Novel production method of gadolinium complex

Abstract

The present invention provides a novel method for removing gadolinium ions from a solution containing gadolinium complexed with DOTA, which is relatively simple and cost-effective compared to known methods.

Description

Technical Field

[0001] The present invention generally relates to a method for removing gadolinium ions from a complex of gadolinium and DOTA. The method uses activated carbon to remove excess gadolinium ions. Also provided is a method for preparing a Gd-DOTA magnetic resonance imaging (MRI) contrast agent, which includes the gadolinium removal method of the present invention.

Background Art

[0002] Lanthanide metals, especially metal complexes of gadolinium, are of interest as MRI contrast agents in the field of in vivo medical imaging. MRI contrast agents based on metal complexes of gadolinium have been extensively reviewed [see, for example, Zhang et al, Curr. Med. Chem., 12, 751-778 (2005) and Aime et al, Adv. Inorg. Chem., 57, 173-237 (2005)].

[0003] However, free gadolinium ions can exhibit significant toxicity in vivo. U.S. Patent No. 5,876,695 addresses this issue by including in the formulation of a gadolinium metal complex an additive that is a "weak metal chelate complex" such as a complex with calcium. The idea is that an excess of the "weak metal chelate complex" efficiently complexes gadolinium ions that may be accidentally released or present, thus improving the safety of the MRI contrast composition.

[0004] Reference Example 3 of European Patent No. 2242515 (EP 2242515 B9) involves laboratory-scale preparation, which prepares Gd-DOTA by reacting DOTA (10 g, 25 mmol) with stoichiometric amounts of gadolinium oxide (Gd2O3, 12.5 mmol) in water maintained at pH 6 to 7 with NaOH at 80 °C. Subsequently, the pH is adjusted to 5 with HCl, stirred with Chelex resin in sodium ion form for 2 hours, and then filtered to remove residual free gadolinium. European Patent No. 2242515 then teaches precipitating the Gd-DOTA complex from aqueous ethanol to obtain sodium gadoterate with an isolation yield of 80% as a white powder. European Patent No. 2242515 does not teach how to adapt the method of Reference Example 3 to provide a liquid pharmaceutical composition having an excess macrocyclic chelator in the range of 0.002% to 0.4% mol / mol, especially on an industrial scale. Further, the use of Chelex resin taught by Example 3 of European Patent No. 2242515 provides a product in sodium salt form unless a further purification step is carried out. Example 3 of European Patent No. 2242515 also describes the preparation of certain gadolinium complexes that require purification and isolation steps that are not suitable for an industrial manufacturing method for preparing liquid pharmaceutical formulations.

[0005] International Publication No. 2016 / 083597 pamphlet discloses a method for preparing a liquid pharmaceutical formulation comprising a metal complex of a lanthanide metal and a macrocyclic chelator, the method comprising contacting with a scavenger resin one or more times, thereby removing excess lanthanide by complexing the excess lanthanide with the scavenger resin.

[0006] Unlike the experimental examples of European Patent No. 2242515, the method described in the International Publication No. 2016 / 083597 pamphlet can be carried out on an industrial scale. This is because by using a solid-phase binding scavenger chelator, a lanthanide chelator metal complex can be obtained without the presence of excess lanthanide ions, thus avoiding the need for measurement and adjustment steps. Since this method provides an intermediate solution of a lanthanide metal complex that does not contain free lanthanide ions, the amount of excess macrocyclic chelator to be added to obtain a desired formulation having a specified excess of free chelator can be easily calculated.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] Nevertheless, there is still a need for an alternative method for removing excess lanthanide metal from a formulation of a lanthanide metal complex of a macrocyclic chelator. The method should preferably be suitable for pharmaceutical manufacturing on an industrial scale and also for the provision of MRI contrast agents containing such formulations.

MEANS FOR SOLVING THE PROBLEM

[0008] In one aspect, the present invention provides the following steps: (i) Complexing a chelate with an excess of gadolinium in a suitable solvent to obtain a first solution containing a Gd-chelate and free gadolinium ions ([Gd 遊離 ); (ii) Removing [Gd 遊離 from the solution by contacting the first solution of step (i) with a certain amount of activated carbon one or more times; (iii) Separating the activated carbon from the first solution of step (ii) to obtain a second solution containing the Gd-chelate that does not contain excess [Gd 遊離 . The present invention relates to a method comprising the above steps.

