Method for producing radioactive metal complexes

Abstract

This method for producing a radioactive metal complex comprises a step for reacting a radioactive metal with DOTA or a ligand, which is a derivative of DOTA, in a reaction solution to form a radioactive metal complex. The reaction solution contains water, a buffer, and a water-soluble organic solvent. The radioactive metal is 89Zr or 225Ac. The ligand may have a group linked to a peptide in the structure thereof. It is also preferable that the content of the water-soluble organic solvent contained in the reaction solution be 2-50 vol%. It is also preferable to react the radioactive metal with the ligand in the reaction solution at a temperature of 30-80°C.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a radioactive metal complex. [Background technology]

[0002] Radioactive metal complexes in which a ligand is coordinated to a radioactive metal have been studied for the purpose of using them as reagents and diagnostic agents for detecting target molecules, or as pharmaceuticals for treating diseases. Patent Document 1 describes a method for conjugating an antibody with DOTA, which is coordinated with a radioactive metal, to bind to the antibody. 90 In addition, Non-Patent Document 1 describes the use of radioactive metals. 89 A method is described in which Zr is reacted with the ligand DOTA in a buffer solution to form a radioactive metal complex. Non-patent document 2 states: 68 Ga or 44 A method is described in which Sc is reacted with DOTATOC, a DOTA derivative, as a ligand in a buffer solution to form a radioactive metal complex. Non-patent document 3 states: 68 Ga or 44 A method is described in which Sc is reacted with DOTA in ethanol-containing saline to form a radioactive metal complex. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US 2005 / 191239 A1 [Non-patent literature]

[0004] [Non-Patent Document 1] Pandya et al., Chem Sci. 2017;8(3):2309-14. [Non-patent document 2] Eppard et al., EJNMMI Radiopharm. Chem. 2017; 1,6. [Non-patent document 3] Perez-Malo et al., Inorg. Chem. 2018, 57(10), 6107-6117. Summary of the Invention

[0005] However, the present inventors have found that when a derivative in which a target molecule other than an antibody, such as a peptide, is bound to DOTA as a ligand, complex formation between DOTA and a specific radioactive metal may not proceed well under the conditions disclosed in Patent Document 1 and Non-Patent Documents 1 to 3. This problem is not limited to DOTA, but also occurs in derivatives similar to DOTA, such as DOTAGA.

[0006] Therefore, an object of the present invention is to provide a method for producing a radioactive metal complex that has excellent complex formation efficiency in a ligand containing DOTA, a derivative thereof, or a structure similar to DOTA.

[0007] The present invention provides a method for producing a radioactive metal complex by reacting a radioactive metal with a ligand represented by the following formula (1) in a reaction solution: the reaction solution comprises water, a buffer, and a water-soluble organic solvent; The radioactive metal 89 Zr or 225 The present invention provides a method for producing a radioactive metal complex, wherein the metal complex is Ac. [ka] (In the formula, R 11 , R 12 and R 13 are each independently -(CH2) p COOH, -(CH2) p C5H5N, -(CH2) p PO3H2 or -(CH2) p A group consisting of CONH2, R 14or R 15 One of the atoms is a hydrogen atom, -(CH2) p COOH, -(CH2) p C5H5N, -(CH2) p PO3H2, -(CH2) p CONH2 or -(CHCOOH)(CH2) p COOH, and the other is -(CH2) p COOH, -(CH2) p C5H5N, -(CH2) p PO3H2 or -(CH2) p A group consisting of CONH2 or a group linked to a peptide, and p is an integer of 0 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0008] This application claims priority based on Japanese Patent Application No. 2019-151480, filed on August 21, 2019, the entire contents of which are incorporated herein by reference.

[0009] According to the present invention, there is provided a method for producing a radioactive metal complex having excellent complex formation efficiency when using a ligand containing DOTA, a derivative thereof, or a structure similar to DOTA. The present invention is particularly effective when using a poorly water-soluble ligand.

[0010] The method for producing a radioactive metal complex of the present invention will be described below based on its preferred embodiments. The production method of the present invention includes a step of reacting a radioactive metal with a ligand in a reaction solution containing water, a buffer, and a water-soluble organic solvent to form a radioactive metal complex (complex formation step).

[0011] In this step, forming a complex between a radioactive metal and a ligand is synonymous with labeling the ligand with a radioactive metal, and the complex formation efficiency and the labeling rate are synonymous. In order to enhance the efficiency of complex formation, the radioactive metal in this step is preferably used in the form of an ionizable radioactive metal compound, more preferably in the form of a radioactive metal ion (hereinafter, these forms are also collectively referred to as "radioactive metal source"). As the radioactive metal source, for example, a radioactive metal ion-containing liquid in which radioactive metal ions are dissolved or dispersed in a solvent mainly composed of water can be used. Specific nuclides of the radioactive metal will be described later.

[0012] The ligand used in this step has a structure represented by the following formula (1): That is, the ligand used in this step is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) or a derivative thereof, or a ligand containing a structure similar to DOTA.

[0013] [ka]

[0014] In formula (1), R 11 , R 12 and R 13 are each independently -(CH2) p COOH, -(CH2) p C5H5N, -(CH2) p PO3H2 or -(CH2) p It is a group consisting of CONH2. Each p is independently an integer of 0 or more and 3 or less.

[0015] In formula (1), R 14 or R 15 One of the atoms is a hydrogen atom, -(CH2) p COOH, -(CH2) p C5H5N, -(CH2) p PO3H2, -(CH2) p CONH2 or -(CHCOOH)(CH2) p COOH, and the other is -(CH2) p COOH, -(CH2) p C5H5N, -(CH2) pPO3H2 or -(CH2) p It is a group consisting of CONH2 or a group linked to a peptide. Each p is independently an integer of 0 to 3. Details of the peptide will be described later.

