Malaria prevention medication

Abstract

To provide a new agent for treating or preventing malaria that can suppress the proliferation of plasmodia.SOLUTION: The present invention discloses a compound of formula (1) or a salt thereof. [R1 is a C1-10 alkyl group. R2 is H or an optionally substituted C1-20 hydrocarbon group. R3 is an optionally substituted C1-20 hydrocarbon group. R2 and R3 may form a cyclic amino group together with N. X1 and X2 independently represent a halogen atom].SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a preventive and therapeutic drug for malaria. [Background technology]

[0002] Malaria, one of the world's three major infectious diseases along with HIV / AIDS and tuberculosis, is a parasitic disease caused by the malaria parasite Plasmodium. It is a typical mosquito-borne infection and is transmitted by the blood-sucking Anopheles mosquito. There are five species of malaria parasites that infect humans, but Plasmodium falciparum, which can cause severe and fatal conditions such as cerebral malaria, is the most widespread in the world, mainly in Africa. More than 200 million new cases of malaria occur annually, primarily in developing countries in tropical and subtropical regions, and 420,000 people die from malaria. In endemic countries, malaria slows economic development, which in turn leads to malaria epidemics, creating a vicious cycle. Malaria and development are inextricably linked, and eradicating malaria will break this vicious cycle and make sustainable development possible. For this reason, the Sustainable Development Goals (SDGs) adopted at the United Nations Summit in September 2015 include preventing the spread of malaria, along with tuberculosis and HIV / AIDS, as goals to be achieved by 2030.

[0003] Malaria parasites have two hosts: humans and mosquitoes, and in humans, they infest the liver and red blood cells. They adapt to each environment by changing their morphology and metabolism within the host and the host. In particular, parasitic parasites within red blood cells (blood-forming parasites) are closely related to the pathology of malaria, and drugs that inhibit the growth and proliferation of blood-forming parasites are expected to have a significant therapeutic effect.

[0004] Various efforts are being made worldwide to eliminate malaria. Two effective methods are widely used to eliminate vector mosquitoes: the distribution of insecticide-treated bed nets and indoor spraying with residual insecticides. Furthermore, early treatment of malaria can prevent deaths. The current first-choice drug is artemisinin combination therapy, which combines an artemisinin derivative with one of the following drugs: lumefantrine, mefloquine, piperaquine, amodiaquine, or fansidar. This treatment rapidly eliminates the parasite and relieves malaria symptoms. Artemisinin combination therapy is now the first-choice treatment in all endemic countries, including those in Africa, and its effectiveness has led to a decline in malaria-related deaths since the mid-2000s.

[0005] However, malaria parasites resistant to artemisinin have appeared in the Mekong River basin in Southeast Asia, and their distribution area is gradually expanding. No new antimalarial drugs with the same effect as artemisinin have yet been approved, and the spread of resistance will not only pose a major problem for malaria control but also for socioeconomic reasons in all endemic regions, not just in Africa, where 90% of malaria patients are concentrated. Therefore, there is a need to develop drugs that selectively inhibit the growth and proliferation of malaria parasites.

[0006] Meanwhile, some of the present inventors have discovered and reported that an amide derivative of differentiation-inducing factor-1 (DIF-1), a differentiation-inducing factor of slime molds that induces stalk cell differentiation in slime molds and is isolated as a degradation product of this factor, has the effects of inducing cellular slime mold differentiation, inhibiting tumor cells, and promoting sugar metabolism (Patent Document 1, Non-Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5476650 [Non-patent literature]

[0008] [Non-Patent Document 1] Kikuchi H, Ishiko S, Oshima Y, Gokan N, Hosaka K, & Kubohara Y. Biological activities of novel derivatives of DIF-1 isolated from Dictyostelium. Biochem. Biophys. Res. Commun. 377(3), 1012-1017. (2008). Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a new preventive and therapeutic drug for malaria that inhibits the proliferation of malaria parasites. [Means for solving the problem]

[0010] Therefore, the present inventors investigated the effect of the above-mentioned DIF-1 amide derivatives, the effect of which on malaria parasites was completely unknown, and found that they have a strong growth inhibitory effect and also exhibit growth inhibitory effect on artemisinin-resistant malaria parasites, thereby completing the present invention.