[0009] In another aspect, the present invention provides the following steps: (A) Performing the method steps (i)-(iii) defined herein to obtain a second solution defined herein; (B) Adding a chelate in non-complexed form to the second solution from step (A) to obtain a liquid pharmaceutical formulation comprising a Gd-chelate together with a chelate in non-complexed form relates to a method comprising.

[0010] In another aspect, the present invention is a method for preparing an MRI contrast agent, comprising: (a) Performing the method steps (A) and (B) defined herein to obtain a liquid pharmaceutical formulation defined herein; (b) Optionally, diluting the liquid pharmaceutical formulation from step (a) with a biocompatible carrier; (c) Dispensing the formulation from step (b) into a pharmaceutically acceptable container or syringe to obtain a dispensed container or syringe; (d) Performing steps (a)-(c) under aseptic manufacturing conditions or performing final sterilization of the dispensed container or syringe from step (c) to obtain an MRI contrast agent in a pharmaceutically acceptable container or syringe in a form suitable for mammalian administration provides a method comprising.

[0011] In another aspect, the present invention provides a solution of a Gd-chelate free of excess [Gd 遊離 that can be obtained by a method comprising the steps (i)-(iii) defined herein.

[0012] In another aspect, the present invention provides a liquid pharmaceutical formulation comprising a Gd-chelate together with a chelate in non-complexed form that can be obtained according to a method comprising the steps (A) and (B) defined herein.

[0013] In another aspect, the present invention provides an MRI contrast agent that can be obtained according to a method comprising the steps (a)-(d) defined herein.

[0014] It has been demonstrated herein that activated carbon can efficiently remove free gadolinium ions from Gd-DOTA meglumine solution. The method of the present invention is a relatively inexpensive and uncomplicated method for producing Gd-chelate as compared with known methods.

[0015] It is demonstrated herein that activated carbon treatment is an efficient method for removing gadolinium ions in gadoteric acid meglumine solution at concentrations and pH ranges representative of gadoteric acid meglumine manufacturing conditions.

[0016] The method of the present invention is further significantly simplified from previous methods (see, for example, WO 2016 / 083597) as no preconditioning step of scavenger resin is required.

Brief Description of Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0018] To more clearly and concisely describe and point out the subject matter of the claimed invention, the following definitions are provided for certain terms used throughout this specification and the claims. Any exemplification of specific terms in this specification should be considered as non-limiting examples.

[0019] The term "comprising" or "comprises" has its conventional meaning throughout this application, indicating that a method must have the essential features or components listed, but other things may additionally be present. The term "comprising" includes "consisting essentially of" as a preferred subset, which means that a method has the steps listed without the presence of other features or steps.

[0020] For use in MRI, paramagnetic metal ions such as gadolinium are administered as metal chelates to avoid the toxic effects of these metal ions in free form. Not only should the paramagnetic metal ions be stably complexed, but the shape of the chelate should be such that the paramagnetic effect of the metal ion is maintained. "Chelate" in the context of the present invention (the term "cheland" is also used to define metal-free chelates) is any ligand capable of producing a highly stable metal chelate complex, for example, having a thermodynamic stability constant of at least 10 12 In various embodiments, the chelate can be a linear, cyclic or branched chelating agent, for example, a linear mono- or polychelate agent, a macrocyclic chelate agent or a branched polychelate agent (e.g., a dendrimer polychelate agent). In one embodiment, the chelate is a polyaminopolyoxy acid (e.g., a polyaminopolycarboxylic acid).

