Method for producing radioactive metal complexes

Abstract

To provide a method for producing a radioactive metal complex with excellent efficiency in forming the complex by using DOTA, a derivative thereof, or a ligand having a structure similar to DOTA.SOLUTION: 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.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for producing radioactive metal complexes. [Background technology]

[0002] Research is underway on radiometal complexes in which ligands are coordinated to radioactive metals, with the aim of using them as reagents and diagnostic agents for detecting target molecules, or as pharmaceuticals for treating diseases. Patent Document 1 describes using DOTA as a chelating agent to conjugate with an antibody, and coordinating it with a radioactive metal to the antibody. 90 Y labeling is performed. Also, Non-Patent Document 1 describes a radioactive metal. 89 A method for forming a radioactive metal complex by reacting Zr with the ligand DOTA in a buffer solution is described. Non-patent document 2 states: 68 Ga or 44 A method for forming a radioactive metal complex is described, which involves reacting Sc with DOTATOC, a DOTA derivative, as a ligand in a buffer solution. Non-patent document 3 states: 68 Ga or 44 A method for forming a radioactive metal complex by reacting Sc and DOTA in ethanol-containing physiological saline is described. [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

Summary of the Invention

[0005] However, when a derivative in which a target molecule other than an antibody such as a peptide is bound to DOTA is used as a ligand, according to the findings of the present inventors, under the conditions disclosed in Patent Document 1 and Non-Patent Documents 1 to 3, the complex formation between DOTA and a specific radioactive metal may not proceed well. Such a 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 having excellent complex formation efficiency in a ligand containing DOTA, a derivative thereof, or a structure similar to DOTA.

[0007] The present invention 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 contains water, a buffer, and a water-soluble organic solvent. The radioactive metal is 89 Zr or 225 Ac, and provides a method for producing a radioactive metal complex.

Chemical Formula

[0008] This application is a priority application claiming based on Japanese Patent Application No. 2019-151480, filed on 21 August 2019, and all contents of Japanese Patent Application No. 2019-151480 are incorporated herein by reference as part of this Specification.

[0009] According to the present invention, it is possible to provide a method for producing radioactive metal complexes with excellent complex formation efficiency using DOTA, its derivatives, or ligands containing structures similar to DOTA. The present invention is particularly effective when using ligands that are poorly water-soluble.

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

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

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

[0013] [ka]

[0014] In formula (1), R 11 , R 12 and R 13 These are, independently, -(CH2) p COOH, -(CH2) p C5H5N, -(CH2) p PO3H2, or -(CH2) p The base consists of CONH2. Each of the above p values ​​is an independent integer between 0 and 3 (inclusive).

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

[0016] In this process, the efficiency of complex formation can be further increased by using poorly water-soluble ligands during complex formation. "Poorly water-soluble" means having the property of satisfying at least one of the following conditions (i) or (ii), preferably at least condition (ii). Poorly water-soluble also includes the meaning of water insolubility, where the ligand is substantially insoluble in water. Similarly, if both (i) and (ii) below are satisfied, it is also referred to as "poorly water-soluble". (i) The octanol-water partition coefficient (LogP value) of the ligand is positive. (ii) The index of the ligand's solubility in water (LogS value) is negative.

[0017] The "octanol-water partition coefficient," one of the indicators of poor water solubility, is an indicator of a compound's hydrophobicity and is defined as the common logarithm of the ratio of the partition concentrations of a substance in 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 phase (oil phase) to its concentration in the aqueous phase (Cw). In other words, this value indicates whether the ligand, as the test substance, 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 poorly water-soluble it is. The octanol-water partition coefficient can be calculated by, for example, the flask shaking method according to JIS Z-7260-107:2000, the HPLC method according to OECD Test Guideline 117, or by computational chemistry estimation based on the substructure and constituent atoms of the substance. In this invention, a ligand is considered to be poorly water-soluble when, in the case of a measured LogP value obtained as the octanol-water partition coefficient of the ligand to be measured, the measured value is positive, or when, in the case of a computationally estimated LogP value obtained as a computational chemistry method, the calculated LogP value is positive.

