Method for producing gadolinium complex solution

Abstract

The present invention relates to [μ-[1-[bis[2-(hydroxy-κO)-3-[4,7,10-tris[(carboxy-κO)methyl]-1,4,7,10-tetraazacyclododecan-1-yl-κN 1 ,κN 4 ,κN 7 ,κN 10 The present invention relates to a method for the preparation of a solution of a dimeric gadolinium complex, such as [propyl]amino]-1-deoxy-D-glucitrate(6-)]digadolinium complex, useful in the field of contrast agents in diagnostic imaging and magnetic resonance imaging (MRI), comprising the step of precipitating the free gadolinium metal ions with a precipitating agent. The present invention further relates to a method for isolating the dimeric gadolinium complex from said solution, and to the solution and isolated dimeric gadolinium complex obtainable by such a method.

Description

Technical Field

[0001] The present invention is characterized by high robustness and is suitable for large-scale production, [μ-[1-[bis[2-(hydroxy-κO)-3-[4,7,10-tris[(carboxy-κO)methyl]-1,4,7,10-tetraazacyclododec-1-yl-κN ,

[0004] ,

[0003] , , 3+ , ,

[0002] , ,

[0005] , , , , ,κN 4 ,κN 7 ,κN 10 propyl]amino]-1-deoxy-D-glucitrate(6-]] digadolinium complex and the like, and relates to a method for producing a solution of a dimeric gadolinium complex. The present invention further relates to a method for isolating a dimeric gadolinium complex from the solution. The dimeric gadolinium complex is useful in the field of contrast agents in diagnostic imaging and magnetic resonance imaging (MRI).

Background Art

[0002] Magnetic resonance imaging (MRI) is a well-known diagnostic imaging technique that is increasingly used in clinical diagnosis for growing symptoms.

[0003] Gadolinium [Gd(III)] complexes are commonly used as contrast agents in MRI due to their long relaxation times. However, the gadolinium metal ion [Gd(H2O)8] 3+ is extremely toxic to the living body even at low dosages (10 - 20 micromol / kg).

[0004] Therefore, in order to be a potentially valuable MRI contrast agent, the Gd(III) complex must exhibit high thermodynamic (and in some cases kinetic) stability to prevent the release of toxic metal ions. Moreover, the process for producing the Gd(III) complex is advantageous if it can effectively and efficiently remove the toxic metal ions present in the reaction mixture after the complexation step.

[0005] WO 2017 / 098044 discloses dimeric paramagnetic complexes useful as contrast agents in MRI. These dimeric complexes, in particular dimeric Gd(III) complexes, exhibit increased relaxation compared to non-specific contrast agents currently used in routine diagnostic practice. Therefore, such dimeric Gd(III) complexes may be used in in vivo imaging at lower doses than those required by currently used contrast agents.

[0006] WO 2017 / 098044 further discloses a process for producing the dimeric paramagnetic complex disclosed herein. Such a process includes the step of complexing a ligand in water using stoichiometric addition of a suitable Gd(III) derivative, such as a salt or oxide of Gd(III). The solution containing the complex is then filtered and evaporated under reduced pressure. The crude product is then purified with an adsorbent resin such as Amberchrome CG161M, and the fraction containing the product is finally pooled and evaporated.

[0007] The solution obtained after the complexation and purification steps of the process disclosed in WO 2017 / 098044 may contain a considerable amount of mono-gadolinized complexes.

[0008] Mono-gadolinized complexes are Gd(III) complexes in which the dimeric ligand disclosed in WO 2017 / 098044 chelates only one gadolinium ion instead of two. These mono-gadolinized complexes do not exhibit the preferred relaxation time measurement characteristics of the di-gadolinized Gd(III) complexes disclosed in WO 2017 / 098044. Therefore, it is advantageous to remove (or substantially reduce the amount of) these mono-gadolinized complexes from the solution obtained from the complexation step. However, methods for removing mono-gadolinized complexes from the reaction mixture are not entirely satisfactory in that complete removal of the mono-gadolinized complexes is difficult to achieve (this is due to the fact that mono-gadolinized complexes have very similar physical characteristics to di-gadolinized complexes). For this reason, it is advantageous to provide a method for producing di-gadolinized Gd(III) complexes, as disclosed in WO 2017 / 098044, which substantially avoids the formation of mono-gadolinized complexes during or after the complexation process.

[0009] Furthermore, the reproducibility of the complexation process disclosed in WO 2017 / 098044 depends on the accurate weighing of the reactants in the complexation process and the accurate determination of their titles. For this reason at least, the robustness of the process disclosed in WO 2017 / 098044 could be improved. [Overview of the project] [Problems that the invention aims to solve]

[0010] Therefore, there is a need for a method to overcome the aforementioned problems with the Gd(III) complex disclosed in WO 2017 / 098044. Specifically, a method is needed that is reproducible, robust, and therefore particularly advantageous for the large-scale production of the dimeric paramagnetic complex disclosed in WO 2017 / 098044, while limiting the formation of mono-gadolinium complexes as much as possible. [Means for solving the problem]

[0011] In a first aspect, the present invention relates to a method for producing a solution of a gadolinium complex represented by formula I

Chemical formula

Chemical formula

[0012] In a preferred embodiment, the present invention relates to a method for producing a solution of the following gadolinium complex (Compound 1)

Chemical formula

[0013] In a second aspect, the present invention relates to a method for producing a gadolinium complex solution according to any embodiment thereof, which is a compound of formula I [ka] (In the formula, R is as defined above.) A solution of the gadolinium complex shown is provided.

[0014] In a third aspect, the present invention relates to formula I [ka] (In the formula, R is as defined above.) A method for producing an isolated gadolinium complex shown in, In any of the embodiments, the process for preparing a solution of the gadolinium complex disclosed herein, and further subsequent steps iv): iv) A step of isolating the gadolinium complex from the purified solution obtained from step iii) above. The present invention provides a manufacturing method that includes the following:

[0015] In a further embodiment, the present invention relates to a method for producing an isolated gadolinium complex according to any of its embodiments, which is obtained by formula I [ka] (In the formula, R is as defined above.) This provides an isolated gadolinium complex shown in [the formula].

[0016] These embodiments and further embodiments, along with their respective models, are disclosed in more detail in the following sections. [Modes for carrying out the invention]

[0017] As used herein, unless otherwise specified, the term “monogadoliniumized complex” refers to a dimeric complex of formula I, or a complex having the same structure as compound 1, but with only one gadolinium metal ion chelated instead of two. For example, a monogadoliniumized complex is a complex of general formula Ic [ka] (In the formula, R is as defined above with respect to formula I.) It is a compound represented by [the formula shown].

[0018] As used herein, unless otherwise specified, the term “precipitant” means an anion or an anion-forming agent added in step iii) under at least the conditions of step iii) when added to the intermediate solution by the production method of the present invention. Such anions can form gadolinium salts as defined herein through ionic bonding (maybe multiple) with free gadolinium metal ions. Precipitants include phosphate ions (PO4 3- ), monohydrogen phosphate (HPO4)2- ), dihydrogen phosphate (H2PO4) - ), orthophosphate (H3PO4), oxalate ion (C2O4) 2- ), hydrogen oxalate ion (HCl2O4 - Selected from the group consisting of ), and oxalic acid (H2C2O4).

[0019] As used herein, unless otherwise specified, the term “gadolinium salt” refers to the salt formed after the addition of the precipitant as defined herein. Gadolinium salts are Gd as a cation. 3+ , and anions as a precipitant or counterions produced by the precipitant. At least under the conditions of step iii) of the production method of the present invention, and preferably under the conditions of the downstream steps of step iii), the gadolinium salt is present in the reaction mixture in solid and filterable physical forms. Examples of gadolinium salts are gadolinium phosphate and gadolinium oxalate.

[0020] As used herein, unless otherwise specified, the term “free gadolinium metal ion” means [Gd(H2O)8] present in solution and not chelated by a dimeric ligand. 3+ This refers to gadolinium ions such as those mentioned above.

[0021] As used herein, unless otherwise specified, the term “intermediate solution” refers to a solution containing the gadolinium complex of formula I, obtained after the complexation step (step ii)) but before the purification step (step iii)).

[0022] In this specification, unless otherwise specified, the term “alkyl” includes any linear or branched hydrocarbon. For example, “C1-C6 alkyl” includes linear or branched hydrocarbons containing 1 to 6 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, isopentyl, tert-pentyl, and n-hexyl. In this specification, unless otherwise specified, the term “tBu” refers to C4 alkyl tert-butyl (or 1,1-dimethylethyl).