[0011] That is, the present invention provides the following inventions [1] to [8]. [1] A preventive and therapeutic drug for malaria, comprising as an active ingredient a compound represented by the following general formula (1) or a salt thereof:

[0012] [ka]

[0013] (In the formula, R 1 represents an alkyl group having 1 to 10 carbon atoms, and R 2 represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, and R 3 represents a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, or R 2 and R 3may combine with the nitrogen atom to form a cyclic amino group, and X 1 and X 2 each independently represents a halogen atom) [2]R 1

[0023] The preventive and therapeutic drug for malaria according to [1], wherein is an alkyl group having 1 to 5 carbon atoms. [3]R 2 represents a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms which may have a substituent, and R 3 represents a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms which may have a substituent, or R 2 and R 3 may form a cyclic amino group having 2 to 8 carbon atoms together with the nitrogen atom. [4]R 2 represents a hydrogen atom or a linear, branched, or cyclic alkyl group having 1 to 12 carbon atoms; R 3 represents a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms, or R 2 and R 3 wherein, together with the nitrogen atom, the aryl group may form a cyclic amino group having 2 to 8 carbon atoms. [5] A growth inhibitor of malaria parasites, comprising as an active ingredient a compound represented by the following general formula (1) or a salt thereof:

[0014] [ka]

[0015] (In the formula, R 1 represents an alkyl group having 1 to 10 carbon atoms, and R 2 represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, and R 3 represents a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, or R 2 and R 3 may combine with the nitrogen atom to form a cyclic amino group, and X 1 and X 2 each independently represents a halogen atom) [6]R1 [5] The growth inhibitor of malaria parasites according to [5], wherein is an alkyl group having 1 to 5 carbon atoms. [7]R 2 represents a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms which may have a substituent, and R 3 represents a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms which may have a substituent, or R 2 and R 3 wherein, together with the nitrogen atom, the compound may form a cyclic amino group having 2 to 8 carbon atoms. [8]R 2 represents a hydrogen atom or a linear, branched, or cyclic alkyl group having 1 to 12 carbon atoms; R 3 represents a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms, or R 2 and R 3 wherein, together with the nitrogen atom, the compound may form a cyclic amino group having 2 to 8 carbon atoms. [Effects of the Invention]

[0016] The compound represented by the general formula (1) or a salt thereof has an excellent inhibitory effect on the proliferation of malaria parasites, and also exhibits an inhibitory effect on the proliferation of artemisinin-resistant malaria parasites, and is therefore useful as a preventive and therapeutic drug for malaria. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 shows the effect of compound (1) on the proliferation of malaria parasite 3D7. DETAILED DESCRIPTION OF THE INVENTION

[0018] The active ingredient of the malaria preventive / therapeutic drug and malaria parasite growth inhibitor of the present invention is a compound represented by the general formula (1) (hereinafter also referred to as compound (1)) or a salt thereof. Compound (1) can be synthesized according to the method described in Patent Document 1. As described in Patent Document 1 and Non-Patent Document 1, this compound (1) is known to have the effects of inducing cellular slime mold differentiation, inhibiting tumor cells, and promoting glucose metabolism, but its effect on malaria parasites is completely unknown.

[0019] In the general formula (1), R 1 represents an alkyl group having 1 to 10 carbon atoms. Here, examples of the alkyl group include linear, branched, and cyclic alkyl groups. R is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. 1 Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and an n-pentyl group, and more preferred are a methyl group, an ethyl group, an n-propyl group, and an isopropyl group.

[0020] R 2 represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent. Here, the hydrocarbon group having 1 to 20 carbon atoms, which may have a substituent, is preferably a linear, branched, or cyclic alkyl group having 1 to 12 carbon atoms, which may have a substituent, and more preferably a linear, branched, or cyclic alkyl group having 1 to 12 carbon atoms. Here, examples of groups that can be substituted on the hydrocarbon group include an alkoxycarbonyl group, a carboxyl group, a hydroxy group, and an alkoxy group. Preferred R 2 Examples of the alkyl group include a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, and an n-dodecyl group.

[0021] R 3 represents a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent. Here, the hydrocarbon group having 1 to 20 carbon atoms, which may have a substituent, is preferably a linear, branched, or cyclic alkyl group having 1 to 12 carbon atoms, which may have a substituent, and more preferably a linear, branched, or cyclic alkyl group having 1 to 12 carbon atoms. Here, examples of groups that can be substituted on the hydrocarbon group include an alkoxycarbonyl group, a carboxyl group, a hydroxy group, and an alkoxy group. Preferred R 3 Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-dodecyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group.

[0022] R 2 and R 3 may combine with the nitrogen atom to form a cyclic amino group. Examples of such a cyclic amino group include cyclic amino groups having 2 to 7 carbon atoms, such as a pyrrolidino group, a piperidino group, and a heptacycloimino group.

[0023] X 1 and X 2 are independently a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a chlorine atom, a bromine atom, and an iodine atom being preferred.

[0024] Preferable specific examples of compound (1) include the following compounds:

[0025] [ka]

[0026] The salt of compound (1) is not limited as long as it is pharmaceutically acceptable, and examples thereof include metal salts such as sodium, potassium, magnesium, and calcium salts, and ammonium salts. Compound (1) may also be a hydrate. When compound (1) has an asymmetric carbon atom in its structure, its optical isomers are also included.