[0018] When computationally estimating the octanol-water partition coefficient, commercially available software can be used. For example, it is preferable to use a value (calculated LogP value) obtained using "Chemdraw Professional" from Perkinelmer or "CLOGP" from Daylight Chemical Information Systems as the octanol-water partition coefficient of the present invention.

[0019] Another indicator of poor water solubility is the "LogS value," which shows the solubility of the test substance in water. The lower the LogS value, the more poorly water-soluble the test substance, i.e., the ligand, is. The LogS value can be calculated using commercially available software such as Perkinelmer's "Chemdraw Professional," and the calculated LogS value can be used as the LogS value in this invention.

[0020] In the above equation (1), R 14 or R 15The peptides that may be included preferably have a molecular weight of 500 Da or more and 10000 Da or less. Furthermore, from the viewpoint of preventing unintended degradation or reaction of the peptide during the complex formation reaction, the peptide may be a peptide containing amino acids that do not constitute endogenous proteins, such as D-amino acids or amino acids modified with N-aliphatic hydrocarbon groups such as N-methyl groups. Peptides containing amino acids that do not constitute endogenous proteins are generally poorly soluble in water, and the ligand to which the peptide is bound exhibits poor water solubility as a whole. In addition, such peptides generally have peptidase resistance and are not easily degraded in vivo, and as a result they have high in vivo stability in the blood, etc., so when a radioactive metal complex containing this peptide is applied to a living organism, it can be easily delivered to the target site. In particular, such peptides are preferably cyclic peptides. Cyclic peptides have a chemically robust structure compared to chain peptides, so their in vivo stability can be further enhanced. R 14 or R 15 The peptides that may be included are not particularly limited as long as they fall within the above molecular weight range and exhibit poor water solubility, but examples include linear peptides such as fisalemin and peptides having a cyclic structure such as daptomycin.

[0021] As described above, the reaction solution in the complex formation process is an aqueous reaction solution containing water, a buffer, and a water-soluble organic solvent. For example, distilled water or deionized water can be used as the water.

[0022] Preferably, one of the following buffers is used in this process: acetic acid and its salts, phosphoric acid and its salts, 2-amino-2-(hydroxymethyl)propane-1,3-diol (Tris), 2-[4-(2-hydroxyethyl)-1-piperazinyl]-ethanesulfonic acid (HEPES), and a basic amino acid. Examples of counterions for the buffer include alkali metal ions such as sodium and potassium, cations such as ammonium and primary to quaternary ammonium salts, and anions such as various halogen ions. In addition, a neutral salt such as sodium chloride may be added. These buffers may also be selected according to the type and combination of radioactive metal nuclides and ligands.

[0023] Of these, it is even more preferable to use one of the following as the buffering agent: acetic acid and its salts, phosphoric acid and its salts, Tris, HEPES, tetramethylammonium acetate, and basic amino acids. That is, it is even more preferable to use a buffer such as acetic acid-sodium acetate buffer (hereinafter also simply called acetic acid buffer), ammonium acetate buffer, phosphate buffer, phosphate-buffered saline, Tris buffer, HEPES buffer, or tetramethylammonium acetate buffer as the buffer obtained by dissolving the buffering agent in water.

[0024] The reaction solution further contains a water-soluble organic solvent. The water-soluble organic solvent in this step is used to increase the solubility of the ligand in the reaction solution and to increase the amount of ligand available for the complex formation reaction, and is particularly suitable for increasing the solubility of poorly water-soluble ligands. In the context of water-soluble organic solvents, water solubility means that when any volume of water and any volume of the organic solvent are mixed, they mix freely without any visible interface between the solvents.

[0025] As water-soluble organic solvents, polar solvents such as protic solvents like methanol and ethanol, and aprotic solvents like acetonitrile, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, and acetone are preferably used. Of these, using at least one selected from acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and ethanol as the water-soluble organic solvent is even more preferable from the viewpoint of enabling the complex formation reaction to proceed smoothly.

