HK1004092B - Pharmacologically active cns compounds - Google Patents

Description

The present invention relates to a pyrimidine compound which is useful in the treatment of central nervous system (CNS) diseases and disorders such as the prevention of cerebral ischaemic damage, to processes for its preparation and to pharmaceutical formulations containing it.

Glutamate is an excitatory amino acid which functions as a neurotransmitter. However, when its extracellular concentration is sufficiently high, glutamate acts as a powerful neurotoxin, capable of killing neurones in the central nervous system (Rothman & Olney (1986) Prog. Brain. Res., 63, 69). The neurotoxic effect of glutamate has been implicated in a number of central nervous system disorders and disease states including cerebral ischaemic damage, epilepsy and chronic neurodegenerative disorders such as Alzheimer's disease, motor system disorders and Huntington's chorea (Meldrum Clinical Science (1985) 68 113-122). In addition, glutamate has been implicated in other neurological disorders such as manic depression, depression, schizophrenia, high pressure neurological syndrome, chronic pain, trigeminal neuralgia and migraine.

EP-A-0169139 discloses piperidino compounds having therapeutic properties on both the central and peripheral nervous systems. Tuomisto et al, Agents and Actions 20, 252-254, 1987 reports the inhibition of sound-induced convulsions by metoprine in the audiogenic seizure susceptible rat. NL-A-6715452 discloses a process for the preparation of halopyrimidines by reacting a nitrile with an isocyanide-dichloride.

EP-A-0158137 discloses pyrimidines useful as components of liquid crystalline phases. Tuomisto et al, Neuropharmacology 25, 955-958, 1986 reports experiments in which metoprine was used to elevate rat brain histamine concentrations. The authors postulate that histamine may be an anticonvulsive inhibitory transmitter. Cavallito et al, Drug Metabolism and Disposition 6, 329-337, 1978 report the physicochemical properties, kinetics and metabolism of a series of lipid-soluble 2,4-diamino-5-phenylpyrimidine folate antagonists including metoprine, etoprine and pyrimethamine.

In EP-A-21121 there is disclosed a group of 3,5-diamino-6-(substituted phenyl)-1,2,4-triazines which are active in the treatment of CNS disorders, for example in the treatment of epilepsy. One compound described in that application, 3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazine (lamotrigine), has been shown to inhibit the release of excitatory amino acids, glutamate and aspartate (Leach et al Epilepsia 27, 490-497, 1986, A.A. Miller et al New anticonvulsant drugs. Ed. Meldrum and Porter 165-177, 1987).

The present inventors have now found that a particular substituted pyrimidine compound is a potent inhibitor of glutamate release. This compound is useful in the treatment of the above-mentioned disorders and disease states of the central nervous system. The compound is also an inhibitor of aspartate release.

Accordingly, the present invention provides 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine and acid addition salts thereof.

4-Amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine and pharmaceutically acceptable acid addition salts thereof are useful in the treatment or prophylaxis of a disease or disorder of the central nervous system of a mammal in which glutamate is implicated. They may be therefore used in the treatment or prophylaxis of acute and chronic disorders of the mammalian central nervous system. The acute condition comprises cerebral ischaemic damage which may arise from a variety of causes including stroke, cardiac arrest, bypass surgery, neonatal anoxia and hypoglycaemia; and also physical injury or trauma of the spinal cord or brain.

Chronic neurodegenerative disorders which may be treated include Alzheimer's disease, Huntington's chorea, olivopontocerebellar atrophy and motor system disorders. Other neurological conditions which may be treated with a compound of the invention include depression, manic depression, schizophrenia, chronic pain, epilepsy, trigeminal neuralgia and migraine.

A compound of the invention can be used in the treatment or prevention of a disease or disorder of the central nervous system of a mammal in which neurotoxic extracellular glutamate is implicated. A mammal predisposed to or having neurotoxic extracellular glutamate levels of the central nervous system can be treated.

