Pain therapeutic agent

Abstract

To provide a pain therapeutic agent targeting glycosphingolipid synthase.SOLUTION: A pain therapeutic agent comprising a substance that inhibits glycosphingolipid synthase.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to pain treatment agents. [Background technology]

[0002] Pain is an unpleasant sensory and emotional experience associated with or resembling actual or potential tissue damage. The International Association for the Study of Pain (IASP) defines chronic pain as pain that persists or recurs for three months or more. In contrast, acute pain is pain that persists or recurs for less than three months. There is pain that can be identified as caused by tissue damage or neurological factors, but there is also pain that is difficult to identify as caused by psychological factors, etc.

[0003] Pain significantly impairs the quality of life (QOL) of affected individuals, and numerous medications (pain medications, analgesics) are used to treat it. Nonsteroidal anti-inflammatory drugs (NSAIDs), acetaminophen, and opioids are commonly used pain medications. On the other hand, certain psychotropic drugs are known to have analgesic effects for some types of pain, such as chronic neuropathic pain. For example, tricyclic antidepressants (TCAs) such as nortriptyline and amitriptyline, serotonin-norepinephrine reuptake inhibitors (SNRIs) such as duloxetine and milnacipran, and antiepileptic drugs such as cabapentin, pregabalin, and carbamazepine are used to treat neuropathic pain.

[0004] Glycolipids are molecules in which lipid molecules and sugars are bound together, and are biosynthesized in vivo. Glycolipids exist on biological membranes, such as cell membranes, and are involved in physiological functions such as cell recognition, adhesion, and signal transduction. Known glycolipids include glycosphingolipids and glyceroglycolipids. Of these, glycosphingolipids are glycolipids in which ceramide and sugar are bound together. The sugar chain portion of glycosphingolipids is highly diverse, and they are biosynthesized through pathways mediated by various enzymes. The first step in the biosynthesis of glycosphingolipids from ceramide involves the conversion of ceramide to galactosylceramide or the conversion of ceramide to glucosylceramide.

[0005] Regarding pain and glycolipids, for example, Patent Document 1 discloses a pain treatment agent containing sialidase as an active ingredient. In Patent Document 1, sialidase is a glycolytic enzyme that hydrolyzes and releases sialic acid from glycolipids and glycoprotein sugar chains. Non-Patent Documents 1 and 2 disclose that administration of sialidase to mice resulted in an analgesic effect. Furthermore, Non-Patent Documents 2 to 4 disclose that exogenous administration of a certain type of glycosphingolipid to mice caused pain in the mice. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-275247 [Non-patent literature]

[0007] [Non-Patent Document 1] Shun Watanabe et al., "Intraplantarinjection of sialidase reduces mechanical allodynia during inflammatory pain", Journal of Pharmacological Sciences 133, (2017) 49-52. [Non-patent document 2] Shun Watanabe et al., "Intraplantarinjection of gangliosides produces nociceptive behavior and hyperalgesia via aglutamate signaling mechanism", PAIN(Registered Trademark) 152, (2011) 327-334. [Non-patent document 3] Motoki Morita et al., "Glycosphingolipid Biosynthesis Pathway in the Spinal Cord and Dorsal Root Ganglia DuringInflammatory Pain: Early and Late Changes in Expression Patterns ofGlycosyltransferase Genes", Neuroscience 428 (2020) 217-227. [Non-patent document 4] Motoki Morita et al., "Sulfatide-selectinsignaling in the spinal cord induces mechanical allodynia", Journal ofNeurochemistry 164, 658-670 (2023). Summary of the Invention [Problem to be solved by the invention]

[0008] To date, no pain therapeutic agent that targets glycolipid synthase has been known. An object of the present disclosure is to provide a pain therapeutic agent that targets glycolipid synthase. [Means for solving the problem]

[0009] The present inventors have found that substances that inhibit glycolipid synthase have an analgesic effect.

[0010] The present disclosure relates, for example, to the following: [1] A pain treatment agent containing a substance that inhibits glycolipid synthesis enzymes. [2] The pain therapeutic agent according to [1], wherein the glycolipid synthase is at least one selected from the group consisting of enzymes in the biosynthetic pathway from ceramide to ganglioside GQ1b and enzymes in the biosynthetic pathway from ceramide to sulfatide. [3] The pain remedy according to [1] or [2], wherein the glycolipid synthase is at least one enzyme in the biosynthetic pathway from ceramide to ganglioside GQ1b. [4] The pain therapeutic agent according to any one of [1] to [3], which is a therapeutic agent for chronic pain. [5] The pain therapeutic agent according to any one of [1] to [4], which is for treating pain at a site where no tissue damage or neurological cause is found. [6] The pain therapeutic agent according to [4] or [5], wherein the chronic pain is chronic primary pain, chronic neuropathic pain, chronic post-surgical pain, or chronic post-traumatic pain. [7] The pain remedy according to [1], wherein the glycolipid synthase is at least one enzyme in the biosynthetic pathway from ceramide to sulfatide. [8] The pain therapeutic agent according to [7], which is for treating pain at a site where tissue damage and / or neural causes are found. [9] A method for treating pain, comprising administering a substance that inhibits glycolipid synthase to a subject in need thereof.

[10] The method of treatment according to [9], wherein the glycolipid synthase is at least one selected from the group consisting of enzymes in the biosynthetic pathway from ceramide to ganglioside GQ1b and enzymes in the biosynthetic pathway from ceramide to sulfatide.

[11] The method of treatment according to [9] or

[10] , wherein the glycolipid synthase is at least one enzyme in the biosynthetic pathway from ceramide to ganglioside GQ1b.

[12] The method for treating pain according to

[11] , wherein the pain is chronic pain.

[13] The method of treatment according to

[11] or

[12] , wherein the pain is pain at a site where no tissue damage or neural cause is found.

[14] The method of treatment according to

[12] or

[13] , wherein the chronic pain is chronic primary pain, chronic neuropathic pain, chronic post-surgical pain, or chronic post-traumatic pain.