[0026] In the complex formation step, the order in which the radioactive metal source and ligand are added does not matter, as long as complex formation between the radioactive metal ion and the ligand is possible. For example, one of the radioactive metal source and ligand may be added first to a reaction vessel containing a mixed solvent including water, a buffer, and a water-soluble organic solvent, and then the other may be added and the reaction carried out. Alternatively, one of the radioactive metal source and ligand may be dissolved in the mixed solvent, and the other may be added to the solution and the reaction carried out. Or, they may be added simultaneously to a reaction vessel containing the mixed solvent and the reaction carried out.

[0027] The reaction conditions in the complex formation step can be, for example, as follows. 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 under heated conditions, but from the viewpoint of suppressing ligand decomposition and improving the efficiency of complex formation, it is preferably heated to 30°C to 80°C, and more preferably to 50°C to 80°C. The reaction time, given the above reaction temperature, is preferably 15 minutes to 150 minutes, and more preferably 30 minutes to 120 minutes.

[0028] The amount of reaction solution in this process is not particularly limited, but from the viewpoint of practicality in the manufacturing process, it is realistic to have 0.01 mL to 100 mL at the start of this process. Furthermore, the concentrations of the radioactive metal ions and ligands in the reaction solution should, independently, be preferably 1 μmol / L to 100 μmol / L at the start of this process from the viewpoint of increasing the yield of the target radioactive metal complex, 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 changed 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 resulting radioactive metal complex may be used as is, or it may be purified using a filtration filter, membrane filter, column packed with various packing materials, chromatography, etc.

[0030] According to the manufacturing method of the present invention having the steps described above, the solubility of the ligand in the reaction solution is increased, allowing the complex formation reaction to proceed sufficiently. This makes it possible to obtain radioactive metal complexes with a high complex formation rate. One of the features of the present invention is that the reaction system contains a water-soluble organic solvent. Therefore, even when using ligands that are poorly water-soluble, such as ligands whose water-soluble structure is partially substituted or modified to exhibit poor water solubility, or ligands that are inherently poorly water-soluble, the complex formation reaction between the radioactive metal and the ligand proceeds well, and radioactive metal complexes can be obtained in excellent yield. In particular, this step is advantageous because even when using radioactive metal nuclides that emit low-energy radiation that is difficult to detect or alpha rays, complex formation proceeds well and the yield of the complex is high, allowing the complex containing the radioactive metal nuclide to be used in subsequent steps in an unpurified state.

[0031] Post-complex formation steps include, for example, a formulation step to obtain a radiopharmaceutical containing the complex with the radioactive metal nuclide as an active ingredient. The formulation step can be carried out by adding a pH adjuster such as citrate buffer, phosphate buffer, or borate buffer, a solubilizer such as polysorbate, a stabilizer, or an antioxidant as appropriate, or by diluting with an isotonic solution such as water or physiological saline. The formulation step may also include a step of preparing the product as an injectable by sterile filtration using a membrane filter or the like.

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

[0033] [ka]

[0034] [ka]

[0035] In particular, in addition to the effects mentioned above, from the viewpoint of achieving both the ease of handling the ligand used and the complex stability of the resulting radioactive metal complex, R 11 , R 12 and R 13 All of these are -(CH2) p It is even more preferable that the carboxyalkyl group is represented as COOH and p is an integer between 1 and 3. In this case, R 14 and R 15 One of them is -(CH2) pPreferably, the chemical structure is represented as COOH, with p being an integer between 1 and 3, and the other component containing a poorly water-soluble peptide.

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

[0037] By selecting the type of water-soluble organic solvent to be used, taking into account 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 according to the type of water-soluble organic solvent used, it is possible to appropriately disperse or dissolve the ligand in the reaction solution while increasing the efficiency of complex formation between the radioactive metal and the ligand. This advantage is particularly pronounced when using ligands that are poorly water-soluble.

