Patent Publication Number: US-2011053985-A1

Title: Novel piperidine-4-carboxylic acid phenyl-alkyl-amide derivatives and their use as monoamine neurotransmitter re-uptake inhibitors

Description:
TECHNICAL FIELD 
     This invention relates to novel piperidine-4-carboxylic acid phenyl-alkyl-amide derivatives useful as monoamine neurotransmitter re-uptake inhibitors. 
     In other aspects the invention relates to the use of these compounds in a method for therapy and to pharmaceutical compositions comprising the compounds of the invention. 
     BACKGROUND ART 
     Serotonin Selective Reuptake Inhibitors (SSRIs) currently provide efficacy in the treatment of several CNS disorders, including depression and panic disorder. SSRIs are generally perceived by psychiatrists and primary care physicians as effective, well-tolerated and easily administered. However, they are associated with a number of undesirable features. 
     Thus, there is still a strong need for compounds with an optimised pharmacological profile as regards the activity on reuptake of the monoamine neurotransmitters serotonin, dopamine and noradrenaline, such as the ratio of the serotonin reuptake versus the noradrenaline and dopamine reuptake activity. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide novel compounds which show activity as monoamine neurotransmitter re-uptake inhibitors. 
     In one aspect, the invention provides a compound of formula (I): 
     
       
         
         
             
             
         
       
     
     any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof; wherein R a , R b  and R c  are as defined below. 
     In another aspect, the invention provides a pharmaceutical composition, comprising a therapeutically effective amount of a compound of the invention, any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof, together with at least one pharmaceutically acceptable carrier, excipient or diluent. 
     In another aspect, the invention provides the use of a compound of the invention, any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof, for the manufacture of a pharmaceutical composition for the treatment, prevention or alleviation of a disease or a disorder or a condition of a mammal, including a human, which disease, disorder or condition is responsive to inhibition of monoamine neurotransmitter re-uptake in the central nervous system. 
     In another aspect, the invention relates to a method for treatment, prevention or alleviation of a disease or a disorder or a condition of a living animal body, including a human, which disorder, disease or condition is responsive to responsive to inhibition of monoamine neurotransmitter re-uptake in the central nervous system, which method comprises the step of administering to such a living animal body in need thereof a therapeutically effective amount of a compound of the invention, any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof. 
     Other objects of the invention will be apparent to the person skilled in the art from the following detailed description and examples. 
    
    
     DETAILED DISCLOSURE OF THE INVENTION 
     In one aspect the present invention provides compounds of formula (I): 
     
       
         
         
             
             
         
       
     
     any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof, wherein
 
R a  represents hydrogen or C 1-6 -alkyl;
 
R b  represents C 1-6 -alkyl or C 3-7 -cycloalkyl;
 
R c  represents a phenyl group; which phenyl group is optionally substituted with one or more substituents independently selected from the group consisting of halo, trifluoromethyl, trifluoromethoxy, cyano and C 1-6 -alkoxy.
 
     In one embodiment of the invention in formula (I), R a  represents hydrogen or C 1-6 -alkyl; R b  represents C 1-6 -alkyl or C 3-7 -cycloalkyl; and R c  represents a phenyl group; which phenyl group is substituted with one or more substituents independently selected from the group consisting of halo, trifluoromethyl, trifluoromethoxy, cyano and C 1-6 -alkoxy. 
     In another embodiment of the invention in formula (I), R a  represents hydrogen or C 1-6 -alkyl; R b  represents C 1-6 -alkyl; and R c  represents a phenyl group; which phenyl group is substituted with one or more substituents independently selected from the group consisting of halo and trifluoromethyl. 
     In another embodiment of the invention in formula (I), R a  represents hydrogen. In another embodiment R a  represents C 1-6 -alkyl, eg methyl. 
     In another embodiment of the invention in formula (I), R b  represents C 1-6 -alkyl, such as C 1-3 -alkyl. In another embodiment, R b  represents methyl. In another embodiment, R b  represents ethyl. In another embodiment, R b  represents propyl. 
     In another embodiment of the invention in formula (I), R c  represents a phenyl group substituted with one or more substituents independently selected from the group consisting of halo, trifluoromethyl and trifluoromethoxy. In another embodiment, R c  represents a phenyl group substituted with one substituent selected from the group consisting of halo and trifluoromethyl. In another embodiment, R c  represents a phenyl group substituted with three substituents independently selected from the group consisting of halo, trifluoromethyl and trifluoromethoxy. In another embodiment, R c  represents a disubstituted phenyl. In another embodiment, R c  represents a dihalosubstituted phenyl. In another embodiment, R c  represents a 3,4-dihalosubstituted phenyl wherein halo is independently selected from the group consisting of chloro and bromo. In another embodiment, R c  represents dichlorophenyl, e.g. 3,4-dichlorophenyl. In another embodiment, R c  represents dibromophenyl, e.g. 3,4-dibromophenyl. 
     In another embodiment of the invention in formula (I), R a  represents hydrogen, R b  represents C 1-6 -alkyl; and R c  represents a disubstituted phenyl. 
     In another embodiment of the invention in formula (I), R a  represents hydrogen, R b  represents ethyl or propyl; and R c  represents 3,4-disubstituted phenyl wherein the substituents are independently selected from chloro and bromo. 
     In another embodiment of the invention in formula (I), R a  represents R a  represents C 1-6 -alkyl, R b  represents C 1-6 -alkyl; and R c  represents a disubstituted phenyl. 
     In another embodiment, the compound of the invention is 
     piperidine-4-carboxylic acid (3,4-dichloro-phenyl)-ethyl-amide;
 
or a pharmaceutically acceptable salt thereof.
 