[15] The method of treatment according to [9], wherein the glycolipid synthase is at least one enzyme in the biosynthetic pathway from ceramide to sulfatide.

[16] The method of treatment according to

[15] , wherein the pain is pain at an area where tissue damage and / or neural factors are present.

[17] A substance that inhibits glycolipid synthesis enzymes for use in the treatment of pain.

[18] The substance according to

[17] , wherein the glycolipid synthase is at least one selected from the group consisting of enzymes in the biosynthetic pathway from ceramide to ganglioside GQ1b and enzymes in the biosynthetic pathway from ceramide to sulfatide.

[19] The substance according to

[17] or

[18] , wherein the glycolipid synthase is at least one enzyme in the biosynthetic pathway from ceramide to ganglioside GQ1b.

[20] The substance according to

[19] , wherein the pain is chronic pain.

[21] The substance according to

[19] or

[20] , wherein the pain is pain at a site where no tissue damage or neural cause is found.

[22] The substance according to

[20] or

[21] , wherein the chronic pain is chronic primary pain, chronic neuropathic pain, chronic post-surgical pain, or chronic post-traumatic pain.

[23] The substance according to

[17] , wherein the glycolipid synthase is at least one enzyme in the biosynthetic pathway from ceramide to sulfatide.

[24] The substance according to

[23] , wherein the pain is pain at a site where tissue damage and / or neural factors are present.

[25] Use of a substance that inhibits glycolipid synthesis enzymes in the manufacture of a pain treatment agent.

[26] The use according to

[25] , wherein the glycolipid synthase is at least one selected from the group consisting of enzymes in the biosynthetic pathway from ceramide to ganglioside GQ1b and enzymes in the biosynthetic pathway from ceramide to sulfatide.

[27] The use according to

[25] or

[26] , wherein the glycolipid synthase is at least one enzyme in the biosynthetic pathway from ceramide to ganglioside GQ1b.

[28] The use according to

[27] , wherein the pain therapeutic agent is a therapeutic agent for chronic pain.

[29] The use according to

[27] or

[28] , wherein the pain therapeutic agent is for treating pain at a site where no tissue damage or neural factors are found.

[30] The use according to

[28] or

[29] , wherein the chronic pain is chronic primary pain, chronic neuropathic pain, chronic post-surgical pain, or chronic post-traumatic pain.

[31] The use according to

[25] , wherein the glycolipid synthase is at least one enzyme in the biosynthetic pathway from ceramide to sulfatide.

[32] The use according to

[31] , wherein the pain therapeutic agent is for treating pain at a site where tissue damage and / or neural factors are present. [Effects of the Invention]

[0011] According to the present disclosure, a pain therapeutic agent containing a substance that inhibits glycolipid synthase can be provided. The pain therapeutic agent containing a substance that inhibits glycolipid synthase can inhibit the biosynthesis of glycolipids, which cause pain.

[0012] Sialidase, the active ingredient in the pain treatment agent described in Patent Document 1, is a protein derived from another organism, and therefore may induce an immune response and cause side effects over the long term. In contrast, the substance that inhibits glycolipid synthase according to the present disclosure can be a synthetic small molecule or a human-derived biopolymer, and is therefore expected to have minimal side effects.

[0013] According to one embodiment of the present disclosure, a pain therapeutic agent can be provided that contains a substance that inhibits at least one enzyme selected from the group consisting of enzymes in the biosynthetic pathway from ceramide to ganglioside GQ1b. Such a pain therapeutic agent can inhibit the biosynthesis of b-series gangliosides (e.g., gangliosides GT1b and GQ1b), which are glycolipids that can be a major cause of pain. Such a pain therapeutic agent can be used to treat pain, and is particularly suitable for treating chronic pain. Furthermore, such a pain therapeutic agent can be suitable for treating pain at sites where no tissue damage or neural causes are observed.

[0014] According to one embodiment of the present disclosure, a pain therapeutic agent can be provided, which contains a substance that inhibits at least one enzyme selected from the group consisting of enzymes in the biosynthetic pathway from ceramide to sulfatide. Such a pain therapeutic agent can inhibit the biosynthesis of sulfatide, a glycolipid that can be a major cause of pain. Such a pain therapeutic agent can be used to treat pain, and is suitable for treating pain at sites where tissue damage and / or neural factors are present. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 shows an outline of the major biosynthetic pathways of glycosphingolipids. [Figure 2] 1(a) is a graph showing the results of the von Frey test when the vehicle was administered in Example 1. FIG. 1(b) is a graph showing the results of the von Frey test when sulfatide was administered in Example 1. [Figure 3] 1(a) is a graph showing the results of a von Frey test on an inflamed paw in Example 2. FIG. 1(b) is a graph showing the results of a von Frey test on a non-inflamed paw in Example 2. [Figure 4](a) is a graph showing the results of a von Frey test when ganglioside GM3, ganglioside GM1, or ganglioside GD1a was administered in Example 3. (b) is a graph showing the results of a von Frey test when vehicle was administered in Example 3. (c) is a graph showing the results of a von Frey test when ganglioside GD3, ganglioside GD1b, or ganglioside GT1b was administered in Example 3. (d) is a graph showing the results of a von Frey test when 0 pmol, 0.1 pmol, 1.0 pmol, 10 pmol, 100 pmol, or 1000 pmol of ganglioside GT1b was administered in Example 3. [Figure 5] 1(a) is a graph showing the results of a von Frey test on an inflamed paw in Example 4. FIG. 1(b) is a graph showing the results of a von Frey test on a non-inflamed paw in Example 4. [Figure 6] 1(a) is a diagram showing the results of a von Frey test on an inflamed paw in Example 5. FIG. 1(b) is a diagram showing the results of a von Frey test on a non-inflamed paw in Example 5. [Figure 7] 1(a) is a diagram showing the results of a von Frey test on an inflamed paw in Example 6. FIG. 1(b) is a diagram showing the results of a von Frey test on a non-inflamed paw in Example 6. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments for carrying out the present disclosure will be described, but the present disclosure is not limited to the following embodiments.

