JPH09323939A - Antidemential agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an antidemential agent excellent in intracerebral transferability, long in effective action time, slight in adverse effect, comprising a liposome preparation containing an acetylcholine esterase inhibitor. SOLUTION: An acetylcholine esterase inhibitor such as an acridine derivative, especially tacrine (chemical name 9-amino-1,2,3,4-tetrahydroacridine) is sealed in a liposome to give a liposome preparation. The pharmaceutical preparation of the Iiposome is carried out by forming a lipid thin membrane by using tacrine, a liposome forming substance (e.g. phosphatidylcholine) and a proper additive and an organic solvent and treating the thin membrane by an ultrasonic waves. The liposome preparation is effective for treating central nerve-based disorders such as senile dementia of Alzheimer and cerebrovascular dementia. The dose of an acetylcholine esterase strong in hepatotoxicity, etc., can be reduced.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an anti-dementia agent, and more particularly to an anti-dementia agent comprising a liposome preparation containing an acetylcholinesterase inhibitor.

[0002]

Background Art Although the cause of senile dementia such as Alzheimer's dementia has not been completely elucidated yet, senile dementia such as Alzheimer's dementia is a cholinergic activator based on the cholinergic theory. Many treatments have been tried with drugs. That is, attempts have been made to treat dementia by activating cholinergic hypofunction by administering an acetylcholinesterase inhibitor to increase the concentration of acetylcholine in the brain.

For example, a treatment example of dementia using a typical acetylcholinesterase inhibitor, tacrine or physostigmine, has been reported (Neurology, 8,397,1978).
Further, JP-A-61-148154, JP-A-63-141980, JP-A-63-166881, JP-A-64-73, and JP-A-1-250353.
No. 2, JP-A-2-167267, and Journal of Medicin
al chemistry, 31 , 1278); ibid. 32 , 1805 (1989), it has been shown that aminoacridine derivatives have an acetylcholinesterase inhibitory action and are effective for the treatment of Alzheimer-type senile dementia. Summers et al. Also reported that administration of tacrine and lecithin to patients with Alzheimer-type dementia improved their symptoms (The N.
ewEngland Journal of Medicine 315, 1241, 1986). The lecithin used in combination here is simply a large amount of lecithin being co-administered, not the drug being liposomed.

On the other hand, efficient drug transfer into the brain is considered to be useful for treating Alzheimer's dementia and other central nervous system patients, but the transfer of the drug into the brain is restricted by the blood-brain barrier. Has been done. Until now, various attempts have been made to cross the blood-brain barrier, but none of them were effective. In addition, liposomes of drugs have been used for the purpose of sustained release of drugs, reaching target sites, etc., but liposomes have been put to practical use for central nervous system drugs for the purpose of transfer to the brain. There is no example.

[0005]

Tacrine, which is an acetylcholinesterase inhibitor, is marketed in the United States as an anti-dementia agent, but it has a problem of causing side effects such as liver damage. This side effect is a serious problem because of its frequency of occurrence. Therefore, there is a demand for the development of a drug that enhances the intracerebral transferability of an acetylcholinesterase inhibitor such as tacrine, can exert its effect at a low dose, and has few side effects.

[0006]

Means for Solving the Problems As a result of focusing attention on liposomes as a drug carrier for treatment of senile dementia, the present inventor has found that acetylcholinesterase inhibitors encapsulated in liposomes efficiently migrate into the brain. The inventors have completed the present invention by finding that the effective action concentration can be maintained for a long period of time and that actually excellent drug effects can be exhibited.

[0007] The present invention is an anti-dementia agent which is composed of a liposome preparation containing an acetylcholinesterase inhibitor and is excellent in penetration into the brain. The acetylcholinesterase inhibitor used is preferably an acridine derivative, particularly tacrine (generic name, chemical name is 9-amino-1,2,3,4-tetrahydroacridine).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The anti-dementia agent according to the present invention is a liposome preparation in which an acetylcholinesterase inhibitor is encapsulated in a liposome.

The acetylcholinesterase inhibitor retained in the liposome is not particularly limited, and any substance known as an acetylcholinesterase inhibitor can be used. Specific examples include tacrine, tacrine derivatives, physostigmine, and physostigmine derivatives. Preferably tacrine is used.