[0027] As will be shown in the Examples below, compound (1) or a salt thereof has an excellent inhibitory effect on the proliferation of malaria parasites, and also exhibits an inhibitory effect on the proliferation of artemisinin-resistant malaria parasites, and is therefore useful as a preventive or therapeutic drug for malaria. Examples of target malaria parasites include malaria parasites (Plasmodium genus parasites) that infect primates and rodents. Examples of malaria parasites that infect humans, which belong to primates, include Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, and Plasmodium ovale, with Plasmodium falciparum being preferred. Also, examples of malaria parasites that infect monkeys, which belong to primates, include Plasmodium knowlesi. In addition, examples of malaria parasites that infect rodents include Plasmodium berghei and Plasmodium vinckei, and examples of malaria parasites that infect mice, which belong to rodents, include Plasmodium berghei, Plasmodium chabaudi, and Plasmodium yoelii.

[0028] The malaria preventive and therapeutic drugs of the present invention include not only medicines that completely cure symptoms caused by infection with malaria parasites, but also medicines that improve symptoms and medicines that prevent the onset of symptoms. Furthermore, the malaria parasite growth inhibitors of the present invention include drugs that reduce the number of malaria parasites, drugs that suppress an increase in the number (growth) of malaria parasites, drugs that inactivate malaria parasites, and the like. In the present invention, "inactivating malaria parasites" includes reducing or suppressing the ability of malaria parasites to reproduce, and an example of a means of inactivation is killing.

[0029] The subjects to which the malaria preventive / therapeutic drug and malaria parasite growth inhibitor of the present invention are administered are animals infected with malaria or animals that have developed malaria. Such animals include, for example, animals belonging to primates and animals belonging to rodents, and specific examples of animals belonging to primates include humans, chimpanzees, and monkeys, and specific examples of animals belonging to rodents are mice. In addition to animals infected with or that have developed malaria as described above, the drugs can also be administered prophylactically to animals that may be infected with malaria.

[0030] A pharmaceutical containing compound (1) or a salt thereof can be prepared into various pharmaceutical preparations by mixing the compound or a salt thereof with a pharmaceutically acceptable carrier or as is, according to a known method commonly used in the production of pharmaceutical preparations. Such pharmaceutical preparations (dosage forms) can be, for example, tablets (including sugar-coated tablets and film-coated tablets), powders, granules, capsules (including soft capsules), liquids, injections, suppositories, sustained-release preparations, etc., and can be administered orally or parenterally (e.g., topically, rectally, intravenously, etc.). Examples of pharmaceutically acceptable carriers include excipients, lubricants, binders, and disintegrants in solid preparations, and solvents, solubilizers, suspending agents, isotonicity agents, buffers, and soothing agents in liquid preparations. Furthermore, conventional additives such as preservatives, antioxidants, coloring agents, sweeteners, adsorbents, and wetting agents can also be used appropriately and in appropriate amounts, if necessary. Examples of excipients include lactose, sucrose, D-mannitol, starch, corn starch, crystalline cellulose, light anhydrous silicic acid, etc. Examples of lubricants include magnesium stearate, calcium stearate, talc, colloidal silica, etc. Examples of binders include crystalline cellulose, sucrose, D-mannitol, dextrin, hydroxypropyl cellulose, hydroxypropylmethylcellulose, polyvinylpyrrolidone, starch, sucrose, gelatin, methylcellulose, sodium carboxymethylcellulose, etc. Examples of disintegrants include starch, carboxymethylcellulose, calcium carboxymethylcellulose, sodium carboxymethylstarch, L-hydroxypropylcellulose, etc. Examples of solvents include water for injection, alcohol, propylene glycol, macrogol, sesame oil, corn oil, olive oil, etc. Examples of solubilizers include polyethylene glycol, propylene glycol, D-mannitol, benzyl benzoate, ethanol, trisaminomethane, cholesterol, triethanolamine, sodium carbonate, sodium citrate, etc. Examples of suspending agents include surfactants such as stearyltriethanolamine, sodium lauryl sulfate, laurylaminopropionic acid, lecithin, benzalkonium chloride, benzethonium chloride, and glycerin monostearate; and hydrophilic polymers such as polyvinyl alcohol, polyvinylpyrrolidone, sodium carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, and hydroxypropylcellulose. Examples of isotonic agents include glucose, D-sorbitol, sodium chloride, glycerin, and D-mannitol. Examples of buffering agents include buffer solutions such as phosphates, acetates, carbonates, and citrates. Examples of soothing agents include benzyl alcohol. Examples of preservatives include parahydroxybenzoates, chlorobutanol, benzyl alcohol, phenethyl alcohol, dehydroacetic acid, sorbic acid, etc. Examples of antioxidants include sulfites, ascorbic acid, α-tocopherol, etc.