[0016] In this step, when a poorly water-soluble ligand is used in complex formation, the efficiency of complex formation can be further improved. "Poorly water-soluble" means having a property that satisfies at least one of the following conditions (i) or (ii), and preferably having a property that satisfies at least condition (ii). Poorly water-soluble also includes the meaning of water-insolubility, i.e., the ligand does not substantially dissolve in water. Note that the case where both the following conditions (i) and (ii) are satisfied is also considered to be "poorly water-soluble." (i) The octanol-water partition coefficient (LogP value) of the ligand is a positive value. (ii) The index (LogS value) showing the solubility of the ligand in water is a negative value.

[0017] The "octanol-water partition coefficient," an index of poor water solubility, is an index of a compound's hydrophobicity and is defined as the common logarithm of the ratio of the concentration of a substance partitioned into each phase of a two-phase solvent system consisting of n-octanol and water. This common logarithm value is based on the ratio (C0 / Cw) of the concentration of the test substance in the n-octanol (oil) phase, C0, to the concentration of the test substance in the aqueous phase, Cw. In other words, this value indicates whether the test substance (ligand) is more soluble in the oil phase or the aqueous phase. Therefore, the larger this value, the more hydrophobic the ligand is, i.e., the more poorly water-soluble it is. The octanol-water partition coefficient can be calculated, for example, by actual measurement using the shake flask method of JIS Z-7260-107:2000 or the HPLC method of OECD Test Guideline 117, or by a computational chemistry estimation method based on the partial structure and constituent atoms of the substance. In the present invention, when the LogP value is actually determined as the octanol-water partition coefficient of the ligand to be measured and the actually measured value is a positive value, or when the LogP value is estimated by computational chemistry and the calculated LogP value is calculated to be a positive value, the ligand is deemed to be "poorly water-soluble."

[0018] When the octanol-water partition coefficient is estimated by computational chemistry, commercially available software can be used. For example, it is preferable to use a value calculated using "Chemdraw Professional" manufactured by PerkinElmer or "CLOGP" manufactured by Daylight Chemical Information Systems (calculated LogP value) as the octanol-water partition coefficient in the present invention.

[0019] Another indicator of poor water solubility is the "LogS value," which indicates the solubility of a test substance in water. The lower the LogS value, the more poorly water-soluble the test substance, i.e., ligand, is. The LogS value can be calculated using commercially available software such as "Chemdraw Professional" manufactured by PerkinElmer, and the calculated LogS value can be used as the LogS value of the present invention.

[0020] In the above formula (1), R 14 or R 15The peptides that can be included in the above preferably have a molecular weight of 500 Da to 10,000 Da. Furthermore, in order to prevent unintended decomposition or reaction of the peptide during the complex formation reaction, the peptide may contain amino acids that do not constitute proteins in vivo, such as D-amino acids or amino acids modified with an N-aliphatic hydrocarbon group, e.g., an N-methyl group. Peptides containing amino acids that do not constitute proteins in vivo are generally poorly water-soluble, and ligands to which such peptides are bound exhibit poor water-solubility as a whole. Furthermore, such peptides are generally peptidase-resistant and difficult to decompose in vivo, resulting in high in vivo stability in blood, etc., and thus can be easily delivered to target sites when radioactive metal complexes containing such peptides are applied to living organisms. In particular, such peptides are preferably cyclic peptides. Cyclic peptides have a chemically stronger structure than linear peptides, thereby further enhancing in vivo stability. R 14 or R 15 The peptides that can be included in the above are not particularly limited as long as they are within the above molecular weight range and exhibit poor water solubility, but examples include linear peptides such as physalemmin and peptides with a cyclic structure such as daptomycin.

[0021] As described above, the reaction solution in the complex formation step is an aqueous reaction solution containing water, a buffer, and a water-soluble organic solvent. The water may be, for example, distilled water or ion-exchanged water.

[0022] The buffers used in this step include acetic acid and its salts, phosphoric acid and its salts, 、2Preferably, one of 2-amino-2-(hydroxymethyl)propane-1,3-diol (Tris), 2-[4-(2-hydroxyethyl)-1-piperazinyl]-ethanesulfonic acid (HEPES), and basic amino acids is used. Examples of counter ions for the buffer include alkali metal ions such as sodium and potassium, cations such as primary to quaternary ammonium ions such as ammonium and tetramethylammonium salts, and anions such as various halogen ions. In addition, neutral salts such as sodium chloride may also be added. It is also preferable to select these buffers depending on the type and combination of radioactive metal nuclides and ligands.

[0023] Among these, it is more preferable to use one of acetic acid and its salts, phosphoric acid and its salts, Tris, HEPES, tetramethylammonium acetate, and basic amino acids as the buffer. That is, it is more preferable to use a buffer solution in which a buffer is dissolved in water, such as acetic acid-sodium acetate buffer (hereinafter also simply referred to as acetate buffer), ammonium acetate buffer, phosphate buffer, phosphate buffered saline, Tris buffer, HEPES buffer, or tetramethylammonium acetate buffer.

[0024] The reaction solution further contains a water-soluble organic solvent. The water-soluble organic solvent in this step is used for the purpose of increasing the solubility of the ligand in the reaction solution and increasing the amount of ligand to be subjected to the complex formation reaction, and is particularly suitable for increasing the solubility of poorly water-soluble ligands. The term "water-soluble" in the context of a water-soluble organic solvent means that when any volumes of water and any volumes of organic solvent are mixed, they are freely miscible with each other without any solvent interface being observed.

[0025] Examples of the water-soluble organic solvent include protic solvents such as methanol and ethanol, and solvents such as acetonitrile, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, and acetone. NoA polar solvent such as a protic solvent is preferably used. Among these, it is more preferable to use at least one selected from acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and ethanol as the water-soluble organic solvent, from the viewpoint of allowing the complex-forming reaction to proceed satisfactorily.

