The present invention relates to therapeutically acti- ve substituted urea compounds, a method of preparing the same, pharmaceutical compositions comprising the compounds, and a method of treating therewith.

EP158265 and EP 235878 describes benzamides and substi- tuted urea compounds having an azabicyclic side chain and possesing 5-HT antagonist activity.

A class of novel, structurally distinct compounds with higher 5HT ₃ ~antagonist activity has now been discover¬ ed. These compounds have 5-HT^-receptor antagonist ac¬ tivity, antiemetic activity and/or gastric motility enhancing activity. Furthermore, these compounds are useful for the treatment of cough and bronchoconstric- tions.

The present invention provides a compound of formula I, or a pharmaceutically acceptable salt thereof:

wherein ^is cS-* ³ . - &

3 wherein R is an oxadiazol, substituted with C._„-al- yl, C ₂ _g-alkenyl, C ₂ _ ₈ alkynyl, C ₃ _„ cycloalkyl, ben¬ zyl, phenyl, C _^ g-alkoxy, C, _β -alkylthio, amino or al¬ kylamino;

R is -H or lower alkyl;

X is 0 or S;

and R is a group of formula II, III or VI

where n is 2 or 3, p is 1 or 2, q is 1 to 3, r is 1-3 and R 4 and R5 are H, C ₁ „ alkyl or C ₃ _ _β cycloalkyl; and N-methylated ammonium derivatives thereof. Some of the compounds of the formula (I) have chiral or prochi- ral centres and are thus capable of existing in a num¬ ber of stereoisomeric forms, including enantiomers. The invention extends to each of these stereoisomeric forms (including enantiomers), and to mixtures thereof (including racemates). The different stereoisomeric forms may be separated one from the other by the usual

methods. This invention furthermore extends to endo- and exo-configurations of compounds of formula (I).

The invention also provides a process for the prepara¬ tion of a compound of formula (I), or a pharmaceutical¬ ly acceptable salt thereof, which process comprises

reacting a compound of formula V:

with a compound of formula VI

J-R ¹ VI

where R 1, R2, R3 are as defined above; g R is COQ, where Q is a group displaceable by a nucleo- phile, R 9 and R10 together =C=0, or R9 is hydrogen

(when R 10 is hydrogen); and when R9 is COQ, or R9-N-R10

2 is N=C=0, J is NH or NHR , or a reactive derivative thereof or when R is hydrogen, J is a group contain¬ ing an activated carbonyl group capable of forming a CO-N-linkage with the compound of formula (V) or

Pharmaceutically acceptable salts of the compounds of this invention may be formed conventionally. The acid addition salts may be formed for example by reaction of the base compound of formula (I) with a pharmaceuti¬ cally acceptable organic or inorganic acid.

Compounds of formula (I), which antagonise the effect of 5-HT at 5-HT ₃ receptors, are useful in the treatment

of conditions such as psychotic disorders (e.g. schizo¬ phrenia and mania); anxiety; panic disorders with and without agoraphobia, agoraphobia alone and obsessive compulsive disorders; and nausea and vomiting, particu- larly that associated with cancer chemotherapy and ra¬ diotherapy. Compounds of formula (I) are also useful in the treatment of gastric stasis; symptoms of gastro¬ intestinal dysfunction such as occur with dyspepsia, peptic ulcer, reflux oesophagitis, flatulence and irri- table bowel syndrome; migraine; and pain. Compounds of formula (I) may also be used in the treatment of depen¬ dency on drugs and substances of abuse, depression, and dementia and other cognitive disorders.

Unlike existing drug treatments for certain of the above conditions, the compounds of the invention, be¬ cause of their high selectivity for 5-HT ₃ receptors, would not be expected to produce undesirable side effects. Thus, for example, neuroleptic drugs may cause extrapyramidal effects, such as tardive dyskinesia, and benzodiazepines may cause dependence.

According to another aspect, the invention provides a method of treatment of a human or animal subject suf- fering from a psychotic disorder such as schizophrenia or mania; or from anxiety; nausea or vomiting, particu¬ larly that associated with cancer chemotherapy and ra¬ diotherapy; gastric stasis; symptoms of gastrointesti¬ nal dysfunction such as dyspepsia, reflux oesophagitis, peptic ulcer, flatulence and irritable bowel syndrome; migraine; pain; dependency on drugs or substances of abuse; depression; or dementia and other cognitive dis¬ orders which comprises administering an effective amount of a compound of formula (I) or a physiologically accept- able salt or solvate thereof. Furthermore, compounds of formula (I) may also be used in the treatment of cough and bronchoconstrictions.

