AU8102098A - 5-(2-ethyl-2H-tetrazol-5-Y1)-1-methyl-1,2,3,6-tetrahydro pyridine maleate - Google Patents

Description

WO 99/01448 PCT/DK98/00294 5-(2-Ethyl-2H-tetrazol-5-yl)-I -methyl-1,2,3,6-tetrahydropyridine maleate The present invention relates to a maleic acid addition salt of 5-(2-ethyl-2H-tetrazol 5-yl)-1l-methyl-1,2,3,6-tetrahydropyridine, pharmaceutical compositions containing 5 the acid addition salt and the use thereof for the treatment of diseases or disorders caused by a malfunction of the cholinergic or muscarinic system. Background of the Invention 10 US patent No. 4,866,077 discloses a series of piperidine and tetrahydropyridine compounds substituted in position 5 with a 1,2,3-triazole or a tetrazole group. These compounds have high affinity to central AcCh receptors, including muscarinic M1 receptors, and are considered useful for the treatment of disorders involving mal function of the cholinergic system, e.g. Alzheimer's disease, senile dementia, and 15is impaired learning or memory function. The structure-activity relationship of these compounds has been described by Moltzen et al., in Med. Chem. 1994, 37, 4085-4099. The compound, 5-(2-ethyl-2H tetrazol-5-yl)-1l-methyl-1,2,3,6-tetrahydropyridine having the formula N= N N N 20 1 which is the subject of the present invention, has been reported to be a partial ago nist at muscarinic M1 receptors and an antagonist at muscarinic M2 and M3 re ceptors (Subtypes of Muscarinic Receptors, The sixth Intemrnational Symposium, 25 Nov. 9-12, 1994, Fort Lauderdale). Ligands at muscarinic receptors with this phar macological profile are considered of particular interest for the treatment of Alz heimer's disease.

WO 99/01448 PCT/DK98/00294 2 Further, it has been demonstrated that 5-(2-ethyl-2H-tetrazol-5-yl)-1l-methyl-1,2,3,6 tetrahydropyridine may be useful for the treatment of traumatic brain injury (TBI) and psychosis or other schizophreniform diseases (WO97/17074 and co-pending PCT application claiming priority from DK 620/97). 5 TBI may be caused by various physical and neurological conditions or diseases such as conditions associated with trauma to the brain or spinal cord e.g. caused by physical forces acting on the scull or spinal column, ischaemia, stroke, arrested breathing, cardiac arrest, cerebral thrombosis or embolism, neurological problems 10 caused by AIDS, cerebral hemorrhage, encephalomyelitis, hydrocephalus, post operative events, cerebral infections, concussions, or elevated intracranial pressure. Psychosis means to include all forms of psychoses such as organic psychoses, drug induced psychoses, Alzheimer related psychoses, and psychoses or related 15 conditions associated with other mental disorders, such as paranoid personality disorder, ect. The terms schizophrenia and schizophreniform diseases include all types of such disorders, e.g. catatonic, disorganised, paranoid, undifferential and residual schizo 20 phrenia, and all conditions associated with such diseases, including the positive and negative symptoms thereof. Unfortunately, the 5-(2-ethyl-2H-tetrazol-5-yl)-l-methyl-1,2,3,6-tetrahydropyridine free base is a liquid and as such not suitable for the production of solid pharmaceu 25 tical preparations, such as tablets or capsules. As oral administration a solid entity is the preferred and most convenient method for the administration of a pharma ceutical, a solid form of 5-(2-ethyl-2H-tetrazol-5-yl)-1 -methyl-1,2,3,6 tetrahydropyridine, suitably a pharmaceutically acceptable salt thereof, which can be mixed with various adjuvants or diluents and formed into tablets or filled in cap 30 sules, is highly desirable. The oxalic acid addition salt of 5-(2-ethyl-2H-tetrazol-5-yl)-1l-methyl-1,2,3,6-tetra- WO 99/01448 PCT/DK98/00294 3 hydropyridine is specifically disclosed in US patent No. 4,866,077. However, while oxalic acid addition salts may be particularly useful for crystallization and purification purposes, they are not suitable for the preparation of pharmaceuticals due to the toxicity of oxalic acid. 5 A pharmaceutically acceptable salt of 5-(2-ethyl-2H-tetrazol-5-yl)-1l-methyl-1,2,3,6 tetrahydropyridine, the tartrate, has been described in Moltzen et al., J. Med. Chem.1994, 37, 4085-4099. Unfortunately, the tartrate is difficult to precipitate and recrystallize in large scale productions. Accordingly, the tartrate salt is not suitable 10 for commercial production of solid pharmaceutical preparations. Surprisingly, it has now been found that precipitation and recrystallization of the cor responding maleic acid addition salt proceed smoothly even in large scale. 15 The Invention It is the object of the present invention to provide a solid pharmaceutically accept able form of 5-(2-ethyl-2H-tetrazol-5-yl)-1l-methyl-1,2,3,6-tetrahydropyridine suitable for large scale production of solid pharmaceutical entities, e.g. tablets or capsules. 20 According to the present invention the maleic acid addition salt of 5-(2-ethyl-2H tetrazol-5-yl)-l1-methyl-1,2,3,6-tetrahydropyridine and pharmaceutical compositions comprising said acid addition salt have been provided. 25 The maleic acid addition salt according to the invention may be obtained by treat ment of 5-(2-ethyl-2H-tetrazol-5-yl)-1-methyl-1,2,3,6-tetrahydropyridine or a salt de rivative thereof with maleic acid in an inert solvent, followed by precipitation, isola tion and optionally recrystallization by known methods and if desired followed by micronisation of the crystalline product by wet or dry milling or another convenient 30 process, or preparation of particles from a solvent-emulsification process.

