WO2005067931A2

WO2005067931A2 - Dopamine uptake inhibitors for the treatment of neurological disease

Info

Publication number: WO2005067931A2
Application number: PCT/GB2005/000119
Authority: WO
Inventors: Paul Goldsmith; Frances Margaret Richards; Derek Thomas Edward Jones; Ann Gail Hayes
Original assignee: Daniolabs Ltd
Current assignee: Daniolabs Ltd
Priority date: 2004-01-14
Filing date: 2005-01-14
Publication date: 2005-07-28
Anticipated expiration: 2006-07-14
Also published as: WO2005067931A3; WO2005067930A3; WO2005067930A2; GB0400802D0

Abstract

Treatment of diseases and disorders related to altered neuronal excitability, especially migraine prophylaxis, mood stabilisation and convulsions, in particular the treatment of convulsions due to epilepsy, also treatment of depression or psychomotor retardation in subjects prone to seizures. Dopamine uptake inhibitors are employed, especially benzhydryloxy-ethyl piperazine derivatives, including GBR12909, GBR12935, GBR13069, GBR13098, GBR13119 and pharmaceutically acceptable salts thereof.

Description

DOPAMINE UPTAKE INHIBITORS FOR THE TREATMENT OF NEUROLOGICAL DISEASE

This invention relates to the treatment of diseases and disorders related to altered neuronal excitability, especially migraine prophylaxis, mood stabilisation and convulsions, in particular the treatment of convulsions due to epilepsy, also treatment of depression or psychomotor retardation in subjects prone to seizures.

Epilepsy is a condition defined as a recurrent propensity to seizures. It is treated with anticonvulsants . Some two thirds of patients are well controlled on existing anticonvulsant therapies, with the remainder being partially or uncontrolled. There is therefore a need for more efficacious anticonvulsant therapies. However the greater clinical need is for compounds that have a better side effect profile than the existing anticonvulsants. The currently prescribed anticonvulsants such as carbamazepine, phenytoin, sodium valproate, lamotrigine, phenobarbitone, gabapentin, ethosuximide, clobazam and vigabatrin all have troublesome side effects. In some cases these can be severe life threatening drugs reactions, such as is seen with Stevens Johnson syndrome, but much more pervasive are the predictable dose related effects of sedation, fatigue, asthenia and often also weight gain. This results in significant impairments in Activities of Daily Living (ADLs) . Typically the greater the dose, the greater the antiepileptic effect, yet concomitant with the dose increase is an increase in the side effects, in particular sedation. Many patients never reach the higher doses and therefore the attendant anticonvulsant benefits. Moreover the poor side effect profile contributes to poor compliance of anticonvulsant drugs . A further problem with anticonvulsants relates to the need for daily and often multi-daily therapy. Cessation of a therapy, even for a day, may result in further seizures, with rebound effects. It is therefore important that a patient is highly compliant with their medication and takes it regularly. Even with the most organised and compliant patients this is not always the case. With many patients there are additional co-morbidities which make the regular taking of medications much less reliable. Epilepsy is often due to an underlying brain disorder, whether that be a developmental problem such as perinatal brain injury, abnormal development from inherited conditions such as a lipid storage disease, or mental retardation, or in the case of adult onset disease, cerebrovascular disease, head injury or tumour. For these groups of patients administration of regular therapies can be very problematic.

Currently there are no good strategies for overcoming these problems. Possible solutions would include the use of a stimulant medication or a medication that does not require daily administration.

Typically a new anticonvulsant will be given in combination with an existing anticonvulsant. This is because discontinuation of the current therapy might lead to an increase in the baseline seizure frequency with attendant risks. In those cases where seizures are controlled fully, but at the expense of unpleasant side effects, the patient may not want to risk seizure recurrence during a switch to a new medication because of the risk of losing their driving license, or causing problems at work etc. Because of this reluctance to manage patients with no anticonvulsant cover it is more typical to add in a 2^nd anticonvulsant. The desirable therapeutic product profile is therefore an anticonvulsant that would act in combination with one of the existing anticonvulsants to increase overall anticonvulsant efficacy whilst improving the overall side effect profile. Currently there are no good strategies for overcoming these problems or theoretical determination of what would be the most beneficial compound profile. Possible solutions would include the use of a stimulant medication or a medication that does not require daily administration. Availability of a depot formulation to improve compliance would be a further benefit .

The invention disclosed herein shows that compound GBR 12909 and analogues, or compounds with a related mechanism of action fulfill these criteria.

Brief Description of the Figure

Figure 1 shows the combined results of at least 3 independent assays for each compound, together with results for negative controls (PTZ alone) and positive controls (carbamazepine and diazepam) in the same assays.