[0017] <Pain treatment agent> One aspect of the present disclosure is a pain therapeutic agent containing a substance that inhibits glycolipid synthase. This aspect can also be referred to as a pharmaceutical composition for pain treatment containing a substance that inhibits glycolipid synthase. A pain therapeutic agent according to one aspect of the present disclosure contains a substance that inhibits glycolipid synthase as an active ingredient. Another aspect of the present disclosure may be a pain therapeutic agent containing a therapeutically effective amount of a substance that inhibits glycolipid synthase.

[0018] Pain is an unpleasant sensory and emotional experience associated with or resembling actual or potential tissue damage. In this disclosure, a pain therapeutic agent (analgesic) refers to a preparation capable of treating pain. In this disclosure, treating pain refers to the temporary or sustained relief or elimination of pain, or the suppression of pain exacerbation.

[0019] The pain treated by the pain therapeutic agent of the present disclosure may be chronic pain. According to the definition of the International Association for the Study of Pain (IASP), chronic pain is pain that persists for three months or more or recurs. Pain therapeutic agents for chronic pain are still in the development stage compared to those for acute pain. Therefore, if the pain treated by the pain therapeutic agent of the present disclosure is chronic pain, it may be possible to treat pain that has been difficult to treat until now.

[0020] The pain treated by the pain therapeutic agent of the present disclosure may be pain at a site where tissue damage is observed, pain at a site where neural causes are observed, or pain at a site where tissue damage or neural causes are not observed (e.g., pain due to psychological causes). Examples of tissue damage that can cause pain include inflammation, malignant tumors, surgery, and trauma. Examples of neurally-caused pain include neuropathic pain. Neuropathic pain is pain caused by a lesion or disease of the somatosensory nervous system. The nerves in neuropathic pain are peripheral nerves or central nerves. One type of neurally-caused pain is known as allodynia, a painful response to stimuli that are not normally painful, such as mechanical allodynia, in which touch is perceived as painful. Another type of neurally-caused pain is hyperalgesia, an increased response to painful stimuli.

[0021] <Glycolipids and their biosynthetic pathways> Glycolipids are molecules formed by the binding of lipid molecules and sugars. Known types of glycolipids include glycosphingolipids and glyceroglycolipids. Of these, glycosphingolipids are glycolipids formed by the binding of ceramide and sugars. The sugar chain moieties of glycosphingolipids are highly diverse and are biosynthesized through pathways mediated by various enzymes.

[0022] The main biosynthetic pathway of glycosphingolipids is explained below. First, sphingosine base is synthesized from serine and palmitoyl CoA as starting materials, and then ceramide is formed by binding a fatty acid to this sphingosine base.

[0023] The biosynthetic pathways of major glycosphingolipids from ceramide are outlined in Figure 1. In one pathway, as shown in Figure 1(a), ceramide is converted to galactosylceramide (GalCer) by the addition of galactose by Ugt8a (UDP galactosyltransferase 8A, ceramide cerebroside, ceramide galactosyltransferase). Next, as shown in Figure 1(b), galactosylceramide is converted to sulfatide by the introduction of a sulfo group into the galactose moiety by Gal3st1 (Galactose-3-O-Sulfotransferase 1). As described above, Ugt8a and Gal3st1 are enzymes that constitute the biosynthetic pathway from ceramide to sulfatide. Furthermore, the enzymes that catalyze the reactions shown in Figure 1(a) and (b) in vivo are also enzymes that constitute the biosynthetic pathway from ceramide to sulfatide.

[0024] In another pathway, ceramide is converted to glucosylceramide (GlcCer) by the addition of glucose by Ugcg (UDP glucose ceramide glucosyltransferase, glucosylceramide synthase, GlcT1), as shown in Figure 1c. Next, galactose is attached to the glucose moiety of glucosylceramide, converting it to lactosylceramide (LacCer), as shown in Figure 1d.

[0025] The synthetic pathway from lactosylceramide branches into several pathways. One of these pathways leads to the biosynthesis of ganglio-series gangliosides (hereinafter simply referred to as "gangliosides"). The biosynthetic pathway for gangliosides branches further depending on the number of sialic acids bound to the galactose moiety of lactosylceramide. Accordingly, gangliosides are classified according to the number of sialic acids bound to the galactose moiety of lactosylceramide. Gangliosides with zero sialic acids bound are called the o-series, those with one sialic acid bound are called the a-series, those with two sialic acids bound are called the b-series, and those with three sialic acids bound are called the c-series.

[0026] First, we will explain the elongation of the sialic acid chain from the galactose moiety of lactosylceramide. Lactosylceramide is converted to ganglioside GM3 by the addition of sialic acid by St3gal5 (ST3 β-Galactoside Alpha-2,3-Sialyltransferase 5) (Fig. 1e). Ganglioside GM3 is converted to ganglioside GD3 by the elongation of the sialic acid chain by St8sia1 (ST8 alpha-N-acetyl-neuraminide alpha-2,8-sialyltransferase 1) (Fig. 1f). Ganglioside GD3 is further converted to ganglioside GT3 by the elongation of the sialic acid chain (Fig. 1g).

[0027] Glycosylation from lactosylceramide, ganglioside GM3, ganglioside GD3, and ganglioside GT3 is carried out by the action of the same enzyme group. The following explains glycosylation from lactosylceramide as an example.

[0028] Lactosylceramide is converted to ganglioside GA2 by the addition of N-acetylgalactosamine to the galactose moiety by B4glant1 (Beta-1,4-N-Acetyl-Galactosaminyltransferase 1) (ho in Figure 1). Ganglioside GA2 is converted to ganglioside GA1 by the addition of galactose to the N-acetylgalactosamine moiety (io in Figure 1). Ganglioside GA1 is converted to ganglioside GM1b by the addition of sialic acid to the galactose moiety (jo in Figure 1). Ganglioside GM1b is converted to ganglioside GD1c by the extension of one sialic acid chain at the galactose moiety (ko in Figure 1).

