Reagent for measuring function of cancer-related amino acid transporter asct

Abstract

To provide a compound applicable to measurement of ASCT function and detection of cancer cells, and to provide a reagent for measuring ASCT function and a cancer cell detection reagent that contain the compound.SOLUTION: There is provided a compound represented by the following general formula (1) or a pharmaceutically acceptable salt thereof. Also provided is a reagent for measuring ASCT function containing the compound or a pharmaceutically acceptable salt thereof. Also provided is a cancer cell detection reagent containing the compound or a pharmaceutically acceptable salt thereof. In formula (1), X represents a radionuclide, Ar represents an aromatic hydrocarbon group which may have a substituent, R1 to R4 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and n1 represents an integer of 1 to 3.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a test agent for measuring the function of the cancer-associated amino acid transporter ASCT, and also to a cancer cell detection agent and compound. [Background technology]

[0002] Radioactive compounds that are specifically taken up by cancer cells are used as diagnostic imaging agents for cancer. Compared to normal cells, cancer cells require more energy because they undergo more active cell proliferation. Glucose is one of the important nutrients for energy production. 2-deoxy-2-[ 18 F]fluoro-D-glucose( 18 Positron emission tomography (PET) using F-FDG is currently used as a clinical imaging test. 18 F-FDG PET testing is also used for cancer screening because it can detect cancer throughout the body at once. 18 F-FDG accumulates in normal tissues such as the brain, kidneys, and bladder, and is therefore effective in detecting cancers occurring in these tissues. 18 It is difficult to detect using F-FDG.

[0003] On the other hand, amino acids are as important nutrients as glucose for the growth of cancer cells. Regarding the uptake of amino acids in cancer cells, there are cancer-related amino acid transporters that are specifically highly expressed in cancer cells. The types of cancer-related amino acid transporters include LAT1 / 3, ASCT2, xCT, and ATB. 0,+ etc. have been reported (Non-Patent Document 1). Radioactive compounds using tyrosine analogs, methionine analogs, etc. have been reported as cancer nuclear medicine diagnostic imaging agents mainly targeting LAT1 / 3 (Non-Patent Documents 2 and 3). In addition, cancer nuclear medicine diagnostic imaging agents targeting multiple cancer-related amino acid transporters such as LAT1 / 3 and ASCT2 have been reported (Non-Patent Document 4). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Lieu EL, Nguyen T, Rhyne S, et al. Amino acids in cancer. Exp Mol Med. 2020;52(1):15-30. [Non-patent document 2] Shikano N, Ogura M, Okudaira H, et al. Uptake of 3-[125I]iodo-α-methyl-l-tyrosine into colon cancer DLD-1 cells: characterization and inhibitory effect of natural amino acids and amino acid-like drugs. Nucl Med Biol. 2010;37(2):197-204. [Non-patent document 3] Kobayashi M, Hashimoto F, Ohe K, et al. Transport mechanism of 11C-labeled L- and D-methionine in human-derived tumor cells. Nucl Med Biol. 2012;39(8):1213-8. [Non-patent document 4] Okudaira et al. Putative Transport Mechanism and Intracellular Fate of Trans-1-Amino-3-18F-Fluorocyclobutanecarboxylic Acid in Human Prostate Cancer. J Nucl Med. 2011 May;52(5):822-9. Summary of the Invention [Problem to be solved by the invention]

[0005] Cancer imaging diagnostic agents that primarily target LAT1 / 3 have difficulty detecting cancer cells that do not express LAT1 / 3. Cancer imaging diagnostic agents that target multiple cancer-related amino acid transporters have difficulty identifying the cancer-related amino acid transporters expressed in cancer cells. ASCT, a cancer-related amino acid transporter, is thought to contribute to cancer cell proliferation. Therefore, the development of diagnostic agents that specifically target ASCT is desirable.

[0006] Therefore, the present invention aims to provide a compound that can specifically target ASCT as a cancer-associated amino acid transporter, as well as a test agent and a cancer cell detection agent for measuring the function of ASCT, which comprise the compound. [Means for solving the problem]

[0007] The present invention includes the following aspects. [1] A compound represented by the following general formula (1) or a pharmaceutically acceptable salt thereof:

[0008] [ka] [In the formula, X represents a radioactive nuclide, Ar represents an aromatic hydrocarbon group which may have a substituent, R1 to R4 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and n1 represents an integer of 1 to 3.]