It was found that the test compounds shown were anticonvulsant .

The present invention is based on the surprising finding that certain compounds can be used in the treatment of convulsions. The identification of the useful compounds has been achieved using a specific model of epilepsy using zebrafish as the disease model. According to a first aspect of the invention, a compound selected from dopamine uptake or reuptake inhibitors is used in -treatment of a disease or disorder of neuronal excitability, such as epilepsy (The terms "uptake or reuptake" in the context of the dopamine uptake or reuptake inhibitors are used herein interchangeably without technical distinction.)

Various aspects and embodiments of the present invention include :

Use of a compound selected dopamine uptake inhibitors in the manufacture of a medicament for the treatment of a neurological disease.

Use where the dopamine uptake inhibitors are benzhydryloxy-ethyl piperazine derivatives.

Use where the compound is selected from the group consisting of vanoxerine (GBR12909) or other benzhydryloxy-ethyl piperazine derivative, for instance GBR12935, GBR13069, GBR13098 or GBR13119, and pharmaceutically acceptable salts and analogues thereof.

Use wherein the compound is a pharmaceutically acceptable salt of, or a prodrug form that is metabolised to, one of the compounds as defined.

Use wherein the neurological disease is selected from the group consisting of epilepsy, chronic, recurrent and paroxysmal headache syndromes, including migraine, cluster headache and chronic daily headache variants, chronic pain states, trigeminal neuralgia, bipolar disease, unipolar disease, neuropathic pain, paroxysmal movement disorders. A method for the treatment of a neurological disease, comprising administering to a patient suffering a neurological disease a compound selected from the class of compounds defined in any of the above.

A method wherein the neurological disease is selected from those defined above.

Use or a method wherein the subject is a non-human animal .

Use or a method wherein the subject is human.

Dopamine uptake inhibitors of use in the present invention include benzhydryloxy-ethyl piperazine derivatives, Vanoxerine (GBR12909) - CAS no. 67469-69-6, GBR12935 - CAS no. 76778-22-8, GBR13069 - CAS no. 77862- 93-2, GBR13098 - CAS no. 77862-94-3, and GBR13119 - CAS no. 76778-23-9.

The compounds of the invention may be prepared in racemic form, or prepared in individual enantiomeric form by specific synthesis or resolution as will be appreciated in the art. The compounds may, for example, be resolved into their enantiomers by standard techniques, such as the formation of diastereomeric pairs by salt formation with an optically active acid followed by fractional crystallisation and regeneration of the free base. Alternatively, the enantiomers of the novel compounds may be separated by HPLC using a chiral column.

The compounds of the invention may be in a protected amino form. The term "protected amino" as used herein refers to an amino group which is protected in a manner familiar to those skilled in the art. For example, an amino group can be protected by a benzyloxycarbonyl, tert-butoxycarbonyl, acetyl or like group, or in the form of a phthalimido or like group.

Some compounds of the formula may exist in the form of solvates, for example hydrates, which also fall within the scope of the present invention.

The compounds of the invention may exist in a prodrug form. Suitable groups will be apparent to the skilled person .

Compounds of the invention may be in the form of pharmaceutically acceptable salts, for example, addition salts of inorganic or organic acids. Such inorganic acid addition salts include, for example, salts of hydrobromic acid, hydrochloric acid, nitric acid, phosphoric acid and sulphuric acid. Organic acid addition salts include, for example, salts of acetic acid, benzenesulphonic acid, benzoic acid, camphorsulphonic acid, citric acid, 2- (4- chlorophenoxy) -2-methylpropionic acid, 1,2- ethanedisulphonic acid, ethanesulphonic acid, ethylenediaminetetraacetic acid (EDTA) , fumaric acid, glucoheptonic acid, gluconic acid, glutamic acid, N-glycolylarsanilic acid, 4-hexylresorcinol, hippuric acid, 2- (4-hydroxybenzoyl) benzoic acid, l-hydroxy-2- naphthoic acid, 3-hydroxy-2-naphthoic acid, 2- hydroxyethanesulphonic acid, lactobionic acid, n-dodecyl sulphate, maleic acid, malic acid, mandelic acid, methanesulphonic acid, methyl sulphate, mucic acid, 2- naphthalenesulphonic acid, pamoic acid, pantothenic acid, phosphanilic acid ( ( 4-aminophenyl) phosphonic acid), picric acid, salicyclic acid, stearic acid, succinic acid, tannic acid, tartaric acid, terephthalic acid, p- toluenesulphonic acid, 10-undecenoic acid and the like. Salts may also be formed with inorganic bases. Such inorganic base salts include, for example, salts of aluminium, bismuth, calcium, lithium, magnesium, potassium, sodium, zinc and the like.