Compounds of formula (I) were tested for their affini¬ ty to the 5HT--receptor using the following method:

5-HT3 Receptor Binding to N1E-115 Neuroblastoma Cells

The binding of 3H-quipazine to N1E-115 neuroblastoma cells in-vitro was determined by a modification of the method of Hoyer and Neijt (Hoyer, D. and Neijt, H.C., 1988, Molecular Pharmacology, 33: 303-309). Mouse neu- roblastoma cells of the clone N1E-115 were grown in

Dulbecco's modified Eagle's medium with HEPES and So¬ dium bicarbonate (pH=7.6) as previously described. The

7 cells were grown to a density of 8-15 X 10 cells per bottle and harvested by vigorous shaking. Harvested cells were homogenized in Tris buffer (20mM, pH=7.5) containing 154 mM NaCl using a Brinkmann Polytron. The homogenate was centrifuged at 900 X g and the superna¬ tant was used directly in the binding assay. The super¬ natant was diluted at a concentration of 2 X 10 cells per ml in Tris buffer. Binding assays consisted of 50 μL 3H-Quipazine (1 nM final concentration), 250 μL mem¬ brane suspension, and 200 μL drug or buffer. Nonspeci¬ fic binding was determined by the addition of 10 μM MDL 72222. Tubes were incubated at 37°C for 60 minutes, followed by filtration through GFB filters under vacu¬ um. The filters were then washed with ice-cold Tris buffer. Non-specific binding represented approximately 12% of total binding.

RESULTS

Using the binding of 3H-Quipazine to 5-HT3 recognition sites located on N1E-115 neuroblastoma cells, a highly specific binding assay for the 5-HT3 receptor has been developed. The specificity for the 5-HT3 receptor site is shown by the inability of 8-OH-DPAT (a specific li- gand for the 5-HT1A receptor), and ketanserin (a speci-

fie ligand for the 5-HT2 receptor) to displace 3H-Qui- pazine. Furthermore, ligands known to specifically bind to the 5-HT3 receptor (quipazine, ICS 205-930, zacopri- de and MDL 72222) are potent displacers of 3H-Quipazi- ne binding.

The compounds of the present invention gave the follow¬ ing results (Table 1):

Inhibition of 5-HT-induced contractions in isolated Guinea Pig ileum

Compounds of formula (I) were tested for their 5HT ₃ - antagonist activity using the following method:

Principle

5-HT produces contractions of the guinea pig ileum via 2 different receptors. 1) direct contractions via 5-HT ₂ receptors on the muscle, 2) indirect contractions via 5-HT ₃ receptors on intrinsic gut neurones, producing acetylcholine release. By administering 5-HT to lengths of ileum in the presence of methysergide (to block 5- HT ₂ receptors) you can assay 5-HT ₃ receptor activity.

Method

Guinea pigs were killed by means of cervical disloca- tion the terminal 15 cm of ileum removed, and 1.5 - 2.0 cm lengths prepared and mounted in 10 ml organ baths containing calcium deficient tyrodes of the fol¬ lowing composition (mM) NaCl (136.9); KCl (2.68); CaCl ₂ (0.9); MgCl ₂ (1.05); NaC0 ₃ (11.9); NaH ₂ P0 ₄ (0.42); glu- cose (5.55) and containing methysergide (10 ^~ M) main¬ tained at 37°C and gassed with 95% 0 ₂ and 5% C0 ₂ « The mechanical activity of the muscle was measured by a HSE 351 isometric transducer connected via a HSE bridge amplifier to a potentio etric pen recorder. Resting tension was 1 g and the tissue left to equilibrate for 1 hour.

First a dose response curve is obtained to acetylcho- line on each tissue. Then one tissue is incubated for 20 min with tyrode and three with tyrode plus the pu¬ tative 5-HT ₃ antagonist. After this incubation dose re¬ sponse curves to 5-HT are constructed to 5-HT in all 4 tissues (one control 3 + test drug). Contact time for 5-HT 30 sec.