     In another embodiment, the compound of the invention is
     piperidine-4-carboxylic acid (3,4-dichloro-phenyl)-methyl-amide;   piperidine-4-carboxylic acid (3,4-dichloro-phenyl)-propyl-amide;   piperidine-4-carboxylic acid (4-chloro-3-fluoro-phenyl)-ethyl-amide;   piperidine-4-carboxylic acid (3-chloro-4-fluoro-phenyl)-ethyl-amide;   piperidine-4-carboxylic acid (2,3-dichloro-phenyl)-ethyl-amide;   piperidine-4-carboxylic acid (3-bromo-4-chloro-phenyl)-ethyl-amide;   piperidine-4-carboxylic acid ethyl-(2,3,4-trichloro-phenyl)-amide;   piperidine-4-carboxylic acid (2,5-dichloro-phenyl)-ethyl-amide;   piperidine-4-carboxylic acid (3,5-dichloro-phenyl)-ethyl-amide;   piperidine-4-carboxylic acid (2,4-dichloro-phenyl)-ethyl-amide;   piperidine-4-carboxylic acid (4-bromo-3-chloro-phenyl)-ethyl-amide;   piperidine-4-carboxylic acid (3,4-dibromo-phenyl)-ethyl-amide;   piperidine-4-carboxylic acid ethyl-(4-trifluoromethyl-phenyl)-amide;   piperidine-4-carboxylic acid (4-chloro-3-iodo-phenyl)-ethyl-amide;   1-methyl-piperidine-4-carboxylic acid (3,4-dichloro-phenyl)-ethyl-amide;   1-methyl-piperidine-4-carboxylic acid ethyl-(4-trifluoromethyl-phenyl)-amide;
 
or a pharmaceutically acceptable salt thereof.
   