It will be appreciated that such salts, provided that they are pharmaceutically acceptable, may be used in therapy. Such salts may be prepared by reacting the compound with a suitable acid or base in a conventional manner .

The compounds of the invention may be used in the treatment of epilepsy, but not limited thereto. They may also be useful in conditions known to respond to anticonvulsant therapy, including chronic pain states, migraine, chronic headaches and mood disorders. The invention is applicable to any disease or disorder of altered neuronal excitability, including epilepsy, migraine prophylaxis and mood stabilisation. It is applicable to treatment of depression and psychomotor retardation in a subject prone to seizures.

In therapeutic use, the active compound may be administered orally, rectally, parenterally, by inhalation (pulmonary delivery) , topically, ocularly, nasally, or to the buccal cavity. Oral administration is preferred. Thus, the therapeutic compositions of the present invention may take the form of any of the known pharmaceutical compositions for such methods of administration. The compositions may be formulated in a manner known to those skilled in the art so as to give a controlled release, for example rapid release or sustained release, of the compounds of the present invention. Pharmaceutically acceptable carriers suitable for use in such compositions are well known in the art. The compositions of the invention may contain 0.1-99% by weight of active compound. The compositions of the invention are generally prepared in unit dosage form. Preferably, a unit dose comprises the active ingredient in an amount of 1-500 g. The excipients used in the preparation of these compositions are the excipients known in the art.

Appropriate dosage levels may be determined by any suitable method known to one skilled in the art. It will be understood, however, that the specific dose level for any particular patient will depend upon a variety of factors including the activity of the specific compound employed, the age, body weight, general health, sex, diet, time of administration, route of administration, rate of excretion, drug combination and the severity of the disease undergoing treatment.

Compositions for oral administration are preferred compositions of the invention and there are known pharmaceutical forms for such administration, for example tablets, capsules, granules, syrups and aqueous or oily suspensions. The pharmaceutical composition containing the active ingredient may be in a form suitable for oral use, for example, as tablets, troches, lozenges, aqueous or oily suspensions, dispersible powders or granules, emulsions, hard or soft capsules, or syrups or elixirs. Compositions intended for oral use may be prepared according to any method known to the art for the manufacture of pharmaceutical compositions, and such compositions may contain one or more agents selected from the group consisting of sweetening agents, flavouring agents, colouring agents and preserving agents in order to provide pharmaceutically elegant and palatable preparations. Tablets contain the active ingredient in admixture with non-toxic pharmaceutically acceptable excipients which are suitable for the manufacture of tablets. These excipients may be, for example, inert diluents, such as calcium carbonate, sodium carbonate, lactose, calcium phosphate or sodium phosphate; granulating and disintegrating agents, for example corn starch or alginic acid; binding agents, for example starch gelatin, acacia, microcrystalline cellulose or polyvinyl pyrrolidone; and lubricating agents, for example magnesium stearate, stearic acid or talc. The tablets may be uncoated or they may be coated by known techniques to delay disintegration and absorption in the gastrointestinal tract and thereby provide a sustained action over a longer period. For example, a time delay material such as glyceryl monostearate or glyceryl distearate may be employed.

Formulations for oral use may also be presented as hard gelatin capsules wherein the active ingredient is mixed with an inert solid diluent, for example calcium carbonate, calcium phosphate or kaolin, or as soft gelatin capsules wherein the active ingredient is mixed with water or an oil medium, for example peanut oil, liquid paraffin or olive oil.

Aqueous suspensions contain the active materials in admixture with excipients suitable for the manufacture of aqueous suspensions. Such excipients are suspending agents, for example sodium carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose, sodium alginate, polyvinyl pyrrolidone, gum tragacanth and gum acacia; dispersing or wetting agents may be a naturally occurring phosphatide, for example lecithin, or condensation products of an alkylene oxide with fatty acids, for example polyoxyethylene stearate, or condensation products of ethylene oxide with long-chain aliphatic alcohols, for example heptadecaethyleneoxycetanol, or condensation products of ethylene oxide with partial esters derived from fatty acids, for example polyoxyethylene sorbitan monooleate. The aqueous suspensions may also contain one or more preservatives, for example ethyl, or n-propyl, p- hydroxybenzoate, one or more colouring agents, one or more flavouring agents, and one or more sweetening agents, such as sucrose or saccharin.

Oily suspensions may be formulated by suspending the active ingredient in a vegetable oil, for example arachis oil, olive oil, sesame oil or coconut oil, or in a mineral oil such as liquid paraffin. The oily suspensions may contain a thickening agent, for example beeswax, hard paraffin or cetyl alcohol. Sweetening agents, such as those set forth above, and flavouring agents may be added to provide a palatable oral preparation. These compositions may be preserved by the addition of an antioxidant such as ascorbic acid.