Results

The maximum response to acetylcholine for each tissue is measured and the responses to 5-HT calculated as per¬ centage maximum of the acetylcholine (Ach) maximum re¬ sponse in that tissue. The peak of the 5-HT response is measured.

For each tissue the concentration of 5-HT giving 100% of the maximum acetylcholine response (measured at 30 sec) is quoted.

The effect of a drug is quantified as the ratio of the concentration of 5-HT producing a 100% maximal Ach re¬ sponse in the presence and absence of the antagonist (dose ratio). The figure quoted is the concentration of the antagonist giving a dose ratio of 2, (A ₂ ).

By testing some compounds of the invention the follow¬ ing results were obtained (A ₂ , mg/ml): example 4 (0.04), example 7 (0.01).

The compound of the invention, together with a conven¬ tional adjuvant, carrier, or diluent, and if desired in the form of a pharmaceutically-acceptable acid addi¬ tion salt thereof, may be placed into the form of phar- maceutical compositions and unit dosages thereof, and in such form may be employed as solids, such as tablets or filled capsules, or liquids, such as solutions, sus¬ pensions, emulsions, elixirs, or capsules filled with the same, all for oral use, in the form of supposito- ries for rectal administration; or in the form of ste¬ rile injectable solutions for parenteral (including subcutaneous) use. Such pharmaceutical compositions and unit dosage forms thereof may comprise conventio¬ nal ingredients in conventional proportions, with or without additional active compounds or principles, and such unit dosage forms may contain any suitable effec¬ tive central nervous system ailment alleviating amount of the active ingredient commensurate with the intend¬ ed daily dosage range to be employed. Tablets contain- ing one (1) milligram of active ingredient or, more broadly, one (1) to thirty (30) milligrams, per tablet, are accordingly suitable representative unit dosage forms.

The compounds of this invention can thus be used for the formulation of pharmaceutical preparations, e.g., for oral and parenteral administration to mammals in-

eluding humans, in accordance with conventional methods of galenic pharmacy.

Conventional excipients are such pharmaceutically ac- ceptable organic or inorganic carrier substances suit¬ able for parenteral or oral application which do not delteriously react with the active compound.

Examples of such carriers are water, salt solutions, alcohols, polyethylene glycols, polyhydroxyethoxylated castor oil, gelatin, lactose, amylose, magnesium stea- rate, talc, silicic acid, fatty acid monoglycerides and diglycerides, pentaerythritol fatty acid esters, hydroxymethylcellulose and polyvinylpyrrolidone.

The pharmaceutical preparations can be sterilized and mixed, if desired, with auxilliary agents, such as lu¬ bricants, preservatives, stabilizers, wetting agents, emulsifiers, salt for influencing osmotic pressure, buffers and/or coloring substances and the like, which do not deleteriously react with the active compound.

For parenteral application, particularly suitable are injectable solutions or suspensions, preferably aqueous solutions with the active compound dissolved in poly- hydroxylated castor oil.

Ampoules are convenient unit dosage forms.

For oral application, particularly suitable are tablets, dragees, or capsules having talc and/or a carbohydrate carrier or binder or the like, the carrier preferably being lactose and/or corn starch and/or potato starch. A syrup, elixir or like can be used when a sweetened vehicle can be employed. Generally, as to broader ran¬ ges, the compound of the invention is dispensed in unit dosage form comprising 0.05-100 mg in a pharmaceutical-

ly-acceptable carrier per unit dosage.

A typical tablet which may be prepared by conventional tabletting techniques contains:

Active compound 1.0 mg

Lactosum 67.9 mg ph.Eur.

Avicel ® 31.4 mg

Amberlite © IRP 88 1.0 mg Magnesii stearas 0.25 mg Ph.Eur.

The invention will now be described in further detail with reference to the following examples:

EXAMPLE 1

3-Amino-2-(3-butyl-l,2,4-oxadiazol-5-yl)thiophene

In 30 ml dry ethanol containing 2 g powdered molecular sieves was dissolved under nitrogen at room temperatu¬ re 0.6 g sodium, n-butylcarboxamidoxim (4.0 g, 35 mmol) was added and the mixture was stirred for 10 min. after which methyl 3-aminothiophene-2-carboxylate (3.1 g, 20 mmol) was added. The mixture was refluxed for 1 hour and then stirred at 70 C for 20 hours, cooled to room temperature and filtered through decalite. The filtrate was concentrated in vacuo and the resulting oil purifi¬ ed by filtration through a short path of silica gel with methylene chloride as eluent giving 3.4 g. M.p. 69-70°C.