[0038] From the viewpoint of suppressing unintended pH changes during the reaction and further improving the efficiency of complex formation, the concentration of the buffer in the reaction solution is preferably 0.05 mol / L or more and 5.0 mol / L or less, and more preferably 0.05 mol / L or more and 2.0 mol / L or less. For example, when sodium acetate or ammonium acetate is included as the buffer, the concentration in the reaction solution is preferably 0.05 mol / L or more and 2.0 mol / L or less, and more preferably 0.1 mol / L or more and 1 mol / L or less. Also, when tetramethylammonium acetate is included as the buffer, the concentration in the reaction solution is preferably 0.01 mol / L or more and 2.0 mol / L or less, and more preferably 0.1 mol / L or more and 1.0 mol / L or less.

[0039] The radioactive metal coordinated in the radioactive metal complex in an ionic state can be a metal nuclide that emits alpha rays, beta rays, gamma rays, or a combination thereof. Examples of such radioactive metal nuclides include alkali metals, alkaline earth metals, lanthanides, actinides, transition metals, or radioactive isotopes of metals other than these. Of these, from the viewpoint of being commercially usable and improving complex formation properties, the radioactive metal nuclide can be: 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 Ac is preferably used. These radioactive metals can be produced according to conventional methods, and it is preferable to obtain them as a solution containing the radioactive metals in an ionized form.

[0040] When the radioactive metal complex is used for the treatment of diseases, from the viewpoint of enhancing the therapeutic effect, it is preferable to use an α-ray-emitting nuclide or a β - ray-emitting nuclide as the radioactive metal. The α-ray-emitting nuclide may be any nuclide that emits α-rays during the decay process of the radioactive metal. Specifically, 212 Bi, 213 Bi, 227 Th or 225 Ac, etc. are preferably used, more preferably 227 Th or 225 Ac, and even more preferably 225 Ac. The β - ray-emitting nuclide may be any nuclide that emits β - rays during the decay process of the radioactive metal. Specifically, 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, etc. are preferably used, more preferably 64 Cu, 67 Cu, 89 Sr or 90 Y is used.

[0041] Also, when the radioactive metal complex is used for the diagnosis of diseases or the detection of lesions, from the viewpoint of enhancing the diagnostic performance, as the radioactive metal, β+ It is preferable to use a radioactive emission nuclide, an electron capture decay nuclide, or a gamma-ray emitting nuclide. + A radioactive emission nuclide can be any nuclide that emits positrons during the decay process of radioactive metals. 44 Sc, 58 Co, 68 Ga, 64 Cu or 89 Zr and the like are preferably used, more 64 Cu or 89 It is Zr. An electron capture decay nuclide can 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 Hg and the like are preferably used. The gamma-ray emitting nuclide can 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 a radioactive metal coordinated in an ionic state to a radioactive metal complex based on its ionic radius, a radioactive metal with an ionic radius of approximately 70-130 pm is considered. 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 Examples include Ac.

[0043] For example, when using radioactive metal complexes for the purpose of treating diseases, the radioactive metal is 225 When Ac is used, any ligand having the structure shown in formulas (1-a) to (1-h) above can suitably form a radioactive metal complex. Furthermore, when radioactive metal-labeled antibodies are used for the purpose of diagnosing diseases or detecting lesions, the radioactive metal can be used as 89 When using Zr, it is preferable to use any ligand having the structure shown in formula (1-b) or (1-d) to (1-h) above, and more preferably to use a ligand having the structure shown in formula (1-b), (1-d), or (1-e) above.

[0044] Furthermore, when radioactive metal complexes are used for both disease treatment and disease diagnosis or lesion detection, it is even more preferable that the ligands constituting the radioactive metal complex manufactured for disease treatment and the radioactive metal complex manufactured for disease diagnosis or lesion detection have the same structure. In other words, in this case, it is even more preferable to manufacture 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 β + The reaction solution contains a linearly emitting radionuclide, sodium acetate or ammonium acetate as a buffer at a concentration of 0.05 mol / L to 2.0 mol / L, and dimethyl sulfoxide as a water-soluble organic solvent at a concentration of 20% to 50% by volume. In this case, β + Radiation-emitting radionuclides are 89 Zr is more preferably used, and the ligand is more preferably one having the structure shown in formula (1-b), (1-d), or (1-e) above.