[0026] In the complex formation step, the order of addition of the radioactive metal source and the ligand does not matter as long as a complex between the radioactive metal ion and the ligand can be formed. For example, one of the radioactive metal source and the ligand may be added and then the other may be added to a reaction vessel previously containing a mixed solvent comprising water, a buffer, and a water-soluble organic solvent that constitutes a reaction solution, and the reaction may be carried out by adding the other to a solution in which one of the radioactive metal source and the ligand is dissolved in a mixed solvent. Alternatively, the two may be simultaneously added to a reaction vessel previously containing a mixed solvent, and the reaction may be carried out by adding them.

[0027] The reaction conditions in the complex formation step can be, for example, the following conditions. The reaction solvent used in this step is a mixed solvent containing water, a buffer, and a water-soluble organic solvent. The reaction temperature may be, for example, room temperature (25°C) or heated. From the viewpoint of simultaneously suppressing decomposition of the ligand and improving the efficiency of complex formation, the reaction is preferably heated to a temperature of 30°C or higher and 80°C or lower, more preferably 50°C or higher and 80°C or lower. The reaction time is preferably 15 minutes or higher and 150 minutes or lower, more preferably 30 minutes or higher and 120 minutes or lower, provided that the reaction temperature is as described above.

[0028] The volume of the reaction solution in this step is not particularly limited, but from the viewpoint of practicality in the production process, a volume of 0.01 mL to 100 mL at the start of this step is practical. Furthermore, the concentrations of the radioactive metal ion and ligand in the reaction solution at the start of this step are each independently preferably 1 μmol / L to 100 μmol / L, more preferably 10 μmol / L to 9000 μmol / L, even more preferably 30 μmol / L to 600 μmol / L, and even more preferably 50 μmol / L to 500 μmol / L. The pH of the reaction solution can be appropriately adjusted depending on the physical properties of the radioactive metal, ligand, and buffer used, but is preferably 4.0 to 7.0, more preferably 4.5 to 6.5, and even more preferably 5.0 to 6.0.

[0029] The radioactive metal complex obtained may be used as it is, or may be purified using a filter, a membrane filter, a column filled with various packing materials, chromatography, or the like.

[0030] According to the production method of the present invention, which includes the above-described steps, the solubility of the ligand in the reaction solution can be increased, allowing the complex formation reaction to proceed sufficiently. This makes it possible to obtain a radioactive metal complex with a high complex formation rate. One of the features of the present invention is that a water-soluble organic solvent is included in the reaction system. Therefore, even when using water-insoluble ligands that have not been used in the prior art for complex formation reactions, such as water-soluble ligands in which a portion of the structure of the water-soluble ligand has been substituted or modified to exhibit water-insolubility, or ligands that are inherently water-insoluble, the complex formation reaction between the radioactive metal and the ligand proceeds smoothly, allowing the production of a radioactive metal complex in excellent yield. This step is particularly advantageous in that, even when using radioactive metal nuclides that emit low-energy radiation or α-rays, which are difficult to detect, the complex formation proceeds smoothly and the complex yield is high. Therefore, the complex containing the radioactive metal nuclide can be subjected to subsequent steps in an unpurified state.

[0031] An example of a process after complex formation is a formulation process for obtaining a radiopharmaceutical containing the complex containing the radioactive metal nuclide as an active ingredient. The formulation process can be carried out by appropriately adding a pH adjuster such as a citrate buffer, a phosphate buffer, or a borate buffer, a solubilizer such as polysorbate, a stabilizer, or an antioxidant, or by diluting with an isotonic solution such as water or physiological saline. The formulation process may also include a subsequent step of sterilizing the mixture through filtration using a membrane filter or the like to prepare it as an injection.

[0032] From the viewpoint of making the above-mentioned effects more pronounced, the ligand used in the present invention preferably has any of the structures shown in the following formulas (1-a) to (1-h). These structures can be appropriately selected depending on the type of radioactive metal and water-soluble organic solvent, which will be described later. The effects of the present invention can be fully achieved with any ligand having any of these structures. In each of the following formulas, P represents a peptide, and is preferably a poorly water-soluble peptide having the above-mentioned structure. The ligands shown in each formula have poorly water-soluble peptides in their structures, and as a result, the ligand as a whole exhibits poor water-solubility.

[0033] [ka]

[0034] [ka]

[0035] In particular, in addition to the above-mentioned effects, from the viewpoint of achieving both ease of handling of the ligand used and stability of the obtained radioactive metal complex, R 11 , R 12 and R 13 are both -(CH2) p It is more preferable that R is a carboxyalkyl group represented by COOH, where p is an integer of 1 or more and 3 or less. 14 and R 15 One of them is -(CH2) pIt is preferable that the compound is a carboxyalkyl group represented by COOH, where p is an integer of 1 to 3, and the other is a chemical structure containing a poorly water-soluble peptide.

[0036] From the viewpoint of achieving high complex formation efficiency while increasing the solubility and dispersibility of the ligand in the reaction solution, the content of the water-soluble organic solvent in the reaction solution is preferably 2% by volume or more, more preferably 5% by volume or more and 70% by volume or less, and even more preferably 5% by volume or more and 50% by volume or less. For example, when ethanol or acetonitrile is used as the water-soluble organic solvent, the content in the reaction liquid is preferably 2% by volume or more, more preferably 5% by volume or more and 70% by volume or less, even more preferably 5% by volume or more and 40% by volume or less, even more preferably 2% by volume or more and 20% by volume or less, and even more preferably 5% by volume or more and 15% by volume or less. When dimethyl sulfoxide is used as the water-soluble organic solvent, the content in the reaction liquid is preferably 20% by volume or more and 70% by volume or less, and more preferably 30% by volume or more and 60% by volume or less.

[0037] By selecting the type of water-soluble organic solvent to be used in consideration of the solubility of the ligand in the reaction solution and by changing the content of the water-soluble organic solvent in the reaction solution within the above-mentioned range depending on the type of water-soluble organic solvent to be used, it is possible to advantageously increase the efficiency of complex formation between the radioactive metal and the ligand while appropriately dispersing or dissolving the ligand in the reaction solution, and this advantage becomes more pronounced when a poorly water-soluble ligand is used.