EXAMPLE 2

3-Amino-2-(3-cyclopropyl-l,2,4-oxadiazol-5-yl)-thio¬ phene

In 50 g dry ethanol containing 3 g powdered molecular sieves was dissolved under nitrogen at room temperatu¬ re 0.8 g sodium. Cyclopropylcarboxamidoxim (3.5 g, 35 mmol) was added and the mixture was stirred for 10 min. after which methyl 3-aminothiophene-2-carboxylate (4.7 g, 30 mmol) was added. The mixture was refluxed for 16 hours, cooled to room temperature, filtered through decalite and concentrated in vacuo. The residue was taken up in water and ethylacetate and the organic phase was washed with saturated sodium chloride and dried with magnesium sulfate. Evaporation of the solvent ga¬ ve 4.9 g of the desired product as. M.p. 51-54 C.

EXAMPLE 3

N-(2-(3-Cyclopropyl-l,2,4 oxadiazol-5-yl)-3-thienyl)- N -(endo-9-methyl-9-azabicyclo[3.3.1]non-3-yl)thiourea

3-Amino-2-(3-cyclopropyl-l,2,4-oxadiazol-5-yl)-thio¬ phene (1.0 g, 5 mmol) in 10 ml dry methylene was added dropwise to a rigorously stirred mixture of thiophos- gene (0.5 ml, 6.5 mmol) in 10 ml H ₂ 0. Upon addition 1.0 ml triethylamine was added and stirring was conti¬ nued for 20 min. whereupon the organic phase was iso¬ lated. The aqueous phase was washed with methylene chlo¬ ride. To the combined organic phases were added endo- 3-amino-9-methyl-9-azabicyclo[3.3.1]nonan (0.9 g, 6 mmol) in 5 ml methylene chloride. The mixture was stirr¬ ed at room temperature for 2 hours. 5 ml saturated so-

dium bicarbonate was added. The product isolated by fil¬ tration, washed with water and dried. Upon washing with warm acetone was isolated 1.3 g of the desired product. M.p. 205-206°C.

EXAMPLE 4

N-( 2-(3-Cyclopropyl-l,2,4-oxadiazol-5-yl)-3-thienyl)-

N -(endo-9-methyl-9-azabicyclo[3.3.1]non-3-yl)urea

To phosgene (7.5 ml, 1.9 M in toluene) dissolved in 25 ml dry methylene chloride stirred at 0 C under nitro¬ gen was added dropwise 3-amino-2-(3-cyclopropyl-l,2,4- oxadiazol-5-yl)thiophene (1.3 g, 2.3 mmol) in 25 ml me¬ thylene chloride. After half of the addition was com¬ pleted, triethylamine (1.8 ml, 12 mmol) was added. Up¬ on completion of the additions the mixture was stirred at room temperature for 2 hours. The solvent was evapo- rated off. The residue was redissolved in methylene chloride and the solvent evaporated off again. The re¬ sidue was dissolved in 25 ml methylene chloride and 2 ml triethylamine and stirred at 0 C whereupon endo-3- amino-9-methyl-9-azabicyclo[3.3.1]nonane (1.2 g, 7.5 mmol) in 25 ml methylene chloride was added and the mixture stirred for 16 hours at room temperature. The mixture was then washed with saturated sodium bicarbo¬ nate, water and saturated sodium bicarbonate, water and saturated sodium chloride, dried over magnesium sulfate and concentrated in vacuo. The resulting crys¬ tals were washed with acetone to give 1.2 g of the de¬ sired product. M.p. 187-188°C.

EXAMPLE 5

N-(2-(3-Cyclopropyl-l,2,4-oxadiazol-5-yl)-3-thienyl)- N -(3-quinuclidinyl)th±ourea

3-Amino-2-(3-cyclopropyl-l,2,4-oxadiazol-5-yl)thiophe- ne (1.0 g, 5 mmol) in 10 ml dry methylene chloride was added dropwise to a vigorously stirred mixture of thio- phosgene (10.5 ml, 6.5 mmol) in 10 ml H _? 0. Upon additi¬ on 1.0 ml triethylamine was added and stirring continu¬ ed for 20 min. whereupon the organic phase was isolat¬ ed and the aqueous phase was washed with methylene chlo¬ ride. The combined organic phases were added to a solu- tion of 3-aminoquinuclidine, dihydrochloride (1.2 g, 6 mmol) dissolved in 1 ml H ₂ 0 and made alkaline with 50% NaOH. This mixture was then stirred at room temperatu¬ re for 6 hours whereupon 5 ml saturated sodium bicarbo- nat was added. The desired product was isolated by fil- tration, washed with water and dried to give 0.2 g. M.p. 155-157°C.