[0046] (b-1) The radioactive metal is an alpha-emitting nuclide, and the reaction solution contains tetramethylammonium acetate at a concentration of 0.1 mol / L to 2.0 mol / L as a buffer, and ethanol or acetonitrile at a concentration of 2% to 30% by volume as a water-soluble organic solvent. In this case, the alpha-emitting nuclide is 225 Ac is more preferably used, and any of the ligands having the structure shown in the above formulas (1-a) to (1-h) is more preferably used. Under the conditions of (b-1) above, as radioactive metal 225 When Ac is used and ethanol is used as the water-soluble organic solvent, this manufacturing method can increase the efficiency of radioactive metal complex formation even at relatively low ethanol concentrations. In addition, it is advantageous in that it can reduce manufacturing costs by reducing the amount of water-soluble organic solvent used. Under the conditions of (b-1) above, when ethanol is used as the water-soluble organic solvent, the ethanol content 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 alpha-emitting nuclide, and the reaction solution contains sodium acetate or ammonium acetate as a buffer at a concentration of 0.05 mol / L to 2.0 mol / L, and ethanol or acetonitrile as a water-soluble organic solvent at a concentration of 2% to 30% by volume. In this case, the alpha-emitting nuclide is 225 Ac is more preferably used, and any of the ligands having the structure shown in the above formulas (1-a) to (1-h) is more preferably used. Under the conditions of (b-2) above, as radioactive metal 225 When Ac is used and ethanol is used as the water-soluble organic solvent, this manufacturing method can increase the efficiency of radioactive metal complex formation even when the ethanol concentration is relatively low and when the ligand concentration is high. It is advantageous in that it can reduce the amount of water-soluble organic solvent used, thereby reducing manufacturing costs, and can achieve high efficiency of radioactive metal complex formation while maintaining solubility in the reaction solution even when a large amount of ligand is used in the commercial production of radioactive metal complexes.

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

[0049] Peptides that can be used in the present invention can be synthesized by methods such as liquid-phase synthesis, solid-phase synthesis, automated peptide synthesis, genetic recombination, phage display, and genetic code reprogramming, RaPID (Random non-standard Peptide Integrated Discovery). During peptide synthesis, the functional groups of the amino acids used may be protected as needed.

[0050] When using a ligand that contains a poorly water-soluble peptide in its structure, it is preferable that the poorly water-soluble peptide and the ligand precursor are linked to each other by an amide bond or a thiourea bond to form a poorly water-soluble ligand. An 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 carboxyl group present in the ligand precursor. Examples of such ligands include those having the structure shown in formula (1-a) or (1-c) above.

[0051] Furthermore, thiourea bonds 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 of the ligand precursor, or by reacting a thiol group derived from the side chain of an amino acid constituting the peptide with a maleimide group of the ligand precursor. Examples of such ligands include those having the structures shown in formulas (1-b) or (1-d) to (1-h) above. [Examples]

[0052] The present invention will be described in more detail below with reference to examples. However, 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 radioactive metallic elements 89 Zr was used as the ligand. In addition, DOTA (in equation (1) above, R 11 , R 12 , R 13 and R 14 All of them are "-CH2COOH" groups, R 15 (This is a hydrogen atom.)

[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 ligand. 0.029 mL of this solution was mixed with a radioactive metal source. 89 A reaction solution prepared 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) with 0.01 mL of 1.5 mol / L acetate buffer (pH 5.5) is reacted under heating conditions. 89 A Zr complex solution was obtained. The reaction mixture was heated to 70°C for 60 minutes. Thin-layer chromatography (Merck, model number: 1.15685.0001, developing solvent: 10% by volume aqueous ammonium chloride solution / methanol (1:1)) was used to remove unreacted components. 89 All Zr 89 For Zr radioactivity count89 The percentage of the radioactivity count of the Zr complex was used as the labeling factor. 89 The labeling efficiency of the Zr complex was 84%.