Dispersible powders and granules suitable for preparation of an aqueous suspension by the addition of water provide the active ingredient in admixture with a dispersing or wetting agent, suspending agent and one or more preservatives. Suitable sweetening, flavouring and colouring agents may also be present.

The pharmaceutical compositions of the invention may also be in the form of oil-in-water emulsions . The oily phase may be a vegetable oil, for example olive oil or arachis oil, or a mineral oil, for example liquid paraffin, or mixtures of these. Suitable emulsifying agents may be naturally occurring gums, for example gum acacia or gum tragacanth, naturally occurring phosphatides, for example soya bean, lecithin, and esters or partial esters derived from fatty acids and hexitol anhydrides, for example sorbitan jnonooleate and condensation products of the said partial esters with ethylene oxide, for example polyoxyethylene sorbitan monooleate. The emulsions may also contain sweetening and flavouring agents.

Syrups and elixirs may be formulated with sweetening agents, for example glycerol, propylene glycol, sorbitol or sucrose. Such formulations may also contain a demulcent, a preservative and flavouring and colouring agents. The pharmaceutical compositions may be in the form of a sterile injectable aqueous or oleagenous suspension. This suspension may be formulated according to the known art using those suitable dispersing or wetting agents and suspending agents which have been mentioned above. The sterile injectable preparation may also be in a sterile injectable solution or suspension in a non-toxic parenterally acceptable diluent or solvent, for example as a solution in 1, 3-butanediol . Among the acceptable vehicles and solvents that may be employed are water, Ringer's solution and isotonic sodium chloride solution. In addition, sterile, fixed oils are conventionally employed as a solvent or suspending medium. For this purpose, any bland fixed oil may be employed including synthetic mono- or diglycerides . In addition, fatty acids such as oleic acid, find use in the preparation of injectables.

The following Examples illustrate the invention. EXPERIMENTATION

Exampl e 1

Screening protocol

Zebrafish in which epilepsy is induced as follows were employed in screens :

1. Zebrafish larvae in 96 well plates are immersed in embryo medium with or without the test compound at a non- toxic concentration, for 24 hours from 6 days post fertilization (6dpf).

2. The fish are then incubated in embryo medium containing the proconvulsant pentylene tetrazole (PTZ) at 15mM, in the presence or absence of the test compound, for a period of 8 to 16 hours. During this time the PTZ- treated fish exhibit multiple seizures and then enter status epilepticus which is manifested by loss of responsiveness to a tap on the dish.

3. Fish are then either scored immediately or transferred to fresh embryo medium and allowed to recover for 16 hours before scoring.

4. The extent of response to PTZ is scored for each fish based on: a. Responsiveness to a tap on the dish, by exhibiting movement b. Viability - alive or dead

As an example of the invention, assays were performed in this zebrafish model of epilepsy with various compounds as shown in Table 1 and Figure 1.

Table 1

Dose response curves were performed for each compound to determine active and toxic doses. The results for at least 3 independent assays for each compound are combined in Table 1. Fish at 6dpf were treated with compound for 22 hours prior to the addition of 15mM PTZ for 6.5 hours, then the fish were allowed to recover in embryo medium for 16 hours prior to scoring the percentage of responsive fish. The mean and standard deviation has been calculated from these figures.

% responsiveness at optimum dose

Example 2

GBRl2909/vanoxerine was tested in mouse and rat models, as follows.

The standard models incorporated into anticonvulsant screening at the ASP include the maximal electroshock test (MES) , the subcutaneous Metrazol test (scMET) , and evaluations of toxicity (TOX) . The data for each condition are presented as N/F, where N=number of animals protected and F=number of animals tested. For tests of toxicity (TOX) , N=number of animals displaying toxic effects and F=number of animals tested. Codes in the C column refer to comments from the technicians performing the experiment and are defined in the comments section if necessary. Any deaths are noted.