     Any combination of two or more of the embodiments as described above is considered within the scope of the present invention. 
     Definition of Substituents 
     As used throughout the present specification and appended claims, the following terms have the indicated meaning: 
     The term “C 1-6 -alkyl” as used herein means a saturated, branched or straight hydrocarbon group having from 1-6 carbon atoms, e.g. C 1-3 -alkyl, C 1-4 -alkyl, C 1-6 -alkyl, C 2-6 -alkyl, C 3-6 -alkyl, and the like. Representative examples are methyl, ethyl, propyl (e.g. prop-1-yl, prop-2-yl (or iso-propyl)), butyl (e.g. 2-methylprop-2-yl (or tert-butyl), but-1-yl, but-2-yl), pentyl (e.g. pent-1-yl, pent-2-yl, pent-3-yl), 2-methylbut-1-yl, 3-methylbut-1-yl, hexyl (e.g. hex-1-yl), and the like. 
     The term “halo” or “halogen” shall mean fluorine, chlorine, bromine or iodine. 
     The term “cyano” shall mean the radical —CN. 
     The term “trihalomethyl” shall mean trifluoromethyl, trichloromethyl, and similar trihalo-substituted methyl groups. 
     The term “C 1-6 -alkoxy” as used herein refers to the radical alkyl-O—. Representative examples are methoxy, ethoxy, propoxy (e.g. 1-propoxy, 2-propoxy), butoxy (e.g. 1-butoxy, 2-butoxy, 2-methyl-2-propoxy), pentoxy (1-pentoxy, 2-pentoxy), hexoxy (1-hexoxy, 3-hexoxy), and the like. 
     The term “trihalomethoxy” shall mean trifluoromethoxy, trichloromethoxy, and similar trihalo-substituted methoxy groups. 
     The term “C 3-7 -cycloalkyl” as used herein represents a saturated monocyclic carbocyclic ring having from 3 to 7 carbon atoms, e.g. C 3-4 -alkyl, C 3-5 -alkyl, C 3-6 -alkyl, C 3-7 -alkyl and the like. Representative examples are cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and the like. 
     Pharmaceutically Acceptable Salts 
     The chemical compound of the invention may be provided in any form suitable for the intended administration. Suitable forms include pharmaceutically (i.e. physiologically) acceptable salts, and pre- or prodrug forms of the chemical compound of the invention. 
     Examples of pharmaceutically acceptable addition salts include, without limitation, the non-toxic inorganic and organic acid addition salts such as the hydrochloride, the hydrobromide, the nitrate, the perchlorate, the phosphate, the sulphate, the formate, the acetate, the aconate, the ascorbate, the benzenesulphonate, the benzoate, the cinnamate, the citrate, the embonate, the enantate, the fumarate, the glutamate, the glycolate, the lactate, the maleate, the malonate, the mandelate, the methanesulphonate, the naphthalene-2-sulphonate, the phthalate, the salicylate, the sorbate, the stearate, the succinate, the tartrate, the toluene-p-sulphonate, and the like. Such salts may be formed by procedures well known and described in the art. 
     Examples of pharmaceutically acceptable cationic salts of a chemical compound of the invention include, without limitation, the sodium, the potassium, the calcium, the magnesium, the zinc, the aluminium, the lithium, the choline, the lysinium, and the ammonium salt, and the like, of a chemical compound of the invention containing an anionic group. Such cationic salts may be formed by procedures well known and described in the art. 
     In the context of this invention the “onium salts” of N-containing compounds are also contemplated as pharmaceutically acceptable salts. Preferred “onium salts” include the alkyl-onium salts, the cycloalkyl-onium salts, and the cycloalky-lalkyl-onium salts. 
     Examples of pre- or prodrug forms of the chemical compound of the invention include examples of suitable prodrugs of the substances according to the invention include compounds modified at one or more reactive or derivatizable groups of the parent compound. Of particular interest are compounds modified at a carboxyl group, a hydroxyl group, or an amino group. Examples of suitable derivatives are esters or amides. 
     The chemical compound of the invention may be provided in dissoluble or indissoluble forms together with a pharmaceutically acceptable solvent such as water, ethanol, and the like. Dissoluble forms may also include hydrated forms such as the monohydrate, the dihydrate, the hemihydrate, the trihydrate, the tetrahydrate, and the like. In general, the dissoluble forms are considered equivalent to indissoluble forms for the purposes of this invention. 
     Steric Isomers 
     It will be appreciated by those skilled in the art that the compounds of the present invention may exist in different stereoisomeric forms—including enantiomers, diastereomers or cis-trans-isomers. 
     The invention includes all such isomers and any mixtures thereof including racemic mixtures. 
     Racemic forms can be resolved into the optical antipodes by known methods and techniques. One way of separating the enantiomeric compounds (including enantiomeric intermediates) is—in the case the compound being a chiral acid—by use of an optically active amine, and liberating the diastereomeric, resolved salt by treatment with an acid. Another method for resolving racemates into the optical antipodes is based upon chromatography on an optical active matrix. Racemic compounds of the present invention can thus be resolved into their optical antipodes, e.g., by fractional crystallisation of  D - or  L -(tartrates, mandelates, or camphorsulphonate) salts for example. 
     The chemical compounds of the present invention may also be resolved by the formation of diastereomeric amides by reaction of the chemical compounds of the present invention with an optically active activated carboxylic acid such as that derived from (+) or (−) phenylalanine, (+) or (−) phenylglycine, (+) or (−) camphanic acid or by the formation of diastereomeric carbamates by reaction of the chemical compound of the present invention with an optically active chloroformate or the like. 
     Additional methods for the resolving the optical isomers are known in the art. Such methods include those described by Jaques J, Collet A, &amp; Wilen S in “ Enantiomers, Racemates, and Resolutions ”, John Wiley and Sons, New York (1981). 
     Optical active compounds can also be prepared from optical active starting materials. 
     Labelled Compounds 
     The compounds of the invention may be used in their labelled or unlabelled form. In the context of this invention the labelled compound has one or more atoms replaced by an atom having an atomic mass or mass number different from the atomic mass or mass number usually found in nature. The labelling will allow easy quantitative detection of said compound. 
     The labelled compounds of the invention may be useful as diagnostic tools, radio tracers, or monitoring agents in various diagnostic methods, and for in vivo receptor imaging. 