[0055] [Examples 1-2] The procedure was carried out under the same conditions as in Example 1-1, 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 efficiency of the Zr complex was 59%.

[0056] [Examples 1-3] The procedure was carried out under the same conditions as in Example 1-1, 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 efficiency of the Zr complex was 55%.

[0057] [Examples 1-4] The procedure was carried out under the same conditions as in Example 1-1, 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 efficiency of the Zr complex was 54%.

[0058] [Examples 2-1 to 2-6: 89 Zr labeling study (concentration of buffering agent)] [Example 2-1] DOTA was used as the ligand, and the ligand was dissolved in 1.5 mol / L acetate buffer (pH 5.5) containing 90 volume% dimethyl sulfoxide as the organic solvent to obtain a solution containing 200 μmol / L of the ligand. 0.029 mL of this solution was used, along with a radioactive metal source. 89 A reaction solution prepared 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 1.5 mol / L acetate buffer (pH 5.5) was reacted under heating conditions. 89A Zr complex solution was obtained. The final concentration of the buffer in the reaction mixture was 0.33 mol / L. The reaction mixture was heated at 70°C for 15 minutes. Thin-layer chromatography was performed under the same conditions as in Example 1. 89 The labeling efficiency of the Zr complex was 60%.

[0059] [Example 2-2] The procedure 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 an organic solvent to obtain 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 efficiency of the Zr complex was 55%.

[0060] [Examples 2-3] DOTA was used as the ligand, and this 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 was used, along with a radioactive metal source. 89 The reaction was carried out under the same conditions as in Example 2-1, except that a reaction solution prepared 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 0.75 mol / L acetate buffer (pH 5.5) was reacted under heating conditions. The final concentration of the buffer in the reaction solution was 0.13 mol / L. 89 The labeling efficiency of the Zr complex was 66%.

[0061] [Examples 2-4] The procedure 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 to obtain 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 mixture was 0.25 mol / L. 89 The labeling efficiency of the Zr complex was 50%.

[0062] [Examples 2-5] The procedure 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 1.5 mol / L acetate buffer (pH 5.5) to obtain 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 mixture was 1.00 mol / L. 89 The labeling efficiency of the Zr complex was 28%.

[0063] [Examples 2-6] Except for using DOTA as the ligand and dissolving the ligand in 3.0 mol / L acetate buffer (pH 5.5) to obtain a solution containing 200 μmol / L of the ligand, the procedure was carried out under the same conditions as in Example 2-1. 89 A Zr complex solution was obtained. 89 The labeling efficiency 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 the ligand, and this 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 was used, along with a radioactive metal source. 89 A reaction solution prepared by mixing 0.02 mL of a Zr ion-containing solution (solvent: 0.1 mol / L hydrochloric acid aqueous solution, radioactivity concentration 28.5 MBq / mL) and 0.01 mL of 1.5 mol / L acetate buffer (pH 5.5) was reacted under heating conditions. 89 A Zr complex solution was obtained. The final concentration of ligand in the reaction solution was 100 μmol / L. The reaction solution was heated at 70°C for 60 minutes. Thin-layer chromatography was performed under the same conditions as in Example 1-1. 89 The labeling efficiency of the Zr complex was 89%.

[0065] [Example 3-2] DOTA was used as the ligand, and the ligand was dissolved in water containing 90% by volume of dimethyl sulfoxide as an organic solvent so that the final concentration of the ligand in the reaction solution was 50 μmol / L. The reaction was carried out under the same conditions as in Example 3-1.89 A Zr complex solution was obtained. 89 The labeling efficiency of the Zr complex was 50%.