[0009] [2] The compound according to [1], wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2), or a pharmaceutically acceptable salt thereof:

[0010] [ka] [In the formula, X represents a radioactive nuclide. R1 to R4 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R5 represents a substituent other than a radioactive nuclide. n1 represents an integer of 1 to 3, n2 represents an integer of 0 to 4, and n1+n2≦5.]

[0011] [3] The compound according to [3], wherein the compound represented by the general formula (2) is a compound represented by the following general formula (3), or a pharmaceutically acceptable salt thereof:

[0012] [ka] [In the formula, X represents a radioactive nuclide. R1 to R4 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R6 represents an alkyl group having 1 to 5 carbon atoms. n3 represents an integer of 0 to 3.]

[0013] [4] A cancer cell detecting agent according to any one of [1] to [3], wherein X in the general formula (1) is a radioactive halogen, or a pharmaceutically acceptable salt thereof. [5] A test agent for measuring ASCT function, comprising the compound according to any one of [1] to [4] or a pharmaceutically acceptable salt thereof. [6] The test agent according to [5], which is a test agent for measuring amino acid transport into cells via ASCT. [7] A cancer cell detection agent comprising the compound according to any one of [1] to [4], or a compound (A) represented by the following general formula (1), or a pharmaceutically acceptable salt of the compound (A): [8] A cancer cell detection drug described in [7], wherein the cancer cells are cancer cells expressing ASCT. [9] A cancer cell detection agent according to [7] or [8], which is a nuclear medicine imaging diagnostic agent for cancer. [Effects of the Invention]

[0014] According to the present invention, there are provided compounds that can specifically target ASCT as a cancer-associated amino acid transporter, as well as test agents and cancer cell detection agents for measuring the function of ASCT, which comprise the compounds. [Brief explanation of the drawings]

[0015] [Figure 1] 1 shows the results of an experiment on intracellular accumulation of compound (A-1) in lung cancer cell lines in Experimental Example 2. [Figure 2] 1 shows the results of an experiment in Experimental Example 2 on the intracellular accumulation of compound (A-1) in a colon cancer cell line. [Figure 3] In Experimental Example 3, the results of investigating amino acid transporters involved in the intracellular accumulation of compound (A-1) using the lung cancer cell line H441 are shown. [Figure 4] In Experimental Example 3, the results of examining amino acid transporters involved in the intracellular accumulation of compound (A-1) using colon cancer cell line LS180 are shown. [Figure 5] In Experimental Example 3, the colon cancer cell line LS180 was used to investigate whether amino acid transporters involved in the intracellular accumulation of compound (A-1) and whether Glutaminase-1 is involved in the intracellular accumulation of compound (A-1) are shown. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Compound or pharmaceutically acceptable salt thereof] A first aspect of the present disclosure is a compound represented by the following general formula (1) (hereinafter also referred to as "compound (A)") or a pharmaceutically acceptable salt thereof.

[0017] [ka] [In the formula, X represents a radioactive nuclide, Ar represents an aromatic hydrocarbon group which may have a substituent, and R 1 ~R 4 each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and n1 represents an integer of 1 to 3.

[0018] In the formula (1), the radioactive nuclide for X is preferably a radioactive halogen. Examples of the radioactive halogen include radioactive iodine, radioactive fluorine, radioactive bromine, and radioactive astatine. Specific examples of the radioactive nuclide include iodine-123 ( 123 I), iodine-124( 124 I), iodine-125( 125 I), iodine-131( 131 I), fluorine 18( 18F), Bromine 76( 76 Br), Bromine 77( 77 Br), Astatine 211( 211 Among them, X is radioactive iodine ( 123 I, 124 I, 125 I, 131 I, etc.) are preferred.

[0019] In the formula (1), Ar represents an aromatic hydrocarbon group which may have a substituent. The aromatic hydrocarbon group is a hydrocarbon group containing an aromatic ring. The aromatic ring may be monocyclic or polycyclic. The aromatic ring may be an aromatic hydrocarbon ring or an aromatic heterocyclic ring. Examples of the aromatic hydrocarbon ring include a benzene ring and a naphthalene ring. Examples of the aromatic hydrocarbon ring include a nitrogen-containing aromatic heterocyclic ring (a pyrrole ring, a pyridine ring, etc.), a sulfur-containing aromatic heterocyclic ring (a thiophene ring, a thiopyran ring, etc.), and an oxygen-containing aromatic heterocyclic ring (a furan, a pyran, etc.). The aromatic ring contained in Ar is preferably an aromatic hydrocarbon ring, and more preferably a benzene ring.