[0029] As explained using lactosylceramide as an example, ganglioside GM3 is converted to ganglioside GM2, ganglioside GM1a, ganglioside GD1a, and ganglioside GT1a in this order (ha, ia, ja, and ka in Figure 1). Ganglioside GD3 is converted to ganglioside GD2, ganglioside GD1b, ganglioside GT1b, and ganglioside GQ1b in this order (hb, ib, jb, and kb in Figure 1). Ganglioside GT3 is converted to ganglioside GT2, ganglioside GT1c, ganglioside GQ1c, and ganglioside GP1c in this order (hc, ic, jc, and kc in Figure 1). The reactions indicated by ho, ha, hb, and hc in Figure 1 are catalyzed by the same enzyme (B4glant1). The reactions denoted io, ia, ib, and ic in Figure 1 are catalyzed by the same enzyme. The reactions denoted jo, ja, jb, and jc in Figure 1 are catalyzed by the same enzyme. The reactions denoted ko, ka, kb, and kc in Figure 1 are catalyzed by the same enzyme.

[0030] As explained above, for example, the enzymes that catalyze the reactions indicated by e, f, hb, ib, jb, and kb in Figure 1 in a living organism are enzymes that constitute the biosynthetic pathway from ceramide to ganglioside GQ1b. Furthermore, for example, the enzymes that catalyze the reactions indicated by e, f, hb, ib, and jb in Figure 1 in a living organism are enzymes that constitute the biosynthetic pathway from ceramide to ganglioside GT1b. However, in the present disclosure, the enzymes that constitute the biosynthetic pathway from ceramide to ganglioside GQ1b or ganglioside GT1b are not limited to those explained above, and may be enzymes that are involved in a pathway not explicitly shown in Figure 1, as long as they constitute a biosynthetic pathway that can convert ceramide to ganglioside GQ1b or ganglioside GT1b in a living organism.

[0031] <Glycolipid synthase> In the present disclosure, a glycolipid synthase is an enzyme that catalyzes at least one step in glycolipid biosynthesis. For example, a glycolipid synthase may be an enzyme that catalyzes the bond between a lipid and a sugar, an enzyme that catalyzes the elongation of a sugar chain on a glycolipid, or an enzyme that catalyzes the modification of a glycolipid with sialic acid. Examples of glycolipid synthases include enzymes that catalyze the reactions shown by a, b, c, d, e, f, g, ho, ha, hb, hc, io, ia, ib, ic, jo, ja, jb, jc, ko, ka, kb, and kc in Figure 1. These are glycolipid synthases (glycosphingolipid synthases) that biosynthesize glycosphingolipids using ceramide as a starting material.

[0032] In the present disclosure, an enzyme constituting a biosynthetic pathway from A to B is also referred to as a "biosynthetic pathway enzyme from A to B." For example, "a biosynthetic pathway enzyme from ceramide to sulfatide" means an enzyme constituting a biosynthetic pathway from ceramide to sulfatide.

[0033] <Substances that inhibit glycolipid synthesis enzymes> A substance that inhibits glycolipid synthase (hereinafter also referred to simply as "inhibitor") is a substance that inhibits the enzymatic reaction catalyzed by glycolipid synthase. For example, the inhibitor may be a synthetic small molecule (e.g., a synthetic small molecule with a molecular weight of 1000 or less), a peptide, a protein, or a nucleic acid, or a complex thereof, that inhibits glycolipid synthase.

[0034] The inhibitor may be at least one selected from the group consisting of the following (a) to (c), and may be (a), (b), or (c): (a) Small molecules that inhibit the enzymatic reaction of glycolipid synthesis enzymes; (b) an antibody that binds to glycolipid synthase (anti-glycolipid synthase antibody) or an antigen-binding fragment thereof; (c) A nucleic acid that inhibits the expression of a glycolipid synthesis enzyme.

[0035] The above (a) may be, for example, a molecule with a molecular weight of 1,000 or less that inhibits the enzymatic reaction of glycolipid synthase. The above (a) may be, for example, a synthetic small molecule or antisense nucleic acid that inhibits the enzymatic reaction of glycolipid synthase. The above (a) may be, for example, a small molecule that inhibits the enzymatic reaction of Ugt8a, Ugcg, or B4glant1, or a small molecule that inhibits the enzymatic reaction of Ugt8a or Ugcg. For example, a small molecule that inhibits the enzymatic reaction of Ugt8a may be UGT8 Inhibitor 19 (CAS No. 2414349-93-0). For example, a small molecule that inhibits the enzymatic reaction of Ugcg may be lucelastat (N-(n-butyl)deoxygalactonojirimycin, CAS No. 141206-42-0, NB-DGJ), miglustat (NB-DNJ), or D-PDMP (D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol).

[0036] In the above (b), the antibody may be a monoclonal antibody or a polyclonal antibody, or may be a monoclonal antibody. In the above (b), the antigen-binding fragment refers to a part of the antibody that recognizes the antigen, and includes the variable domain of the antibody or at least the antigen-binding region. For example, the antigen-binding fragment may be Fab, F(ab'), or the like. 2 , Fab' or scFv.

[0037] In the above (c), the nucleic acid that inhibits the expression of glycolipid synthase is not particularly limited as long as it can inhibit the expression of glycolipid synthase. The nucleic acid that inhibits the expression of glycolipid synthase may be, for example, a small interfering RNA (siRNA) that targets the glycolipid synthase.

[0038] <Target glycolipid biosynthetic enzyme> The glycolipid synthase inhibited by the inhibitor may be a glycosphingolipid synthase. The glycolipid synthase inhibited by the inhibitor may be at least one selected from the group consisting of enzymes in the biosynthetic pathway from ceramide to ganglioside GQ1b and enzymes in the biosynthetic pathway from ceramide to sulfatide. The present inventors have found that pain can be effectively treated by inhibiting these biosynthetic pathway enzymes. Until now, it was completely unknown that pain could be treated by reducing the levels of ganglioside GT1b and sulfatide present in the body through inhibition of biosynthetic pathway enzymes.

