include cellulose, mannitol, lactose and other similar agents. Suitable disintegrants include starch, polyvinylpyrrolidone and starch derivatives such as sodium starch glycollate. Suitable lubricants include, for example, magnesium stearate. Suitable pharmaceutically acceptable wetting agents include sodium lauryl sulphate.

Solid oral compositions may be prepared by conventional methods of blending, filling, tabletting or the like. Repeated blending operations may be used to distribute the active agent throughout those compositions employing large quantities of fillers. Such operations are, of course, conventional in the art. 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, 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 esters of glycerine, propylene glycol, or ethyl alcohol; preservatives, for example methyl or propyl β-hydroxybenzoate or sorbic acid, and if desired conventional flavouring or colouring agents.

For parenteral administration, fluid unit dose forms are prepared containing a compound of the present invention and a sterile vehicle. The compound, depending on the vehicle and the concentration, can be either suspended or dissolved. Parenteral solutions are normally prepared by dissolving the active compound in a vehicle and filter sterilising before filling into a suitable vial or ampoule and sealing.

Advantageously, adjuvants such as a local anaesthetic, preservatives and buffering agents are also dissolved in the vehicle. To enhance the stability, the composition can be frozen after filling into the vial and the water removed under vacuum.

Parenteral suspensions are prepared in substantially the same manner except that the active compound is suspended in the vehicle instead of being dissolved and 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 active compound.

For topical administration, the composition may be in the form of a transdermal ointment or patch for systemic delivery of the compound and may be prepared in a conventional manner, for example, as described in the standard textbooks such as 'Dermatological Formulations' - B.W. Barry (Drugs and the Pharmaceutical Sciences - Dekker) or Harrys Cosmeticology (Leonard Hill Books).

In addition such compositions may contain further active agents such as anti-hypertensive agents and diuretics.

As is common practice, the compositions will usually be accompanied by written or printed directions for use in the medical treatment concerned. As used herein the term 'pharmaceutically acceptable' embraces compounds, compositions and ingredients for both human and veterinary use: for example the term 'pharmaceutically acceptable salt' embraces a veterinarily acceptable salt.

The present invention further provides a method for the treatment and/or prophylaxis of arrhythmia, especially cardiac arrhythmia such as ventricular arrhythmia, and also ischemic rhythm disorders in a human or non-human mammal which comprises administering an effective, non-toxic, amount of a compound of the general formula (I), or a pharmaceutically acceptable salt thereof and/or a pharmaceutically acceptable solvate thereof to a human or non-human mammal in need thereof. Conveniently, the active ingredient may be administered as a pharmaceutical composition hereinbefore defined, and this forms a particular aspect of the present invention.

In the treatment and/or prophylaxis of arrhythmia and/or ischeamic arrhythmia disorders the compound of the general formula (I), or a pharmaceutically acceptable salt thereof and/or a pharmaceutically acceptable solvate thereof, may be taken in doses, such as those described above.

Similar dosage regimens are suitable for the treatment and/or prophylaxis of non-human mammals.

In a further aspect the present invention provides the use of a compound of formula (I), or a pharmaceutically acceptable salt thereof and/or a pharmaceutically acceptable solvate thereof, for the manufacture of a medicament for the treatment of arrhythmia, especially cardiac arrhythmia such as ventricular arrhythmia, and also ischemic rhythm disorders.

The following Examples illustrate the invention but do not limit it in any way.

Example 1

N-(3,4-Dimethoxyphenyl)-N-[3-[[2-(3,4-dimethoxyphenyl]eth yI] methylamino]propyl]-4-nitro-2-thiophenecarboxamide, hydrochloride.

To an ice cooled stirred solution of 2.8 g (7.5 mmol) of N,-(3,4-dimethoxyphenyl)- N'-[3-[[2-(3,4-dimethoxyphenyl]ethyl]-N'-methyl-l,3-propaned iamine and 0.75 g (7.5 mmol) of triethylamine in 40 ml of chloroform, 1.43 g (7.5 mmol) of 4-nitro-2- thiophenecarboxylic acid chloride were added dropwise over a period of 15 min..The mixture was left to come to room temperature and stirred for additional 4 hours. Then 100 ml of methylene chloride were added and the organic phase was washed three times with 100 ml water, dried over MgSO4 and concentrated in vacuo. Purification by flash chromatography on silica gel using 98:2 ethyl acetate : methanol followed by concentration and trituration in ether yielded of a yellow crystalline product.The product was then dissolved in 20ml ethyl acetate, 0.25ml of 5.5N anhydrous HC1 in ether was added.The mixture was concentrated in vacuo to afford 0.7g (23%) of a yellow solid. mp.: 100°C

!H NMR(DMSO-dό) d = 1.97 (m,2H,CH ₂ ); 2.79 (s,3H,NCH ₃ ); 2.93 (m,2H,CH ₂ ); 3.24 (m,4H,CH ₂ x2); 3.72-3.85 (m,14H,OCH ₃ x4 + CH ₂ NCO); 6.76-7.15 (m,7H,Ar); 8.81 (d,lH,Ar); 10.30(s,lH,exch.D ₂ O,NH+)ppm.