[0023] The term “hydroxyalkyl” (or “polyol” as used interchangeably herein) includes, in its meaning, a corresponding linear or branched hydrocarbon chain in which one or more hydrogen atoms are replaced by hydroxyl groups.

[0024] For example, unless otherwise specified, "C3~C 12 Polyol (or "C3~C") 12 The term "polyhydroxyalkyl" refers to a compound where two or more hydrogen atoms, for example, 2 to 11 hydrogen atoms, are replaced by hydroxyl groups, corresponding to C3-C3 atoms. 12 It includes either a straight-chain or branched hydrocarbon chain. Among these, C3~C 10 Polyols are preferred, and C5-C7 polyols are particularly preferred. Examples of C5-C7 polyols include pentyl polyols (or polyhydroxypentyl), such as pentyl-diol, pentyl-triol, pentyl-tetraol, and pentyl-pentaol, which contain 2, 3, 4, and 5 hydroxyl groups on the C5 alkyl chain, respectively; hexyl polyols (or polyhydroxyhexyl), which similarly contain 2 to 6 hydroxyl groups on the C6 alkyl chain; and heptyl polyols (or polyhydroxyheptyl), which contain 2 to 7 hydroxyl groups on the C7 alkyl chain.

[0025] In this specification, the term “protecting group” refers to a protecting group suitable for preserving the function of the group to which it is bonded. In particular, protecting groups may be used to preserve amino, hydroxyl, or carboxyl functional groups. Suitable carboxyl protecting groups include, for example, benzyl, alkyl, or other substituents commonly used to protect such functional groups, such as tert-butyl or benzyl esters, all of which are well known to those skilled in the art [see, for general reference, TWGreen and PGMWuts; Protective Groups in Organic Synthesis, Wiley, NY 1999, third edition].

[0026] Furthermore, the terms “part” or “residue” are intended to be defined herein as a residue portion of a given molecule that is bound or complexed with the rest of the molecule, either directly or via any preferred linker.

[0027] For example, the compounds disclosed herein, such as the compound of formula I and compound 1, may have one or more asymmetric carbon atoms, also referred to as chiral carbon atoms, and thus may give rise to diastereomers and optical isomers. Unless otherwise specified, the present invention further includes all such possible diastereomers, as well as racemic mixtures thereof, substantially pure isolated enantiomers thereof, all possible geometric isomers, and pharmaceutically acceptable salts thereof.

[0028] The present invention further relates to a method for producing a complex of formula I, or a solution of compound 1, in which each of the acidic groups contained (e.g., on R) may be deprotonated. In such a case, the acidic groups contained in the dimeric ligand of formula Ia, or compound 1a, may be, for example, in their respective deprotonated forms.

[0029] The present invention further relates to a method for producing a complex of formula I, or a solution of compound 1, in which each of the basic groups contained (e.g., a tertiary amine) may be protonated. In such a case, the basic groups contained in the dimeric ligand of formula Ia, or compound 1a, may be, for example, in their respective protonated forms.

[0030] This invention relates to formula I [ka] (In the formula, R is a C3-C3 group containing at least two hydroxyl groups) 12 A method for producing a solution of a gadolinium complex represented by (a hydroxyalkyl group); i) Formula Ia [ka] (In the formula, R is as defined above.) A step of providing a solution of the dimeric ligand shown; ii) Adding a molar excess of gadolinium metal ions to the solution from the previous step to complexize the dimeric ligand provided in step i), thereby obtaining an intermediate solution containing the gadolinium complex of formula I, and iii) A step of adding at least a precipitating agent to the solution from the previous step to precipitate free gadolinium metal ions as gadolinium salts, thereby obtaining a solution of the gadolinium complex of formula I. Includes, The precipitating agent contains phosphate ions (PO4 3- ), monohydrogen phosphate (HPO4) 2- ), dihydrogen phosphate (H2PO4) - ), orthophosphate (H3PO4), oxalate ion (C2O4) 2- ), hydrogen oxalate ion (HCl2O4 - Selected from the group consisting of ), and oxalic acid (H2C2O4), Regarding the manufacturing method.

[0031] The manufacturing method of the present invention is robust and therefore overcomes the problems of prior art processes. In fact, the addition of molar excess gadolinium metal ions significantly reduces the burden of accurately weighing the reactants and determining the title product in the complexation step. Because the manufacturing method of the present invention is robust, reproducible, and efficient, it can be more easily implemented in large-scale production. Moreover, by adding molar excess gadolinium metal ions, the presence of mono-gadolinized complexes in the final product is significantly reduced compared to the addition of stoichiometric amounts.

[0032] The addition of molar excess gadolinium metal ions results in a larger amount of free gadolinium metal ions after complexation compared to the addition of stoichiometric or less than stoichiometric amounts of gadolinium metal ions; however, it has been found that this large amount of free gadolinium metal ions can be effectively and efficiently removed by performing step iii) of the present invention, i.e., by precipitating the free gadolinium metal ions using a precipitant as disclosed herein. Thus, by combining steps ii) and iii), a particularly effective method of the present invention is provided, in that a solution containing the complex of formula I, with both the mono-gadolinized complex and free gadolinium metal ions in low amounts, is obtained by a robust method suitable for large-scale production.

[0033] The applicant has also found that precipitating free gadolinium metal ions by methods other than those described in the present invention to prepare a solution of the complex of formula I and remove free gadolinium ions can result in a solution containing high and therefore undesirable amounts of free gadolinium metal ions and / or mono-gadolinized complexes. Specifically, as will be demonstrated in the experimental section below by comparative examples, methods known in the prior art for precipitating gadolinium ions may not be suitable for obtaining a solution of the gadolinium complex of formula I containing a suitable amount of free gadolinium metal ions and / or mono-gadolinized complexes. For example, it is known, for instance, from "Preparation, Purification, and Characterization of Lanthanide Complexes for Use as Contrast Agents for Magnetic Resonance Imaging", Averill et al., Journal of Visualized Experiments, that free gadolinium metal ions precipitate as Gd(OH)3 when the pH of a solution containing free gadolinium metal ions is raised to a sufficiently high pH. However, as demonstrated in the experimental section below by comparative examples, this precipitation method for free gadolinium metal ions by basicization is ineffective when applied to a solution of the gadolinium complex of formula I, because gadolinium hydroxide does not precipitate. Therefore, this basicization method does not reduce the amount of the target gadolinium complex, i.e., the amount of free gadolinium metal ions in the solution of formula I.

[0034] To the surprise of the applicant, in order to precipitate free gadolinium metal ions as gadolinium salts, phosphate ions (PO4) were used. 3- ), monohydrogen phosphate (HPO4) 2- ), dihydrogen phosphate (H2PO4) - ), orthophosphate (H3PO4), oxalate ion (C2O4) 2- ), hydrogen oxalate ion (HCl2O4 -We have found that by adding a precipitating agent selected from the group consisting of ), and oxalic acid (H2C2O4), preferably in the amounts disclosed below, and especially when the pH is adjusted and / or maintained within the range disclosed below during and / or after the precipitation step, it is possible to effectively remove large amounts of free gadolinium metal ions without generating large amounts of mono-gadolinized complexes.

[0035] The manufacturing method of the present invention can precipitate a portion, specifically a substantial portion, of the free gadolinium metal ions. In fact, as shown in the experimental section below, precipitation step iii) allows for the precipitation of a substantial portion of the free gadolinium metal ions present after complexing step ii), thereby reducing the free gadolinium metal ion content from approximately tens of thousands of ppm to as little as 100 ppm or even tens of ppm (relative to the amount of gadolinium complex). Therefore, the manufacturing method of the present invention provides a method for producing a solution containing the gadolinium complex disclosed herein, which has a low free gadolinium metal ion content, specifically, a method in which the amount of free gadolinium metal ions in such a solution may be less than 350 ppm, preferably less than 150 ppm, more preferably less than 100 ppm, and even more preferably less than 80 ppm, relative to the amount of gadolinium complex, after precipitation step iii) and before any further purification steps thereafter. According to the present invention, high ppm values ​​of free gadolinium metal ions (e.g., ppm values ​​of 4000 ppm or higher) are determined by conventional complex titration using EDTA in the presence of xylenol orange, while lower ppm values ​​of free gadolinium metal ions (e.g., ppm values ​​lower than 4000 ppm) are preferably determined by performing HPLC procedure 1 as presented in the experimental section below.

