Use of heterocyclic derivatives in the treatment of cognitive disorders

Abstract: The invention relates to the use of certain compounds which act as antagonists of 5-hydroxytryptamine (5-HT) at 5-HT₃ receptors for the treatment of cognitive disorders such as attentional and memory deficits and dementia states.

Description: This invention relates to a new medical use for certain chemical compounds and pharmaceutical compositions containing them. In particular it relates to the use in the treatment of attentional and memory deficits and dementia states of certain compounds which act as antagonists of 5-hydroxytryptamine (5-HT) at receptors known in the art as 5-HT₃,, 5-HT'M' or 5-HT 'M'-like receptors. Such receptors have been described for example by Fozard et al ., Eur. J. Pharmacol., 1979, 59 , 195-210; Ireland, Straughan and Tyers, Br. J. Pharmacol., 1982, 75 , 16P; Humphrey, Neuropharm., 1984, 23 , 1503-1570; Richardson et al ., Nature, 1985, 316 , 126-131; and Bradley et al ., Neuropharm., 1986, 25 , 563-576. Receptors of this type are now designated as 5-HT₃ receptors. 5-HT receptors of this type are located, for example, on the terminals of afferent sensory neurones, in the isolated guinea-pig ileum preparation and are also present in the central nervous system. Compounds which act as antagonists of 5-HT at 5-HT₃ receptors may be identified using standard tests, for example, in vitro by measuring their inhibition of the depolarising effect of 5-HT on the rat or rabbit isolated vagus nerve, or the tachycardia produced by 5-HT in the rabbit isolated heart or the contraction produced by 5-HT in the guinea-pig isolated ileum, or in vivo by measuring their effect on the Von Bezold-Jarisch reflex (induced by 5-HT) as described, for example, in the above-mentioned references. A variety of compounds which act as antagonists of 5-HT at 5-HT₃ receptors have been described in the art. Such compounds have been disclosed inter alia in published UK Patent Applications Nos. 2100259, 2125398, 2131420, 2132189, 2145416, 2152049, 2153821 and 2169292, published European Patent Applications Nos. 111608, 116255, 158265, 191562, 200444, 210840, 214772, 219193, 221702, 226267, 227215, 230718, 235878 and 242973, and published Australian Patent Application No. 87/67121. The compounds disclosed in published European Patent Applications Nos. 13138, 67615 and 94742 have also been described as antagonists of 5-HT at 5-HT₃ receptors, in published European Patent Applications Nos. 215545 and 220011. The compounds disclosed in these specifications have been described as being of use in a variety of conditions, including migraine. A paper by Essman, (Adv. Biochem. Psychopharmacol., 11 , 265-274 (1974)) reviews evidence relating to the role of 5-HT in memory. However, the article does not suggest how mechanisms involving 5-HT might be modulated to achieve a therapeutic benefit. In addition, there is no mention of 5-HT₃ receptors or of compounds which are antagonists at such receptors. Altman and Normille (Psychopharmacology, 90 , 24-27 (1986)) report the results of a study which also implies the involvement of 5-HT in memory, more particularly a study on the enhancement of the memory of a previously learned aversive habit following pre-test administration of a variety of serotonergic antagonists in mice. However, the compounds whose effects were studied are primarily antagonists at 5-HT₂ receptors. There is no reference to 5-HT₃ receptors or to compounds which are antagonists at such receptors. EP-A-0 190 920 discloses a wide range of arylamido- and arylthioamidoazabicycloalkanes of differing structures as being potentially useful in the improvement of memory. No rationale is presented as to why the compounds may be effective and there is no reference to 5-HT or 5-HT₃ receptors although a small number of the compounds concerned have subsequently be shown to be 5-HT₃ antagonists (GB-A-2125398). The compounds disclosed in EP-A-0 190 920 show clear structural differences from the compounds of formula (I) referred to in more detail below. We have now found that compounds which are disclosed