Maximal Electroshock Test (MES)

The MES is a model for generalized tonic-clonic seizures and provides an indication of a compound' s ability to prevent seizure spread when all neuronal circuits in the brain are maximally active. These seizures are highly reproducible and are electrophysiologically consistent with human seizures. For all tests based on MES convulsions, 60Hz of alternating current (50 A in mice, 150 in rats) is delivered for 2s by corneal electrodes which have been primed with an electrolyte solution containing an anesthetic agent (0.5% tetracaine HCL). For Test 1, mice are tested at various intervals following doses of 30, 100 and 300 mg/kg of test compound given by i.p. injection of a volume of 0.01 mL/g. In Test 2, rats are tested after a dose of 30 mg/kg (p.o.) in a volume of 0.04 mL/g. Test 3 uses varying doses administered via i.p. injection, again in a volume of 0.04 ml/g. An animal is considered "protected" from MES-induced seizures upon abolition of the hindlimb tonic extensor component of the seizure (Swinyard et al . , 1989, General principles: experimental selection, quantification, and evaluation of anticonvulsants, in Antiepileptic Drugs (R.H.Levy RHM, B. Melrum, J.K. Penry and F.E. Dreifuss ed) pp 85-102, Raven Press, New York.; White et al . , 1995a, Ital J Neurol Sci 16:73-7; White et al . , 1995b, General principles: experimental selection, quantification, and evaluation of antiepileptic drugs, in Antiepileptic Drugs (Levy RHM, R.H.; Meldrum, B.S. ed) pp 99-110, Raven Press, New York) .

Subcutaneous Metrazol Seizure Threshold Test (scMET)

Subcutaneous injection of the convulsant Metrazol produces clonic seizures in laboratory animals. The scMET test detects the ability of a test compound to raise the seizure threshold of an animal and thus protect it from exhibiting a clonic seizure. Animals are pretreated with various doses of the test compound (in a similar manner to the MES test, although a dose of 50 mg/kg (p.o.) is the standard for Test 2 scMET) . At the previously determined TPE of the test compound, the dose of Metrazol which will induce convulsions in 97% of animals (CD₉ : 85 mg/kg mice) is injected into a loose fold of skin in the midline of the neck. The animals are placed in isolation cages to minimize stress (Swinyard et al., 1961, J Physiol 132:97-102) and observed for the next 30 minutes for the presence or absence of a seizure. An episode of clonic spasms, approximately 3-5 seconds, of the fore and/or hindlimbs, jaws, or vibrissae is taken as the endpoint. Animals which do not meet this criterion are considered protected.

Acute Toxicity—Minimal Motor Impairment

To assess a compound'^' s undesirable side effects (toxicity) , animals are monitored for overt signs of impaired neurological or muscular function. In mice, the rotorod (Dunham and Miya, 1957, J. Amer . Pharm . Ass . Sci . Ed. 46:208-209) procedure is used to disclose minimal muscular or neurological impairment. When a mouse is placed on a rod that rotates at a speed of 6 rpm, the animal can maintain its equilibrium for long periods of time. The animal is considered toxic if it falls off this rotating rod three times during a 1-min period. In rats, minimal motor deficit is indicated by ataxia, which is manifested by an abnormal, uncoordinated gait. Rats used for evaluating toxicity are examined before the test drug is administered, since individual animals may have peculiarities in gait, equilibrium, placing response, etc., which might be attributed erroneously to the test substance. In addition to MMI, animals may exhibit a circular or zigzag gait, abnormal body posture and spread of the legs, tremors, hyperactivity, lack of exploratory behavior, somnolence, stupor, catalepsy, loss of placing response and changes in muscle tone.

Results are shown in Table 2 (Test 1), Table 3 (Test 2) and Table 4 (Test 3) . In these tables the solvent code MC indicates that the compound was suspended in 0.5% methylcellulose (in distilled water) . Under solvent prep, M&P/SB indicates that the compound was ground with a mortar and pestle to make the suspension, followed by a 10 minute incubation in a sonabath (sonicator) . Similarly, in the test results area, at each dose, it is indicated whether the compound was in suspension (SUS) or solution (SOL) .

Abbrevia tions

DAT - DA uptake transporter

NET - Norepinephrine transporter

DISCUSSION

As reported herein, anticonvulsant activity was seen in zebrafish at 1.52uM with no apparent sedative or retardive effect. The Rodent data confirmed this with a protective effect being seen 30 mg/kg ip in mice and muscle spasms, and falling off the rotarod at lOOmg/kg. Similarly a protective effect was seen in anticonvulsant tests in rats at 30 mg/kg ip, and po, with hyperesthesia and aggression being noted at those doses .

GBR12909 has been used for some time as the prototypical DA reuptake inhibitor on account of its very high potency for inhibition of DA reuptake [Heikkila, 1984 #6] , disproportionate to its effects on other transporters and other cellular targets. Andersen PH [Andersen, 1989 #7] reported IC50s vs DAT of InM; vs NET of 440nM and vs of

170nM. Both GBR 12909 and cocaine appear to competitively displace 3H-GBR12035 binding suggesting that they bind to

DAT, (although not necessarily at the same site) , but

GBR12909 is not a substrate for the carrier. Ex vivo uptake studies revealed an ED50 of 53 mg/kg po and 26 mg/kg ip for DAT, and >100 vs NET (for both po and ip administration) , 2h pre decapitation (Andersen 1989) . The author also reported binding to HI receptors with an IC50 of 18nM and 3H-batrachotoxinin binding with an IC50 of

184nM (vs flunarizine which had an IC50 of 310nM)

[Andersen, 1989 #7]. 3H(+)PPP binding to the sigma receptor has been reported with an IC50 of 48nM in rat.