[0038] From the viewpoint of suppressing unintended pH changes during the reaction and further increasing the efficiency of complex formation, the concentration of the buffer in the reaction solution is preferably 0.05 mol / L to 5.0 mol / L, more preferably 0.05 mol / L to 2.0 mol / L. For example, when sodium acetate or ammonium acetate is contained as the buffer, the concentration in the reaction solution is preferably 0.05 mol / L to 2.0 mol / L, more preferably 0.1 mol / L to 1 mol / L. Furthermore, when tetramethylammonium acetate is contained as the buffer, the concentration in the reaction solution is preferably 0.01 mol / L to 2.0 mol / L, more preferably 0.1 mol / L to 1 mol / L.

[0039] The radioactive metal to be coordinated in the radioactive metal complex in an ionic state can be a metal nuclide that emits α-rays, β-rays, γ-rays, or a combination thereof. Examples of such radioactive metal nuclides include alkali metals, alkaline earth metals, lanthanides, actinides, transition metals, and radioactive isotopes of metals other than these metals. Among these, the following radioactive metal nuclides are preferred from the viewpoint of commercial applicability and improving complex formation ability: 44 Sc, 51 Cr, 57 Co, 58 Co, 60 Co, 59 Fe, 67 Ga, 68 Ga, 64 Cu, 67 Cu, 89 Sr, 89 Zr, 90 Y, 99m Tc, 103 Ru, 111 In, 153 Sm, 165 Dy, 166 Ho, 177 Lu, 186 Re, 188 Re, 198 Au, 201 Tl, 197 Hg, 203 Hg, 212 Bi,213 Bi, 212 Pb, 227 Th or 225 It is preferable to use Ac. These radioactive metals can be produced by conventional methods, and are preferably obtained as a solution containing the radioactive metal in an ionized state.

[0040] When a radioactive metal complex is used for the purpose of treating a disease, it is preferable to use an α-ray emitting nuclide or a β-ray emitting nuclide as the radioactive metal in order to enhance the therapeutic effect. - It is preferable to use an α-ray emitting nuclide. The α-ray emitting nuclide may be any nuclide that emits α-rays in the decay process of a radioactive metal. 212 Bi, 213 Bi, 227 Th or 225 Ac and the like are preferably used, and more preferably 227 Th or 225 Ac, and more preferably 225 Ac. β - The radioactive nuclides are generated by the β - Any nuclide that emits radiation is acceptable. In detail, 60 Co, 59 Fe, 64 Cu, 67 Cu, 89 Sr, 90 Y, 99m Tc, 103 Ru, 153 Sm, 165 Dy, 166 Ho, 177 Lu, 186 Re, 188 Re, 198 Au, 203 Hg, 212 Bi, 213 Bi or 212 Pb and the like are preferably used, and more preferably 64 Cu, 67 Cu, 89 Sr or 90 Y is used.

[0041] In addition, when a radioactive metal complex is used for the purpose of diagnosing a disease or detecting a lesion, it is preferable to use a β+ It is preferable to use a β-ray emitting nuclide, an electron capture decay nuclide, or a gamma ray emitting nuclide. + The radiation-emitting nuclide may be any nuclide that emits positrons during the decay process of a radioactive metal. 44 Sc, 58 Co, 68 Ga, 64 Cu or 89 Zr and the like are preferably used, and more preferably 64 Cu or 89 The electron capture decay nuclide may be any nuclide that emits Auger electrons or characteristic X-rays during the decay process of a radioactive metal. 51 Cr, 57 Co, 58 Co, 67 Ga, 68 Ga, 64 Cu, 89 Zr, 111 In, 186 Re, 201 Tl or 197 The gamma-ray-emitting nuclide may be any nuclide that emits gamma rays through gamma decay. Examples of nuclides that emit gamma rays through gamma decay include: 99m Tc, 68 Ga or 201 Tl is preferably used.

[0042] When selecting radiometals that are coordinated in an ionic state in a radiometal complex based on their ionic radius, radiometals with an ionic radius of about 70 to 130 pm are: 67 Ga, 68 Ga, 64 Cu, 67 Cu, 89 Zr, 90 Y, 99m Tc, 103 Ru, 111 In, 153 Sm, 165 Dy, 166 Ho, 177 Lu, 186 Re, 188 Re, 198 Au, 201 Tl, 197 Hg, 203 Hg, 212Bi, 213 Bi, 212 Pb, 225 Ac etc.

[0043] For example, when a radioactive metal complex is used for the purpose of treating a disease, 225 When Ac is used, any of the ligands having the structures represented by the above formulas (1-a) to (1-h) can suitably form a radioactive metal complex. In addition, when a radioactive metal-labeled antibody is used for the purpose of diagnosing a disease or detecting a lesion, 89 When Zr is used, it is preferable to use any of the ligands having a structure represented by the above formula (1-b) or (1-d) to (1-h), and it is more preferable to use a ligand having a structure represented by the above formula (1-b), (1-d) or (1-e).

[0044] Furthermore, when a radioactive metal complex is used for the purposes of both disease treatment and disease diagnosis or lesion detection, it is more preferable that the ligands constituting the radioactive metal complex produced for the purpose of disease treatment and the radioactive metal complex produced for the purpose of disease diagnosis or lesion detection have the same structure. That is, in this case, it is more preferable to produce the radioactive metal complex using ligands having the same structure.

[0045] Suitable combinations of radioactive metal, buffer and water-soluble organic solvent include, but are not limited to, the following combinations. (a) Radioactive metals are converted into β + The reaction solution contains a buffer containing sodium acetate or ammonium acetate at a concentration of 0.05 mol / L to 2.0 mol / L, and a water-soluble organic solvent containing 20% ​​by volume to 50% by volume of dimethyl sulfoxide. + The radiation-emitting nuclide is 89 Zr is more preferably used, and the ligand is more preferably a ligand having a structure represented by the above formula (1-b), (1-d) or (1-e).