[0036] Furthermore, the present invention provides a method for producing a solution containing a gadolinium complex disclosed herein, wherein the amount of mono-gadolinized complex in such a solution is low, i.e., less than 550 ppm relative to the amount of gadolinium complex, and preferably lower than the limit of quantification (LoQ) of the analytical method used to quantify the mono-gadolinized complex, i.e., less than 400 ppm. These ppm values ​​of mono-gadolinized complexes, as well as all ppm values ​​of mono-gadolinized complexes in the present invention, are determined by performing HPLC procedure 2 presented in the Experimental section below. Such low amounts of mono-gadolinized complex in the final solution of the present invention, i.e., less than 550 ppm, preferably less than 400 ppm relative to the amount of gadolinium complex, do not significantly affect, or even adversely affect, the relaxability of the final isolated complex.

[0037] Advantageously, step iii) of the manufacturing method of the present invention provides for the production of a solution of the gadolinium complex disclosed herein, wherein the amount of free gadolinium metal ions in such a solution is less than 150 ppm, preferably less than 125 ppm, more preferably less than 80 ppm, and even more preferably less than 50 ppm, relative to the amount of the gadolinium complex, and the amount of mono-gadolinized complex is less than 400 ppm, relative to the amount of the gadolinium complex.

[0038] Preferred compounds of formulas I and Ia are those in which R is C3-C 12 C3-C3 molecules having 2-11, preferably 3-10, hydroxyl groups on the alkyl chain. 12 Polyhydroxyalkyl (or C3~C 12The compound comprises a polyol. Preferably, R is a C5-C7 polyol residue selected from, for example, a pentyl polyol (or polyhydroxypentyl) having at least two, preferably two to four, hydroxyl groups on a C5 alkyl chain; a hexyl polyol having at least two, preferably two to five, hydroxyl groups on a C6 alkyl chain; or a heptyl polyol having at least two, preferably three to six, hydroxyl groups on a C7 alkyl chain.

[0039] In one preferred embodiment, the manufacturing method of the present invention is for producing a solution of the gadolinium complex of formula I, wherein R in formulas I and Ia is preferably formula [ka] Pentyl-tetraol and formula shown in [ka] A C5-C7 polyol selected from hexyl-pentaols represented by , comprising steps i), ii), and iii) disclosed herein by any embodiment thereof.

[0040] In a particularly preferred embodiment, the manufacturing method of the present invention involves the following gadolinium complex (compound 1): [ka] The present invention relates to the preparation of a solution comprising steps i), ii), and iii) disclosed herein by any embodiment thereof. Compound 1 is particularly preferred as it exhibits high relaxability as shown in WO 2017 / 098044.

[0041] If the manufacturing method of the present invention is a method for producing a solution of gadolinium complex compound 1, then the dimer ligand provided in step i) is the corresponding dimer ligand compound 1a [ka] That is the case.

[0042] Step i) of the manufacturing method of the present invention, namely the step of providing a dimerized ligand of formula Ia or a solution of compound 1a, is carried out by performing, for example, a known process for preparing an uncomplexed dimerized ligand of formula Ia or a solution of compound 1a, as disclosed in WO 2017 / 098044. Preferably, the dimerized ligand is provided by deprotecting the corresponding protected dimerized ligand by a deprotection method disclosed herein.

[0043] The solution provided in step i), as well as the intermediate and final solutions of the gadolinium complex produced by the manufacturing method of the present invention, are preferably aqueous solutions.

[0044] Step ii) of the manufacturing method of the present invention is carried out by adding a molar excess of gadolinium metal ions to the solution from the previous step to complex the dimerized ligand provided in step i) to obtain an intermediate solution containing the gadolinium complex of formula I, or compound 1. Thus, step ii) of the manufacturing method of the present invention provides the complexation of the dimerized ligand of formula Ia, or any other dimerized ligand disclosed herein, with gadolinium.

[0045] The dimerized ligand provided in step i) has two chelates, and one dimerized ligand can chelate two gadolinium metal ions. Therefore, the term "molar excess," when referring to step ii) of the manufacturing method of the present invention, refers to a molar amount of gadolinium metal ions greater than twice the molar amount of dimerized coordination. Accordingly, the term "molar excess," when referring to step ii) of the manufacturing method of the present invention, refers to more than 2 moles of gadolinium metal ions per mole of dimerized ligand. For example, 2.05 moles or more, preferably 2.05 to 2.50 moles, more preferably up to 2.20 moles, and even more preferably up to 2.12 moles of gadolinium metal ions are added to the solution per mole of the dimerized ligand provided in step i).

[0046] According to step ii) of the manufacturing method of the present invention, gadolinium metal ions are added by adding a gadolinium derivative, such as a soluble gadolinium salt, to the solution. Suitable gadolinium derivatives may be oxides such as Gd2O3 or soluble gadolinium salts such as GdCl3.

[0047] Step ii) is preferably carried out while maintaining the solution at a temperature in the range of 20 to 50°C, more preferably 30 to 45°C, and even more preferably 37 to 43°C. After the addition of gadolinium metal ions in step ii), the reaction mixture is preferably maintained for 1 to 5 hours, more preferably 2 to 4 hours, at the temperature range described above, for example, before carrying out the subsequent steps.

[0048] During and / or after the addition of gadolinium metal ions in step ii), the pH is adjusted and / or maintained to a range of preferably 5.0 to 7.0, more preferably 5.0 to 6.0, for example, at the time and / or temperature described above. This pH adjustment and / or maintenance can be done, for example, by adding a suitable base, such as sodium hydroxide, to the solution in step ii).

[0049] According to a preferred embodiment, after step ii) and optionally before step iii), the production method of the present invention includes a further step of desalting the (intermediate) solution of the gadolinium complex, preferably via nanofiltration. This desalting (e.g., nanofiltration) step allows for the removal of salts generated in the complexing step, such as salts formed after the addition of soluble gadolinium salts, as well as salts formed by an optional deprotection method (if implemented). The desalting step does not remove free gadolinium metal ions or the mono-gadolinized complex, and the removal of salts is useful to improve subsequent optional steps of treating the solution to remove precipitants.

[0050] The desalting step may be carried out until the conductivity of the solution is 5.0 mS / cm or less, preferably 1 mS / cm or less, and more preferably 0.8 mS / cm or less.

[0051] Step iii) of the manufacturing method of the present invention involves adding a precipitating agent to the intermediate solution from the step prior to iii) to precipitate the free gadolinium metal ions. In fact, the free gadolinium metal ions precipitate as gadolinium salts, and a solution of the gadolinium complex of formula I is obtained, in which the amount of free gadolinium metal complex is low, for example, the ppm amount described above. In order to precipitate the free gadolinium metal ions and avoid the formation of mono-gadolinized complexes, the precipitating agent is phosphate ions (PO4). 3- ), monohydrogen phosphate (HPO4) 2- ), dihydrogen phosphate (H2PO4) - ), orthophosphate (H3PO4), oxalate ion (C2O4) 2- ), hydrogen oxalate ion (HCl2O4 - The precipitant must be at least one selected from the group consisting of ), and oxalic acid (H2C2O4). Preferably, the precipitant is phosphate ions (PO4 3- ), oxalate ion (C2O4 2- ), and monohydrogen phosphate (HPO4) 2- At least one anion selected from the group consisting of ), more preferably a monohydrogen phosphate (HPO4) 2- )

[0052] The precipitation step (step iii)) removes excess free gadolinium metal ions that did not react in the previous complexation step (step ii)) from the solution by precipitation of the free gadolinium metal ions.

[0053] Precipitating agents can be added, for example, by mixing a solution containing the precipitating agent with the intermediate solution, or, for example, by directly adding the precipitating agent to the intermediate solution if the precipitating agent is contained in the precipitated salt.

[0054] As used herein, unless otherwise specified, the term “precipitated salt” refers to the salt added in step iii), comprising the precipitant as an anion and any suitable countercation. The precipitated salt is soluble at least in the intermediate solution and under the conditions of step iii), and can dissolve in the intermediate solution and release the precipitant. For example, a preferred precipitated salt is monohydrogen phosphate (HPO4) of the precipitant. 2- This is Na2HPO4, which contains ) as an anion and sodium as a countercation.

[0055] When the precipitant is added in step iii) by adding a precipitated salt containing the precipitant, suitable countercations of the precipitated salt include cations selected from, for example, alkali metals, alkaline earth metals, ammonium, and organic cations. For example, the countercations of the precipitated salt are selected from sodium and potassium; sodium is particularly preferred. The precipitated salt is preferably sodium phosphate (Na3PO4), potassium phosphate (K3PO4), sodium hydrogen phosphate (Na2HPO4), potassium hydrogen phosphate (K2HPO4), sodium dihydrogen phosphate (NaH2PO4), potassium dihydrogen phosphate (KH2PO4), sodium oxalate (Na2C2O4), potassium oxalate (K2C2O4), sodium hydrogen oxalate (NaHC2O4), and potassium hydrogen oxalate (KHC2O4) - Selected from the group consisting of ).