[0039] The glycolipid synthase inhibited by the inhibitor may be at least one enzyme in the biosynthetic pathway that synthesizes b-series glycolipids from ceramide. For example, the glycolipid synthase inhibited by the inhibitor may be at least one enzyme in the biosynthetic pathway that leads from ceramide to ganglioside GQ1b. In one embodiment, the glycolipid synthase inhibited by the inhibitor may be at least one enzyme that catalyzes the reaction of converting ceramide to glucosylceramide, the reaction of converting glucosylceramide to lactosylceramide, the reaction of converting lactosylceramide to ganglioside GM3, the reaction of converting ganglioside GM3 to ganglioside GD3, the reaction of converting ganglioside GD3 to ganglioside GD2, the reaction of converting ganglioside GD2 to ganglioside GD1b, the reaction of converting ganglioside GD1b to ganglioside GT1b, or the reaction of converting ganglioside GT1b to ganglioside GQ1b.

[0040] In a preferred embodiment, the glycolipid synthase inhibited by the inhibitor may be an enzyme in the biosynthetic pathway from ceramide to ganglioside GT1b. In a more preferred embodiment, the glycolipid synthase inhibited by the inhibitor may be at least one of enzymes that catalyze the reaction of converting ceramide to glucosylceramide, the reaction of converting glucosylceramide to lactosylceramide, the reaction of converting lactosylceramide to ganglioside GM3, the reaction of converting ganglioside GM3 to ganglioside GD3, the reaction of converting ganglioside GD3 to ganglioside GD2, the reaction of converting ganglioside GD2 to ganglioside GD1b, or the reaction of converting ganglioside GD1b to ganglioside GT1b. In a more preferred embodiment, the glycolipid synthesis enzyme inhibited by the inhibitor may be an enzyme that converts ceramide to glucosylceramide (glucosylceramide synthase), and may be Ugcg, St3gal5, St8sia1, or B4glant1, or may be Ugcg.

[0041] Substances that inhibit Ugcg include lucerastat (NB-DGJ), miglustat (NB-DNJ), and D-PDMP. NB-DGJ and NB-DNJ are primarily imino acids. NB-DGJ is a substance used in matrix synthesis inhibition therapy for Gaucher disease, a genetic disease. NB-DNJ is a substance undergoing clinical trials as a matrix synthesis inhibition therapy for Fabry disease. Normally, glycolipids are processed in the body by sequential degradation of their sugar chains in lysosomes. Gaucher disease and Fabry disease are genetic diseases in which a deficiency in the enzyme responsible for this sugar chain degradation leads to the accumulation of undegraded glycolipids, resulting in lysosome enlargement and cell damage in various organs. The glycolipids that accumulate in Gaucher disease and Fabry disease are both glycolipids synthesized from glucosylceramide. Therefore, substances that inhibit Ugcg, the enzyme that synthesizes glucosylceramide, are used to treat Gaucher disease and Fabry disease in order to suppress glycolipid accumulation. In addition, Fabry disease, a type of lysosomal disease, causes neuropathic pain due to neuropathy, so administering NB-DNJ to treat Fabry disease may alleviate the neuropathy and thus the pain. In contrast, the pain therapeutic agent of the present disclosure can exert an analgesic effect without relying on the alleviation of neuropathy. The pain therapeutic agent of the present disclosure may be used to treat pain other than pain caused by lysosomal disease, or may be used to treat pain other than pain caused by neuropathy.

[0042] As described above, when the glycolipid synthase inhibited by the inhibitor is an enzyme in the biosynthetic pathway that synthesizes b-series glycolipids from ceramide, the pain to be treated may be chronic pain. That is, when the glycolipid synthase inhibited by the inhibitor is an enzyme in the biosynthetic pathway that synthesizes b-series glycolipids from ceramide, the pain therapeutic agent of this aspect may be an agent for treating chronic pain. The present inventors have found that a substance that inhibits an enzyme in the biosynthetic pathway that synthesizes b-series glycolipids from ceramide can be suitably used in the treatment of chronic pain.

[0043] When the glycolipid synthase inhibited by the inhibitor is a biosynthetic pathway enzyme that synthesizes b-series glycolipids from ceramide, the pain (e.g., chronic pain) may be pain at a site where no tissue damage or neural factors are found. That is, in the above case, the pain therapeutic agent may be for treating pain at a site where no tissue damage or neural factors are found. There are pains where the cause can be identified, such as pain caused by tissue damage and neural factors, and pains where the cause is difficult to identify, such as pain caused by psychological factors. The present inventors have found that inhibiting the biosynthetic pathway enzyme that synthesizes b-series glycolipids from ceramide can treat not only pain at a site where tissue damage or neural factors are found, but also pain at a site where no tissue damage or neural factors are found (e.g., pain at a non-inflamed site caused by mechanical allodynia in a subject with inflammation in a part of the body).

[0044] When the glycolipid synthase inhibited by the inhibitor is a biosynthetic pathway enzyme that synthesizes b-series glycolipids from ceramide and the target of treatment is chronic pain, the chronic pain may be chronic primary pain, chronic neuropathic pain, chronic post-surgical pain, or chronic post-traumatic pain. These forms of chronic pain are classified and defined in the International Classification of Diseases (ICD-11) established by the International Association for the Study of Pain (IASP) and the World Health Organization (WHO). All of these chronic pains occur in areas where no tissue damage or neural causes are found.

[0045] When the glycolipid synthase inhibited by the inhibitor is an enzyme in the biosynthetic pathway that synthesizes b-series glycolipids from ceramide, the pain therapeutic agent may be characterized by being administered at least at a predetermined interval. The predetermined interval may be, for example, 1, 2, 3, 4, 5, 7, 10, 14, 21, or 28 days, and in one embodiment, 4 days. The present inventors have found that administration of a substance that inhibits the biosynthetic pathway enzyme that synthesizes b-series glycolipids from ceramide results in a prolonged analgesic effect. Therefore, compared to pain therapeutic agents such as acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs), whose analgesic effect lasts for only a few hours, the pain therapeutic agent in this case exerts its analgesic effect even when administered at a longer interval. This reduces the number of times a patient takes medication, contributing to the patient's quality of life (QOL).