GBR 12909 and related structures possess high affinity for a piperazine binding site in the brain and periphery; this is also inhibited by flunarizine (IC50 = lOOnM) , suggesting this may be a novel site on a sodium channel.

Andersen notes previous behavioral studies showing activity in assays thought to predict antidepressant activity, such as the learned helplessness model and the Porsholt swimming test [Andersen, 1989 #7], suggesting that blockade of DA could be useful in the treatment of depression. Andersen [Andersen, 1989 #7] also relays a personal communication (pg501 2^nd column, 2^nd paragraph) that: "the weak anticonvulsant properties of GBR12909 (E.B. Nielsen, personal communication) may be explained by this effect", namely the sodium channel blocking activity, although provide no data to support this.

GBR had also been reported to produce ipsilateral rotations in 60HDA lesioned rats at 7.5 mg/kg ip and at 20mg/kg ip to produce increases in locomotor activity [Heikkila, 1984 #6] . Similarly Elmer [Elmer, 1996 #8] report increased locomotor activity and stereotypy at 15 to 30 mg/kg ip in rats for GBR 12909 with an ED50 for cocaine drug discrimination in rat was 13mg/kg ip . Moreover it does not induce sedation and indeed promotes wakefulness. Wisor [Wisor, 2001 #9] undertook polygraphic recordings and caudate microdialyzate dopamine measurements in narcoleptic dogs and showed that the wake-promoting antinarcoleptic compounds modafinil and amphetamine increase extracellular dopamine in a hypocretin receptor 2-independent manner. In mice, deletion of the dopamine transporter (DAT) gene reduced non-rapid eye movement sleep time and increased wakefulness consolidation independently from locomotor effects . DAT knock-out mice were also unresponsive to the normally robust wake-promoting action of modafinil, methamphetamine, and GBR12909 but were hypersensitive to the wake-promoting effects of caffeine. The authors concluded that dopamine transporters may play an important role in sleep regulation and are necessary for the specific wake-promoting action of amphetamines and modafinil. [Wisor, 2001 #9].

We have found that in actual fact it has strong anticonvulsant effects that moreover, occur at doses that have psychomotor stimulant effects, for example the hyperaesthesia and aggression seen in our rodent assays, as opposed to the typical side effects seen with anticonvulsants of sedation and hyporesponsiveness .

The potency of the effect observed in our studies suggests that this may in large part be mediated through the primary activity of GBR 12909, namely its DAT inhibition, given the relative IC50s of GBR12909, particularly at doses resulting in sub lOOnM brain concentrations, i.e. a >100 fold higher affinity for inhibition of DA reuptake in vitro than at dopaminergic, serotonergic receptors or sodium channels. At higher doses effects are likely to also be mediated through both sodium channels and the sigma receptor, and indeed a combination of effects through these three mechanisms may add to the beneficial anticonvulsant activity thereby seen.

The potency of an effect through dopamine is in itself surprising.

Dopaminergic Agents and Epilepsy

D2 agonists like lisuride and quinpirole possess anticonvulsant activity that is blocked by D2 antagonists [Farjo, 1979 #10; Loscher, 1986 #11; al-Tajir, 1991 #12; al-Tajir, 1991 #13] whilst Dl agonists are generally proconvulsant [Weinshenker, 2002 #14] . Apomorphine produces anticonvulsant effects in humans, particularly in seizures caused by sensitivity to light ( [Neumeyer, 1981 #15; Quesney, 1981 #16] , progressive myoclonus epilepsy [Obeso, 1985 #17] and action myoclonus [Van Woert, 1975 #18], although other types are not responsive to apomorphine. Amphetamines have been shown to have anticonvulsant effects in petit mal, but not grand mal . Apomorphine has shown anti-convulsant activity in animals in a range of models: genetically prone gerbils, baboons, rats and mice; MES; PTZ. It is particularly effective vs myoclonic seizures precipitated by light. Starr [Starr, 1996 #19] concludes that D2 agonist activity could be beneficial in epilepsy, but only if one could divorce it from the emetic, behavioural and endocrine side effects. However the effect of an agonist or antagonist is different from that of a reuptake blocker, with no studies describing pro/anticonvulsant effects of DA reuptake block.