Suitable acid addition salts of 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine include those formed with both organic and inorganic acids. Such acid addition salts will normally be pharmaceutically acceptable. Thus, preferred salts include those formed from hydrochloric, hydrobromic, sulphuric, citric, tartaric, phosphoric, lactic, pyruvic, acetic, succinic, fumaric, maleic, oxaloacetic, methanesulphonic, ethanesulphonic, p-toluenesulphonic, benzenesulphonic and isethionic acids. These salts can be made by reacting 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine as the free base with the appropriate acid.

While it is possible for the 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine to be administered as the raw chemical, it is preferable to present it as a pharmaceutical formulation. A pharmaceutical formulation of the present invention comprises 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine or a pharmaceutically acceptable acid addition salt thereof together with one or more acceptable carriers therefor and optionally other therapeutic ingredients. The carrier(s) must be "acceptable" in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient thereof.

The formulations include those suitable for oral, parenteral (including subcutaneous, intradermal, intramuscular and intravenous), rectal and topical (including dermal, buccal and sublingual) administration although the most suitable route may depend upon for example the condition and disorder of the recipient. The formulations may conveniently be presented in unit dosage form and may be prepared by any of the methods well known in the art of pharmacy. All methods include the step of bringing into association 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine or a pharmaceutically acceptable acid addition salt thereof ("active ingredient") with the carrier which constitutes one or more accessory ingredients. In general the formulations are prepared by uniformly and intimately bringing into association the active ingredient with liquid carriers or finely divided solid carriers or both and then, if necessary, shaping the product into the desired formulation.

Formulations of the present invention suitable for oral administration may be presented as discrete units such as capsules, cachets or tablets each containing a predetermined amount of the active ingredient; as a powder or granules; as a solution or a suspension in an aqueous liquid or a non-aqueous liquid; or as an oil-in-water liquid emulsion or a water-in-oil liquid emulsion. The active ingredient may also be presented as a bolus, electuary or paste.

A tablet may be made by compression or moulding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine the active ingredient in a free-flowing form such as a powder or granules, optionally mixed with a binder, lubricant, inert diluent, lubricating, surface active or dispersing agent. Moulded tablets may be made by moulding in a suitable machine a mixture of the powdered compound moistened with an inert liquid diluent. The tablets may optionally be coated or scored and may be formulated so as to provide slow or controlled release of the active ingredient therein.

Formulations for parenteral administration include aqueous and non-aqueous sterile injection solutions which may contain anti-oxidants, buffers, bacteriostats and solutes which render the formulation isotonic with the blood of the intended recipient; and aqueous and non-aqueous sterile suspensions which may include suspending agents and thickening agents. The formulations may be presented in unit-dose or multi-dose containers, for example sealed ampoules and vials, and may be stored in a freeze-dried (lyophilised) condition requiring only the addition of a sterile liquid carrier, for example, water-for-injection, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules and tablets of the kind previously described.

Formulations for rectal administration may be presented as a suppository with the usual carriers such as cocoa butter or polyethylene glycol.

Formulations for topical administration in the mouth, for example buccally or sublingually, include lozenges comprising the active ingredient in a flavoured basis such as sucrose and acacia or tragacanth, and pastilles comprising the active ingredient in a basis such as gelatin and glycerin or sucrose and acacia.

Preferred unit dosage formulations are those containing an effective dose, as hereinbelow recited, or an appropriate fraction thereof, of the active ingredient.

It should be understood that in addition to the ingredients particularly mentioned above, the formulations of this invention may include other agents conventional in the art having regard to the type of formulation in question, for example those suitable for oral administration may include flavouring agents.

Tablets and other forms of presentation provided in discrete units may conveniently contain an amount of 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine which is effective at such dosage or as a multiple of the same, for instance, units containing 5 mg to 500 mg, usually around 10 mg to 250 mg.

The 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine is preferably used to treat CNS disorders or diseases by oral administration or injection (intraparenteral or subcutaneous). The precise amount of compound administered to a patient will be the responsibility of the attendant physician. However the dose employed will depend on a number of factors, including the age and sex of the patient, the precise disorder being treated, and its severity. Thus for example when treating a patient with epilepsy the dose range is likely to be significantly lower than when treating a patient after stroke to alleviate cerebral ischaemic damage. Also the route of administration is likely to vary depending on the condition and its severity.