The liposome formulation of the acetylcholinesterase inhibitor is carried out, for example, as follows.
First, as the substance forming the liposome, any of natural phospholipids or synthetic phospholipids can be used, and as the natural phospholipids, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, sphingomyelin, dicetylphosphate, stearylamine,
Phosphatidyl glycerol, phosphatidic acid, phosphatidyl inositol and the like can be mentioned. Further, these hydrogenated products can also be used. A film-forming auxiliary agent such as cholesterol may be used in combination with these liposome-forming substances.

Encapsulation of the drug in the liposome may be carried out by a commonly used method. For example, a liposome-forming substance, an additive such as a film-forming auxiliary agent added as necessary, and a drug to be encapsulated are dissolved in an organic solvent such as chloroform, and the organic solvent is removed by an appropriate means to obtain a uniform lipid thin film. . Glass beads and a buffer solution are added to the lipid thin film to peel it off, and after ultrasonic treatment, the liposome fraction is collected through a Sephadex column to obtain fine liposomes having a particle size of about 10 to 500 nm. The obtained liposome holds the acetylcholinesterase inhibitor inside.

The liposome preparation of the present invention is an anti-dementia agent which is excellent in the transferability to the brain, has a long effective action time and has few side effects, and is useful for treating central nervous system disorders such as Alzheimer-type dementia and cerebrovascular dementia. Useful for treatment. According to the present invention, the dose of an acetylcholinesterase inhibitor having strong hepatotoxicity and the like can be reduced, so that it has a very high practical value.

In order to prepare a therapeutic agent, the liposome aqueous dispersion obtained as described above may be used as it is as a liquid preparation by adding a conventional additive, if necessary, or as a freeze-dried preparation. It can also be used as an aqueous solution at the time of use.

As the administration method, oral administration, intravenous administration, subcutaneous administration, rectal administration and the like are used, and the dosage forms may be selected depending on the administration method. For example,
Syrups, dry syrups, capsules and the like can be used for oral administration, and injections can be used for intravenous administration. The dose is 5 to 100 mg / day for oral administration. The present invention will be described in detail by the following examples and test examples.

[0015]

【Example】

[0016]

Example 1 A liposome preparation in which 9-amino-1,2,3,4-tetrahydroacridine (sometimes abbreviated as tacrine or THA) is encapsulated in a liposome is produced. In consideration of encapsulation efficiency in liposomes, commercially available tacrine hydrochloride is dissolved in chloroform and then treated with an aqueous solution of sodium carbonate to give a free form, which is prepared by the following procedure.

Dehydrochlorination of tacrine hydrochloride 5 g of commercially available tacrine hydrochloride (SIGMA) was dissolved in 200 ml of chloroform, shaken with 100 ml of a 10% sodium carbonate aqueous solution in a separating funnel, and further thoroughly washed with water. It is dried over anhydrous sodium sulfate, concentrated to dryness, and dried to obtain free tacrine. Do not recrystallize.

Preparation of liposomes Hydrogenated egg yolk phosphatidylcholine (Nippon Seika) 184 mg
(250 μmol), cholesterol (Wako) 81.8 mg (200 μmo
l), diceryl phosphate (Nacalai) 27.4 mg (50 μmol) and the free tacrine 10 mg or 20 mg obtained above are dissolved in chloroform 100 ml, and concentrated to dryness by a rotary evaporator to form a uniform lipid thin film. Further, it is left overnight in a vacuum desiccator to remove the residual organic solvent. to this
Add 10 ml of PBS and hydrate by hand shaking in a 45 ° C water bath,
Disperse into liposomes. This liposome dispersion is ultrasonically irradiated with a probe-type sonicator until it becomes translucent to obtain fine liposome preparation 1 (for 0.5 mg / kg) or liposome preparation 2 (for 1 mg / kg). The obtained liposome preparation has a particle size of about 30 to 50 nm.

[0019]

Test Example The following test example shows that the liposome preparation of the present invention can exert its effect in the brain. The effect was confirmed by the improvement of spatial cognitive impairment by scopolamine in rats (Test Example 1).

[0020]

[Test Example 1] Spatial cognition by scopolamine in an 8-way radial maze task
In rats that caused the space cognitive impairment due to the effect of scopolamine administration of liposome preparations for disorders, examined the effect of improving the administration of the present invention liposomal formulations. The liposome preparation produced in Example 1 was
Comparative study with non-liposome THA aqueous solution at drug doses of 0.5 mg / kg and 1 mg / kg.

<Drugs used> As scopolamine for inducing spatial cognitive impairment in rats, scopolamine hydrobromide dissolved in 0.9% physiological saline is used.