Subsequent to our priority application it was reported by Clinckers et al . [Clinckers, 2004 #1; Clinckers, 2004 #2] that GBR 12909, when perfused into the hippocampus via a microdialysis probe, increased DA levels at lOOuM, decreased pilocarpine induced seizures (due to direct administration of pilocarpine into hippocampus). This effect was antagonized by remoxipride at 4uM, indicating that the effect of GBR12909 on seizure suppression was through its dopaminergic actions.

Sigma receptors

Chou [Chou, 1999 #20] reported that dextromethorphan, dextrorphan and dimemorphan all had high affinity for sigmai receptors (151, 205, 144nM) and all had anticonvulsant effects in MES in mice. Similarly, Kim [Kim, 2003 #21] reported that dextromethorphan (DM) , dextrorphan (DX) , CPK5 and CPK6 all had anticonvulsant effects vs MES and were all high affinity sigmai ligands .

Sodium Channels

Mike et al [Mike, 2004 #22; Mike, 2003 #23] undertook _. hippocampal neuronal cultures and measured sodium currents using patch clamp. The authors found that GBR 12909 inhibited sodium currents in a voltage and frequency dependent fashion, at low uM doses. It stabilized an inactivated state of the channel in a similar way to other anticonvulsants, (at -70mV the rate of recovery from inactivation was slowed with luM GBR) ; but the mechanism appears to be different, with the mechanism is not based on binding equilibrium but on a gating equilibrium of liganded sodium channels.

A compound with a combination of sig a, sodium channel inactivation and dopamine reuptake inhibition effects, together with psychomotor activation effects would be a highly useful anticonvulsant.

An additional problem with treating epilepsy patients is that with the exception of topiramate, all other anticonvulsants induce weight gain. This induces its own morbidity and also contributes to non-compliance with medication. An anti-epileptic with no appetite stimulating, or more preferably, if to be used in combination with another anti-epileptic drug, with appetite suppressing actions, would be highly desirable. It is a further element of the invention, therefore, that GBR 12909 may possess the combined effects of appetite suppressant at doses which also have anti-seizure effects. Van der Hoek report that when 5-20 mg/kg GBR12909 was injected ip 2 h before a 60 min observation test, a significant reduction in food intake was seen [van der Hoek, 1994 #24].

Humans

The human pharmacokinetics of vanoxerine (GBR 12909) were studied in 14 normal subjects with a multiple-dose regimen. In a crossover design, each subject received daily oral doses of 25, 75, and 125 mg for 14 days at each dose level with washout periods of 7 days duration. Drug accumulation was observed, during dosing at the 2 highest dose levels, but near steady-state conditions were attained within 9-11 days of dosing. Estimates of steady-state concentrations all showed statistically significant deviations from dose linearity in the form of disproportionately higher concentrations. At higher dose levels than expected from drug concentrations in serum at lower doses. The nonlinear pharmacokinetics was most likely due to increasing bioavailability with dose. The mean elimination half-lives were 53.5 and 66.0 h at 75 and 125 mg/day, respectively [Ingwersen, 1993 #25] .

No sedative effects were reported.

It is possible to synthesize a decanoate of GBR12909 which, like its parent GBR 12909, has also been shown to display anti-addictive effects [Baumann, 2002 #26] . The decanoate is a long acting depot preparation which would be of benefit to anti-epileptic patients who had difficulty taking oral therapies or remembering to take medications on a daily basis.

Cardiovascular safety considerations

WO03/072030 entitled "Methods for preventing or treating cardiac arrhythmias with vanoxerine" suggests that GBR12909 is unlikely to have any QT prolonging effect.

In preferred embodiments, the GBR12909 or other dopamine uptake inhibitor compound employed in the present invention may be administered to a patient with side- effects or characteristics in which the effects of the compound beyond anti-convulsive activity are beneficial, e.g. in a patient, especially an epilepsy patient, with tendency towards psychomotor retardation, fatigue, sleepiness, weight gain or inanition. Such a tendency may result from side-effects caused by medication. The compound employed in the invention, e.g. GBR12909 or other inhibitor as disclosed, may be co-administered with medication that causes or exacerbates this tendency. The medication may be anti-convulsive and may be antiepileptic. Co-administration may be as a combined preparation for simultaneous or separate, sequential use. A combined preparation of a compound and such medication for simultaneous, separate or sequential use is provided as a further aspect of the present invention.

Preferably in accordance with the present invention administration is to provide a dose of the compound that both promotes psychomotor activation and has an antiepileptic effect.

Antonio Preti, Current opinion on Investigational Drugs, 2000, vol 1 241-251, provides information on human dose equivalents, based on clinical trials, with human pharmacokinetic data, plus data for other species including rat and mouse, marmosets, baboons and rhesus monkeys .