The 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine may be administered orally or via injection at a dose of from 0.1 to 30 mg/kg per day. The dose range for adult humans is generally from 8 to 2,400 mg/day and preferably 35 to 1,050 mg/day. The compound is long-acting. It may therefore be advantageous to administer it at an initial dose of 70 to 2,400 mg on the first day and then at a lower dose of 20 to 1,200 mg on subsequent days.

A long acting compound is advantageous in the clinic because it is easier to manage. In the chronic situation, it may be administered without infusion and there is the minimum of direct medical intervention. Also in acute conditions, patient compliance is encouraged by minimising daily dosing.

The present invention provides a process for the preparation of 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine or an acid addition salt thereof, which process comprises reacting a compound of formula (I): wherein L is a leaving group and Y is cyano, with the compound of formula (II): or a salt thereof; and isolating the thus formed 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine as the free base or as an acid addition salt thereof.

Examples of suitable leaving groups (L) include C_1-4 alkoxy, halo, anilino, morpholino C_1-4 alkylamino, benzylamino and alkylthio. Preferably the reaction of the compounds of formulae (I) and (II) is carried out in a non-aqueous solvent, for example an alkanol such as ethanol, at elevated temperature (e.g. between 50 and 110°C) in a base, preferably an alkanoxide, preferably under reflux using sodium ethoxide as the base.

Compounds of formula (I) may be made by methods known in the art (JACS, 1951, 73, 3763-3770), for example by the reaction of the compound of formula (III): wherein Y is cyano, with diazomethane or with alkylorthoesters (JACS, 1952, 74, 1310-1313) or by condensation with an amine. The compound of formula (III) can be made by methods known in the art JACS supra.

The compound of formula (II) can be made by standard methods, for example by reaction of a known compound of formula H₂N-C(NH)-R₁ where R₁ is alkylthio with N-methylpiperazine. This reaction preferably takes place at room temperature in water.

The invention additionally provides a process for the preparation of 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine, which process comprises reacting a compound of formula (IV): wherein Y is cyano and R₁₀ and R₁₁ are both alkyl or together form a group -(C(R)₂)_n- where R is hydrogen or alkyl and n is an integer from 2 to 4, with the compound of formula (II) as defined above. Preferably the reaction is carried out in a non-aqueous solvent, eg. ethanol, under reflux in the presence of sodium ethoxide as a base.

The following Example illustrates the invention. Two Reference Examples are provided.

REFERENCE EXAMPLE 1 Preparation of N-methylpiperazinoformamidine hydriodide

Thiourea (10.8 g) was dissolved in acetone (250 ml) at 50°C. Iodomethane (10 ml) was added and the reaction was stirred at 50°C for 4 hours. After cooling, the solution was diluted with ether (1 litre) and the methiodide salt was filtered, washed with ether and dried in vacuo, 29.2 g, mp. 113-115°C. The methiodide salt (5 g) was dissolved in water (30 ml) and N-methylpiperazine was added. The solution was stirred, with nitrogen bubbled through, at room temperature for 24 hours. The solution was concentrated in vacuo. The residue was slurried with ethanol, filtered and dried in vacuo, 4.98 g, mp. 230-242°C.

REFERENCE EXAMPLE 2

• 1. Preparation of 2,3,5-trichlorobenzylalcohol To a solution of 2,3,5-trichlorobenzaldehyde (Aldrich, 50 gms) in ethanol (1.0 l) at room temperature was added NaBH4 (7.00 gms) and the resulting mixture stirred for 3.5 hours. The reaction was quenched with water and the solvent evaporated invacuo before partitioning the residue between CHCl3 and saturated NaHCO3 solution. The organic phase was washed with brine, dried over MgSO4, filtered and the solvent evaporated invacuo to leave a white solid, 43.00 gms, mp. 90-93°C.
• 2. Preparation of 2,3,5-trichlorobenzyl bromide To a solution of the alcohol in benzene (400 ml) under N2 was added PBr3 (126.58 gms) and the mixture stirred at 55-60°C for 3.5 hours. After cooling, the mixture was poured onto crushed ice (2 l) and the benzene layer separated. The aqueous phase was washed with benzene (x3) and the combined benzene extracts washed with saturated NaHCO3 solution and water, dried over MgSO4, filtered and the solvent evaporated to leave a brownish liquid which solidified on standing, 37.53 gms, mp. 40-42°C.
• 3. Preparation of 2,3,5-trichlorophenylacetonitrile The bromide was suspended in dimethylformamide (DMF) (130 ml)/water (86.67 ml) at 0°C and KCN (12.99 gms) added in portions. After stirring at 30-35°C for 3 hours, the suspension was diluted with water and extracted with diethyl ether (Et2O). The combined ether extracts were washed with water, dried over MgSO4, filtered and the solvent evaporated invacuo. Chromatography on silica gel eluting with hexane to 20% ether-hexane gave the desired product as a white solid, 18.52 gms, mp. 60-62°C.