     The labelled isomer of the invention preferably contains at least one radionuclide as a label. Positron emitting radionuclides are all candidates for usage. In the context of this invention the radionuclide is preferably selected from  2 H (deuterium),  3 H (tritium),  11 C,  13 C,  14 C,  131 I,  125 I,  123 I, and  18 F. 
     The physical method for detecting the labelled isomer of the present invention may be selected from Position Emission Tomography (PET), Single Photon Imaging Computed Tomography (SPECT), Magnetic Resonance Spectroscopy (MRS), Magnetic Resonance Imaging (MRI), and Computed Axial X-ray Tomography (CAT), or combinations thereof. 
     Methods of Preparation 
     The chemical compounds of the invention may be prepared by conventional methods for chemical synthesis, e.g. those described in the working examples. The starting materials for the processes described in the present application are known or may readily be prepared by conventional methods from commercially available chemicals. 
     Also one compound of the invention can be converted to another compound of the invention using conventional methods. 
     The end products of the reactions described herein may be isolated by conventional techniques, e.g. by extraction, crystallisation, distillation, chromatography, etc. 
     Biological Activity 
     Compounds of the invention may be tested for their ability to inhibit re-uptake of the monoamines dopamine, noradrenaline and serotonin in synaptosomes e.g. such as described in WO 97/30997 (NeuroSearch A/S) or WO 97/16451 (NeuroSearch NS). Based on the balanced activity observed in these tests the compound of the invention is considered useful for the treatment, prevention or alleviation of a disease or a disorder or a condition of a mammal, including a human, which disease, disorder or condition is responsive to inhibition of monoamine neurotransmitter re-uptake in the central nervous system. 
     In a special embodiment, the compounds of the invention are considered useful for the treatment, prevention or alleviation of: mood disorder, depression, atypical depression, depression secondary to pain, major depressive disorder, dysthymic disorder, bipolar disorder, bipolar I disorder, bipolar II disorder, cyclothymic disorder, mood disorder due to a general medical condition, substance-induced mood disorder, pseudodementia, Ganser&#39;s syndrome, obsessive compulsive disorder, panic disorder, panic disorder without agoraphobia, panic disorder with agoraphobia, agoraphobia without history of panic disorder, panic attack, memory deficits, memory loss, attention deficit hyperactivity disorder (ADHD), obesity, anxiety, generalized anxiety disorder, eating disorder, Parkinson&#39;s disease, parkinsonism, dementia, dementia of ageing, senile dementia, Alzheimer&#39;s disease, Down&#39;s syndrome, acquired immunodeficiency syndrome dementia complex, memory dysfunction in ageing, specific phobia, social phobia, social anxiety disorder, post-traumatic stress disorder, acute stress disorder, drug addiction, drug abuse, drug abuse liability, cocaine abuse, nicotine abuse, tobacco abuse, alcohol addiction, alcoholism, kleptomania, withdrawal symptoms caused by termination of use of addictive substances, pain, chronic pain, inflammatory pain, neuropathic pain, migraine pain, tension-type headache, chronic tension-type headache, pain associated with depression, fibromyalgia, arthritis, osteoarthritis, rheumatoid arthritis, back pain, cancer pain, irritable bowel pain, irritable bowel syndrome, post-operative pain, post-mastectomy pain syndrome (PMPS), post-stroke pain, drug-induced neuropathy, diabetic neuropathy, sympathetically-maintained pain, trigeminal neuralgia, dental pain, myofacial pain, phantom-limb pain, bulimia, premenstrual syndrome, premenstrual dysphoric disorder, late luteal phase syndrome, post-traumatic syndrome, chronic fatigue syndrome, persistent vegetative state, urinary incontinence, stress incontinence, urge incontinence, nocturnal incontinence, sexual dysfunction, premature ejaculation, erectile difficulty, erectile dysfunction, premature female orgasm, restless leg syndrome, periodic limb movement disorder, eating disorders, anorexia nervosa, sleep disorders, pervasive developmental disorders, autism, Asperger&#39;s disorder, Rett&#39;s disorder, childhood disintegrative disorder, learning disabilities, motor skills disorders, mutism, trichotillomania, narcolepsy, post-stroke depression, stroke-induced brain damage, stroke-induced neuronal damage, Gilles de la Tourettes disease, tinnitus, tic disorders, body dysmorphic disorders, oppositional defiant disorder or post-stroke disabilities. In another special embodiment, the compounds are considered useful for the treatment, prevention or alleviation of depression. In another special embodiment, the compounds are considered useful for the treatment, prevention or alleviation attention deficit hyperactivity disorder (ADHD). 
     It is at present contemplated that a suitable dosage of the active pharmaceutical ingredient (API) is within the range of from about 0.1 to about 1000 mg API per day, more preferred of from about 10 to about 500 mg API per day, most preferred of from about 30 to about 100 mg API per day, dependent, however, upon the exact mode of administration, the form in which it is administered, the indication considered, the subject and in particular the body weight of the subject involved, and further the preference and experience of the physician or veterinarian in charge. 
     Preferred compounds of the invention show a biological activity in the sub-micromolar and micromolar range, i.e. of from below 1 to about 100 μM. 
     Pharmaceutical Compositions 
     In another aspect the invention provides novel pharmaceutical compositions comprising a therapeutically effective amount of the compound of the invention. 
     While a compound of the invention for use in therapy may be administered in the form of the raw chemical compound, it is preferred to introduce the active ingredient, optionally in the form of a physiologically acceptable salt, in a pharmaceutical composition together with one or more adjuvants, excipients, carriers, buffers, diluents, and/or other customary pharmaceutical auxiliaries. 
     In one embodiment, the invention provides pharmaceutical compositions comprising the compound of the invention, or a pharmaceutically acceptable salt or derivative thereof, together with one or more pharmaceutically acceptable carriers, and, optionally, other therapeutic and/or prophylactic ingredients, known and used in the art. The carrier(s) must be “acceptable” in the sense of being compatible with the other ingredients of the formulation and not harmful to the recipient thereof. 