[0020] The aromatic hydrocarbon group in Ar may have a substituent. Examples of the substituent include a hydroxy group, a halogen atom (non-radioactive), and an alkyl group having 1 to 5 carbon atoms. Examples of the halogen atom include a fluorine atom, an iodine atom, bromine, and astatine. The alkyl group having 1 to 5 carbon atoms may be linear or branched. The alkyl group as the substituent in Ar preferably has 1 to 3 carbon atoms, and more preferably a methyl group or an ethyl group. The aromatic hydrocarbon group in Ar preferably has at least one substituent, and preferably has at least one hydroxy group.

[0021] In the formula (1), R 1 ~R 4The alkyl group having 1 to 5 carbon atoms in the formula (I) preferably has 1 to 3 carbon atoms, more preferably 1 or 2 carbon atoms. The alkyl group may be linear or branched. The linear alkyl group preferably has 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group. The branched alkyl group preferably has 3 or 4 carbon atoms, preferably an isopropyl group. R 1 ~R 4 is preferably a hydrogen atom or a methyl group, more preferably a hydrogen atom.

[0022] In the formula (1), n1 is preferably 1 or 2, and more preferably 1. When n1 is an integer of 2 or more, the two or more Xs may be the same or different from each other.

[0023] The compound (A) is preferably a compound represented by the following general formula (2).

[0024] [ka] [Wherein, X represents a radionuclide. R 1 ~R 4 R each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. 5 represents a substituent other than a radionuclide; n1 represents an integer of 1 to 3, n2 represents an integer of 0 to 4, and n1+n2≦5.

[0025] In the formula (2), X and R 1 ~R 4 , and n1 are the same as those in the formula (1).

[0026] In the formula (2), R 5 Examples of the substituent in R include those exemplified as the substituent in the aromatic hydrocarbon group of Ar in the formula (1). 5 At least one of these is preferably a hydroxy group.

[0027] In the formula (2), n2 is preferably an integer of 1 to 4, more preferably an integer of 1 to 3, and more preferably 1 or 2. When n2 is an integer of 2 or more, two or more R 5 may be the same as or different from each other.

[0028] The compound (A) is preferably a compound represented by the following general formula (3).

[0029] [ka] [Wherein, X represents a radionuclide. R 1 ~R 4 R each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. 6 represents an alkyl group having 1 to 5 carbon atoms. n3 represents an integer of 0 to 3.

[0030] In the formula (3), X and R 1 ~R 4 are the same as those in the above formula (1).

[0031] In the formula (3), R 6 The alkyl group having 1 to 5 carbon atoms in the formula (I) preferably has 1 to 3 carbon atoms, more preferably 1 or 2 carbon atoms. The alkyl group may be linear or branched. The linear alkyl group preferably has 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group. The branched alkyl group preferably has 3 or 4 carbon atoms, more preferably an isopropyl group.

[0032] In the formula (3), n3 is preferably an integer of 0 to 2, more preferably 0 or 1, and more preferably 0.

[0033] The compound (A) is preferably a compound represented by the following general formula (4).

[0034] [ka] [Wherein, X represents a radionuclide. R 1 ~R 4R each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. 6 represents an alkyl group having 1 to 5 carbon atoms. n3 represents an integer of 0 to 3.

[0035] In the formula (4), X and R 1 ~R 4 , R 5 , and n3 are the same as those in the formula (3).

[0036] The compound (A) is preferably a compound represented by the following general formula (5).

[0037] [ka] [wherein X represents a radionuclide.]

[0038] In the formula (4), X is the same as in the formula (1).

[0039] Specific examples of the compound (A) are shown below, but are not limited thereto.

[0040] [ka]

[0041] Compound (A) may be in the form of a pharmaceutically acceptable salt. "Pharmaceutically acceptable salt" refers to a salt form that does not inhibit the function of compound (A) as a cancer cell detection drug and does not exhibit substantial toxicity to the subject to which it is administered. The activity of compound (A) as a cancer cell detection drug includes its ability to accumulate in cancer cells. "Exhibiting substantial toxicity" means that the component does not exhibit toxicity to the subject to which it is administered at a dose normally used. Examples of pharmaceutically acceptable salts include inorganic acid salts, organic acid salts, inorganic base salts, and organic base salts. Pharmaceutically acceptable salts may also include hydrates that can be formed when a compound absorbs water and solvates that can be formed when a compound absorbs a solvent.