The test drug was the liposome preparation of Example 1.
(Stock solution 2 mg / ml), THA aqueous solution (stock solution 2 mg / ml), and liposome. Distilled water was used to dilute the formulation.

The THA aqueous solution is prepared by dissolving commercially available tacrine hydrochloride in an isotonic phosphate buffer solution (PBS) at a specified concentration (1 ml / 200 g for rat administration).

Preparation of THA Aqueous Solution Commercially available tacrine hydrochloride (SIGMA) 10 mg and 20 mg were respectively added to PBS (12 mM NaH ₂ PO ₄ , 51 mM Na ₂ HPO ₄ , 77 mM NaCl, p).
H7.4, 280mOmsm / kg) Dissolved in 10ml,
mg / kg) and aqueous solution 2 (10 mg / kg).

<Test method> Wistar male 7-week-old (body weight: 200 to 250 g) rats under restricted diet were fed with an 8-way radial maze.
They were placed on a central platform (diameter 25 cm) of (arm length 48 cm, width 10 cm, ground height 40 cm), and training was carried out for 2-3 weeks until the food placed on the tip of the arm could be efficiently consumed. Scopolamine 0 only in rats that have acquired the task.
5 mg / kg was intraperitoneally administered, and 30 minutes later, an 8-direction radial maze task was performed. The measurement was performed on the number of positive selections of the arm that the rat first visited, the number of incorrect selections of the arm that visited more than once, and the running time until the end of the trial (up to 10 minutes). Also, one arm was selected. The time it takes to perform
It was calculated as [level q actibity (sec / entry)]. The criterion for the rats with completed acquisition of spatial cognition used in this experiment is to show the results of initial positive selection number of 7 or more and false selection number of 1 or less for 3 consecutive trials.

Scopolamine was administered to the rats that acquired the task, and rats with significant spatial cognitive impairment were used as test animals. The test drug was orally administered (po) to the rats, and 60 minutes later, the 8-direction radial maze task was performed. The test was conducted.

<Statistical processing> Wi for the 8-way radial maze task
Statistical processing was performed using the lCoxon runk test.

<Results> The number of positive selections of the rats that completed the acquisition of spatial cognition was 7.7 ± 0.1, the number of incorrect selections was 0.3 ± 0.1, and the running time was 51.5 ± 3.5 seconds. When scopolamine 0.5 mg / kg (ip) was administered to these rats, the positive selection number was
The number was significantly decreased to 5.6 ± 0.1 (p <0.001), and conversely, the number of misselections was significantly increased to 9.7 ± 0.9 (p <0.001), indicating so-called spatial cognitive impairment (Fig. 1). Also, a significant (p <0.001) prolongation was observed in the running time of 19.4 ± 17.5 seconds.

Next, the effect of the test drug on the rats with spatial cognitive impairment was examined. The liposome preparation of Example 1 showed a marked increase in the number of positive selections and misselection at doses of 0.5 and 1 mg / kg. A decrease in the number, that is, improvement in spatial cognitive impairment was observed (Fig. 1). Also, THA aqueous solution is 2 mg
A marked improvement in spatial cognitive impairment was observed at a dose of / kg, but liposome alone had no effect (Fig. 1). That is, the formulation of Example 1 is 1/4 of the THA aqueous solution.
Was found to improve spatial cognitive impairment.

Therefore, the effect of improving the spatial cognitive impairment caused by scopolamine is four times that of the liposome preparation of Example 1 as compared with the THA aqueous solution.

[0031]

INDUSTRIAL APPLICABILITY According to the present invention, by encapsulating an acetylcholinesterase inhibitor in a liposome, these drugs can be efficiently transferred into the brain and an effective action concentration can be maintained for a long time, which is excellent in improving dementia. It is possible to provide an anti-dementia agent that can exert the above effects and has few side effects.

[Brief description of drawings]

FIG. 1 is a graph showing the improving effect of the liposome preparation of the present invention on spatial cognitive impairment caused by scopolamine in an 8-direction radial maze task.

Claims (3)

[Claims] 1. An anti-dementia agent which is composed of a liposome preparation containing an acetylcholinesterase inhibitor and is excellent in intracerebral transfer. 2. The anti-dementia agent according to claim 1, wherein the acetylcholinesterase inhibitor is an acridine derivative. 3. The anti-dementia agent according to claim 2, wherein the acetylcholinesterase inhibitor is tacrine.