A preferred dose in accordance with the present invention for GBR12909, or other compound as disclosed, is 1- 200mg/day, preferably 50-100mg/day in a human.

A preferred dose in accordance with the present invention equates to provision of a serum concentration of the order of 50-100nM.

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Table 2 Test 1 Results - Mice I.P. Identification

Solvent Code: MC Solvent Prep: M&P.SB Animal Weight: 19.0 to 23.5 g

Response iiiiiiiiiiiiiil ifel SHIP iϊpp ill Ililiii lϊi-i pj llϋ! ϋii I Mf iiii Mil BII I Hfil lull illlllSi iiii MES 10 SOL o π 0 /1 / 1 / / / / / MES 30 SUS 1 /3 0 /3 / 1 / / / / / MES 100 SUS 1 /1 1 /1 / ! / / / / / SCMET 10 ! SOL o n 0 M / / / / / / / SCMET 30 j SUS 0 / 1 0 /1 / I / / / I / / SCMET 100 ^: SUS 0 / 1 0 /1 / ! / / / / / TOX 10 SOL 0 14 0 /2 ' I / / / / / TOX 30 SUS 0 Iβ 0 /4 / 1 / / / / / TOX : 100 SUS 4 14 * 0 /2 / 1 / ! / / /

Response Comments

Table 3 Test 2 Results - Rat P.O. Identification

Solvent Code: MC Solvent Prep: M&P.SB Animal Weight: 100 to 130 g

Response

Response Comments

Table 4 Test 3 Results -Anticonvulsant Identification (Rats I.P.) ITT; A ^ ^ ^ y

>»' A. Sv *^• ' ^.fe ^*^^y t. l'; An A ^l øK >\ A 1 J t. ^■- JΑ Solvent Code: MC Solvent Prep: M&P.SB Animal Weight: 100 to 145g A •* ' t'ϊ A^f VAAΑ A?A' ¹ i ( f i, < Time to Peak Effect

Response Comments

t l iJ'l >*>.KftW^™ -ι.Iι.vSl^,«<.

Claims

1. Use of a compound which is a dopamine uptake or reuptake inhibitor in the manufacture of a medicament for the treatment in a mammal of a neurological disease or disorder related to altered neuronal excitability.

2. Use according to claim 1 wherein the medicament is for treatment of epilepsy, depression, a parkinsonian syndrome or an addictive tendency, for migraine prophylaxis or for mood stabilisation.

3. Use according to claim 2 wherein the medicament is for treatment of epilepsy.

4. Use according to any one of claims 1 to 3 wherein the mammal has tendency towards psychomotor retardation, fatigue, sleepiness, weight gain or inanition.

5. Use according to claim 4 wherein the mammal is subject to anti-epileptic medication with a side-effect profile causing or exacerbating said tendency.

6. Use according to claim 5 wherein said medicament is for co-administration with said medication.

7. Use according to any one of claims 1 to β wherein the compound which is a dopamine uptake or reuptake inhibitor has a sodium channel blocking effect.

8. Use according to claim 7 wherein the compound is a sigma receptor antagonist.

9. Use according to any one of the preceding claims, wherein the compound is a benzhydryloxy-ethyl piperazine derivative .

10. Use according to claim 9 wherein the compound is selected from GBR12909, GBR12935, GBR13069, GBR13098, GBR13119 and pharmaceutically acceptable salts thereof.

11. Use according to claim 10 wherein the compound is GBR12909, or a pharmaceutically acceptable salt.

12. Use according to claim 11 wherein the compound is GBR12909 decanoate.

13. Use according to any one of claims 1 to 12 wherein the medicament is for administration to provide a dose of the compound that both promotes psychomotor activation and has an antiepileptic effect.

14. Use according to claim 13 wherein the mammal is human and the dose provides l-200mg of the compound per day.

15. Use according to claim 14 wherein the dose is 50- lOOmg/day .

16. A method of treatment of a neurological disorder in a mammal, the method comprising administering a compound which is a dopamine uptake or reuptake inhibitor to the mammal in an amount effective to treat the disorder.

17. A method according to claim 16 wherein the treatment is of a disease or disorder as recited in any one of claims 2 to 5.

18. A method according to claim 16 or claim 17 wherein the compound is co-administered with an anti-epileptic medication with a side-effect profile causing or exacerbating a tendency in the mammal towards psychomotor retardation, fatigue, sleepiness, weight gain or inanition.

19. A method according to claim 16, claim 17 or claim 18 wherein the compound is as recited in any one of claims 7 to 12.

20. A method according to claim 16, claim 17, claim 18 or claim 19 wherein the compound is provided in a dose as recited in claim 13, claim 14 or claim 15.