[0042] The cancer cell detecting agent contains at least one selected from the group consisting of compound (A) and pharmaceutically acceptable salts of compound (A). The compound (A) or salts of compound (A) may be one type or two or more types.

[0043] (Method for producing compound (A)) Compound (A) can be produced by known methods. For example, compound (A) can be produced by introducing a radionuclide into a glutamine derivative in which an aromatic ring has been introduced into the amino group in the side chain of glutamine. Introduction of a radionuclide into a glutamine derivative can be carried out, for example, by the chloramine T method. Specific examples of glutamine derivatives that can be used to produce compound (A) include N-(p-hydroxyphenyl)-L-glutamine.

[0044] Compound (A) or a pharmaceutically acceptable salt of compound (A) is transported into cells by ASCT (particularly ASCT2). On the other hand, compound (A) or a pharmaceutically acceptable salt thereof is thought to be hardly transported into cells by other cancer-related amino acid transporters (e.g., LAT1, SNAT2). Therefore, ASCT activity in cells can be specifically measured by using compound (A) or a pharmaceutically acceptable salt of compound (A). Compound (A) or a pharmaceutically acceptable salt thereof can be used as a test agent for measuring the function of ASCT, a cancer cell detection agent, etc., as described below.

[0045] [Test drug for measuring ASCT function] A second aspect of the present invention is a test agent for measuring ASCT function (hereinafter also referred to as "ASCT function test agent"). The ASCT function test agent comprises compound (A) or a pharmaceutically acceptable salt thereof.

[0046] "ASCT" stands for alanine-serine-cycteine-transporter and is known as a cancer-associated amino acid transporter. ASCT is a sodium-dependent amino acid transporter involved in the intracellular transport of neutral amino acids. Known ASCTs include ASCT1 and ASCT2. ASCT2 is also called SLC1A5 (solute carrier family 1 member 5). ASCT2 is involved in the intracellular transport of glutamine in cancer cells. Examples of the amino acid sequence of human ASCT2 include GenBank accession numbers NP_001138616.1, NP_001138617.1, and NP_005619.1. In one embodiment, the ASCT to be measured is ASCT2.

[0047] Compound (A) is transported into cells via ASCT. Therefore, the function of ASCT in cells can be measured by measuring the amount of compound (A) taken up into cells. "ASCT function" refers to the amino acid transport function of ASCT. The function of ASCT may be, for example, the activity of ASCT-mediated amino acid transport into cells. The cells in which ASCT function is measured may be cells expressing ASCT or cells not expressing ASCT. Cells not expressing ASCT are evaluated as having no or almost no ASCT function.

[0048] <How to use> The test agent for ASCT function can be used, for example, as follows: The test agent for ASCT function is contacted with cells to be tested. The contact may be performed in vitro, ex vivo, or in vivo.

[0049] In vitro, the ASCT function test agent can be added to the culture medium of the cells to be tested, thereby bringing the cells into contact with the ASCT function test agent. After culturing the cells for a desired period of time in the presence of the ASCT function test agent, the amount of compound (A) accumulated in the cells is measured. The culture time is not particularly limited, but may be, for example, about 10 to 500 minutes. The amount of compound (A) accumulated in the cells can be measured by known methods. For example, after culturing, the cells are recovered from the culture medium by centrifugation or the like, washed appropriately, and then lysed. The radioactivity in this cell lysate is measured using a radiation counter or the like. This allows the amount of compound (A) accumulated in the cells to be measured.

[0050] In the case of ex vivo testing, the ASCT function test agent can be added to the culture medium of the cells or tissues to be tested, thereby bringing the test agent into contact with the cells or tissues. After culturing the cells or tissues for a desired period of time in the presence of the ASCT function test agent, the amount of compound (A) accumulated in the cells is measured. The culture time is not particularly limited, but may be, for example, about 10 to 500 minutes. The amount of compound (A) accumulated in the cells can be measured by known methods. For example, the cells or tissues are recovered from the culture medium by centrifugation or the like, washed appropriately, and then lysed. The radioactivity in the cell lysate or tissue lysate is measured using a radiation counter or the like. This allows the amount of compound (A) accumulated in the cells or tissues to be measured.