in the above specifications and act as 5-HT antagonists at 5-HT₃ receptors are useful in the treatment of attentional and memory deficits and dementia states. These types of condition occur in, for example, senile dementia of the Alzheimer's type, ageing, cerebrovascular deficiency and Parkinson's disease. The effectiveness of the compounds for use in the treatment of cognitive disorders may be demonstrated in rats in the spontaneous alternation test and in marmosets given learning tasks in the Wisconsin General Test Apparatus. References in this specification to treatment include prophylactic treatment as well as the acute alleviation of symptoms. The present invention provides the use of compounds of formula (I) or a physiologically acceptable salt or solvate thereof for the manufacture of a medicament for the treatment of attentional and memory deficits and dementia states, for example dementia: wherein R₁ and R₂ independently represent hydrogen, halogen, C₁₋₄alkyl, C₁₋₄alkoxy, hydroxy, amino, C₁₋₄alkylamino, di(C₁₋₄)alkylamino, mercapto or C₁₋₄alkylthio; R₃ represents hydrogen, C₁₋₄alkyl, C₃₋₅alkenyl, aryl or arylC₁₋₄alkyl, where aryl as a group or part of a group represents phenyl or phenyl mono- or poly-substituted by C₁₋₄alkyl, halogen, hydroxy or C₁₋₄alkoxy; R₄ represents hydrogen, C₁₋₇alkyl, C₃₋₅ alkenyl or arylC₁₋₄alkyl, where aryl is as defined above; n is 2 or 3; the free valence is attached to either fused ring, and the azabicyclic ring is in either the exo or endo configuration. Compounds of formula (I) are described GB-A-2125398. Acid addition salts and quaternary ammonium salts may be mentioned specifically as physiologically acceptable salts. In the compounds of formula (I) R₁ and R₂ may, for example, independently represent hydrogen, halogen or C₁₋₄alkyl, R₃ may be, for example, hydrogen or C₁₋₄alkyl and R₄ may be, for example, hydrogen, C₁₋₇alkyl or C₁₋₄arylalkyl, conveniently benzyl. The carbonyl group is preferably attached to the 3-position of the indole ring. The azabicyclic ring is preferably in the endo configuration. A particularly preferred compound for use according to the present invention is (3α-tropanyl)-1 H -indole-3-carboxylic acid ester and physiologically acceptable salts and solvates thereof. Pharmaceutical compositions (medicaments) according to the present invention may be formulated in conventional manner, optionally with one or more physiologically acceptable carriers and/or excipients. For example, the compounds of formula (I) may be formulated in the manner described in GB-A-2125398. Compounds of formula (I) may be formulated for oral, buccal, parenteral, rectal or transdermal administration or in a form suitable for administration by inhalation or insufflation (either through the mouth or the nose). For oral administration, the pharmaceutical compositions may take the form of, for example, tablets or capsules prepared by conventional means with pharmaceutically acceptable excipients such as binding agents (e.g. pregelatinised maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose); fillers (e.g. lactose, microcrystalline cellulose or calcium hydrogen phosphate); lubricants (e.g. magnesium stearate, talc or silica); disintegrants (e.g. potato starch or sodium starch glycollate); or wetting agents (e.g. sodium lauryl sulphate). The tablets may be coated by methods well known in the art. Liquid preparations for oral administration may take the form of, for example, solutions, syrups or suspensions, or they may be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may be prepared by conventional means with pharmaceutically acceptable additives such as suspending agents (e.g. sorbitol syrup, cellulose derivatives or hydrogenated edible fats); emulsifying agents (e.g. lecithin or acacia); non-aqueous vehicles (e.g. almond oil, oily esters, ethyl alcohol or fractionated vegetable oils); and preservatives (e.g. methyl or propyl- p -hydroxybenzoates or sorbic acid). The preparations may also contain buffer salts, flavouring, colouring and sweetening agents as appropriate. Preparations for oral administration may be suitably