[0056] According to step iii) of the manufacturing method of the present invention, the precipitant is preferably added in an amount at least stoichiometric in relation to the free gadolinium metal ions in the intermediate solution. Advantageously, the precipitant is added in an amount of at least 1.1 moles, preferably 1.1 to 5 moles, more preferably 1.2 to 3 moles, even more preferably 1.4 to 2.5 moles, and most preferably 1.4 to 1.6 moles, per mole of gadolinium metal ions in the intermediate solution. As demonstrated in the experimental section by comparative examples, adding these preferred amounts of precipitant yields a solution containing both a low amount of free gadolinium metal ions (i.e., a lower amount of free gadolinium metal ions than defined above) and a low amount of mono-gadolinium complex (i.e., a lower amount of less than 550 ppm, preferably a lower LoQ of the mono-gadolinium complex (<400 ppm relative to the amount of gadolinium complex) as determined by the method used to determine the amount of the mono-gadolinium complex). Conversely, if the precipitating agent is added in a larger amount than the preferred amount described above in step iii), the resulting solution may contain a large amount of mono-gadolinium complex (i.e., more than 600 ppm).

[0057] If step iii) of the manufacturing method of the present invention is carried out by adding the preferred amount of precipitant specified above, the manufacturing method of the present invention preferably includes a further step of determining the amount of free gadolinium metal ions in the intermediate solution before adding the precipitant, so that the precipitant may be added in the preferred amount specified above. This determination step may be carried out by known methods for determining the amount of free gadolinium metal ions, for example, by the methods disclosed herein.

[0058] Step iii) is preferably carried out by maintaining the temperature of the solution within the range of 15 to 40°C, more preferably 20 to 30°C. After the precipitant is added in step iii), the reaction mixture is preferably maintained for 1 to 4 hours, preferably 1.5 to 3 hours, more preferably 2 hours, in the temperature range described above, for example, before carrying out any subsequent steps.

[0059] In preferred embodiments, during and / or after the addition of the precipitant in step iii), the pH is adjusted and / or maintained to a value of 4.5 or higher, preferably 4.7 or higher, more preferably 4.9 or higher, and even more preferably 5.5 or higher, for example, for the time and / or temperature described in the paragraph above. Preferably, this pH is maintained at least until the precipitated gadolinium salt is filtered off from the solution of the gadolinium complex. Also, as demonstrated by comparative examples in the following experimental section, the applicant has found that by precipitation of free gadolinium metal ions while adjusting and / or maintaining the pH to these values, a solution containing a low amount of the mono-gadolinized complex (for example, a solution containing less than 550 ppm, preferably less than 400 ppm, of the mono-gadolinized complex relative to the gadolinium complex) is obtained after an optional filtration step and before an optional further purification step.

[0060] In a further preferred embodiment, during and / or after the addition of the precipitant in step iii), the pH may be adjusted and / or maintained, for example, at the time and / or temperature described above, to be higher than the values ​​shown above and 10.0 or less, preferably 9.0 or less, more preferably 8.5 or less, even more preferably 7.5 or less, and most preferably 6.5 or less. Preferably, this pH is maintained at least until the precipitated gadolinium salt is filtered off from the solution of the gadolinium complex. The applicant has found, to their surprise, that operating below these pH values ​​reduces the amount of free gadolinium metal ions in the solution after the precipitation step and before any further purification steps.

[0061] According to a more preferred embodiment, during and / or after the addition of the precipitant in step iii), the pH may be adjusted and / or maintained in the range of 4.5 to 9.0, more preferably 4.7 to 8.5, even more preferably 4.9 to 7.3, most preferably 6 to 6.5 or 5.5 to 6.5, for example, for the time and / or temperature described above. Preferably, this pH is maintained at least until the precipitated gadolinium salt is filtered off from the solution of the gadolinium complex. The applicant has found, to their surprise, that by adjusting and / or maintaining the pH within the range shown above, it is possible to obtain a solution having particularly low content of free gadolinium metal ions and mono-gadolinized complexes (e.g., a solution with lower content compared to the same process in which the pH is not adjusted and / or maintained to such a pH) after an optional precipitation step and before an optional further purification step.

[0062] pH adjustment can be performed by adding a suitable acid, such as HCl, or a suitable base, such as NaOH, to the solution. This adjustment is particularly useful for offsetting any pH changes that may occur due to the addition of a precipitant. It is clear that pH adjustment is not necessary if the addition of a precipitant does not cause a pH change that causes the pH of the resulting solution to fall outside the preferred range disclosed above (for example, because the pKa of the precipitant is within the preferred values ​​above, and / or because the pH of the resulting solution does not fall outside the preferred range disclosed above due to the addition of a small amount of precipitant).

[0063] Preferably, the pH at the preferred value disclosed above is maintained at least until the precipitated gadolinium salt is filtered off from the solution of the gadolinium complex.

[0064] In a more preferred embodiment, after step iii), the manufacturing method of the present invention further comprises filtering the solution of the obtained gadolinium complex to remove the gadolinium salt from the solution, thereby separating the gadolinium salt from such solution. This filtration step can be carried out by filtration methods known in the art, for example, by using a pharmaceutical membrane filter.

[0065] In a more preferred embodiment, the manufacturing method of the present invention includes a further step of treating the solution of the gadolinium complex of formula I obtained after step iii) to remove any precipitant (if present) that did not react with free gadolinium metal ions to form a gadolinium salt. This treatment step does not remove either free gadolinium metal ions or the mono-gadolinized complex.

[0066] This processing step can be carried out, for example, by loading a solution of the gadolinium complex into an ion exchange resin, preferably at a flow rate of 1 to 3 BV / hour. Alternatively, or in addition to loading the complex into an ion exchange resin, the processing step may be carried out by (A) adding gadolinium metal ions Gd to the solution of the gadolinium complex. 3+ This can be carried out by adding a different precipitated cation to precipitate the precipitant or anion produced by the precipitant, thereby precipitating at least such anion together with the precipitated cation as a salt, and removing the salt thus formed by a filtration step such as that disclosed above (B). Advantageously, a single filtration step may be performed to remove both the gadolinium salt and the salt formed by the precipitant and the precipitated cation.

[0067] As used herein, unless otherwise specified, the term “precipitated cation” means gadolinium metal ions Gd added during any processing step of a solution of the gadolinium complex of formula I. 3+ This refers to a cation different from the one mentioned above. A precipitated cation can, at least under the conditions of the reaction mixture during the addition of the precipitated cation, together with the precipitant or anion produced by the precipitant, form a salt, which is a solid physical form.

[0068] The addition of the precipitated cation can be carried out, for example, by adding a soluble salt containing the precipitated cation as its cation to a solution of the gadolinium complex of formula I, and / or by mixing the solution containing the precipitated cation with the solution of the gadolinium complex of formula I.

[0069] Precipitated cations can be preferably selected by those skilled in the art based on the salt formed by the ionic bond between the precipitated cation and the anion which is or is generated by the precipitant. In fact, a suitable precipitated cation can be used as long as the salt formed by the precipitated cation and such anion precipitates under the conditions of the reaction mixture at least during the addition of the precipitated cation, thereby at least some of the precipitated salt is removed, for example, by filtration. For example, precipitated cation Ca 2+ The anions and cations of the gadolinium complex are added to the solution by the optional processing steps disclosed above: when the pH of the solution reaches about 9, such anions and cations of Ca precipitate. 2+ The salt formed by this process precipitates and is later removed, for example, by filtration. In this example, precipitated cation Ca 2+ It is added to a solution of the gadolinium complex of formula I as a soluble salt, or preferably as a hydroxide such as Ca(OH)2, and when added to the solution it dissolves and thus precipitates the cation Ca 2+ It releases.

[0070] In one embodiment, the method for providing a solution of the gadolinium complex of the present invention includes at least one further purification step after step iii), preferably after a processing step (if performed) for removing the precipitant. This further purification step is useful for further reducing the amount of residual free gadolinium metal ions present after precipitation in step iii) in order to provide a solution of the gadolinium complex with the lowest possible content of free gadolinium metal ions. Specifically, according to this embodiment of the manufacturing method of the present invention, most of the free gadolinium metal ions are removed by precipitation step iii) (where the amount of free gadolinium metal ions is reduced from several thousand ppm to several hundred or even tens of ppm relative to the gadolinium complex), and a smaller amount of free gadolinium metal ions are removed by at least one further purification step.