[0051] In the case of in vivo testing, the ASCT function test agent can be contacted with cells in the living body by parenterally administering the ASCT function test agent to the living body being tested. Examples of parenteral administration include intravenous administration. After a desired time has elapsed since administration of the ASCT function test agent, the distribution of compound (A) in the living body is detected using a radiation detection device or the like. Examples of radiation detection devices include a gamma camera device. Examples of gamma camera devices include PET (Positron Emission Tomography) and SPECT (Single Photon Emission Computed Tomography). The time from administration to radiation detection can be, for example, about 10 to 180 minutes. By measuring the distribution of compound (A) in the living body, the distribution of cells with high ASCT function or cells with low ASCT function in the living body can be measured.

[0052] <Optional ingredients> In one embodiment, the ASCT functional test agent may contain other components in addition to compound (A) and / or a pharmaceutically acceptable salt of compound (A). Examples of other components include pharmaceutically acceptable carriers. The term "pharmaceutically acceptable carrier" refers to a carrier that does not inhibit the function of compound (A) as an ASCT functional test agent and does not exhibit substantial toxicity to the subject to which it is administered. Examples of pharmaceutically acceptable carriers include water, buffer solutions (phosphate buffer, phosphate-buffered saline, etc.), saline, Ringer's solution, etc.

[0053] In one embodiment, the ASCT functional test reagent may contain other components in addition to the above components, such as, but not limited to, pH adjusters, antiseptics, stabilizers, preservatives, disinfectants, etc.

[0054] [Cancer cell detection drug] A third aspect of the present invention is a cancer cell detecting agent, which comprises compound (A) or a pharmaceutically acceptable salt thereof.

[0055] <Optional ingredients> In one embodiment, the cancer cell detecting agent may contain other components in addition to compound (A) and / or a pharmaceutically acceptable salt of compound (A). Examples of other components include pharmaceutically acceptable carriers. A "pharmaceutically acceptable carrier" refers to a carrier that does not inhibit the function of compound (A) as a cancer cell detecting agent and does not exhibit substantial toxicity to the subject to which it is administered. Examples of pharmaceutically acceptable carriers include water, buffer solutions (phosphate buffer, phosphate-buffered saline, etc.), saline, Ringer's solution, etc.

[0056] In one embodiment, the cancer cell detection agent may contain other components in addition to the above components, such as, but not limited to, pH adjusters, antiseptics, stabilizers, preservatives, disinfectants, etc.

[0057] <How to use> The cancer cell detecting agent can be used to detect cancer cells. The cancer cells to be detected include cancer cells expressing ASCT. In one embodiment, the cancer cells to be detected are cancer cells expressing ASCT2.

[0058] Compound (A) taken up into cancer cells via ASCT2 may be converted to a glutamic acid backbone by glutaminase if present in the cells. Furthermore, compounds with a glutamic acid backbone may be excreted extracellularly by xCT in cells expressing xCT. Therefore, cancer cells to be detected may be cancer cells that express ASCT2 but do not express glutaminase or express glutaminase at low levels. Alternatively, cancer cells to be detected may be cancer cells that express ASCT2 but do not express or express at low levels of xCT, a cystine-glutamate transporter. Glutaminase is an enzyme that converts glutamine to glutamic acid. Examples of the amino acid sequence of human xCT include GenBank accession number NP_001243239.1. xCT is an amino acid transporter that exchanges and transports extracellular cystine for intracellular glutamic acid. xCT is also known as SLC7A11 (solute carrier family 7 member 11). An example of the amino acid sequence of human xCT is GenBank Accession No. NP_055146.1.

[0059] Examples of cancer cell types include, but are not limited to, lung cancer, colon cancer, stomach cancer, pancreatic cancer, liver cancer, kidney cancer, prostate cancer, ovarian cancer, cervical cancer, head and neck cancer, skin cancer, osteosarcoma, chondrosarcoma, blood cancer, brain tumors, and the like.

[0060] The cancer cell detecting agent may be used in vitro or in vivo. When used in vivo, the cancer cell detecting agent may be used as a nuclear medicine imaging agent for cancer.