     Pharmaceutical compositions of the invention may be those suitable for oral, rectal, bronchial, nasal, pulmonal, topical (including buccal and sub-lingual), transdermal, vaginal or parenteral (including cutaneous, subcutaneous, intramuscular, intraperitoneal, intravenous, intraarterial, intracerebral, intraocular injection or infusion) administration, or those in a form suitable for administration by inhalation or insufflation, including powders and liquid aerosol administration, or by sustained release systems. Suitable examples of sustained release systems include semipermeable matrices of solid hydrophobic polymers containing the compound of the invention, which matrices may be in form of shaped articles, e.g. films or microcapsules. 
     The compound of the invention, together with a conventional adjuvant, carrier, or diluent, may thus be placed into the form of pharmaceutical compositions and unit dosages thereof. Such forms include solids, and in particular tablets, filled capsules, powder and pellet forms, and liquids, in particular aqueous or non-aqueous solutions, suspensions, emulsions, elixirs, and capsules filled with the same, all for oral use, suppositories for rectal administration, and sterile injectable solutions for parenteral use. Such pharmaceutical compositions and unit dosage forms thereof may comprise conventional ingredients in conventional proportions, with or without additional active compounds or principles, and such unit dosage forms may contain any suitable effective amount of the active ingredient commensurate with the intended daily dosage range to be employed. 
     The compound of the invention can be administered in a wide variety of oral and parenteral dosage forms. It will be obvious to those skilled in the art that the following dosage forms may comprise, as the active component, either a compound of the invention or a pharmaceutically acceptable salt of a compound of the invention. 
     For preparing pharmaceutical compositions from a compound of the present invention, pharmaceutically acceptable carriers can be either solid or liquid. Solid form preparations include powders, tablets, pills, capsules, cachets, suppositories, and dispersible granules. A solid carrier can be one or more substances which may also act as diluents, flavouring agents, solubilizers, lubricants, suspending agents, binders, preservatives, tablet disintegrating agents, or an encapsulating material. 
     In powders, the carrier is a finely divided solid, which is in a mixture with the finely divided active component. 
     In tablets, the active component is mixed with the carrier having the necessary binding capacity in suitable proportions and compacted in the shape and size desired. 
     The powders and tablets may contain from five or ten to about seventy percent of the active compound. Suitable carriers are magnesium carbonate, magnesium stearate, talc, sugar, lactose, pectin, dextrin, cellulose, starch, gelatin, tragacanth, methylcellulose, sodium carboxymethylcellulose, a low melting wax, cocoa butter, and the like. The term “preparation” is intended to include the formulation of the active compound with encapsulating material as carrier providing a capsule in which the active component, with or without carriers, is surrounded by a carrier, which is thus in association with it. Similarly, cachets and lozenges are included. Tablets, powders, capsules, pills, cachets, and lozenges can be used as solid forms suitable for oral administration. 
     For preparing suppositories, a low melting wax, such as a mixture of fatty acid glyceride or cocoa butter, is first melted and the active component is dispersed homogeneously therein, as by stirring. The molten homogenous mixture is then poured into convenient sized moulds, allowed to cool, and thereby to solidify. 
     Compositions suitable for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams or sprays containing in addition to the active ingredient such carriers as are known in the art to be appropriate. 
     Liquid preparations include solutions, suspensions, and emulsions, for example, water or water-propylene glycol solutions. For example, parenteral injection liquid preparations can be formulated as solutions in aqueous polyethylene glycol solution. 
     The compound according to the present invention may thus be formulated for parenteral administration (e.g. by injection, for example bolus injection or continuous infusion) and may be presented in unit dose form in ampoules, pre-filled syringes, small volume infusion or in multi-dose containers with an added preservative. The compositions may take such forms as suspensions, solutions, or emulsions in oily or aqueous vehicles, and may contain formulation agents such as suspending, stabilising and/or dispersing agents. Alternatively, the active ingredient may be in powder form, obtained by aseptic isolation of sterile solid or by lyophilization from solution, for constitution with a suitable vehicle, e.g. sterile, pyrogen-free water, before use. 
     Aqueous solutions suitable for oral use can be prepared by dissolving the active component in water and adding suitable colorants, flavours, stabilising and thickening agents, as desired. 
     Aqueous suspensions suitable for oral use can be made by dispersing the finely divided active component in water with viscous material, such as natural or synthetic gums, resins, methylcellulose, sodium carboxymethylcellulose, or other well known suspending agents. 
     Also included are solid form preparations, intended for conversion shortly before use to liquid form preparations for oral administration. Such liquid forms include solutions, suspensions, and emulsions. In addition to the active component such preparations may comprise colorants, flavours, stabilisers, buffers, artificial and natural sweeteners, dispersants, thickeners, solubilizing agents, and the like. 
     For topical administration to the epidermis the compound of the invention may be formulated as ointments, creams or lotions, or as a transdermal patch. Ointments and creams may, for example, be formulated with an aqueous or oily base with the addition of suitable thickening and/or gelling agents. Lotions may be formulated with an aqueous or oily base and will in general also contain one or more emulsifying agents, stabilising agents, dispersing agents, suspending agents, thickening agents, or colouring agents. 
     Compositions suitable for topical administration in the mouth include lozenges comprising the active agent in a flavoured base, usually sucrose and acacia or tragacanth; pastilles comprising the active ingredient in an inert base such as gelatin and glycerine or sucrose and acacia; and mouthwashes comprising the active ingredient in a suitable liquid carrier. 