[0071] For example, this further purification step involves loading the gadolinium complex solution onto a suitable resin, such as an adsorbent resin (e.g., Amberlite XAD1600), thereby removing any remaining free gadolinium metal ions from the solution. Preferably, before loading the solution onto the resin, the solution is concentrated until the amount of gadolinium complex is in the range of 15-30% w / w, more preferably 20-25% w / w (e.g., by distilling the aqueous solvent under vacuum).

[0072] In further embodiments, a method for providing a solution of the gadolinium complex of the present invention after step iii) and optionally after at least one further purification step includes a step of treating the solution of the gadolinium complex with carbon. This step enables the removal of endotoxins and promotes decolorization of the solution.

[0073] In another aspect, the present invention relates to a solution of the gadolinium complex of formula I (wherein R is as defined above), or compound 1, which can be obtained by any embodiment of the method for producing the solution disclosed herein. Preferably, in the solution of the present invention, which can be obtained by any embodiment of the method for producing the present invention disclosed herein, the amount of free gadolinium metal ions is less than 350 ppm, preferably less than 150 ppm, more preferably less than 100 ppm, and even more preferably less than 80 ppm, relative to the amount of the gadolinium complex, and / or the amount of the mono-gadolinium complex is less than 550 ppm, preferably less than 400 ppm, relative to the amount of the gadolinium complex. A solution of the gadolinium complex of formula I (wherein R is as defined above), or compound 1, in which the content of free gadolinium metal ions and / or the mono-gadolinium complex is as described above, is also a further aspect of the present invention.

[0074] In a further embodiment, the present invention relates to Formula I [ka] (In the formula, R is as defined above.) A method for producing an isolated gadolinium complex shown in or compound 1, comprising a process for producing a solution of the gadolinium complex disclosed herein by any embodiment thereof, and further step iv): iv) Steps to isolate the gadolinium complex and Includes.

[0075] The method for producing isolated gadolinium complexes of the present invention enables the acquisition of the isolated gadolinium complexes disclosed herein by a robust and efficient method suitable for large-scale production.

[0076] The isolation step (step iv)) can be carried out by any suitable isolation method known to those skilled in the art that enables the separation of the complex from the solvent of the solution obtained in step iii).

[0077] For example, the isolation step (step iv) is carried out by drying a solution of the gadolinium complex of formula I (or compound 1), optionally under vacuum, as disclosed in WO 2017 / 098044, for example. The crude complex thus obtained is then further dried (e.g., in an oven), thereby obtaining the gadolinium complex as a powder solid.

[0078] In a further embodiment, the present invention relates to Formula I [ka] (In the formula, R is as defined above.) An isolated gadolinium complex represented by or compound 1, which can be obtained by any embodiment of the method for producing an isolated gadolinium complex disclosed herein.

[0079] In a further embodiment, the present invention relates to formula Ib [ka] (In the formula, R is a C3-C3 group containing at least two hydroxyl groups) 12 It is a hydroxyalkyl group, and preferably R is For example, formula [ka] Pentyl-tetraol and formula [ka] Hexyl-pentaol A C5-C7 polyol selected from; n is 1 or 2, preferably n is 1; m is 1, 2, 3, 4, 5, or 6, preferably m is 1; R 1(The alkyl group is C1-C6 alkyl, preferably C4 alkyl, and more preferably t-butyl.) Deprotect the protected dimer ligand shown by Formula Id [ka] (In the formula, R, n, and m are as defined above with respect to formula Ib.) This is a method for obtaining a solution of the corresponding dimer ligand shown, The following steps: a) A step of providing a solution, preferably an aqueous solution, of a protected dimer ligand; b) A step of adding an acid, preferably an inorganic acid, to the solution from the previous step to lower its pH; c) During and / or after step b), heating and / or maintaining the temperature of the reaction mixture to a temperature higher than 40°C, preferably higher than 40°C and up to 60°C, more preferably in the range of 45 to 55°C, to deprotect the protected dimer ligand, thereby obtaining a solution containing the dimer ligand; and d) Depending on the case, a step of neutralizing the dimer ligand by adding a base such as NaOH to the solution containing the dimer ligand obtained in step c), thereby protonating the carboxyl group of the dimer ligand. Includes.

[0080] According to a preferred embodiment of the deprotection method, in formulas Ib and Id, n and m are independently 1 or 2, more preferably both n and m are 1; in this latter more preferred case, formula Id corresponds to formula Ia described above.

[0081] According to a more preferred embodiment of the deprotection method, the protected dimer ligand is compound 1b [ka] The resulting solution contains the corresponding dimer ligand of compound 1a [ka] That is the case.

[0082] As shown in the Experiment section, this deprotection method, specifically step c), is very advantageous because it allows for deprotection in a very short time (specifically, less than 24 hours, for example, 8 to 20 hours, preferably 12 to 18 hours, more preferably 16 hours).

[0083] Furthermore, this deprotection method, specifically step c), deprotects the protected dimerized ligand by using a small amount of acid in step b). In fact, 10 to 45 moles, preferably 10 to 35 moles, and more preferably 15 to 25 moles of acid (e.g., those mentioned above, preferably HCl) per mole of protected dimerized ligand may be used in this deprotection method. This has the advantage of saving reagents and reducing salt formation during the deprotection method. For example, if HCl is used as the acid in step b), using a small amount of HCl reduces the amount of NaCl salt formed later when NaOH is optionally used in step d) to neutralize the dimerized ligand; the same applies if other acids are used in step b).

[0084] Preferably, the acid added in step c) is an inorganic acid such as H2SO4, H3PO4, HCl, or HBr. Inorganic acids containing monovalent negatively charged counterions, such as HCl and HBr, are particularly preferred because they do not tend to interact with free gadolinium metal ions and are more readily removed during the purification process (e.g., by nanofiltration), especially when used upstream of the method for producing a solution of the gadolinium complex as detailed herein by a deprotection method.

[0085] Due to the many advantages of this deprotection method, the dimer ligand solution of the method for producing a gadolinium complex solution described herein is preferably provided by performing the deprotection method disclosed herein by any embodiment, particularly when both m and n of formulas Ib and Id are 1, or when the protected dimer ligand is compound 1b.

[0086] According to one embodiment of the deprotection method, when HCl is used as the acid, HCl is added to the solution in step b) as a 34% w / w aqueous hydrochloric acid solution.

[0087] According to a preferred embodiment of the deprotection method, the initial concentration of the protected dimer ligand in the solution of step a) is in the range of 5% to 20% (w / w), preferably in the range of 12% to 18% (w / w).

[0088] According to a preferred embodiment of the deprotection method, optional step d) (neutralization of the dimer ligand) may be carried out by adjusting the pH of the reaction mixture to a value of 4 to 7, preferably 5 to 6, more preferably 5.3 to 5.7, and even more preferably 5.5. This is preferably done by adding a suitable amount of base, NaOH, etc., to reach the above pH.

[0089] After step c) of the deprotection method, i.e., C1-C6 alkyl group R 1 (or, if compound 1b is a protected dimer ligand, C4 alkyltBu) after hydrolysis, the corresponding deprotected dimer ligand and R 1 A solution containing the corresponding alcohol of (or tBu) is obtained. Therefore, according to a more preferred embodiment, after step c), preferably after optional step d) (if performed), tBuOH(R 1 (If it is tBu) etc. 1The corresponding alcohol is removed from the solution containing the deprotected dimerized ligand, preferably by distillation of such solution. According to a preferred embodiment, the solution containing the dimerized ligand is distilled until the final concentration of the dimerized ligand is in the range of 8% to 12% (w / w), more preferably 9% to 11% (w / w), and even more preferably 10% (w / w).

[0090] Experiment Section The following examples further illustrate the present invention and do not imply any limitation of its scope. [Examples]

[0091] Example 1 - Deprotection of dimeric ligand Protected dimeric ligand compound 1b in water (186.08 g, 0.141 mol) [ka] To the mixture (1501.56 g, concentration 12.4% (w / w)), a 34% w / w aqueous hydrochloric acid solution (435.65 g, 4.06 mol, 30 equivalent mol per compound 1b) is added while maintaining the temperature at 30°C. At the end of the addition, the mixture is heated to 50°C and held under stirring for 16 hours. After complete deprotection, a 30% w / w aqueous sodium hydroxide solution is added to obtain compound 1a by pH 5.6. The t-butanol formed as a by-product is removed by distillation. The solution containing compound 1a is concentrated by distillation under vacuum at 50°C to a final concentration of approximately 10% (w / w).