formulated to give controlled release of the active compound. For buccal administration the compositions may take the form of tablets or lozenges formulated in conventional manner. Compounds of formula (I) may be formulated for parenteral administration by injection e.g. by bolus injection or continuous infusion. Formulations for injection may be presented in unit dosage form e.g. in ampoules or in multi-dose containers, with an added preservative. The compositions may take such forms a suspensions, solutions or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilising and/or dispersing agents. Alternatively, the active ingredient may be in powder form for constitution with a suitable vehicle, e.g. sterile pyrogen-free water, before use. Compounds of formula (I) may also be formulated in rectal compositions such as suppositories or retention enemas, e.g. containing conventional suppository bases such as cocoa butter or other glycerides. In addition to the formulations described previously, the compounds may also be formulated as a depot preparation. Such long acting formulations may be administered by implantation (for example subcutaneously, transcutaneously or intramuscularly) or by intramuscular injection. Thus, for example, the compounds of formula (I) may be formulated with suitable polymeric or hydrophobic materials (for example as an emulsion in an acceptable oil) or ion exchange resins, or as sparingly soluble derivatives, for example, as a sparingly soluble salt. The dose at which the compounds may be administered to man will depend upon the route of administration, the body weight of the patient, the severity of the condition to be treated and the potency of the compounds. For example, the compounds disclosed in GB-A-2125398 may be administered at doses in the ranges specified therein, or at lower doses, for example 0.5µg to 20 mg e.g. 0.005 to 20 mg, preferably 0.05 to 10 mg per unit dose which may be administered, for example, 1 to 4 times per day. Thus a unit dose of a compound of formula (I) may contain from 0.2 to 250 mg of the active ingredient, and may be administered for example up to four times per day, such that the overall daily dose is in the range o.5 to 500 mg. The following examples illustrate pharmaceutical formulations for use according to the invention, containing (3α-tropanyl)-1 H -indole-3-carboxylic acid ester as the active ingredient. Other compounds of formula (I) may be formulated in a similar manner. TABLETS FOR ORAL ADMINISTRATION Tablets may be prepared by the normal methods such as direct compression or wet granulation. The tablets may be film coated with suitable film forming materials, such as hydroxypropyl methylcellulose, using standard techniques. Alternatively the tablets may be sugar coated. Direct Compression Tablet mg/tablet Active Ingredient 0.50 Calcium Hydrogen Phosphate BP 87.25 Croscarmellose Sodium NF 1.8 Magnesium Stearate BP 0.45 Compression Weight 90.0 The active ingredient is passed through a 60 mesh sieve, blended with the calcium hydrogen phosphate, croscarmellose sodium and magnesium stearate. The resultant mix is compressed into tablets using a Manesty F3 tablet machine fitted with 5.5 mm, flat bevelled edge punches. Tablets of other strengths may be prepared by altering the ratio of active ingredient to excipients or the compression weight and using punches to suit. CAPSULES mg/capsule Active Ingredient 0.5 Starch 1500 98.5 Magnesium Stearate BP 1.0 Fill Weight 100.0 The active ingredient is sieved and blended with the excipients. The mix is filled into size No. 2 hard gelatin capsules using suitable machinery. Other doses may be prepared by altering the fill weight and if necessary changing the capsule size to suit. SYRUP This may be either a sucrose or sucrose free presentation. Sucrose-Free mg/5ml dose Active Ingredient 0.5 Hydroxypropylmethylcellulose USP (viscosity type 4000) 22.5 Buffer ) as required Flavour ) Colour ) Preservative ) Sweetener ) Purified Water BP to 5.0ml The hydroxypropylmethylcellulose is dispersed in hot water, cooled and then mixed with an aqueous solution containing the