     Solutions or suspensions are applied directly to the nasal cavity by conventional means, for example with a dropper, pipette or spray. The compositions may be provided in single or multi-dose form. In the latter case of a dropper or pipette, this may be achieved by the patient administering an appropriate, predetermined volume of the solution or suspension. In the case of a spray, this may be achieved for example by means of a metering atomizing spray pump. 
     Administration to the respiratory tract may also be achieved by means of an aerosol formulation in which the active ingredient is provided in a pressurised pack with a suitable propellant such as a chlorofluorocarbon (CFC) for example dichlorodifluoromethane, trichlorofluoromethane, or dichlorotetrafluoroethane, carbon dioxide, or other suitable gas. The aerosol may conveniently also contain a surfactant such as lecithin. The dose of drug may be controlled by provision of a metered valve. 
     Alternatively the active ingredients may be provided in the form of a dry powder, for example a powder mix of the compound in a suitable powder base such as lactose, starch, starch derivatives such as hydroxypropylmethyl cellulose and polyvinylpyrrolidone (PVP). Conveniently the powder carrier will form a gel in the nasal cavity. The powder composition may be presented in unit dose form for example in capsules or cartridges of, e.g., gelatin, or blister packs from which the powder may be administered by means of an inhaler. 
     In compositions intended for administration to the respiratory tract, including intranasal compositions, the compound will generally have a small particle size for example of the order of 5 microns or less. Such a particle size may be obtained by means known in the art, for example by micronization. 
     When desired, compositions adapted to give sustained release of the active ingredient may be employed. 
     The pharmaceutical preparations are preferably in unit dosage forms. In such form, the preparation is subdivided into unit doses containing appropriate quantities of the active component. The unit dosage form can be a packaged preparation, the package containing discrete quantities of preparation, such as packaged tablets, capsules, and powders in vials or ampoules. Also, the unit dosage form can be a capsule, tablet, cachet, or lozenge itself, or it can be the appropriate number of any of these in packaged form. 
     In one embodiment, the invention provides tablets or capsules for oral administration. 
     In another embodiment, the invention provides liquids for intravenous administration and continuous infusion. 
     Further details on techniques for formulation and administration may be found in the latest edition of  Remington&#39;s Pharmaceutical Sciences  (Maack Publishing Co., Easton, Pa.). 
     The dose administered must of course be carefully adjusted to the age, weight and condition of the individual being treated, as well as the route of administration, dosage form and regimen, and the result desired, and the exact dosage should of course be determined by the practitioner. 
     The actual dosage depends on the nature and severity of the disease being treated, and is within the discretion of the physician, and may be varied by titration of the dosage to the particular circumstances of this invention to produce the desired therapeutic effect. However, it is presently contemplated that pharmaceutical compositions containing of from about 0.1 to about 500 mg of active ingredient per individual dose, preferably of from about 1 to about 100 mg, most preferred of from about 1 to about 10 mg, are suitable for therapeutic treatments. 
     The active ingredient may be administered in one or several doses per day. A satisfactory result can, in certain instances, be obtained at a dosage as low as 0.1 μg/kg i.v. and 1 μg/kg p.o. The upper limit of the dosage range is presently considered to be about 10 mg/kg i.v. and 100 mg/kg p.o. Ranges are from about 0.1 μg/kg to about 10 mg/kg/day i.v., and from about 1 μg/kg to about 100 mg/kg/day p.o. 
     Methods of Therapy 
     In another aspect the invention provides a method for the treatment, prevention or alleviation of a disease or a disorder or a condition of a living animal body, including a human, which disease, disorder or condition is responsive to inhibition of monoamine neurotransmitter re-uptake in the central nervous system, and which method comprises administering to such a living animal body, including a human, in need thereof an effective amount of a chemical compound of the invention. 
     It is at present contemplated that suitable dosage ranges are 0.1 to 1000 milligrams daily, 10-500 milligrams daily, and especially 30-100 milligrams daily, dependent as usual upon the exact mode of administration, form in which administered, the indication toward which the administration is directed, the subject involved and the body weight of the subject involved, and further the preference and experience of the physician or veterinarian in charge. 
     EXAMPLES 
     The following examples and general procedures refer to intermediate compounds and final products for general formula (I) identified in the specification. The preparation of the compounds of general formula (I) of the present invention is described in detail using the following examples. Occasionally, the reaction may not be applicable as described to each compound included within the disclosed scope of the invention. The compounds for which this occurs will be readily recognized by those skilled in the art. In these cases the reactions can be successfully performed by conventional modifications known to those skilled in the art, which is, by appropriate protection of interfering groups, by changing to other conventional reagents, or by routine modification of reaction conditions. Alternatively, other reactions disclosed herein or otherwise conventional will be applicable to the preparation of the corresponding compounds of the invention. In all preparative methods, all starting materials are known or may easily be prepared from known starting materials. 
     All reactions involving air sensitive reagents or intermediates are performed under nitrogen and in anhydrous solvents. Magnesium sulphate is used as drying agent in the workup-procedures and solvents are evaporated under reduced pressure. 
     The abbreviations which may be used in the examples have the following meaning: 
     DCM: Dichloromethane 
     DMSO: Dimethylsulfoxide 
     EtOAc: Ethyl acetate 
     THF: Tetrahydrofuran 