[0092] Example 2 - Preparation of a solution of a dimeric gadolinium complex The dimeric ligand obtained in Example 1 is 1-[bis[2-hydroxy-3-[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododeca-1-yl]propyl]amino]-1-deoxy-D-glucitol (compound 1a) [ka] Place the solution into the first reactor and heat to 40°C. Add gadolinium chloride solution (2.1 moles per mole of compound 1a) while maintaining the temperature in the range of 37-43°C. At the end of the addition, add 10% w / w sodium hydroxide aqueous solution to adjust the pH to 5.5. Maintain the mixture at 40°C for 3 hours. Gadolinium complex [μ-[1-[bis[2-(hydroxy-κO)-3-[4,7,10-tris[(carboxy-κO)methyl]-1,4,7,10-tetraazacyclododeca-1-yl-κN 1 κN 4 κN 7 κN 10 ]propyl]amino]-1-deoxy-D-glucitrate(6-)]]digadolinium (compound 1) [ka] An intermediate solution containing the above is obtained in this manner, and the amounts of the mono-gadolinium complex (mono-Gd) and free gadolinium metal ions (free Gd) are measured. Next, the salts produced in Example 1 and the complexation step are removed by nanofiltration; diafiltration is performed until the conductivity value is less than 1.0 mS / cm. This desalting step does not remove free gadolinium metal ions or the mono-gadolinium complex. At the end of nanofiltration, the mixture is concentrated to 10-12% w / w, and 1.5 mol / mol of Na2HPO4 is added to the solution relative to the free gadolinium metal ions (free Gd). After the addition of Na2HPO4, the pH of the solution is measured for each test and is shown in Table I below ("pH at start" column); the formation of a white precipitate is observed. Next, the pH is adjusted to the value shown in the "pH at end" column of Table I. The mixture is held under stirring for 2 hours. Finally, the suspension is filtered, and the amounts of the mono-gadolinium complex (mono-Gd) and free gadolinium metal ions (free Gd) are measured. These amounts, as well as the amounts obtained after complexation, are shown in Table I below. [Table 1] Based on the results shown in Table I, a significant decrease in the amount of free Gd can be observed for all of the tests 1-11 shown above. All solutions in tests 1-5 and 7-11 contain an unquantifiable amount of mono-Gd, i.e., less than 400 ppm of mono-Gd; test 6 has a higher amount of mono-Gd than LoQ at pH 4.54, i.e., 538 ppm per compound 1. Table I also shows that a lower amount of mono-Gd than LoQ and a low amount of free Gd can be obtained while maintaining the pH within the range of 4.9-8.3.

[0093] Example 3 - Removal of residual phosphate The solutions from Tests 1-9 obtained in Example 2 were loaded onto an ion exchange resin (Diaion PA308, pre-activated) at a flow rate of 1-3 BV / hour. Most of the residual phosphate was removed from the solution in this manner.

[0094] Example 4 - Removal of residual phosphate To the solutions of Tests 1-9 obtained in Example 2, Ca(OH)2 (1 mol / mol relative to Na2HPO4) was added to raise the pH to approximately 9. Thus, the formation of an insoluble white precipitate containing precipitated anions (but not gadolinium) was observed. The mixture was held under stirring for 2 hours. Next, the suspension was filtered, and the cake was washed with water, thus achieving the removal of most of the residual phosphate.

[0095] Example 5 - Further purification and isolation of the dimeric gadolinium complex The solutions from Example 3 were placed in the second reactor, and the pH of each solution was adjusted to 5.7-6.3 by adding dilute HCl. The water was then distilled under vacuum at 45-55°C until the gadolinium complex analysis result was approximately 20-25% w / w. The concentrated solution was loaded into a pre-activated Amberlite XAD1600 (resin amount: 30 mL / g of product) at a flow rate of 0.5 BV / hour. Purification was carried out using water and a mixture of isopropanol and water. The high-purity fraction (evaluated by HPLC-FLD / UV) is placed in a separate reactor. After pre-concentration, a carbon treatment is performed. The suspension is filtered to remove the carbon, and the solution is concentrated to a concentration of 25% w / w under vacuum at 45-55°C. Gadolinium complex compound 1 [ka] The gadolinium complex compound 1 is finally isolated by drying the solution containing under vacuum.

[0096] Example 6 - Precipitation of free gadolinium ions using disodium oxalate (Comparative Example) For comparison, we conducted an experiment using an excess amount of a precipitating agent such as sodium oxalate in the precipitation process. In this case, we added disodium oxalate and then adjusted the pH. The amounts of mono-gadolinium complex (mono-Gd) and free gadolinium metal ions (free Gd) were measured in a 20% w / w solution of compound 1 containing free gadolinium, obtained by complexation under the reaction conditions of Example 1, and are shown in Table IV below. Next, an excess amount of disodium oxalate was added (10 mol per 1 mol of free Gd). After the addition of oxalate, the pH rises from 5.91 to 8.45, and the formation of a white solid is immediately observed. Next, the pH is lowered to approximately 6 using 1N HCl and maintained at that level. At the end of the sodium oxalate addition, the mixture is cooled to 5°C and maintained at this temperature for 2 hours. After filtering the suspension, the content of mono-gadolinium complexes and free gadolinium metal ions was measured and is shown in Table IV. [Table 2] As shown in Table IV above, precipitation of free gadolinium metal ions using oxalate provides a solution containing a higher amount of mono-gadolinized complex than LoQ. As mentioned above, the mono-gadolinized complex does not exhibit the desirable properties of the (di-gadolinized)Gd(III) complex, e.g., complex compound 1. Therefore, precipitation of free gadolinium metal ions using an excess amount of precipitant, such as an excess amount of oxalate, provides a solution containing an amount of mono-gadolinized complex exceeding LoQ, i.e., more than 400 ppm.

[0097] Example 7 - Precipitation of free gadolinium ions using tripotassium phosphate The content of mono-gadolinium complex (mono-Gd) and free gadolinium metal ions (free Gd) in a 10% w / w solution of compound 1 containing free gadolinium, obtained by complexation under the reaction conditions of Example 2, is measured. Next, K3PO4 is added to the solution (1.5 mol relative to the moles of free Gd). After the addition of phosphate, the pH rises from 5.42 to 9.00, and the formation of a white solid is immediately observed. The mixture is maintained at pH 9.00 at room temperature for 2 hours under stirring, and then the solid is filtered to obtain the solution. The content of free gadolinium metal ions (free Gd) and mono-gadolinium complexes (mono-Gd) is measured and shown in Table V below. [Table 3] Based on the results shown in Table V, a significant decrease in the amount of free Gd can be observed by precipitation using phosphate as a precipitating agent. Furthermore, the amount of mono-Gd in the solution is unquantifiable (i.e., less than 400 ppm). In addition, Table V shows that at pH 9.0, it is possible to reduce the amount of free Gd to a low level and the amount of mono-Gd to less than LoQ.

[0098] Example 8 - Precipitation of free gadolinium ions using potassium bitartrate (Comparative example) To a 10% w / w solution of compound 1 containing free gadolinium, obtained by complexation under the reaction conditions of Example 2, potassium bitartrate was added (2 moles per 1 mole of free Gd), and a slight suspension was observed. After the addition of bitartrate, the pH decreases from 5.42 to 4.21. The mixture is maintained at room temperature for 2 hours under stirring, and then the solid is filtered to obtain the solution. The content of free gadolinium metal ions (free Gd) and mono-gadolinium complexes (mono-Gd) is measured and shown in Table VI below. [Table 4] As shown in Table VI above, precipitation of free gadolinium metal ions using bitartrate yields a solution containing high amounts of free gadolinium metal ions, which is unsatisfactory. This is because such high amounts of free gadolinium metal ions cannot be efficiently and effectively reduced to a suitable pharmaceutically acceptable level by, for example, at least one further purification step.

[0099] Example 9 - Precipitation of free gadolinium ions using disodium hydrogen citrate (Comparative Example) To a 10% w / w solution of compound 1 containing free gadolinium, obtained by complexation under the reaction conditions of Example 2, disodium hydrogen citrate is added (1.5 mol per 1 mol of free Gd). No precipitate was observed, and therefore the test is terminated. The absence of precipitate suggests that the amount of free gadolinium metal ions in the solution of compound 1 is too high and unsatisfactory. Such a high amount of free gadolinium metal ions cannot be efficiently and effectively reduced to a suitable pharmaceutically acceptable level, for example, by at least one further purification step.

[0100] Example 10 - Precipitation of free gadolinium ions using sodium acetate (Comparative example) Sodium acetate is added to a 10% w / w solution of compound 1 containing free gadolinium, obtained by complexation under the reaction conditions of Example 2 (4.5 mol per 1 mol of free Gd). No precipitate was observed, and therefore the test is terminated. The absence of precipitate suggests that the amount of free gadolinium metal ions in the solution of compound 1 is too high and unsatisfactory. Such a high amount of free gadolinium metal ions cannot be efficiently and effectively reduced to a suitable pharmaceutically acceptable level, for example, by at least one further purification step.