[0061] When used as a cancer imaging diagnostic agent, the cancer cell detecting agent is administered to a subject, for example, intravenously. For example, after administration of the cancer cell detecting agent, radiation generated from compound (A) is captured using a gamma camera or the like. By detecting the accumulation of compound (A) in the obtained image, cancer cells in the subject's body can be detected. This makes it possible to diagnose whether or not cancer has occurred in the subject. Examples of gamma camera devices include PET (Positron Emission Tomography) and SPECT (Single Photon Emission Computed Tomography).

[0062] Compound (A) is thought to be transported into cancer cells by ASCT (particularly ASCT2). Therefore, the cancer cell detecting agent may be used to detect cells expressing ASCT2. For example, the cancer cell detecting agent may be used in a subject suffering from cancer to determine whether the cancer expresses ASCT. Therefore, in one embodiment, the cancer cell detecting reagent may be an agent for detecting ASCT (particularly ASCT2)-expressing cells, comprising compound (A) or a pharmaceutically acceptable salt of compound (A). The agent for detecting ASCT-expressing cells may be an agent for detecting cells that express ASCT and do not express xCT or have a low expression level of xCT. In one embodiment, the cancer cell detecting agent may be an agent for measuring the expression level of ASCT (particularly ASCT2) in cells.

[0063] The cancer cell detecting agent of this embodiment contains compound (A) or a pharmaceutically acceptable salt thereof, and therefore can specifically detect cancer cells expressing ASCT (particularly ASCT2). Therefore, it is possible to determine whether or not the cancer in a subject expresses ASCT from an image obtained using the cancer cell detecting agent of this embodiment. It is believed that obtaining such information can enable appropriate formulation of a cancer treatment strategy.

[0064] [Other aspects] In one aspect, the present disclosure provides a method for diagnosing cancer, comprising administering Compound (A) or a pharmaceutically acceptable salt of Compound (A) to a subject, and optionally, obtaining a radiological image of the subject after the administration. In one aspect, the present disclosure provides a method for detecting cancer cells, comprising administering compound (A) or a pharmaceutically acceptable salt of compound (A) to a subject. In one aspect, the present disclosure provides the use of Compound (A) or a pharmaceutically acceptable salt of Compound (A) in the manufacture of a nuclear medicine imaging agent for cancer. In one aspect, the present disclosure provides Compound (A) or a pharmaceutically acceptable salt of Compound (A) for use in nuclear medicine imaging of cancer. In one aspect, the present disclosure provides the use of Compound (A) or a pharmaceutically acceptable salt of Compound (A) for nuclear medicine imaging of cancer. [Example]

[0065] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0066] [Experimental Example 1] (Production of Compounds) Based on previous reports (Biotechnology and Bioprocess Engineering 2013, 18, 358; Biochemistry 2001, 40, 12678), N-(p-hydroxyphenyl)-L-glutamine (also known as yL-glutarninyl-4-hydroxybenzene) was synthesized by the following reaction.

[0067] [ka]

[0068] The chloramine T method was used to determine the amount of N-(p-hydroxyphenyl)-L-glutamine. 125 I labeling was performed. 125I-NaI (1.5 MBq) was diluted to 10 μL with phosphate buffered saline (pH 6.0), and N-(p-hydroxyphenyl)-L-glutamine (10 mM, 50 μl) dissolved in phosphate buffered saline (pH 6.0) and an aqueous chloramine T solution (Nacalai Tesque, 10 mM, 50 μl, dissolved in ultrapure water) were added and stirred well, followed by reacting at 25 °C for 20 minutes. Then, 25 μL of a 1 / 10 saturated solution of sodium pyrosulfite was added to stop the reaction. The reaction solution was concentrated under a nitrogen stream, and compound (A-1) was obtained by simultaneously performing purification and fractionation by high performance liquid chromatography (HPLC). The elution conditions of compound (A-1) in HPLC are shown below. The success or failure of the synthesis of compound (A-1) was 127 confirmed by the coincidence of the retention time in HPLC with the standard labeled with I.