[0031] Furthermore, the pharmaceutical of the present invention may be used in combination with antimalarial drugs other than compound (1) or other drugs. The content of compound (1) or a salt thereof in the pharmaceutical composition of the present invention is 0.01 to 100% by mass of the entire preparation. The dosage of compound (1) or a salt thereof varies depending on the subject, symptoms, body weight, administration method, etc., and is not particularly limited. In general, however, the dosage is preferably 0.1 to 5 g, more preferably 0.1 to 1 g, and even more preferably 0.1 to 0.5 g per day for a patient (body weight 60 kg). [Example]

[0032] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0033] Example 1 The following compounds were synthesized according to the method described in Patent Document 1.

[0034] [ka] The above compounds (hereinafter also referred to as DIF amides) were all colorless amorphous solids. These DIF amides were dissolved in DMSO to form 10 mM solutions and stored at -20°C.

[0035] (Existing antimalarial drugs as control) For drug testing, the existing antimalarial drug chloroquine was used as a positive control. Chloroquine was dissolved in ultrapure water. The artemisinin drug resistance assay system was excluded from the control because it uses a special method.

[0036] Example 2 (Study of antimalarial activity of DIF amide) (Culture strain used) Here, we used the cultured Plasmodium falciparum strain 3D7 and the artemisinin-resistant strains MRA1236 and MRA1240 (which are also resistant to chloroquine).

[0037] (Antimalarial activity screening) Plasmodium growth rates were compared in the presence of DIF amide (10 μM) or 0.1% DMSO (control). Plasmodium were cultured at a hematocrit of 2% and an infectivity of 0.05% for 72 hours at 37°C under a gas mixture (90% N2, 5% O2, 5% CO2). Standard Malaria Complete Medium (MCM) was used, consisting of RPMI 1640 (GIBCO), hypoxanthine, Gentamicin Reagent Solution (GIBCO), Sodium Bicarbonate Solution, AlbuMAX1 (GIBCO), and decontaminated Serum (gift from the Japanese Red Cross Society). Plasmodium counts were measured using an ELISA assay targeting the malaria-specific antigen HRP-2. A 40% or greater inhibition of growth with 10 μM DIF amide was considered to have inhibitory activity against parasite growth. The results are shown in Figure 1. Figure 1 shows that the DIF amide had antiproliferative activity.

[0038] Example 3 (IC 50 Antimalarial activity evaluation by ATP value) Three types of Plasmodium falciparum strains were cultured in the presence of DIF amides diluted in 7 stages with DMSO, and their growth inhibitory effect was examined. The growth inhibitory effect was evaluated by the number of parasites. The culture conditions and the method for measuring the number of parasites were the same as in Example 2. IC 50 The values ​​were determined using the sigmoid Emax method, and the results are shown in Table 1.

[0039] [Table 1]

[0040] DIF1[A+3], DIF-1[A+4], Amide4 IC 50The concentrations of Amide4 in the artemisinin-resistant strains were 0.5-2.05 μM. These concentrations are close to the 1-2 μM target for selecting lead compounds as antimalarial drugs. MRA1236 and MRA1240 were artemisinin-resistant strains, and Amide4 showed growth effects on the artemisinin-resistant strains similar to those on the susceptible strains.

Claims

1. A preventive and therapeutic drug for malaria, comprising as an active ingredient a compound represented by the following general formula (1) or a salt thereof. 【Chemical 1】 (In the formula, R 1 represents an alkyl group having 1 to 10 carbon atoms, and R 2 represents a hydrogen atom or a linear, branched or cyclic alkyl group having 5 to 12 carbon atoms; R 3 represents a linear, branched or cyclic alkyl group having 5 to 12 carbon atoms, or R 2 and R 3 may combine with the nitrogen atom to form a cyclic amino group having 5 to 8 carbon atoms, and X 1 and X 2 each independently represents a halogen atom)

2. R 1 The preventive and therapeutic drug for malaria according to claim 1, wherein is an alkyl group having 1 to 5 carbon atoms.

3. A growth inhibitor of malaria parasites, comprising as an active ingredient a compound represented by the following general formula (1) or a salt thereof: 【Chemistry 2】 (In the formula, R 1 represents an alkyl group having 1 to 10 carbon atoms, and R 2 represents a hydrogen atom or a linear, branched or cyclic alkyl group having 5 to 12 carbon atoms; R 3 represents a linear, branched or cyclic alkyl group having 5 to 12 carbon atoms, or R 2 and R 3 may combine with the nitrogen atom to form a cyclic amino group having 5 to 8 carbon atoms, and X 1 and X 2 each independently represents a halogen atom)

4. R 1 The growth inhibitor of malaria parasites according to claim 3, wherein is an alkyl group having 1 to 5 carbon atoms.

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