[0046] (b-1) The radioactive metal is an α-ray emitting nuclide, and the reaction solution contains tetramethylammonium acetate at a concentration of 0.1 mol / L or more and 2.0 mol / L or less as a buffer, and ethanol or acetonitrile at a concentration of 2% by volume or more and 30% by volume or less as a water-soluble organic solvent. In this case, the α-ray emitting nuclide is 225 Ac is more preferably used, and the ligand is more preferably any of the ligands having the structure represented by the above formulas (1-a) to (1-h). Under the conditions of (b-1) above, as a radioactive metal 225 When Ac is used and ethanol is used as the water-soluble organic solvent, the production method of the present invention can increase the efficiency of radioactive metal complex formation even when the ethanol concentration is relatively low. In addition, it is advantageous in that the amount of water-soluble organic solvent used can be reduced, thereby reducing production costs. In the above condition (b-1), when ethanol is used as the water-soluble organic solvent, the content of ethanol in the reaction solution is preferably 2% by volume or more and 30% by volume or less, more preferably 2% by volume or more and 20% by volume or less.

[0047] (b-2) The radioactive metal is an α-ray emitting nuclide, and the reaction solution contains sodium acetate or ammonium acetate at a concentration of 0.05 mol / L or more and 2.0 mol / L or less as a buffer, and ethanol or acetonitrile at a concentration of 2% by volume or more and 30% by volume or less as a water-soluble organic solvent. In this case, the α-ray emitting nuclide is 225 Ac is more preferably used, and the ligand is more preferably any of the ligands having the structure represented by the above formulas (1-a) to (1-h). As a radioactive metal under the conditions of (b-2) above 225 When Ac is used and ethanol is used as the water-soluble organic solvent, the production method of the present invention can increase the efficiency of radioactive metal complex formation even when the ethanol concentration is relatively low and the ligand concentration is high. This method is advantageous in that it can reduce the amount of water-soluble organic solvent used, thereby reducing production costs, and can achieve high radioactive metal complex formation efficiency while maintaining the solubility of the ligand in the reaction solution even when a large amount of ligand is used in commercial production of radioactive metal complexes.

[0048] (b-3) The radioactive metal is an α-ray emitting nuclide, and the reaction solution contains sodium acetate or ammonium acetate at a concentration of 0.05 mol / L or more and 2.0 mol / L or less as a buffer, and 10% by volume or more and 50% by volume or less of dimethyl sulfoxide as a water-soluble organic solvent. In this case, the α-ray emitting nuclide is 225 Ac is more preferably used, and the ligand is more preferably any of the ligands having the structure represented by the above formulas (1-a) to (1-h). Under the conditions of (b-3) above, as a radioactive metal 225 When Ac is used and dimethyl sulfoxide is used as the water-soluble organic solvent, the production method of this invention can increase the efficiency of radioactive metal complex formation even when the ligand concentration is increased. This is advantageous in that even when a large amount of ligand is used in commercial production of radioactive metal complexes, high radioactive metal complex formation efficiency can be achieved while maintaining the solubility of the ligand in the reaction solution.

[0049] Peptides that can be used in the present invention can be synthesized by techniques such as liquid phase synthesis, solid phase synthesis, automated peptide synthesis, genetic recombination, phage display, genetic code reprogramming, RaPID (Random Non-Standard Peptide Integrated Discovery), etc. When synthesizing peptides, the functional groups of the amino acids used may be protected as necessary.

[0050] When a ligand containing a poorly water-soluble peptide in its structure is used as the ligand, it is preferable that the poorly water-soluble peptide and the ligand precursor are linked to each other via an amide bond or a thiourea bond to form the poorly water-soluble ligand. The amide bond can be formed, for example, by reacting an amino group derived from the side chain of an amino acid constituting the peptide with a carboxy group of the ligand precursor. Examples of such ligands include ligands having the structure represented by the above formula (1-a) or (1-c).

[0051] The thiourea bond can be formed, for example, by reacting an amino group derived from the side chain of an amino acid constituting the peptide with an isothiocyanate group possessed by a ligand precursor, or by reacting a thiol group derived from the side chain of an amino acid constituting the peptide with a maleimide group possessed by a ligand precursor. Examples of such ligands include those having the structures represented by the above formulas (1-b) or (1-d) to (1-h). [Example]

[0052] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0053] Examples 1-1 to 1-4: 89 Zr labeling study (type of organic solvent)] [Example 1-1] As a radioactive metal element 89 Zr was used. DOTA (in the above formula (1), R 11 , R 12 , R 13 and R 14 are all "-CH2COOH" groups, and R 15 is a hydrogen atom.) was used.

[0054] The above ligand was dissolved in water containing 90% by volume of dimethyl sulfoxide as an organic solvent to prepare a solution containing 200 μmol / L of the above ligand. 89 A reaction solution obtained by mixing 0.02 mL of a Zr ion-containing solution (solvent: 0.1 mol / L hydrochloric acid aqueous solution, radioactivity concentration 33.4 MBq / mL) and 0.01 mL of a 1.5 mol / L acetate buffer solution (pH 5.5) was reacted under heating conditions. 89 A Zr complex solution was obtained. The reaction solution was heated to 70°C for 60 minutes. Using thin layer chromatography (Merck, model number: 1.15685.0001, developing solvent: 10% by volume aqueous ammonium chloride solution / methanol (1:1)), unreacted Zr complex was separated. 89 All Zr-containing 89 For Zr radioactivity counts89 The percentage of radioactive counts of the Zr complex was taken as the labeling rate. 89 The labeling rate of the Zr complex was 84%.

[0055] [Example 1-2] The same conditions as in Example 1-1 were used, except that DOTA was used as the ligand and the ligand was dissolved in water containing 90% by volume of acetonitrile as the organic solvent. 89 The labeling rate of the Zr complex was 59%.

[0056] [Examples 1-3] The same conditions as in Example 1-1 were used, except that DOTA was used as the ligand and the ligand was dissolved in water containing 90% by volume of ethanol as the organic solvent. 89 The labeling rate of the Zr complex was 55%.