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

[0067] [Examples 3-4] DOTA was used as the ligand, and the ligand was dissolved in water containing 90% by volume of dimethyl sulfoxide as an organic solvent so that the final ligand concentration in the reaction solution was 1 μmol / L. The reaction was carried out under the same conditions as in Example 3-1. 89 A Zr complex solution was obtained. 89 The labeling efficiency 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 the ligand, and the ligand was dissolved in water containing 10% by volume of ethanol as the organic solvent to prepare a solution containing 100 μmol / L of the ligand. 0.039 mL of this solution was used, along with a radioactive metal source. 225 A reaction solution prepared by mixing 0.02 mL of Ac ion-containing solution (solvent: 0.2 mol / L hydrochloric acid aqueous solution, radioactivity concentration 5 MBq / mL) and 0.016 mL of 0.5 mol / L tetramethylammonium acetate buffer (pH 7.8) is reacted under heating conditions. 225 An Ac complex solution was obtained. The reaction solution was heated to a temperature of 70°C for 60 minutes. Thin-layer chromatography was performed under the same conditions as in Example 1-1. 225 The labeling efficiency 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 Ac saline solution was obtained. 225 The labeling efficiency of the Ac complex was 86%.

[0070] [Examples 4-3 to 4-4] Except for using DOTA as the ligand and dissolving the ligand in water containing 90% or 50% by volume of ethanol as the organic solvent to obtain a solution containing 100 μmol / L of the ligand, the reaction was carried out under the same conditions as in Example 4-1. 225 Ac saline solution was obtained. 225 The labeling efficacy of the Ac complexes was 25% or 67%, respectively.

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

[0072] [Comparative Example 1] The procedure was carried out under the same conditions as in Example 1-1, except that DOTA was used as the ligand and the ligand was dissolved in 0.5 mol / L phosphate buffer (pH 5.5) to obtain a solution containing 2 mmol / L of the ligand. This comparative example did not contain any water-soluble organic solvents in the reaction solution. 89 The labeling efficiency of the Zr complex was 0%, indicating that the complex formation reaction did not proceed at all.

[0073] [Examples 5-1 and 5-2] The reaction is carried out under the same reaction conditions as in Example 1, except that a ligand is used that has DOTA in its structure and a peptide whose computationally estimated LogS value is negative, and the ligand as a whole has a negative calculated LogS value. In this case, the complex formation reaction proceeds. 89 A Zr complex solution is obtained. In detail, this example used ligands obtained by conventionally linking p-SCN-Bn-DOTA with either physaremin (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) as a peptide. These ligands have the structure represented by formula (1-b) above, and contain both a DOTA-derived structure and a peptide within the structure. The details of the chemical structure are shown in formulas (E1) and (E2) below. Since these ligands have negative calculated LogS values, they are poorly water-soluble.

[0074] [ka]

[0075] The details of the manufacturing method in this embodiment are as follows. First, each ligand was dissolved in a 1.5 mol / L acetate buffer (pH 5.5) containing 45 volume% dimethyl sulfoxide (DMSO) as a water-soluble organic solvent to prepare a solution. This solution was then mixed with a radioactive metal source. 89 A reaction solution containing Zr ions (solvent: 0.1 mol / L hydrochloric acid aqueous solution, radioactivity concentration 33.4 MBq / mL) and 1.5 mol / L acetate buffer (pH 5.5) was mixed and 59 μL of the reaction solution was 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 analyzed using thin-layer chromatography (Agilent iTLC-SG, developing solvent: water / acetonitrile (1:1)) to remove any unreacted particles. 89 All Zr 89 For Zr radioactivity count 89 The percentage of radioactivity count of the Zr complex was defined as the labeling efficiency (%). 89 The results of the labeling efficiency 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 formation reaction did not proceed.

[0078] [Examples 6-1 and 6-2] Using the ligands shown in formulas (E1) and (E2) above, the ligands were dissolved in water containing ethanol as an organic solvent to prepare a solution. This solution was then mixed with a radioactive metal source. 225 A reaction solution containing Ac ions (solvent: 0.2 mol / L hydrochloric acid aqueous solution, radioactivity concentration 5 MBq / mL) and 0.5 mol / L tetramethylammonium acetate buffer (pH 7.8) was mixed and reacted in 79 μL under heating conditions of 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 water-soluble organic solvent (ethanol) in the reaction solution was 10% by volume. Thin-layer chromatography was performed under the same conditions as in Example 5-1. 225 The results for the labeling efficiency (%) of the Ac complex are shown in Table 2 below.