     DMF: N,N-dimethylformamide 
     Method A 
     4-(3,4-Dichloro-phenylcarbamoyl)-piperidine-1-carboxylic acid tert-butyl ester 
     1-Propenephosphonic acid cyclic anhydride (8.33 g, 13.1 mmol) was added dropwise to a mixture of piperidine-1,4-dicarboxylic acid mono-tert-butyl ester (1.0 g, 4.36 mmol) and DCM (50 ml) at 0° C. The mixture was stirred at room-temperature for 20 min, followed by addition of 3,4-dichloroaniline and stirring at room-temperature for 15 h. The reaction mixture was diluted with water (30 ml) and extracted with DCM (2×200 ml), the organic phase was washed with aqueous saturated sodium chloride (20 ml). The mixture was dried and evaporated and purified by column chromatography (neutral Al 2 O 3 ), using a mixture of EtOAc and petroleum ether (30:70) as eluent. The pure product was isolated 900 mg (56%). 
     Method B 
     4-[(3,4-Dichloro-phenyl)-ethyl-carbamoyl]-piperidine-1-carboxylic acid-tert-butyl ester 
     To a suspension of sodium hydride (0.080 g, 2.00 mmol) in DMF, cooled to 0° C., 4-(3,4-dichloro-phenylcarbamoyl)-piperidine-1-carboxylic acid tert-butyl ester (0.50 g, 1.34 mmol) was added dropwise over 10 min. Bromoethane (0.22 g, 2.01 mmol) was added dropwise and stirred and stirred at room-temperature over night. The reaction mixture was quenched with water (10 ml) and extracted with EtOAc (2×100 ml). The product was isolated in quantitative yield. 
     Method C 
     Piperidine-4-carboxylic acid (3,4-dichloro-phenyl)-ethyl-amide trifluoroacetic acid salt (Compound C1) 
     To a mixture of 4-[(3,4-dichloro-phenyl)-ethyl-carbamoyl]-piperidine-1-carboxylic acid-tert-butyl ester (0.60 g, 1.49 mmol) and DCM (20 ml), trifluoroacetic acid (5 ml) was added at 0° C. The mixture was stirred at room-temperature overnight. The mixture was evaporated and recrystallised from methanol. The white solid was filtered and was washed with petroleum ether. Yield 220 mg (36%). Mp 159.3-160.7° C. 
     LC-ESI-HRMS of [M+H]+ shows 301.0877 Da. Calc. 301.087444 Da, dev. 0.9 ppm. 
     Piperidine-4-carboxylic acid (3,4-dichloro-phenyl)-methyl-amide hydrochloric acid salt (Compound C2) 
     Was prepared according to method C. LC-ESI-HRMS of [M+H]+ shows 287.071 Da. Calc. 287.071794 Da, dev. −2.8 ppm. 
     Piperidine-4-carboxylic acid (3,4-dichloro-phenyl)-propyl-amide hydrochloric acid salt (Compound C3) 
     Was prepared according to method C. LC-ESI-HRMS of [M+H]+ shows 315.102 Da. Calc. 315.103094 Da, dev. −3.5 ppm. 
     Piperidine-4-carboxylic acid (4-chloro-3-fluoro-phenyl)-ethyl-amide hydrochloric acid salt (Compound C4) 
     Was prepared according to method C. LC-ESI-HRMS of [M+H]+ shows 285.1182 Da. Calc. 285.116994 Da, dev. 4.2 ppm. 
     Piperidine-4-carboxylic acid (3-chloro-4-fluoro-phenyl)-ethyl-amide hydrochloric acid salt (Compound C5) 
     Was prepared according to method C. LC-ESI-HRMS of [M+H]+ shows 285.1163 Da. Calc. 285.116994 Da, dev. −2.4 ppm. 
     Piperidine-4-carboxylic acid (2,3-dichloro-phenyl)-ethyl-amide hydrochloric acid salt (Compound C6) 
     Was prepared according to method C. LC-ESI-HRMS of [M+H]+ shows 301.0869 Da. Calc. 301.087444 Da, dev. −1.8 ppm. 
     Piperidine-4-carboxylic acid (3-bromo-4-chloro-phenyl)-ethyl-amide hydrochloric acid salt (Compound C7) 
     Was prepared according to method C. LC-ESI-HRMS of [M+H]+ shows 345.0359 Da. Calc. 345.036384 Da, dev. −1.4 ppm. 
     Piperidine-4-carboxylic acid ethyl-(2,3,4-trichloro-phenyl)-amide hydrochloric acid salt (Compound C8) 
     Was prepared according to method C. LC-ESI-HRMS of [M+H]+ shows 335.0475 Da. Calc. 335.047927 Da, dev. −1.3 ppm. 
     Piperidine-4-carboxylic acid (2,5-dichloro-phenyl)-ethyl-amide hydrochloric acid salt (Compound C9) 
     Was prepared according to method C. LC-ESI-HRMS of [M+H]+ shows 301.0869 Da. Calc. 301.086899 Da, dev. 0 ppm. 
     Piperidine-4-carboxylic acid (3,5-dichloro-phenyl)-ethyl-amide hydrochloric acid salt (Compound C10) 
     Was prepared according to method C. LC-ESI-HRMS of [M+H]+ shows 301.0875 Da. Calc. 301.086899 Da, dev. 2 ppm. 
     Piperidine-4-carboxylic acid (2,4-dichloro-phenyl)-ethyl-amide hydrochloric acid salt (Compound C11) 
     Was prepared according to method C. LC-ESI-HRMS of M+ shows 300.081 Da. Calc. 300.079619 Da, dev. 4.6 ppm. 
     Piperidine-4-carboxylic acid (4-bromo-3-chloro-phenyl)-ethyl-amide hydrochloric acid salt (Compound C12) 
     Was prepared according to method C. LC-ESI-HRMS of [M+H]+ shows 345.0359 Da. Calc. 345.036384 Da, dev. −1.4 ppm. 
     Piperidine-4-carboxylic acid (3,4-dibromo-phenyl)-ethyl-amide hydrochloric acid salt (Compound C13) 
     Was prepared according to method C. LC-ESI-HRMS of [M+H]+ shows 388.9855 Da. Calc. 388.985869 Da, dev. −0.9 ppm. 
     Piperidine-4-carboxylic acid ethyl-(4-trifluoromethyl-phenyl)-amide hydrochloric acid salt (Compound C14) 
     Was prepared according to method C. LC-ESI-HRMS of [M+H]+ shows 301.1518 Da. Calc. 301.152227 Da, dev. −1.4 ppm. 
     Piperidine-4-carboxylic acid (4-chloro-3-iodo-phenyl)-ethyl-amide hydrochloric acid salt (Compound C15) 
     Was prepared according to method C. LC-ESI-HRMS of [M+H]+ shows 393.0218 Da. Calc. 393.022546 Da, dev. −1.9 ppm. 
     Method D 
     1-Methyl-piperidine-4-carboxylic acid (3,4-dichloro-phenyl)-ethyl-amide hydrochloric acid salt (Compound D1) 
     A mixture of piperidine-4-carboxylic acid (3,4-dichloro-phenyl)-ethyl-amide trifluoroacetic acid salt (0.50 g, 1.66 mmol), formaldehyde (37%), (5 ml, 182 mmol) and formic acid (5 ml, 133 mmol) was stirred at 90° C. for 15 h. Ice and excess of aqueous ammonia was added. The mixture was extracted with diethylether and the product was precipitated by adding HCl in EtOH (0.65 ml, 3 M). The solid was filtered. Yield 0.44 g (75%). 
     LC-ESI-HRMS of [M+H]+ shows 315.1036 Da. Calc. 315.102549 Da, dev. 3.3 ppm. 
     1-Methyl-piperidine-4-carboxylic acid ethyl-(4-trifluoromethyl-phenyl)-amide hydrochloric acid salt (Compound D2) 
     Was prepared according to method D. LC-ESI-HRMS of [M+H]+ shows 315.1676 Da. Calc. 315.167877 Da, dev. −0.9 ppm. 
     In Vitro Inhibition Activity 
     Compounds were tested for their ability to inhibit the reuptake of the monoamine neurotransmitters dopamine (DA) noradrenaline (NA) and serotonine (5-HT) in synaptosomes as described in WO 97/16451 (NeuroSearch A/S). 
     The test values are given as IC 50  (the concentration (μM) of the test substance which inhibits the specific binding of  3 H-DA,  3 H-NA, or  3 H-5-HT by 50%). 
     Test results obtained by testing compounds of the present invention appear from the below table: 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 5-HT-uptake 
                 DA-uptake 
                 NA-uptake 
               