[0057] [Examples 1-4] The same conditions as in Example 1-1 were used, except that DOTA was used as the ligand and the ligand was dissolved in water containing 90% by volume of N,N-dimethylformaldehyde as the organic solvent. 89 The labeling rate of the Zr complex was 54%.

[0058] Examples 2-1 to 2-6: 89 Zr labeling study (buffer concentration)] [Example 2-1] DOTA was used as a ligand, and the ligand was dissolved in 1.5 mol / L acetate buffer (pH 5.5) containing 90% by volume of dimethyl sulfoxide as an organic solvent to prepare a solution containing 200 μmol / L of the ligand. 0.029 mL of this solution and 100 μmol / L of dimethyl sulfoxide as a radioactive metal source were added. 89 A reaction solution obtained by mixing 0.02 mL of a Zr ion-containing solution (solvent: 0.1 mol / L hydrochloric acid aqueous solution, radioactivity concentration 25.2 MBq / mL) and 0.01 mL of a 1.5 mol / L acetate buffer solution (pH 5.5) was reacted under heating conditions. 89A Zr complex solution was obtained. The final concentration of the buffer in the reaction solution was 0.33 mol / L. The reaction solution was heated to 70°C for 15 minutes. Thin layer chromatography was performed under the same conditions as in Example 1. 89 The labeling rate of the Zr complex was 60%.

[0059] [Example 2-2] The reaction was carried out under the same conditions as in Example 2-1, except that DOTA was used as the ligand and the ligand was dissolved in water containing 90% by volume of dimethyl sulfoxide as the organic solvent to prepare a solution containing 200 μmol / L of the ligand. The final concentration of the buffer in the reaction solution was 0.25 mol / L. 89 The labeling rate of the Zr complex was 55%.

[0060] [Example 2-3] DOTA was used as a ligand, and the ligand was dissolved in water containing 90% by volume of dimethyl sulfoxide as an organic solvent to prepare a solution containing 200 μmol / L of the ligand. 0.029 mL of this solution and 100 μg of dimethyl sulfoxide as a radioactive metal source were mixed. 89 The reaction was carried out under the same conditions as in Example 2-1, except that a reaction mixture containing 0.02 mL of a Zr ion-containing solution (solvent: 0.1 mol / L aqueous hydrochloric acid solution, radioactivity concentration 25.2 MBq / mL) and 0.01 mL of a 0.75 mol / L acetate buffer (pH 5.5) was heated. The final concentration of the buffer in the reaction mixture was 0.13 mol / L. 89 The labeling rate of the Zr complex was 66%.

[0061] [Example 2-4] The same conditions as in Example 2-1 were used except that DOTA was used as the ligand and the ligand was dissolved in water to prepare a solution containing 200 μmol / L of the ligand. 89 A Zr complex solution was obtained. The final concentration of the buffer in the reaction solution was 0.25 mol / L. 89 The labeling rate of the Zr complex was 50%.

[0062] [Example 2-5] The same conditions as in Example 2-1 were used except that DOTA was used as the ligand and the ligand was dissolved in 1.5 mol / L acetate buffer (pH 5.5) to prepare a solution containing 200 μmol / L of the ligand. 89 A Zr complex solution was obtained. The final concentration of the buffer in the reaction solution was 1.00 mol / L. 89 The labeling rate of the Zr complex was 28%.

[0063] [Example 2-6] The same conditions as in Example 2-1 were used, except that DOTA was used as the ligand and the ligand was dissolved in 3.0 mol / L acetate buffer (pH 5.5) to prepare a solution containing 200 μmol / L of the ligand. 89 A Zr complex solution was obtained. 89 The labeling rate of the Zr complex was 10%.

[0064] Examples 3-1 to 3-4: 89 Zr labeling study (ligand concentration)] [Example 3-1] DOTA was used as a ligand, and the ligand was dissolved in water containing 90% by volume of dimethyl sulfoxide as an organic solvent to prepare a solution containing 200 μmol / L of the ligand. 0.029 mL of this solution and 100 μg of dimethyl sulfoxide as a radioactive metal source were mixed. 89 A reaction solution obtained by mixing 0.02 mL of a Zr ion-containing solution (solvent: 0.1 mol / L aqueous hydrochloric acid solution, radioactivity concentration 28.5 MBq / mL) and 0.01 mL of a 1.5 mol / L acetate buffer solution (pH 5.5) was reacted under heating conditions. 89 A Zr complex solution was obtained. The final concentration of the ligand in the reaction solution was 100 μmol / L. The reaction solution was heated to 70° C. for 60 minutes. Thin layer chromatography was performed under the same conditions as in Example 1-1. 89 The labeling rate of the Zr complex was 89%.

[0065] [Example 3-2] The reaction was carried out under the same conditions as in Example 3-1, except that DOTA was used as the ligand and the ligand was dissolved in water containing 90% by volume of dimethyl sulfoxide as the organic solvent so that the final concentration of the ligand in the reaction solution was 50 μmol / L.89 A Zr complex solution was obtained. 89 The labeling rate of the Zr complex was 50%.

[0066] [Example 3-3] The reaction was carried out under the same conditions as in Example 3-1, except that DOTA was used as the ligand and the ligand was dissolved in water containing 90% by volume of dimethyl sulfoxide as the organic solvent so that the final concentration of the ligand in the reaction solution was 10 μmol / L. 89 A Zr complex solution was obtained. 89 The labeling rate of the Zr complex was 12%.

[0067] [Example 3-4] The reaction was carried out under the same conditions as in Example 3-1, except that DOTA was used as the ligand and the ligand was dissolved in water containing 90% by volume of dimethyl sulfoxide as the organic solvent so that the final concentration of the ligand in the reaction solution was 1 μmol / L. 89 A Zr complex solution was obtained. 89 The labeling rate of the Zr complex was 9%.