[0069] <Elution conditions of compound (A-1) using the gradient method of HPLC> Column: Column C18-MS-II for reverse phase chromatography (COSMOSIL, Nacalai Tesque) Temperature: Room temperature Mobile phase: Acetonitrile: 0.1 v / v% trichloroacetic acid: water At the start of injection of compound (A-1): Acetonitrile: 0.1 v / v% trichloroacetic acid: water = 10:50:40 15 minutes after injection of compound (A-1): Acetonitrile: 0.1 v / v% trichloroacetic acid: water = 100:0:0

[0070]

Chemical formula

[0071] For the measurement of the 125 I labeling rate of the obtained compound (A-1), thin layer chromatography was used. As the developing solvent for thin layer chromatography, a mixed solvent of methanol and acetic acid (methanol: acetic acid = 100:1, mixing ratio) was used. The labeling rate was 23 - 46%.

[0072] The radiochemical purity of the obtained compound (A-1) was calculated by dividing the peak area of ​​compound (A-1) by the total waveform area in the HPLC waveform during purification. The radiochemical purity was about 96%.

[0073] [Experimental Example 2] (Intracellular accumulation experiment in cancer cell lines) Human cancer cell lines used were the lung adenocarcinoma cell line H441 (American Type Culture Collection (ATCC)), lung adenocarcinoma cell line PC-14 (Riken Cell Bank), colon cancer cell line LS180 (ATCC), and colon cancer cell line DLD-1 (ATCC). Human normal cell lines used included the human normal epidermal keratinocyte cell line HaCaT (CLI). H441 was cultured in RPMI-1640 (Fujifilm Wako Pure Chemical Industries, Ltd.) supplemented with 10% fetal bovine serum (FBS). PC-14, DLD-1, and HaCaT were cultured in Dulbecco's Modified Eagle's Medium (DMEM, Fujifilm Wako Pure Chemical Industries, Ltd.) supplemented with 10% FBS. LS180 was cultured in Eagle's minimum essential medium (EMEM, Fujifilm Wako Pure Chemical Industries, Ltd.). All cells were cultured under conditions of 5% CO2 and 37°C.

[0074] 2.0 x 10 cells in a 12-well cell culture multi-plate 5Cells were seeded at 100 cells / well, and the intracellular accumulation experiment was performed approximately 24 hours later. On the day of the experiment, the culture medium was removed and replaced with a buffer solution for the intracellular accumulation experiment. Phosphate buffered saline (PBS) was used as the buffer solution for the intracellular accumulation experiment. Preincubation was then performed for 5–10 minutes. Compound (A-1) was added to each well at 10 kBq / well. The cells were then incubated for 5, 10, 30, or 60 minutes. The PBS containing unincorporated compound (A-1) was then removed, and each cell was washed twice with fresh PBS. The cells were then lysed using 0.1 N NaOH aqueous solution (Nacalai Tesque). Gamma radiation from each cell lysate was measured using an autowell gamma counter (AccuFLEX γ7000, Aloka). Protein content in each cell lysate was measured using a BCA protein quantification assay kit (T9300A, Takara). The gamma ray measurement value for each cell lysate was corrected using the protein amount in each cell lysate to calculate the amount of intracellular accumulation. 18 F)(F 18 A similar test was performed using FDG.

[0075] The results for lung cancer cell lines are shown in Figure 1. The results for colon cancer cell lines are shown in Figure 2. In the lung cancer cell lines H441 and PC14, the amount of compound (A-1) accumulated was 18 In the colon cancer cell line LS180, the accumulation of compound (A-1) was 18 The amount of compound (A-1) accumulated in the colon cancer cell line LS180 was greater than the amount of compound (A-1) accumulated in the normal human keratinocyte cell line HaCaT (Figure 2).

[0076] ASCT2 is predicted to be involved in the intracellular transport of compound (A-1). Microarray analysis of the gene expression levels of each transporter revealed that ASCT2 gene expression was high in LS180 and DLD-1, moderate in H441, and low in PC-14. Expression of glutaminase, an enzyme that converts glutamine to glutamate, and expression of the cystine / glutamate transporter xCT, which exports glutamate, were confirmed in DLD-1 and PC-14. Therefore, it is possible that the glutamine moiety of compound (A-1) taken up into the cell by ASCT2 was converted to a glutamate-glutamine moiety and then exported from the cell by xCT.

[0077] [Experimental Example 3] (Evaluation of transporters involved in intracellular transport of compound (A-1)) The transporters involved in the intracellular transport of compound (A-1) were investigated using the lung cancer cell line H441 and the colon cancer cell line LS180. The intracellular accumulation experiment was carried out in the same manner as in Experimental Example 2, except that the following buffer solution was used for the intracellular accumulation experiment and an amino acid transporter inhibitor was added to the wells. The incubation time after addition of compound (A-1) was 5 minutes.