WO 99/01448 PCT/DK98/00294 4 Precipitation of the maleate salt is carried out in an inert aprotic solvent, preferably tetrahydrofuran (THF). The maleate acid addition salt of the invention may be administered in any suitable 5 way e.g. orally or parenterally, and the compounds may be presented in any sui table form for such administration, e.g. in the form of tablets, capsules, powders, syrups or solutions or dispersions for injection. Preferably, and in accordance with the purpose of the present invention, the maleate of the invention is administered in the form of a solid pharmaceutical entity, suitably as a tablet or a capsule. 10 Methods for the preparation of solid pharmaceutical preparations are well known in the art. Tablets may thus be prepared by mixing the active ingredients with ordinary adjuvants and/or diluents and subsequently compressing the mixture in a conve nient tabletting machine. Examples of adjuvants or diluents comprise: corn starch, 15 lactose, talcum, magnesium stearate, gelatine, lactose, gums, and the like. Any other adjuvant or additive colourings, aroma, preservatives, etc. may also be used provided that they are compatible with the active ingredients. The compound of the invention is most conveniently administered orally in unit dos 20 age forms such as tablets or capsules, containing the active ingredient in an amount from about 10 [tg/day/kg to 15 mg/day/kg body weight, preferably 25 pg/day/kg to 10 mg/day/kg and most preferred 4-5- mg/kg/day body weight. Ac cordingly, a suitable daily dose is 500 pg to 1000 mg/day, preferably 1.0 to 500 mg/day and most preferred 300-400 mg/day. 25 The maleate acid addition salt according to the invention is readily soluble in water, alcohol and other polar solvents and may, if desired, be used for the preparation of solutions for injection. Solutions for injections may be prepared by dissolving the active ingredient and 30 possible additives in a part of the vehicle, preferably sterile water, adjusting the so lution to the desired volume, sterilization of the solution, and filling in suitable am- WO 99/01448 PCT/DK98/00294 5 poules or vials. Any suitable additive conventionally used in the art may be added, such as tonicity agents, preservatives, antioxidants, ect. The invention will be illustrated in the following examples. The examples may not 5 be construed as limiting. The 5-(2-ethyl-2H-tetrazol-5-yl)-1l-methyl-1,2,3,6-tetrahydropyridine, oxalate starting material can be prepared as described in US patent No. 4,866,077.