[0046] When the glycolipid synthase inhibited by the inhibitor is a biosynthetic pathway enzyme that synthesizes b-series glycolipids from ceramide, the pain therapeutic agent may provide a blood concentration of the inhibitor after a predetermined period of time following a single administration that is 50% or more of the maximum blood concentration of the inhibitor after a single administration. The predetermined interval may be, for example, 1, 2, 3, 4, 5, 7, 10, 14, 21, or 28 days, and in one embodiment, 4 days. The present inventors have found that administration of a substance that inhibits a biosynthetic pathway enzyme that synthesizes b-series glycolipids from ceramide results in an analgesic effect that lasts for longer than several hours. Therefore, if the pain therapeutic agent satisfies the above-mentioned blood concentration, it can reduce the number of times a patient takes medication, contributing to the patient's quality of life (QOL).

[0047] The glycolipid synthase inhibited by the inhibitor may be at least one enzyme in the biosynthetic pathway from ceramide to sulfatide. The glycolipid synthase inhibited by the inhibitor may be at least one enzyme that converts ceramide to galactosylceramide, or at least one enzyme that converts galactosylceramide to sulfatide. The glycolipid synthase inhibited by the inhibitor may be an enzyme that converts ceramide to galactosylceramide (galactosylceramide synthase), or may be Ugt8a.

[0048] UGT8 Inhibitor 19 (CAS No. 2414349-93-0) is an example of a substance that inhibits the enzymatic reaction of UGT8a. In metachromatic leukodystrophy, a genetic disease, a deficiency in the lysosomal enzyme arylsulfatase A, which breaks down sulfatides, causes sulfatides to accumulate in the body, resulting in central and peripheral neuropathy. Therefore, UGT8 Inhibitor 19 is a promising drug for use in matrix synthesis inhibition therapy for metachromatic leukodystrophy.

[0049] When the glycolipid synthase inhibited by the inhibitor is at least one enzyme in the biosynthetic pathway from ceramide to sulfatide, the pain therapeutic agent may be for treating pain at a site where tissue damage and / or neural factors are present. The present inventors have found that inhibition of an enzyme in the biosynthetic pathway from ceramide to sulfatide can suitably treat pain at a site where tissue damage and / or neural factors are present.

[0050] <Formulation> In this embodiment, the content of the inhibitor in the pain therapeutic agent is not particularly limited, and may be, for example, 0.001 to 100% by mass based on the total amount of the preparation.

[0051] The pain therapeutic agent according to this embodiment may be composed solely of components that increase the expression level of an inhibitory substance, or may contain, in addition to the inhibitory substance, additives commonly used in the pharmaceutical technology field, such as excipients, buffers, stabilizers, antioxidants, binders, disintegrants, fillers, emulsifiers, and flow additives.

[0052] The inhibitor contained in the pain therapeutic agent according to this embodiment may be encapsulated in a drug carrier capable of delivering a component that does not have cell membrane permeability into cells. For example, the drug carrier may be a liposome or a capsid.

[0053] The pain therapeutic agent according to this embodiment may be administered orally or parenterally. Parenteral administration may be by intravenous injection, subcutaneous injection, intramuscular injection, spinal injection, transdermal administration, eye drops, nasal drops, or other methods. Oral administration may be preferred. As an example of a specific dosage, when administered to a human adult male (body weight 60 kg), the daily dosage of the formulation is usually 0.0001 μg to 10,000 mg per day per person, calculated as the amount of active ingredient.

[0054] The pain therapeutic agent according to the present embodiment may be administered at a predetermined interval. The administration interval may be, for example, half a day or more, 1 day or more, 2 days or more, 3 days or more, 4 days or more, 5 days or more, 7 days or more, 10 days or more, 14 days or more, 21 days or more, 28 days or more, 45 days or more, or 60 days or more, or may be 100 days or less, 70 days or less, 50 days or less, 40 days or less, 30 days or less, 25 days or less, 20 days or less, 15 days or less, 12 days or less, 9 days or less, 6 days or less, 5 days or less, 4 days or less, or 3 days or less. Furthermore, the pain therapeutic agent according to the present embodiment may be administered in a single dose at the start of administration so that the intracellular concentration thereof achieves an analgesic effect, and then administered at the above-mentioned predetermined interval in a dose lower than that of the single administration so that the intracellular concentration is maintained.

[0055] The subject to which the pain therapeutic agent of the present embodiment is administered may be a human or a non-human animal, and may be a human. For example, the non-human animal may be a mammal, such as a mouse, rat, hamster, guinea pig, rabbit, dog, cat, monkey, or chimpanzee. The subject to which the pain therapeutic agent of the present embodiment is administered may be a subject who has developed pain, or a subject who is predicted to develop pain due to a postoperative or post-traumatic course, a side effect of a drug, or the like. In one embodiment, the subject may not be suffering from a lysosomal disease (e.g., Fabry disease), Gaucher disease, or metachromatic leukodystrophy, may not have a genetic deficiency in glycolipid synthase or glycolipid degrading enzyme, or may not be suffering from a genetic disease.

[0056] <Other aspects> Another aspect of the present disclosure is a method for treating pain, comprising administering a substance that inhibits glycolipid synthase to a subject in need thereof. The substance that inhibits glycolipid synthase, the pain to be treated, the subject to which it is administered, and the method and form of administration thereof according to this aspect are the same as those described for the pain therapeutic agent according to the other aspect.

[0057] Another aspect of the present disclosure is a substance that inhibits glycolipid synthase for use in treating pain. The substance that inhibits glycolipid synthase, the pain to be treated, the subject to which it is administered, and the method and form of administration thereof according to this aspect are the same as those described for the pain therapeutic agent according to the other aspect.