[0068] Examples 4-1 to 4-6: 225 Ac labeling study (type and concentration of organic solvent)] [Example 4-1] DOTA was used as a ligand, and the ligand was dissolved in water containing 10% by volume of ethanol as an organic solvent to prepare a solution containing 100 μmol / L of the ligand. 225 A reaction solution obtained by mixing 0.02 mL of an Ac ion-containing solution (solvent: 0.2 mol / L hydrochloric acid aqueous solution, radioactivity concentration 5 MBq / mL) and 0.016 mL of a 0.5 mol / L tetramethylammonium acetate buffer solution (pH 7.8) was reacted under heating conditions. 225 An Ac complex solution was obtained. The reaction solution was heated to 70° C. for 60 minutes. Thin layer chromatography was performed under the same conditions as in Example 1-1. 225 The labeling rate of the Ac complex was 83%.

[0069] [Example 4-2] The reaction was carried out under the same conditions as in Example 4-1, except that DOTA was used as the ligand and the ligand was dissolved in water containing 10% by volume of acetonitrile as the organic solvent. 225 An Ac complex solution was obtained. 225 The labeling rate of the Ac complex was 86%.

[0070] [Examples 4-3 to 4-4] The reaction was carried out under the same conditions as in Example 4-1, except that DOTA was used as the ligand and the ligand was dissolved in water containing 90% by volume or 50% by volume of ethanol as the organic solvent to prepare a solution containing 100 μmol / L of the ligand. 225 An Ac complex solution was obtained. 225 The labeling efficiency of the Ac complex was 25% and 67%, respectively.

[0071] [Examples 4-5 to 4-6] The reaction was carried out under the same conditions as in Example 4-1, except that the ligand was dissolved in water containing 90% by volume or 50% by volume of acetonitrile as an organic solvent to prepare a solution containing 100 μmol / L of the ligand. 225 An Ac complex solution was obtained. 225 The labeling efficiency of the Ac complex was 27% and 69%, respectively.

[0072] [Comparative Example 1] The same conditions as in Example 1-1 were used, except that DOTA was used as the ligand and the ligand was dissolved in 0.5 mol / L phosphate buffer (pH 5.5) to prepare a solution containing 2 mmol / L of the ligand. In this comparative example, no water-soluble organic solvent was contained in the reaction solution. 89 The labeling rate of the Zr complex was 0%, and the complex formation reaction did not proceed at all.

[0073] [Examples 5-1 and 5-2] The reaction was carried out under the same reaction conditions as in Example 1, except that the ligand used had a negative calculated LogS value as a whole and contained DOTA and a peptide whose calculated LogS value was negative as a result of computational chemistry. 89 A Zr complex solution is obtained. Specifically, in this example, a ligand was used in which p-SCN-Bn-DOTA was bound to the peptide physalemmin (Example 5-1; molecular weight: 1265 Da, calculated LogS value: -6.664) or daptomycin (Example 5-2; molecular weight: 1619 Da, calculated LogS value: -9.777) by a conventional method. These ligands have a structure represented by the above formula (1-b), which contains a DOTA-derived structure and a peptide within the structure. Details of the chemical structure are shown in the following formulas (E1) and (E2). These ligands are poorly water-soluble, as their calculated LogS values ​​are negative.

[0074] [ka]

[0075] The details of the production method in this example are as follows: First, each ligand was dissolved in a 1.5 mol / L acetate buffer solution (pH 5.5) containing 45% by volume of dimethyl sulfoxide (DMSO) as a water-soluble organic solvent to prepare a solution. 89 A reaction solution (59 μL) containing Zr ions (solvent: 0.1 mol / L hydrochloric acid aqueous solution, radioactivity concentration 33.4 MBq / mL) was mixed with a 1.5 mol / L acetate buffer solution (pH 5.5) and reacted at 70°C for 2 hours under heating conditions. 89 A Zr complex solution was obtained. The ligand concentration and radioactivity in the reaction solution at the start of the reaction were as shown in Table 1 below. obtained 89 The Zr complex was separated by thin layer chromatography (Agilent, iTLC-SG, developing solvent: water / acetonitrile (1:1)) to remove unreacted 89 All Zr-containing 89 For Zr radioactivity counts 89 The percentage of radioactive counts of the Zr complex was taken as the labeling efficiency (%). 89 The results of the labeling rate of the Zr complex are shown in Table 1 below.

[0076] [Table 1]

[0077] Comparative Example 2 The reaction was carried out under the same reaction conditions as in Example 5, except that the reaction solution did not contain a water-soluble organic solvent. In this case, the complex-forming reaction did not proceed.

[0078] [Examples 6-1 and 6-2] The ligands represented by the formulas (E1) and (E2) were dissolved in water containing ethanol as an organic solvent to prepare a solution. 225 79 μL of a reaction solution prepared by mixing an Ac ion-containing solution (solvent: 0.2 mol / L hydrochloric acid aqueous solution, radioactivity concentration 5 MBq / mL) and a 0.5 mol / L tetramethylammonium acetate buffer solution (pH 7.8) was reacted under heating conditions at 70°C for 1 hour. 225 An Ac complex solution was obtained. The ligand concentration and radioactivity in the reaction solution at the start of the reaction were as shown in Table 2 below. The concentration of the water-soluble organic solvent (ethanol) in the reaction solution was 10% by volume. Thin layer chromatography was carried out under the same conditions as in Example 5-1. 225 The results of the labeling rate (%) of Ac complexes are shown in Table 2 below.

[0079] [Table 2]

[0080] [Examples 7-1 to 7-4] In this example, the ligand represented by the above formula (E2) was used. The ligand concentration in the reaction solution at the start of the reaction and 225 The amount of Ac radioactivity was as shown in Table 3 below. The type and concentration of the water-soluble organic solvent in the reaction solution was changed as shown in Table 3 below. Other than this, the reaction was carried out under the same reaction conditions as in Example 6-1. 225 An Ac complex solution was obtained. 225 The results of the labeling rate (%) of Ac complexes are shown in Table 3 below.