EXAMPLE 6

N-(2-(3-Butyl-l,2,4-oxadiazol-5-yl)-3-thienyl)-N ¹ - (endo-9-methyl-9-azabicyclo[3.3.1]non-3-yl)thiourea

N-(2-(3-Butyl-l,2,4-oxadiazol 5-yl)thiophene (0.6 g, 2.65 mmol) in 5 ml dry methylene chloride was added dropwise to a rigorously stirred mixture of thiophos- gene (0.3 ml, 3.9 mmol) in 5 ml H ₂ 0. Upon addition 0.5 ml triethylamine was added and stirring continued for 30 minutes whereupon the organic phase was isolated. The aqueous phase was extracted with methylene chlori¬ de. The combined organic phases were added to a solu¬ tion of endo-3-amino-9-methyl-9-azabiσyclo[3.3.1]nonan

in 5 ml methylene. The mixture was stirred for 1 hour at room temperature and then washed with saturated so¬ dium bicarbonate, water and saturated sodium chloride, dried over magnesium sulfate and concentrated in vacuo. The resulting crystals were washed with acetone and methanol to give 650 mg of the desired product. M.p. 171-172°C.

EXAMPLE 7

N-(2-(3-Butyl-l,2,4-oxadiazol-5-yl)-3-thienyl)-N ¹ - (endo-9-methyl-9-azabicyclo[3.3.l]non-3-yl)urea

3-Amino-2-(3-butyl-l,2,4-oxadiazol-5-yl)thiophene (0.9 g, 4 mmol) in 30 ml dry methylene chloride was added dropwise to a stirred mixture of phosgene (5.3 ml, 1.9 M in toluene) and 30 ml dry methylene chloride under nitrogen at 0 C. After 15 ml of the solution was added, 1.4 ml triethylamine was added. Upon completion of the addition the mixture was stirred at room temperature for 2 hours and then concentrated in vacuo. The result¬ ing oil was redissolved in methylene chloride and re- evaporated. The product was dissolved in 25 ml dry me- thylene chloride and 1.4 ml triethylamine and stirred at 0 C. Endo-3-amino-9-methyl-9-azabicyclo[3.3.1]nona- ne (1.0 g, 6.3 mmol) was added whereupon the mixture was stirred at room temperature for 16 hours. The mix¬ ture was washed with saturated sodium bicarbonate, wa- ter and saturated sodium chloride, dried over magnesi¬ um sulphate and concentrated in vacuo. Upon washing with methanol 0.2 g of the desired product was isolat¬ ed. M.p. 220-223°C.

EXAMPLE 8

N-(2-(3-Butyl-l,2,4-oxadiazol-5-yl)-3-thienyl )-N ¹ -(3- quinuclidinyl)thiourea, oxalate

3-Amino-2-(3-butyl-l,2,4-oxadiazol-5-yl)-thiophene (0.6 g, 2.6 mmol) in 5 ml methylene chloride was added dropwise to a rigorously stirred mixture of thiophos- gene (0.3 ml, 3.9 mmol) in 2.5 ml water. 0.5 ml trie- thylamin was added and stirring continued for additio¬ nal 30 minutes whereupon the phases were separated. The aqueous phase was extracted with methylene chlori¬ de. To the combined organic phases were added a solu- tion of 3-aminoquinuclidine dihydrochloride (1.1 g, 6 mmol) in 5 ml water which was made alkaline with 4N NaOH. The mixture was stirred for 16 hours and then washed with saturated sodium bicarbonate, water, and saturated sodium chloride. After evaporation of the solvent the product was purified by colomn chro ato- graphy (silica gel, merck 60, methylene chloride, me¬ thanol, concentrated amonium hydroxide; 90:10:0.5 (V/V/V)). The product was dissolved in acetone and pre¬ cipitated as the oxalate by addition of oxalic acid. Yield: 0.12 g. M.p. 174-175°C.