[0101] Example 11 - Precipitation of free gadolinium ions as Gd(OH)3 by basicization (Comparative Example) To a 16% w / w solution of compound 1 containing 7000 ppm of free gadolinium per compound 1, add a 30% NaOH solution until the pH reaches 8.65. No precipitate was observed. The above tests were repeated using several solutions containing (i) various concentrations of compound 1 (specifically, compound 1 at concentrations of 16-20% w / w) and (ii) various amounts of free gadolinium metal ions (specifically, 230-25,000 ppm of free gadolinium metal ions per compound 1). In all cases, no precipitate is observed. Therefore, although gadolinium ions are known to precipitate as Gd(OH)3 under basic conditions, this basification procedure cannot be used to suitably reduce free gadolinium metal ions in solutions of gadolinium complexes as defined herein, such as a solution of compound 1.

[0102] Example 12 - Precipitation of free gadolinium ions using disodium oxalate The content of mono-gadolinium complex (mono-Gd) and free gadolinium metal ions (free Gd) is measured in a 10% w / w solution of compound 1 containing free gadolinium, obtained by complexation under the reaction conditions of Example 2. Next, disodium oxalate is added to the solution (2.25 mol / mol relative to free Gd). After adding the oxalate, the pH rises from 5.56 to 7.78, and the formation of a white solid is immediately observed. Next, the pH is lowered to 6.43 using 1N HCl. At the end of the mixing, the mixture is maintained at room temperature for 2 hours. After filtering the suspension, the content of mono-gadolinium complexes and free gadolinium metal ions is measured. The content of mono-gadolinium complexes (mono-Gd) and free gadolinium metal ions (free Gd) is shown in Table VII below. [Table 5] Table VII clearly shows that by performing the above tests (particularly those involving a suitable amount of oxalate as a precipitating agent), a solution with a very low free Gd content and a mono-Gd content lower than LoQ can be obtained.

[0103] HPLC Procedure 1 - Determination of the amount of free gadolinium metal ions (free -Gd) The amount of free gadolinium metal ions relative to the amount of gadolinium complex (e.g., compound 1) is determined by reverse-phase HPLC (high-performance liquid chromatography) equipped with an FLD (fluorescence detector). EDTA (ethylenediaminetetraacetic acid) is used as the mobile phase to form a Gd(EDTA) complex from the free Gd(III) present in the sample. chromatography conditions The equipment includes an Agilent 1100 liquid chromatograph equipped with a solvent delivery system, a refrigerated autosampler at 5°C, a column thermostat, a degassing system, and a fluorescence detector or equivalent. Column: YMC-PACK ODS-AQ, 250 x 4.6 mm, 5 μm particle size (YMC, cod.AQ12S05-2546WT) Temperature: 40℃ Mobile phase: A: CH3COONH4 (1.5g / L), EDTA (0.55g / L) B: methanol Flow rate: 1mL / min Detection (FLD): Wavelength excitation = 275 nm Wavelength emission = 314nm Execution time: 25 minutes Acquisition time: 6 minutes Injection volume: 20μL Reference peak: Gd(EDTA) Elution: Gradient Time (minutes) %B 0 0 5 0 10 50 15 50 16 0 25 0

[0104] Solution preparation mobile phase Accurately weigh 1.5 g of ammonium acetate into a 1000 mL volumetric flask, dissolve it in purified water, add 0.70 g of anhydrous ethylenediaminetetraacetate disodium salt, and then dilute to the desired volume with purified water. Diluted solution Accurately weigh 3 g of ammonium acetate into a 1000 mL volumetric flask, dissolve it in purified water, add 1.4 g of anhydrous ethylenediaminetetraacetate disodium salt, and then dilute to the desired volume with purified water. Blank solution Transfer 0.5 mL of purified water to a vial and add 0.5 mL of the diluent. Mix well and inject directly into the chromatographic system. Reference solution Weigh 0.32 g of gadolinium acetate hydrate (expressed on anhydrous basis; determine water content before use) into a 50 mL volumetric flask and dilute to the desired volume with the mobile phase. The gadolinium concentration is 3 mg / mL. Transfer 0.1 mL of this solution to a 100 mL volumetric flask and dilute to the desired volume using the mobile phase. The gadolinium concentration is 0.003 mg / mL. LOQ solution Transfer 1 mL of the reference solution to a 5 mL volumetric flask and dilute it to the desired volume with the mobile phase. The gadolinium concentration is 0.0006 mg / mL. Test solution Accurately weigh 600 mg of the test sample into a 10 mL volumetric flask (expressed on anhydrous basis) and dilute to the desired volume with purified water. The concentration of the dimeric gadolinium complex of formula I (e.g., compound 1) is approximately 60 mg / mL. Transfer 0.5 mL of this solution to a vial and add 0.5 mL of the diluent. Mix the sample thoroughly. After dilution, immediately place the sample in a refrigerated autosampler (5-8°C) and inject the sample within 5 minutes of dilution. The final concentration of the dimeric gadolinium complex of formula I (e.g., compound 1) is approximately 30 mg / mL.

[0105] Analysis Sequence Blank n=1 LOQ solution n=1 Reference solution n=6 Test solution n=6 Reference solution n=1

[0106] System Conformity Testing A System Suitability Test (SST) will be performed each time this manufacturing method is applied. - After equilibrating the chromatography system, inject a blank solution once and verify that no interference peaks are present. - Inject the LOQ solution once. If the Gd(EDTA) peak has an S / N ratio of ≥ 10, the results of the analytical sequencing are useful. - Inject the first reference solution six times and verify whether the following requirements regarding the Gd(EDTA) peak are met: - Area reproducibility of Gd(EDTA) expressed as a percentage Relative standard deviation (RSD%, n=6) ≤ 10% - Reproducibility of retention time of Gd(EDTA) peak expressed as a percentage Relative standard deviation (RSD%, n=6) ≤ 2% - Symmetry factor T related to the Gd(EDTA) peak, Calculated using Equation 1: 0.7~2.0 T=w 0.05 / 2f expression 1 During the ceremony: w 0.05= Width (min) at 1 / 20 of the peak height f = Distance (min) between the perpendicular line drawn from the peak maximum value and the peak rising edge at 1 / 20 of the peak height

[0107] Calculation The percentage content, free Gd%, is calculated by Equation 2:

Number

[0108] HPLC Procedure 2 - Determination of the amount of mono - gadolinated complex (mono - Gd) The content of mono - Gd impurities in the dimer complex of Formula I (e.g., Compound 1) is quantified by reverse - phase HPLC using any FLD detector in the same chromatography. The quantification of the specified impurity mono-Gd (specifically, the mono-Gd complex of compound 1a having only one gadolinium metal ion) is performed by FLD detection using the reference sample mono-Gd as a sodium salt. The mono-Gd sodium salt (reference sample) can be obtained by complexing the dimeric ligand compound 1a with a gadolinium ion less than the stoichiometric amount to obtain mono-Gd, adjusting the pH to neutral with NaOH, and then concentrating it down to the residue for isolation. chromatography conditions Equipment: Solvent delivery system, autosampler, column thermostat, degassing unit, UV diode array detector and fluorescence detector. HPLC Agilent 1100 equipped with 2475 Waters or equivalent. Column: Xselect® HSS T3, 3.5 μm, 150 × 3.0 mm (Waters, Part No. 186004781) Temperature: 40℃ Mobile phase: Solvent A: Mobile phase A (40 mM potassium phosphate in water - 0.02 mM EDTA, pH 6.2) Solvent B: Mobile phase B (solvent A / acetonitrile, 60 / 40 v / v) Flow rate: 0.35mL / min Detection (FLD): Wavelength excitation (λex) = 275 nm Wavelength emission (λem) = 314 nm Detection (UV): Wavelength = 210nm / Bw: 8nm; Ref. Wavelength = 480nm / Bw: 80nm Execution time analysis: 50 minutes Acquisition time: 32 minutes Injection volume: 10μL Eluition: Gradient Time (minutes) %B 0 0 4 0 20 15 25 15 30 100 40 100 43 0 50 0