Example 2

N-(3,4-DimethoxyphenyI)-N-[3-[[2-(3,4-dimethoxyphenyl)eth yl]methyl- amino]propyl]-5-nitro-2-furancarboxamide, hydrochloride

Starting from 800 mg (2.0 mmol) of N-(3,4-dimethoxyphenyl)-N'-[2-(3,4- dimethoxyphenyl) ethyl] -N'-methyl-l,3-propanediamine and 434 mg (2.5 mmol) of 5-nitro-2-furancarbonyl chloride and following the method described in example 1, yielded 560 mg (50%) of the title compound as a yellow solid. The compound was purified as free base by two successive chromatographies on silica gel using methylene chloride:methanol first 98:2 then 99:1. m.p = 98-ll l°C iH NMR(DMSO-ΛJ) δ = 1.82-2.04 (m,2H,CH ₂ ); 2.80 (d,3H,J=4.0Hz,CH3NH); 2.85-3.00 (m,2H,CH ₂ ); 3.08-3.43 (m,4H,CH ₂ x2); 3.73 (ls,6H,CH ₃ Ox2); 3.75 and 3.79 (2s,6H,CH ₃ Ox2); 3.75-3.93 (m,2H,CH ₂ ); 5.82 (d,lH,J=3.6Hz,Ar); 6.78-7.13 (m,6H,Ar); 7.51 (d,lH,J=3.6Hz,Ar); 10.19 (s,lH,exchD ₂ O,NH+) ppm.

Example 3

N-(3,4-Dimethoxyphenyl)-N-[3-[[2-(3,4- dimethoxyphenyl)ethyl]methylamino]propyl]-5-benzofurazancarb oxamide hydrochloride hydrate.

Starting from 680 mg (1.75 mmol) of N-3,4-dimethoxyphenyl)-N'-[2-(3,4- dimethoxyphenyl)ethyl]-N'-methyl-l,3-propanediamine and 306 mg (1.67 mmol) of

5-benzofurazancarbonyl chloride in 20 ml of methylene chloride and following the procedure described in example 1, yielded 414 mg (43%) of the title compound as a yellow solid.

The compound was purified as free base by flash chromatography on silica gel using methylene chloride: methanol 95:5 m.p. =90°C

!H NMR(DMSO-d6) δ = 1.99(m, 2H, CH ₂ ); 2.8 l(s, 3H, NCH ₃ ); 2.95(m, 2H, CH ₂ ); 3.27(m, 4H, CH ₂ x2); 3.64, 3.66, 3.73 and 3.75(4s, 12H, OCH ₃ x4); 3.94(m, 2H,

CH ₂ NCO); 6.75-6.93(m, 5H, Ar); 7.06(s, IH, Ar); 7.54(d, IH, Ar); 7.92-8.02(m, 2H,

Ar); 10.36(broad band, IH, exch. D2O, NH ⁺ )ppm.

Pharmacological data

Methodology

Guinea pigs (300-350 g) were anesthetized by intravenous injection of sodium pentobarbital (60 mg/kg). After thoracotomy the heart was rapidly excised and placed in oxygenated Tyrode solution. Papillary muscles were removed from the right ventricle. Preparations were then fixed to the silastic base of a 5 ml organ bath and superfused with oxygenated Tyrode solution maintained at 37 ± 1 °C. The modified Tyrode solution (pH 7.35) contained the following (mM) : NaCl 125, KCl 4.0, MgC-20.5, CaCl ₂ 1.8, NaHCO ₃ 24, NaH ₂ PO40.9 and glucose 5.5. The solution was equilibrated with a gas mixture of 95% O2 - 5% CO2. After a stabilisation period (at least lh), transmembrane action potentials were recorded with conventional microelectrodes (10 MOh ) connected to a high input impedance amplifier (BIOLOGIC VF 180). External stimuli were delivered to the preparation with bipolar platinum electrodes placed at one end of the muscle. The pulse duration was 1 ms and the amplitude was twice threshold. The basic cycle length was 1000 ms (PULSAR 6i stimulator). The signals were monitored on a storage oscilloscope (GOULD 1602) and simultaneously recorded on a digital tape recorder (BIOLOGIC DTR 1200) for further analysis. Measurements were made on resting membrane potential (RMP), action potential amplitude (APA) and action potential durations at 30, 50, and 90% repolarization (APD30, APD50 and APD90 respectively). Recordings were made after 30 min of equilibration for each concentration. Only recordings in which the same impalement was maintained throughout the entire experiment were used for analysis.

Concentration (μM)

Effect of compound of example 1 on action potential duration (APD) recorded in guinea-pig papillary muscle. Action potential duration was mesured at 30% (APD30), 50%(APD50) and 90% (APD90) of repolarization.

Concentration (μM)

Effect of compound of example 2 on action potential duration (APD) recorded in guinea-pig papillary muscle. Action potential duration was mesured at 30% (APD30), 50%(APD50) and 90% (APD90) of repolarization.