[0058] Another aspect of the present disclosure is use of a substance that inhibits glycolipid synthase in the manufacture of a pain therapeutic agent. The substance that inhibits glycolipid synthase, the pain to be treated, the subject to which it is administered, and the method and form of administration thereof according to this aspect are the same as those described for the pain therapeutic agent according to the other aspect. [Example]

[0059] The present disclosure will be described in more detail below using examples, but the present disclosure is not limited to the following examples. Five- to seven-week-old male ICR mice (manufactured by CLEA Japan, Inc.) were used as mice in the following examples.

[0060] In this example, the von Frey test was performed as described below. Eight different von Frey hair filaments (2.36-4.17) were applied to the paw, which was the measurement site, and the 50% paw withdrawal threshold (g) was measured as the pressure that elicits a withdrawal response. In the von Frey test, a smaller 50% paw withdrawal threshold indicates greater sensitivity to pain, i.e., the occurrence of stronger pain (mechanical allodynia).

[0061] Example 1: Pain test in mice administered intrathecal sulfatide Mice were intrathecally administered vehicle or 0.1 pmol, 1.0 pmol, or 10 pmol of sulfatide. Mechanical allodynia was assessed by von Frey testing of the hind paw immediately before administration (baseline), and 20, 40, 80, or 160 minutes after administration.

[0062] The results for vehicle administration are shown in Figure 2(a). The results for sulfatide administration are shown in Figure 2(b). The results in Figure 2 show that mice administered sulfatide intrathecally exhibited escape behavior even when small pressure was applied, demonstrating that they had developed mechanical allodynia. Furthermore, the mechanical allodynia in mice administered sulfatide intrathecally was dependent on the sulfatide concentration. This demonstrates that increased sulfatide concentrations induce pain.

[0063] Example 2: Pain treatment effect of galactosylceramide synthesis inhibitors We investigated whether inhibitors of galactosylceramide synthesis, an enzyme in the biosynthetic pathway from ceramide to sulfatide, have therapeutic effects on pain.

[0064] UGT8 inhibitor 19 was dissolved in 0.1% DMSO in saline to a concentration of 5 μM (inhibitor solution). 5 μL of the inhibitor solution was administered intrathecally to mice on days −1 and 0. Twenty minutes after administration of the inhibitor solution on day 0, complete Freund's adjuvant (CFA), an inflammatory substance, was administered into the plantar surface of one hind paw to induce inflammation. Furthermore, 5 μL of the inhibitor solution was administered intrathecally on days 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19. The von Frey test was performed on both hind paws before administration of the inhibitor solution on day −1 (baseline) and on days 0, 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, and 27. When the inhibitor solution and the von Frey test were administered on the same day, the von Frey test was performed before administration of the inhibitor solution. A group in which the vehicle was administered instead of the inhibitor solution was also prepared and tested.

[0065] The results for the CFA-administered hind paw (inflamed paw) are shown in Figure 3(a). The results for the non-CFA-administered hind paw (non-inflamed paw) are shown in Figure 3(b). The results in Figures 3(a) and 3(b) are shown as mean ± standard error (n=6), with * and ** indicating p values ​​less than 0.05 and 0.01, respectively. The underlines below the values ​​on the horizontal axis indicate the approximate administration period. Figure 3(a) shows that the galactosylceramide synthesis inhibitor significantly suppressed pain in the inflamed paw from the day after CFA administration. Furthermore, Figure 3(a) shows that the galactosylceramide synthesis inhibitor significantly suppressed pain on days 21 and 27, after the 19th day when administration was terminated. These results demonstrate that enzymes involved in the biosynthetic pathway from ceramide to sulfatide can be used effectively to treat pain, particularly at sites where tissue damage and / or neural factors are present, and can be used to treat, for example, chronic pain.

[0066] Example 3: Pain test in mice administered intrathecally with a-series or b-series gangliosides Mice were intrathecally administered vehicle or a-series or b-series gangliosides. Mechanical allodynia was assessed by the von Frey test in the hind paw immediately before (baseline), and 20, 40, 80, or 160 minutes after administration.

[0067] The results of administering 1 nmol of ganglioside GM3, ganglioside GM1, or ganglioside GD1a are shown in Figure 4(a). The results of administering vehicle are shown in Figure 4(b). The results of administering 1 nmol of ganglioside GD3, ganglioside GD1b, or ganglioside GT1b are shown in Figure 4(c). In Figure 4(c), * and ** indicate p values ​​less than 0.05 and 0.01, respectively. According to the results in Figures 4(a) to 4(c), mechanical allodynia was observed in mice administered the b-series gangliosides shown in Figure 4(c). This demonstrates that increased concentrations of b-series gangliosides induce pain.

[0068] The results when ganglioside GT1b was administered at 0 pmol, 0.1 pmol, 1.0 pmol, 10 pmol, 100 pmol, or 1000 pmol are shown in Figure 4(d). In Figure 4(d), *, **, and *** indicate p values ​​less than 0.05, less than 0.01, and less than 0.001, respectively. Figure 4(d) shows that the administered ganglioside GT1b exacerbated mechanical allodynia in a concentration-dependent manner. This demonstrates that increased ganglioside GT1b concentrations induce pain.

[0069] Example 4: Pain treatment effect of glucosylceramide synthesis inhibitors We investigated whether inhibitors of glucosylceramide synthesis, an enzyme in the biosynthetic pathway from ceramide to ganglioside GQ1b, have therapeutic effects for pain.

[0070] NB-DGJ was dissolved in saline to a concentration of 400 μM (NB-DGJ solution). 5 μL of NB-DGJ solution was administered intrathecally to mice on days −1 and 0. Twenty minutes after administration of NB-DGJ solution on day 0, complete Freund's adjuvant (CFA), an inflammatory substance, was administered to the plantar surface of one hind paw to induce inflammation. Furthermore, 5 μL of NB-DGJ solution was administered intrathecally on days 1, 2, 5, 7, 9, 12, 14, 16, 17, 19, and 21. A von Frey test was performed on both hind paws before administration of NB-DGJ solution on day −1 (baseline) and on days 1, 5, 7, 15, 17, 22, 35, 42, and 49. When the NB-DGJ solution and the von Frey test were administered on the same day, the von Frey test was performed before administration of NB-DGJ solution. A group in which the vehicle was administered instead of the NB-DGJ solution was also prepared and tested.