[0109] Solution preparation Mobile phase A In a 2000 mL volumetric flask: - 8.56 g potassium dihydrogen phosphate - 3.97 g of dipotassium hydrogen phosphate trihydrate - 0.015g of Titriplex(registered trademark) III (EDTA disodium salt) Accurately measure out the required amount, then dilute it to the desired volume with purified water. Filter it through a 0.22 μm membrane filter. Mobile phase B Transfer 600 mL of mobile phase A to a 1000 mL volumetric flask and dilute with acetonitrile to the desired volume. Mix thoroughly. CaCl 2 Solution Accurately measure 165 mg of CaCl2 (expressed on anhydrous basis) into a 50 mL volumetric flask and dilute it to the desired volume with purified water. The concentration is approximately 3.3 mg / mL. Mono-Gd storage solution Accurately measure 25 mg of mono-Gd sodium salt (expressed on anhydrous basis and purity) into a 50 mL volumetric flask and dilute to the desired volume with purified water. The concentration of mono-Gd is approximately 0.5 mg / mL. Weight of mono-Gd = Weight of mono-Gd sodium salt × 1140.31 / 1162.29 Reference solution for mono-Gd Accurately transfer 0.45 mL of mono-Gd storage solution to a 5 mL volumetric flask. Add 1 mL of CaCl2 solution and dilute to the correct volume with purified water. The standard concentration is 0.045 mg / mL. LoQ solution of mono-Gd Accurately transfer 0.1 mL of mono-Gd storage solution to a 5 mL volumetric flask. Add 1 mL of CaCl2 solution and dilute to the desired volume with purified water. The concentration of mono-Gd is approximately 0.01 mg / mL. Blank solution Transfer 0.8 mL of the aqueous solution to a vial and add 0.2 mL of CaCl2 solution. Mix well. Test solution Accurately weigh 125 mg of the test sample (expressed on anhydrous basis) into a 5 mL volumetric flask. Add 1 mL of CaCl2 solution and dilute to the desired volume with purified water. The concentration of compound 1 is approximately 25 mg / mL.

[0110] Analysis Sequence Blank n=1 LoQ solution n=1 Reference solution n=6 Test solution n=6 Reference solution n=1

[0111] calculation The percentage content of mono-Gd is calculated using Equation 3 after obtaining FLD data.

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Claims

1. Equation I 【Chemistry 1】 (wherein R is a C containing at least two hydroxyl groups) ３ ~C １２ (It is a hydroxyalkyl group.) A method for producing a solution of the gadolinium complex shown, i) Equation Ia 【Chemistry 2】 (In the formula, R is as defined above.) A step of providing a solution of the dimeric ligand shown, ii) Adding more than 2 moles of gadolinium metal ions per 1 mole of dimeric ligand to the solution from the previous step to complexize the dimeric ligand provided in step i), thereby obtaining an intermediate solution containing the gadolinium complex of formula I. iii) In the intermediate solution of the previous step, in order to precipitate free gadolinium metal ions as a gadolinium salt, phosphate ions (PO₄ ３－ ), hydrogen phosphate ions (HPO ４ ２－ ), dihydrogen phosphate ions (H ２ PO ４ － ), orthophosphoric acid (H ３ PO ４ ), oxalate ions (C ２ O ４ ２－ ), hydrogen oxalate ions (HC ２ O ４ － ), and oxalic acid (H ２ C ２ O ４ ) are added as a precipitating agent, thereby precipitating free gadolinium metal ions as a gadolinium salt to obtain a solution of the gadolinium complex of Formula I. Includes, A method for producing a product, wherein the precipitant is added in an amount of 1.1 to 5 moles per mole of free gadolinium metal ions in the intermediate solution, and the pH is adjusted and / or maintained to a value of 4.7 or higher during and / or after the addition of the precipitant in step iii).

2. R in equations I and Ia is C ５ ~C ７ The method for producing polyhydroxyalkyl according to claim 1.

3. The aforementioned polyhydroxyalkyl is, 【Transformation 3】 Tetrahydroxypentyl and formula shown in 【Chemistry 4】 The manufacturing method according to claim 2, selected from pentahydroxyhexyl represented by .

4. The gadolinium complex is given by the following formula 【Transformation 5】 Complex compound 1 having the following characteristics: The dimeric ligand is given by the following formula: 【Transformation 6】 The manufacturing method according to claim 3, wherein the ligand compound 1a has the ligand compound 1a having the ligand compound 1a.

5. The precipitating agent is phosphate ions (PO ４ ３－ ), oxalate ion (C ２ O ４ ２－ ) and monohydrogen phosphate (HPO ４ ２－ A manufacturing method according to any one of claims 1 to 4, selected from the group consisting of ).

6. The manufacturing method according to any one of claims 1 to 4, wherein the precipitant is added to the intermediate solution by adding a precipitated salt containing the precipitant.

7. The aforementioned precipitated salt is sodium phosphate (Na ３ PO ４ ), potassium phosphate (K ３ PO ４ ), sodium hydrogen phosphate (Na ２ HPO ４ ), potassium hydrogen phosphate (K ２ HPO ４ ), sodium dihydrogen phosphate (NaH ２ PO ４ ), potassium dihydrogen phosphate (KH ２ PO ４ ), sodium oxalate (Na ２ C ２ O ４ ), potassium oxalate (K ２ C ２ O ４ ), sodium hydrogen oxalate (NaHCl ２ O ４ ), and potassium hydrogen oxalate (KHC ２ The manufacturing method according to claim 6, selected from the group consisting of O4.

8. The manufacturing method according to any one of claims 1 to 4, wherein the precipitating agent is added in an amount of 1.2 to 3 moles per mole of gadolinium metal ions in the intermediate solution.

9. The manufacturing method according to claim 8, wherein the precipitating agent is added in an amount of 1.4 to 2.5 moles per mole of gadolinium metal ions in the intermediate solution.

10. The manufacturing method according to claim 9, wherein the precipitating agent is added in an amount of 1.4 to 1.6 moles per mole of gadolinium metal ions in the intermediate solution.

11. The manufacturing method according to claim 1, wherein the pH is adjusted and / or maintained to a value of 4.9 or higher during and / or after the addition of the precipitating agent in step iii).

12. The manufacturing method according to claim 11, wherein the pH is adjusted and / or maintained to a value of 5.5 or higher during and / or after the addition of the precipitating agent in step iii).

13. The manufacturing method according to any one of claims 1 to 4, wherein the pH is adjusted and / or maintained to a value of 10.0 or less during and / or after the addition of the precipitating agent in step iii).

14. The manufacturing method according to claim 13, wherein the pH is adjusted and / or maintained to a value of 9.0 or less during and / or after the addition of the precipitating agent in step iii).

15. The manufacturing method according to claim 14, wherein the pH is adjusted and / or maintained to a value of 8.5 or less during and / or after the addition of the precipitating agent in step iii).

16. The manufacturing method according to claim 15, wherein the pH is adjusted and / or maintained to a value of 7.5 or less during and / or after the addition of the precipitating agent in step iii).

17. The manufacturing method according to claim 16, wherein the pH is adjusted and / or maintained to a value of 6.5 or less during and / or after the addition of the precipitating agent in step iii).

18. The solution of the dimer ligand provided in step i) is used in the following steps: a) Equation Ib 【Transformation 7】 (wherein R is a C containing at least two hydroxyl groups) ３ ~C １２ It is a hydroxyalkyl, n and m are 1; R １ is C １ ~C ６ (It is alkyl.) A step of providing a solution of the protected dimerized ligand shown; b) A step of adding acid to the solution from the previous step to lower its pH; c) During and / or after step b), heating and / or maintaining the temperature of the reaction mixture to a temperature higher than 40°C to deprotect the protected dimer ligand, thereby obtaining a solution containing the dimer ligand; and d) If applicable, a base is added to the solution containing the dimer ligand obtained in step c) to protonate the carboxyl group of the dimer ligand. Obtained by, The manufacturing method according to any one of claims 1 to 4.

19. The manufacturing method according to any one of claims 1 to 4, further comprising at least one further purification step after step iii) in order to further reduce the amount of residual free gadolinium metal ions after step iii).

20. The method for producing the gadolinium complex according to any one of claims 1 to 4, wherein, after performing step iii) and before performing at least one optional further purification step, the amount of free gadolinium metal ions in the solution of the gadolinium complex is less than 350 ppm relative to the amount of the gadolinium complex, and / or the amount of mono-gadolinized complex in the solution of the gadolinium complex is less than 550 ppm relative to the amount of the gadolinium complex.

21. Equation I 【Transformation 8】 (wherein R is a C containing at least two hydroxyl groups) ３ ~C １２ (It is a hydroxyalkyl group.) A method for producing an isolated gadolinium complex shown in, A process for producing a gadolinium complex solution according to any one of claims 1 to 4, and a further step iv): iv) A step of isolating the gadolinium complex from the solution of the gadolinium complex. A manufacturing method that includes this.

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