               
                   
                 Test compound 
                 IC 50 (μM)  
                 IC 50 (μM) 
                 IC 50 (μM) 
               
               
                   
                   
               
             
            
               
                   
                 C1 
                 0.37 
                 0.021  
                 0.0097 
               
               
                   
                 C7 
                 0.14 
                 0.0078 
                 0.0058 
               
               
                   
                  C13 
                 0.12 
                 0.0040 
                 0.0031 
               
               
                   
                   
               
            
           
         
       
     
     From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not to be limited as by the appended claims. 
     The features disclosed in the foregoing description, in the claims and/or in the accompanying drawings, may both separately and in any combination thereof, be material for realising the invention in diverse forms thereof. 
     Features of the Invention: 
     1. A compound of formula (I): 
     
       
         
         
             
             
         
       
     
     any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof, wherein
 
R a  represents hydrogen or C 1-6 -alkyl;
 
R b  represents C 1-6 -alkyl or C 3-7 -cycloalkyl;
 
R c  represents a phenyl group; which phenyl group is optionally substituted with one or more substituents independently selected from the group consisting of halo, trifluoromethyl, trifluoromethoxy, cyano and C 1-6 -alkoxy.
 
2. The compound according to clause 1, any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof, wherein R a  represents hydrogen.
 
3. The compound according to clauses 1 or 2, any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof, wherein R b  represents C 1-6 -alkyl.
 
4. The compound according to any one of clauses 1-3, any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof, wherein R c  represents dihalophenyl.
 
5. The compound according to clause 1, which is
 
piperidine-4-carboxylic acid (3,4-dichloro-phenyl)-ethyl-amide;
 
any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof.
 
6. A pharmaceutical composition, comprising a therapeutically effective amount of a compound of any one of clauses 1-5, any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof, together with at least one pharmaceutically acceptable carrier, excipient or diluent.
 
7. Use of the chemical compound of any of clauses 1-6, any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament.
 
8. The use according to clause 7, for the manufacture of a pharmaceutical pharmaceutical composition for the treatment, prevention or alleviation of a disease or a disorder or a condition of a mammal, including a human, which disease, disorder or condition is responsive to inhibition of monoamine neurotransmitter re-uptake in the central nervous system.
 
9. The use according to clause 8, wherein the disease, disorder or condition is mood disorder, depression, atypical depression, depression secondary to pain, major depressive disorder, dysthymic disorder, bipolar disorder, bipolar I disorder, bipolar II disorder, cyclothymic disorder, mood disorder due to a general medical condition, substance-induced mood disorder, pseudodementia, Ganser&#39;s syndrome, obsessive compulsive disorder, panic disorder, panic disorder without agoraphobia, panic disorder with agoraphobia, agoraphobia without history of panic disorder, panic attack, memory deficits, memory loss, attention deficit hyperactivity disorder (ADHD), obesity, anxiety, generalized anxiety disorder, eating disorder, Parkinson&#39;s disease, parkinsonism, dementia, dementia of ageing, senile dementia, Alzheimer&#39;s disease, Down&#39;s syndrome, acquired immunodeficiency syndrome dementia complex, memory dysfunction in ageing, specific phobia, social phobia, social anxiety disorder, post-traumatic stress disorder, acute stress disorder, drug addiction, drug abuse, drug abuse liability, cocaine abuse, nicotine abuse, tobacco abuse, alcohol addiction, alcoholism, kleptomania, withdrawal symptoms caused by termination of use of addictive substances, pain, chronic pain, inflammatory pain, neuropathic pain, migraine pain, tension-type headache, chronic tension-type headache, pain associated with depression, fibromyalgia, arthritis, osteoarthritis, rheumatoid arthritis, back pain, cancer pain, irritable bowel pain, irritable bowel syndrome, post-operative pain, post-mastectomy pain syndrome (PMPS), post-stroke pain, drug-induced neuropathy, diabetic neuropathy, sympathetically-maintained pain, trigeminal neuralgia, dental pain, myofacial pain, phantom-limb pain, bulimia, premenstrual syndrome, premenstrual dysphoric disorder, late luteal phase syndrome, post-traumatic syndrome, chronic fatigue syndrome, persistent vegetative state, urinary incontinence, stress incontinence, urge incontinence, nocturnal incontinence, sexual dysfunction, premature ejaculation, erectile difficulty, erectile dysfunction, premature female orgasm, restless leg syndrome, periodic limb movement disorder, eating disorders, anorexia nervosa, sleep disorders, pervasive developmental disorders, autism, Asperger&#39;s disorder, Rett&#39;s disorder, childhood disintegrative disorder, learning disabilities, motor skills disorders, mutism, trichotillomania, narcolepsy, post-stroke depression, stroke-induced brain damage, stroke-induced neuronal damage, Gilles de la Tourettes disease, tinnitus, tic disorders, body dysmorphic disorders, oppositional defiant disorder or post-stroke disabilities.
 
10. A method for treatment, prevention or alleviation of a disease or a disorder or a condition of a living animal body, including a human, which disorder, disease or condition is responsive to inhibition of monoamine neurotransmitter re-uptake in the central nervous system, which method comprises the step of administering to such a living animal body in need thereof a therapeutically effective amount of a compound according to any one of the clauses 1-5, or any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof.
 
     11. A compound according to any one of clauses 1-5, any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof, for use as a medicament. 
     12. A compound according to any one of clauses 1-5, any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof, for use in the treatment, prevention or alleviation of a disease or a disorder or a condition of a mammal, including a human, which disease, disorder or condition is responsive to inhibition of monoamine neurotransmitter re-uptake in the central nervous system.