EXAMPLE Synthesis of 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine mesylate

• 1. Preparation of 2-(2,3,5-trichlorophenyl)-3-oxo-propionitrile sodium saltTo a solution of sodium ethoxide (NaOEt)(from 0.803 g of sodium) in ethanol (55 ml) cooled in ice, under nitrogen, was added 2,3,5-trichlorophenylacetonitrile (Reference Example 2). Ethyl formate (5.1 ml) was added and the mixture was stirred at room temperature overnight. After stirring for a further 2.5 hours at 50°C, the mixture was cooled and filtered. The filtrate was evaporated, and the residue was triturated with diethyl ether, filtered and dried (6.82 g).
• 2. Preparation of 2-(2,3,5-trichlorophenyl)-3-methoxyacrylonitrile The above solid was dissolved in DMF (36 ml) and methyliodide (2 ml) was added. The reaction vessel was sealed before stirring the contents at 40°C for 3 hours. The solvent was then evaporated. The residue was partitioned between water and ethyl acetate. The organic phase was washed with water, dried (MgSO4) and the solvent evaporated to give the crude product as a red-brown oil that solidified on standing (5.04 g).
• 3. Preparation of 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine To a solution of NaOEt (from 0.21 g of sodium) in ethanol (20 ml) was added N-methylpiperazinoformamidine hydriodide (2.06 g) (Reference Example 1). After stirring for a further 10 minutes, the 2-(2,3,5-trichlorophenyl)-3-methoxyacrylonitrile was added and the mixture was stirred at reflux for 4 hours. The mixture was left standing at room temperature overnight and then filtered. The filtrate was concentrated and the residue was purified by chromatography on SiO2, eluting with CHCl3 to 4% MeOH/CHCl3 to give the title compound as the free base, 0.89 g, mp. 162-164°C. The free base (0.805 g) was then dissolved in ethanol (35 ml) and cooled in an ice bath. Methanesulphonic acid (0.21 g) was added and the reaction was stirred at room temperature for 2 hours. The solvent was then evaporated and the residue was triturated with diethyl ether, filtered, dissolved in cold water and freeze dried to give the title salt as a pale green solid, 0.98 g, mp. 143-146°C. 1H NMR data (δ), dimethylsulphoxide (DMS0)-d6: 7.8(d,1H), 7.65(s,1H), 7.36(d,1H), 6.33-6.23(brs,2H), 3.68(t,4H), 2.32(t,4H), 2.2(s,3H). In the foregoing, the signals have been abbreviated as follows: s = singlet; d = doublet; t = triplet; brs = broad singlet.

Pharmacological Activity Inhibition of Glutamate release and Inhibition of Rat Liver DHFR

4-Amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine was tested for its effect on veratrine-evoked release of glutamate from rat brain slices according to the protocol described in Epilepsia 27(5): 490-497, 1986. The protocol for testing for inhibition of DHFR activity was a modification of that set out in Biochemical Pharmacology Vol. 20 pp 561-574, 1971. The results are given in Table 1, the IC₅₀ being the concentration of compound to cause 50% inhibition of (a) veratrine-evoked release of glutamate and (b) DHFR enzyme activity. TABLE 1

2.15 (0.90-5.10)	> 100

Pharmaceutical Formulation Examples A. Injection

The salt of 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine was dissolved in sterile water for injection. In the following Pharmaceutical Formulation Examples B to D, the active compound may be 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine or a pharmaceutically acceptable acid addition salt thereof.