[0079] [Table 2]

[0080] [Examples 7-1 to 7-4] This example used the ligand shown in formula (E2) above. 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. Furthermore, the type and concentration of the water-soluble organic solvent in the reaction solution were changed as shown in Table 3 below. Other than these changes, the reaction was carried out under the same reaction conditions as in Example 6-1. 225 Ac saline solution was obtained. 225 The results for the labeling efficiency (%) of the Ac complex are shown in Table 3 below.

[0081] [Examples 7-5 to 7-11] This example used the ligand shown in formula (E2) above. 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. Furthermore, the type of buffer in the reaction solution, as well as the type and concentration of the water-soluble organic solvent, were changed as shown in Table 3 below. Other than these changes, the reaction was carried out under the same conditions as in Example 6-1. 225 Ac saline solution was obtained. 225 The results for the labeling efficiency (%) of the Ac complex are shown in Table 3 below.

[0082] [Table 3]

[0083] As described above, it can be seen that the complex formation reaction proceeds well when a water-soluble organic solvent is used in the reaction solution. Furthermore, it can be seen that the complex formation reaction proceeds well by adjusting the concentrations of the water-soluble organic solvent and buffer, or the ligand, to an appropriate concentration range depending on the type of buffer. 89 In manufacturing conditions using Zr and poorly water-soluble ligands, it has been found that adopting a combination of DMSO and acetate buffer at a predetermined concentration results in an even better complex formation rate (labeling efficiency). 225 In manufacturing conditions using Ac and poorly water-soluble ligands, it has been found that the complex formation rate (labeling rate) is further improved by using a combination of ethanol at a predetermined concentration and acetate buffer or tetramethylammonium acetate buffer, or by using a combination of DMSO at a predetermined concentration and acetate buffer. Therefore, the manufacturing method of the present invention exhibits excellent complex formation efficiency, and this effect is particularly pronounced when using poorly water-soluble ligands.

Claims

1. The process 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 aforementioned radioactive metal ２２５ It is Ac, The reaction solution contains tetramethylammonium acetate as the buffer, A method for producing a radioactive metal complex, wherein the reaction solution contains only acetonitrile in an amount of 2% to 20% by volume as the water-soluble organic solvent. 【Chemistry 1】 (wherein, 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 PO ３ H ２ , or —(CH ２ ) ｐ CONH ２ ; and one of R １４ or R １５ is a hydrogen atom, —(CH ２ ) ｐ COOH, —(CH ２ ) ｐ C ５ H ５ N, —(CH ２ ) ｐ PO 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 PO ３ H ２ , or —(CH ２ ) ｐ CONH ２ ; or a group linked to a peptide; and p is an integer of 0 or more and 3 or less.).

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

3. In the above formula, R １１ , R １２ and R １３ All of them are - (CH ２ ) ｐ It is a group consisting of COOH, R １４ or R １５ One of them is a hydrogen atom, or -(CH ２ ) ｐ It is a group consisting of COOH, and the other is -(CH ２ ) ｐ It is a group consisting of COOH, or a group linked to a peptide. R １４ If it is a group linked to the peptide, R １５ It is a hydrogen atom, R １４ If it is not a group linked to the peptide, then R １５ The method for producing a radioactive metal complex according to claim 1 or 2, wherein is a group linked to a peptide.

4. A method for producing a radioactive metal complex according to any one of claims 1 to 3, 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.

5. The method for producing a radioactive metal complex according to claim 4, wherein the reaction solution contains tetramethylammonium acetate in a buffering agent of 0.1 mol / L or more and 2.0 mol / L or less.

6. A method for producing a radioactive metal complex according to any one of claims 1 to 5, comprising reacting the radioactive metal with the ligand in the reaction solution at a temperature of 30°C to 80°C.

7. The method for producing a radioactive metal complex according to any one of claims 1 to 6, wherein the peptide has a molecular weight of 500 Da or more and 10000 Da or less.

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