[0078] To investigate the sodium dependency of the intracellular transport of compound (A-1), PBS (also referred to as "Na-PBS" in Experimental Example 3) or Ch-PBS (PBS in which NaCl was replaced with choline chloride and NaHPO was replaced with choline dihydrogen phosphate) was used as the buffer for the intracellular accumulation experiment. To investigate the amino acid transporter involved in the intracellular transport of compound (A-1), one of the amino acid transporter inhibitors shown in Table 1 was added to each well 30 seconds before the addition of compound (A-1).

[0079] [Table 1]

[0080] The results for the lung cancer cell line H441 are shown in Figure 3. The results for the colon cancer cell line LS180 are shown in Figure 4. In Figures 3 and 4, "control" refers to cells to which no inhibitor was added. Student's t test was used to test for significance.

[0081] In both Figures 3 and 4, the amount of intracellular accumulation of compound (A-1) was higher in the control case when Na-PBS was used as the buffer solution for the intracellular accumulation experiment than in the case when Ch-PBS was used. These results confirmed that the intracellular transport of compound (A-1) is sodium-dependent. In both Figures 3 and 4, the addition of the ASCT2 inhibitor V-9302 significantly reduced the intracellular accumulation of compound (A-1) compared to the control. On the other hand, the addition of the LAT1 inhibitor BCH or the ANAT2 inhibitor MeAIB did not significantly reduce the intracellular accumulation of compound (A-1) compared to the control. These results suggest that ASCT2 is involved in the intracellular transport of compound (A-1).

[0082] Figure 5 also shows the results of incubation with BPTES (Sigma-Aldrich), an inhibitor of glutamine metabolic enzyme Glutaminase-1 (GLS-1). BPTES was added to the wells at 1 mM 30 seconds before the addition of compound (A-1). When BPTES was added, the incubation time after the addition of compound (A-1) was 5 or 60 minutes. The addition of BPTES reduced the accumulation of compound (A-1), suggesting that compound (A-1) may be accumulated in mitochondria by GLS-1.

[0083] These results confirmed that compound (A-1) specifically accumulates in cancer cells. The intracellular accumulation of compound (A-1) in cancer cells was sodium-dependent, suggesting the involvement of ASCT2. Therefore, compound (A-1) can be used to detect cancer cells (especially those expressing ASCT2). [Industrial Applicability]

[0084] According to the present invention, a novel cancer cell detecting agent and a compound that can be used for the cancer cell detecting agent are provided.

Claims

1. A compound represented by the following general formula (1) or a pharmaceutically acceptable salt thereof: 【Chemical 1】 [In the formula, X represents a radioactive nuclide. Ar represents an aromatic hydrocarbon group which may have a substituent. R １ ~R ４ each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and n1 represents an integer of 1 to 3.

2. 2. The compound according to claim 1, wherein the compound represented by general formula (1) is a compound represented by the following general formula (2), or a pharmaceutically acceptable salt thereof: 【Chemistry 2】 [wherein X represents a radionuclide. １ ~R ４ R each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. ５ represents a substituent other than a radionuclide, n1 represents an integer of 1 to 3, n2 represents an integer of 0 to 4, and n1+n2≦5.

3. The compound according to claim 2, wherein the compound represented by the general formula (2) is a compound represented by the following general formula (3), or a pharmaceutically acceptable salt thereof: 【Chemistry 3】 [wherein X represents a radionuclide. １ ~R ４ R each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. ６ represents an alkyl group having 1 to 5 carbon atoms; and n3 represents an integer of 0 to 3.

4. 2. The compound or pharmaceutically acceptable salt thereof according to claim 1, wherein X in the general formula (1) is a radioactive halogen.

5. A test agent for measuring ASCT function, comprising the compound according to any one of claims 1 to 4 or a pharmaceutically acceptable salt thereof.

6. The test agent according to claim 5, which is a test agent for measuring ASCT-mediated transport of amino acids into cells.

7. A cancer cell detection agent comprising the compound according to any one of claims 1 to 4 or a pharmaceutically acceptable salt thereof.

8. The cancer cell detection agent according to claim 7 , wherein the cancer cells are cancer cells expressing ASCT.

9. The cancer cell detecting agent according to claim 7, which is a nuclear medicine imaging diagnostic agent for cancer.

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