WO 99/01448 PCT/DK98/00294 6 Example 1 5-(2-ethyl-2H-tetrazol-5-yl)-l -methyl-1,2,3,6-tetrahydropyridine, maleate 5 5-(2-ethyl-2H-tetrazol-5-yl)-1l-methyl-1,2,3,6-tetrahydropyridine, oxalate (5.6 kg) was suspended in demineralized water (22 L). Ethyl acetate (17 L) was added, and a cooled solution (15-20 OC) of potassium hydroxide (2.8 kg) in demineralized water (12.5 L) was added with stirring and cooling. pH was adjusted to 10 by adding aqueous potassium hydroxide. The aqueous layer was further extracted with ethyl 10 acetate (2 x 11 L). The combined organic extracts were dried with sodium sulphate (3.8 kg) and evaporated in vacuo until a pot temperature of 75-80 oC was reached. The residue was dissolved in tetrahydrofuran (11 L), and a solution of maleic acid (2.4 kg) in tetrahydrofuran (11 L) was added with stirring. The solution was cooled to approximately 15 OC and stirred for a minimum of 1 hour. 15 The precipitate was isolated on a nutche filter, and washed with tetrahydrofuran (2 x 2 L). The wet filtercake was recrystallized once from tetrahydrofuran (13 L). The recrystallized material was isolated on a nutche filter, washed with tetrahydrofuran (5 L), and finally dried in vacuo at 65 OC overnight. Yield 5.0. kg (83%) mono 20 maleate. M.p. 116 OC. Example 2 5-(2-ethyl-2H-tetrazol-5-yl)-1-methyl-1,2,3,6-tetrahydropyridine, maleate 25 Liberation of the free base: A nitrogen purged reactor was charged with 62-64 kg 5-(2-ethyl-2H-tetrazol-5-yl)-1l-methyl-1,2,3,6-tetrahydropyridine, oxalate, water, and toluene. The mixture was stirred and cooled to below 10 oC while adding potassium hydroxide pellets dissolved in water until pH > 12 was achieved. The layers were 30 separated, the aqueous layer re-extracted with toluene and subsequently dis carded.

WO 99/01448 PCT/DK98/00294 7 The combined organic phases were washed with water. Toluene was distilled off in vacuo at a temperature of not more than 50 OC. Precipitation: The residue was re-dissolved by adding THF and maleic acid (26.5 5 27.5 kg) while heating to reflux. The temperature of the reaction mixture was ad justed to approx. 50 oC. The solution was left with slow agitation and voluntary cooling for crystallization ( 1 ). The slurry was cooled to below 20 0C and isolated. The product was washed with tetrahydrofuran and dried in vacuo yielding 5-(2-ethyl-2H tetrazol-5-yl)-l-methyl-1,2,3,6-tetrahydropyridine, mono-maleate. 10 Recrystallisation: A reactor was charged with 5-(2-ethyl-2H-tetrazol-5-yl)-l-methyl 1,2,3,6-tetrahydropyridine, maleate, and tetrahydrofuran. The solution was heated to reflux and then allowed to crystallize ('). The product was isolated, washed sev eral times with THF, and dried in vacuo. 15 () If necessary, the solution may be seeded with 5-(2-ethyl-2H-tetrazol-5-yl)-1 methyl-1,2,3,6-tetrahydropyridine, maleate from a previous batch. 20 25

Claims (8)

1. A maleic acid addition salt of 2-ethyl-5-(1 -methyl-1,2,5,6-tetrahydro-3 pyridyl)-2H-tetrazole. 5

2. The maleic acid addition salt according to claim 1 which is the mono-maleic acid addition salt.

3. A pharmaceutical composition comprising a maleic acid addition salt 10 according to claims 1 to 2 together with at least one pharmaceutically ac ceptable carrier or diluent.

4. A method for the treatment of a disorder or disease caused by malfunction of the acetylcholine (AcCh) or muscarinic system, comprising administering a 15is therapeutically effective amount of a maleic acid addition salt according to claims 1 to 2 to a subject suffering from such a disorder.

5. The method according to claim 3 wherein Alzheimer's disease, traumatic brain injury, or psychotic disorders are treated. 20

6. The use of a maleic acid addition salt according to claims 1 to 2 for the preparation of a pharmaceutical composition for the treatment of a disorder or disease caused by malfunction of the acetylcholine (AcCh) or muscarinic system. 25

7. The use according to claim 5 wherein the disease or disorder is Alzheimer's disease, traumatic brain injury, or psychotic disorders.

8. A method for the preparation of maleic acid addition salt according to claims 30 1 to 2 characterized in that the acid addition salt is precipitated from a solu tion of 2-ethyl-5-(1-methyl-1,2,5,6-tetrahydro-3-pyridyl)-2H-tetrazole, THF and maleic acid.