B. Capsule formulations Capsule Formulation A

Formulation A may be prepared by admixing the following ingredients and filling two-part hard gelatin capsules with the resulting mixture:

	mg/capsule
(a) Active ingredient	250
(b) Lactose B.P.	143
(c) Sodium Starch Glycollate	25
(d) Magnesium Stearate	2

Capsule Formulation B

	mg/capsule
(a) Active ingredient	250
(b) Macrogel 4000 BP	350

Capsules may be prepared by melting the Macrogel 4000 BP, dispersing the active ingredient in the melt, and filling two-part hard gelatin capsules therewith.

Capsule Formulation C (Controlled-release capsule)

	mg/capsule
(a) Active ingredient	250
(b) Microcrystalline cellulose	125
(c) Lactose BP	125
(d) Ethyl Cellulose	13

The controlled-release capsule formulation may be prepared by extruding mixed ingredients (a) to (c) using an extruder, then spheronising and drying the extrudate. The dried pellets are coated with ethyl cellulose (d) as a controlled-release membrane and filled into two-part hard gelatin capsules.

C. Syrup formulation

Active ingredient	0.2500 g
Sorbitol Solution	1.5000 g
Glycerol	1.0000 g
Sodium Benzoate	0.0050 g
Flavour	0.0125 ml
Purified Water   q.s. to	5.0 ml

The sodium benzoate is dissolved in a portion of the purified water and the sorbitol solution added. The active ingredient is added and dissolved. The resulting solution is mixed with the glycerol and then made up to the required volume with the purified water.

D. Suppository formulation

	mg/suppository
Active ingredient (63 µm)*	250
Hard Fat, BP (Witepsol H15 - Dynamit Nobel)	1770

* The active ingredient is used as a powder wherein at least 90% of the particles are of 63 µm diameter or less.

One-fifth of the Witepsol H15 is melted in a steam-jacketed pan at 45°C maximum. The active ingredient is sifted through a 200 µm sieve and added to the molten base with mixing, using a Silverson fitted with a cutting head, until a smooth dispersion is achieved. Maintaining the mixture at 45°C, the remaining Witepsol H15 is added to the suspension which is stirred to ensure a homogeneous mix. The entire suspension is then passed through a 250µm stainless steel screen and, with continuous stirring, allowed to cool to 40°C. At a temperature of 38-40°C, 2.02g aliquots of the mixture are filled into suitable plastics moulds and the suppositories are allowed to cool to room temperature.

Claims (17)

1. A process for the preparation of 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine or an acid addition salt thereof, which process comprises reacting a compound of formula (I): wherein L is a leaving group and Y is cyano, with the compound of formula (II): or a salt thereof; and isolating the thus formed 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine as the free base or as an acid addition salt thereof.
2. A process according to claim 1, wherein L is C_1-4 alkoxy.
3. A process according to claim 1 or 2, wherein the said reaction is carried out in a non-aqueous solvent at elevated temperature in the presence of a base.
4. A process according to claim 3, wherein the said reaction is carried out under reflux.
5. A process according to claim 3 or 4, wherein the solvent is an alkanol.
6. A process according to claim 5, wherein the solvent is ethanol.
7. A process according to any one of the preceding claims, wherein the said salt is a salt formed from hydrochloric, hydrobromic, sulphuric, citric, tartaric, phosphoric, lactic, pyruvic, acetic, succinic, fumaric, maleic, oxaloacetic, methanesulphonic, ethanesulphonic, p-toluenesulphonic, benzenesulphonic or isethionic acid.
8. A process for the preparation of 4-amino-2-(4-methylpiperazin-1-yl)-5-(2,3,5-trichlorophenyl)pyrimidine, which process comprises reacting a compound of formula (IV): wherein Y is cyano and R₁₀ and R₁₁ are both alkyl or together form a group -(C(R)₂)_n- where R is hydrogen or alkyl and n is an integer from 2 to 4, with the compound of formula (II) as defined in claim 1.
9. A process according to claim 8, wherein the said reaction is carried out in a non-aqueous solvent under reflux in the presence of, as a base, sodium ethoxide.