[0071] The results for the hind paw (inflamed paw) on the side where CFA was administered are shown in Figure 5(a). The results for the hind paw (non-inflamed paw) on the side where CFA was not administered are shown in Figure 5(b). The results in Figures 5(a) and (b) are shown as mean ± standard error for n=5, with * and ** indicating p values ​​less than 0.05 and 0.01, respectively. The underlines below the values ​​on the horizontal axis indicate the approximate administration period.

[0072] As shown in Figures 5(a) and 5(b), the glucosylceramide synthesis inhibitor significantly suppressed pain in both the inflamed and non-inflamed paws, even after administration was terminated on day 21, continuing for an additional two weeks, up to day 35. This demonstrates that the enzymes involved in the biosynthetic pathway from ceramide to ganglioside GQ1b can treat pain even when administered at intervals. Such pain treatment agents can be suitably used to treat chronic pain.

[0073] Furthermore, as shown in Figure 5(b), the glucosylceramide synthesis inhibitor significantly suppressed pain even in the paw that was not administered CFA, i.e., the non-inflamed paw. This demonstrates that the enzymes in the biosynthetic pathway from ceramide to ganglioside GQ1b can be used to treat pain in areas where no tissue damage or neural factors are present.

[0074] Example 5: Pain suppression effect of prophylactic administration of a glucosylceramide synthesis inhibitor We investigated whether a glucosylceramide synthesis inhibitor would have a therapeutic effect on pain when administered prophylactically before pain induction (before CFA administration).

[0075] Mice were intrathecally administered 5 μL of NB-DGJ solution on days −15, −13, −11, −8, −6, −4, −1, and 0. Twenty minutes after NB-DGJ solution administration on day 0, complete Freund's adjuvant (CFA), an inflammatory substance, was administered into the plantar surface of one hind paw to induce inflammation. Furthermore, 5 μL of NB-DGJ solution was intrathecally administered on days 1, 3, 6, and 8. The von Frey test was performed on both hind paws before NB-DGJ solution administration on day −15 (baseline) and on days 1, 3, 7, 11, and 15. When the NB-DGJ solution and the von Frey test were administered on the same day, the von Frey test was performed before NB-DGJ solution administration. A group receiving vehicle instead of NB-DGJ solution was also prepared and tested.

[0076] The results for the hind paw (inflamed paw) on the side where CFA was administered are shown in Figure 6(a). The results for the hind paw (non-inflamed paw) on the side where CFA was not administered are shown in Figure 6(b). The results in Figures 6(a) and 6(b) are shown as mean ± standard error for n=6, with * and ** indicating p values ​​less than 0.05 and 0.01, respectively. The underlines below the values ​​on the horizontal axis indicate the approximate administration period.

[0077] As shown in Figures 6(a) and (b), the glucosylceramide synthesis inhibitor suppressed pain in the inflamed paw even when administered prophylactically, demonstrating a pain treatment effect.

[0078] Example 6: Pain suppression effect of therapeutic administration of glucosylceramide synthesis inhibitor We investigated whether a glucosylceramide synthesis inhibitor has a therapeutic effect on pain when administered therapeutically after pain induction (after CFA administration).

[0079] On day 0, mice were injected with complete Freund's adjuvant (CFA), an inflammatory substance, into the plantar surface of one hind paw to induce inflammation. On days 18, 20, 22, 25, 27, and 29, 5 μL of NB-DGJ solution was intrathecally administered. The von Frey test was performed on both hind paws before CFA administration (baseline) and on days 1, 18, 19, 21, 23, 26, 28, 30, 37, 44, and 56. When the NB-DGJ solution and the von Frey test were administered on the same day, the von Frey test was performed before administration of the NB-DGJ solution. A group receiving vehicle instead of the NB-DGJ solution was also prepared and tested.

[0080] The results for the hind paw (inflamed paw) on the side where CFA was administered are shown in Figure 7(a). The results for the hind paw (non-inflamed paw) on the side where CFA was not administered are shown in Figure 7(b). The results in Figures 7(a) and (b) are shown as mean ± standard error for n=6, with * and ** indicating p values ​​less than 0.05 and 0.01, respectively. The underlines below the values ​​on the horizontal axis indicate the approximate administration period.

[0081] 7(a) and (b), the glucosylceramide synthesis inhibitor suppressed pain in both the inflamed and non-inflamed paws, even when administered 18 days after the onset of pain, demonstrating its pain therapeutic effect. Furthermore, similar to the results of Example 4, the pain therapeutic effect persisted for a long period after the end of administration.

Claims

1. A pain treatment agent containing a substance that inhibits glycolipid synthesis enzymes.

2. 2. The pain remedy according to claim 1, wherein the glycolipid synthase is at least one selected from the group consisting of enzymes in the biosynthetic pathway from ceramide to ganglioside GQ1b and enzymes in the biosynthetic pathway from ceramide to sulfatide.

3. 2. The pain remedy according to claim 1, wherein the glycolipid synthase is at least one enzyme in the biosynthetic pathway from ceramide to ganglioside GQ1b.

4. The pain therapeutic agent according to claim 3 , which is a therapeutic agent for chronic pain.

5. The pain therapeutic agent according to claim 4, which is for treating pain at a site where no tissue damage or neural factors are found.

6. The pain therapeutic agent according to claim 4 or 5, wherein the chronic pain is chronic primary pain, chronic neuropathic pain, chronic post-surgical pain, or chronic post-traumatic pain.

7. 2. The pain remedy according to claim 1, wherein the glycolipid synthase is at least one enzyme in the biosynthetic pathway from ceramide to sulfatide.

8. The pain therapeutic agent according to claim 7, which is for treating pain at a site where tissue damage and / or neural factors are found.

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