[0081] [Examples 7-5 to 7-11] In this example, the ligand represented by the above formula (E2) was used. The ligand concentration in the reaction solution at the start of the reaction and 225 The amount of Ac radioactivity was as shown in Table 3 below. The type of buffer in the reaction solution and the type and concentration of the water-soluble organic solvent were changed as shown in Table 3 below. Other than this, the reaction was carried out under the same reaction conditions as in Example 6-1. 225 An Ac complex solution was obtained. 225 The results of the labeling rate (%) of Ac complexes are shown in Table 3 below.

[0082] [Table 3]

[0083] As described above, it is clear that the complex formation reaction proceeds well when a water-soluble organic solvent is used in the reaction solution. It is also clear that the complex formation reaction proceeds well by adjusting the concentrations of the water-soluble organic solvent and buffer or the ligand concentration to an appropriate range depending on the type of water-soluble organic solvent and buffer. 89 It is clear that under production conditions using Zr and a poorly water-soluble ligand, the complex formation rate (labeling rate) is further improved by adopting a combination of DMSO and an acetate buffer solution at a predetermined concentration. 225 Under the production conditions using Ac and a poorly water-soluble ligand, it is found that the complex formation rate (labeling rate) is improved by adopting a combination of a predetermined concentration of ethanol and an acetate buffer solution or a tetramethylammonium acetate buffer solution, or by adopting a combination of a predetermined concentration of DMSO and an acetate buffer solution. Therefore, the production method of the present invention has excellent complex formation efficiency, and this effect is particularly remarkable when a poorly water-soluble ligand is used.

Claims

1. The method includes a step of reacting a radioactive metal with a ligand represented by the following formula (1) in a reaction solution to form a radioactive metal complex, the reaction solution comprises water, a buffer, and a water-soluble organic solvent; The radioactive metal ８９ Zr, the reaction solution contains 0.05 mol / L or more and 0.33 mol / L or less of acetic acid and a salt thereof as the buffer; the water-soluble organic solvent is at least one selected from acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and ethanol; the reaction liquid contains 20% by volume or more and 50% by volume or less of dimethyl sulfoxide as the water-soluble organic solvent, the concentration of the ligand in the reaction solution is 30 μmol / L or more at the start of the reaction. 【Chemical 1】 (In the formula, R １１ , R １２ and R １３ are each independently -(CH ２ ) ｐ COOH, -(CH ２ ) ｐ C ５ H ５ N, -(CH ２ ) ｐ P.O. ３ H ２ , or -(CH ２ ) ｐ CONH ２ is a group consisting of １４ or R １５ One of the groups is a hydrogen atom, -(CH ２ ) ｐ COOH, -(CH ２ ) ｐ C ５ H ５ N, -(CH ２ ) ｐ P.O. ３ H ２ , -(CH ２ ) ｐ CONH ２ , or -(CHCOOH)(CH ２ ) ｐ COOH, and the other is -(CH ２ ) ｐ COOH, -(CH ２ ) ｐ C ５ H ５ N, -(CH ２ ) ｐ P.O. ３ H ２ , or -(CH ２ ) ｐ CONH ２ or a group linked to a peptide, where p is an integer of 0 to 3.

2. A method for producing a radioactive metal complex, comprising the step of reacting a radioactive metal with a ligand represented by the following formula (1) in a reaction solution, the reaction solution comprises water, a buffer, and a water-soluble organic solvent; the radioactive metal is 89Zr; the reaction solution contains 0.05 mol / L or more and 0.33 mol / L or less of acetic acid and a salt thereof as the buffer; the water-soluble organic solvent is at least one selected from acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and ethanol; the reaction liquid contains 2% by volume or more and 50% by volume or less of ethanol or acetonitrile as the water-soluble organic solvent, the concentration of the ligand in the reaction solution is 30 μmol / L or more at the start of the reaction. 【Chemistry 2】 (In the formula, R １１ , R １２ and R １３ are each independently -(CH ２ ) ｐ COOH, -(CH ２ ) ｐ C ５ H ５ N, -(CH ２ ) ｐ P.O. ３ H ２ , or -(CH ２ ) ｐ CONH ２ is a group consisting of １４ or R １５ One of the groups is a hydrogen atom, -(CH ２ ) ｐ COOH, -(CH ２ ) ｐ C ５ H ５ N, -(CH ２ ) ｐ P.O. ３ H ２ , -(CH ２ ) ｐ CONH ２ , or -(CHCOOH)(CH ２ ) ｐ COOH, and the other is -(CH ２ ) ｐ COOH, -(CH ２ ) ｐ C ５ H ５ N, -(CH ２ ) ｐ P.O. ３ H ２ , or -(CH ２ ) ｐ CONH ２ or a group linked to a peptide, where p is an integer of 0 to 3.

3. 3. The method for producing a radioactive metal complex according to claim 1, wherein the ligand is a poorly water-soluble ligand.

4. In the above formula, R １１ , R １２ and R １３ are both -(CH ２ ) ｐ COOH, and R １４ or R １５ is a hydrogen atom or -(CH ２ ) ｐ COOH, and the other is -(CH ２ ) ｐ a group consisting of COOH or a group linking to a peptide, R １４ is the group linking the peptide, R １５ is a hydrogen atom, R １４ is not the group linked to the peptide, R １５ The method for producing a radioactive metal complex according to any one of claims 1 to 3, wherein is a group linking to the peptide.

5. 5. The method for producing a radioactive metal complex according to claim 1, wherein the concentration of the buffer contained in the reaction solution is 0.01 mol / L or more and 5.0 mol / L or less.

6. The method for producing a radioactive metal complex according to claim 1 , wherein the radioactive metal and the ligand are reacted in the reaction solution at a temperature of 30° C. or higher and 80° C. or lower.

7. 7. The method for producing a radioactive metal complex according to claim 1, wherein the peptide has a molecular weight of 500 Da or more and 10,000 Da or less.

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