active ingredient and the other components of the formulation. The resultant solution is adjusted to volume and mixed. The syrup is clarified by filtration. INJECTION FOR INTRAVENOUS ADMINISTRATION mg/ml Active Ingredient 0.05 0.5 Sodium Chloride BP as required as required Water for Injection BP to 1.0ml 1.0ml Sodium chloride may be added to adjust the tonicity of the solution and the pH may be adjusted, using acid or alkali, to that of optimum stability and/or facilitate solution of the active ingredient. Alternatively suitable buffer salts may be used. The solution is prepared, clarified and filled into appropriate size ampoules sealed by fusion of the glass. The injection is sterilised by heating in an autoclave using one of the acceptable cycles. Alternatively the solution may be sterilised by filtration and filled into sterile ampoules under aseptic conditions. The solution may be packed under an inert atmosphere of nitrogen or other suitable gas. SUPPOSITORY Active Ingredient 0.5 mg Witepsol H15 to 1.0 g A suspension of the active ingredient is prepared in the molten Witepsol and filled, using suitable machinery, into 1g size suppository moulds. The efficacy of the compounds of formula (I) in the treatment of cognitive disorders has been demonstrated in marmosets given learning tasks in the Wisconsin General Test Apparatus. Test compound : (3α-Tropanyl)-1 H -indole-3-carboxylic acid ester. Marmoset learning tasks in the Wisconsin General Test Apparatus Introduction and Test Procedure Common marmosets were tested for performance in a discriminative learning task and reverse learning task using the Wisconsin General Test Apparatus described by Harlow H.F. Psychological review, 56 , 51-65, 1949. The experiments were essentially carried out following the experimental protocol of Baker H.F. Ridley R.M. and Drewett, B., Psychopharmacology, 91 , 512-514, 1987. The test compound was administered into the hind leg of the marmoset as a subcutaneous (s.c.) injection in 1ml of saline. Results Administration of the test compound at a dose of 10 ng/kg s.c. twice a day throughout testing improved the performance of the marmosets in the reverse learning task.

Claims: The use of compounds of formula (I) or a physiologically acceptable salt or solvate thereof for the manufacture of a medicament for the treatment of attentional and memory deficits and dementia states: wherein R₁ and R₂ independently represent hydrogen, halogen, C₁₋₄alkyl, C₁₋₄alkoxy, hydroxy, amino, C₁₋₄alkylamino, di(C₁₋₄)alkylamino, mercapto or C₁₋₄alkylthio; R₃ represents hydrogen, C₁₋₄alkyl, C₃₋₅alkenyl, aryl or arylC₁₋₄alkyl, where aryl as a group or part of a group represents phenyl or phenyl mono- or poly-substituted by C₁₋₄alkyl, halogen, hydroxy or C₁₋₄alkoxy; R₄ represents hydrogen, C₁₋₇alkyl, C₃₋₅ alkenyl or arylC₁₋₄alkyl, where aryl is as defined above; n is 2 or 3; the free valence is attached to either fused ring, and the azabicyclic ring is in either the exo or endo configuration. Use according to Claim 1 for the manufacture of a medicament for the treatment of dementia. Use according to Claim 1 or 2 in which the compound is a compound of formula (I) wherein R₁ and R₂ independently represent hydrogen, halogen or C₁₋₄alkyl; R₃ represents hydrogen or C₁₋₄alkyl; R₄ represents hydrogen, C₁₋₇alkyl or aralkyl; the carbonyl group is attached to the 3-position of the indole ring and the azabicyclic ring is in the endo configuration. Use according to Claim 1 or 2 wherein the compound of formula (I) is of (3α-tropanyl)-1 H -indole-3-carboxylic acid ester or a physiologically acceptable salt or solvate thereof. Use according to any of Claims 1 to 4 for the manufacture of a medicament in unit dose form containing from 0.5µg to 20 mg of the active ingredient per unit dose. Use according to Claim 5 wherein the amount of active ingredient per unit dose is from 0.05 mg to 10 mg.

Inventors: TYERS MICHAEL BRIAN, TYERS, MICHAEL BRIAN
Applicants: GLAXO GROUP LTD, GLAXO GROUP LIMITED
Application year: 1987
Main classification: A61K31
IPC codes: A61K31, C07D403, C07D451, C07D453, A61P43, C07D471, C07D487, A61P25