[0021] In one embodiment of the present invention, the chelate is the following (or a derivative thereof): diethylenetriaminepentaacetic acid (DTPA); 4-carboxy-5,8,11-tris(carboxymethyl)-1-phenyl-2-oxa-5,8,11-triazatridecane-13-acid (BOPTA); 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A); 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA); ethylenediaminetetraacetic acid (EDTA); 10-(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (HP-DO3A); 2-methyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (MCTA); tetramethyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTMA); 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (PCTA); N,N'-bis(2-aminoethyl)-1,2-ethanediamine (TETA); 1,4,7,10-tetraazacyclotridecane-N,N',N'',N'''-tetraacetic acid (TRITA); 1,12-dicarbonyl,15-(4-isothiocyanatobenzyl)1,4,7,10,13-pentaazacyclohexadecane-N,N',N''-triacetic acid (HETA); [(2S,5S,8S,11S)-4,7-bis-carboxymethyl-2,5,8,11-tetramethyl-1,4,7,10-tetraazacyclo-dodecan-1-yl]acetic acid, (M4DO3A); 10-phosphonomethyl-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (MPDO3A); hydroxybenzyl-ethylenediamine-diacetic acid (HBED); N,N'-ethylenebis-[2-(o-hydroxyphenyl)glycine] (EHPG); 10-[(1SR,2RS)-2,3-dihydroxy-1-hydroxymethylpropyl]-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (BT-DO3A); and 2-[bis[2-[carboxylatomethyl-[2-(2-methoxyethylamino)-2-oxoethyl]amino]ethyl]amino]acetate (DTPA-BMEA), selected from the group comprising.

[0022] In one embodiment, the chelate is selected from DTPA, DOTA or derivatives thereof. In a further embodiment, the chelate or its derivative is selected from EOB-DTPA, DTPA-BMA, DTPA-BMEA, DTPA, DOTA, BOPTA, HP-DO3A and BT-DO3A. In one embodiment, the chelate is DOTA.

[0023] The terms "chelates in non-complexed form", "chelates containing no coordinated gadolinium ions" and "free chelates" refer to any of the above chelates of the present invention in which gadolinium is not coordinated thereto. For example, DOTA in non-complexed form has the following structure:

[0024]

Chemical formula

[0025] "Complex of gadolinium and chelate" refers to a chelate containing a coordinated metal. For example, the complex of gadolinium and DOTA (or "Gd-DOTA chelate" and also referred to herein as Gd-DOTA or gadoteric acid) is as follows:

[0026]

Chemical formula

[0027] "Meglumine salt of Gd-DOTA" or "meglumine salt of Gd-DOTA chelate" is as follows:

[0028]

Chemical formula

[0029] The term "activated carbon" (also commonly referred to as activated charcoal, wood charcoal, activated powder, carbon black, Carboraffin, Carborafine) refers to any activated carbon known in the art, including activated carbon in the form of carbon that has been processed to have small low-volume pores in order to provide a large surface area. This term as used herein also encompasses surface-modified forms of activated carbon. Activated carbon may be provided as particles, pellets or as a mesh, all of which are readily commercially available. One non-limiting example of commercially available activated carbon is activated carbon mesh 100 (161551-175-D) from Sigma Aldrich. Activated carbon is commonly used at the laboratory scale to purify solutions of organic molecules containing unwanted colored organic impurities. Filtration through activated carbon is well known in large-scale fine chemical and pharmaceutical processes for the same purpose.

[0030] As used herein, the term "purify" refers to the process of obtaining a version of the desired product that is substantially free of gadolinium ions, i.e., a Gd-chelate from which 遊離 [Gd 遊離 ] has been removed. The term "substantially" refers to an action, characteristic, property, state, structure, item, or result that is complete or nearly complete or to a degree or extent. The term "substantially pure" as used herein encompasses Gd-chelates in which [Gd 遊離 ] is zero and Gd-chelates in which only trace amounts of [Gd 遊離 ] remain such that subsequent steps can be successfully carried out. The phrase "containing no excess [Gd

[0031] ]" can be understood to be synonymous with "substantially pure". 遊離 ]" refers to Gd 3+ in solution that is not complexed with a chelate.

[0032] As used herein, the term "complexed" refers to the process by which a metal ion (here gadolinium ion) binds through multiple ligands of a chelating agent.

[0033] The term "suitable solvent" refers to any solvent or solvent system in which complexation of the chelate with gadolinium can occur. Water is an example of a suitable solvent, and water for injection (WFI) is particularly suitable.

[0034] The term "contacting" in the context of contacting the reaction solution with activated carbon can be interpreted to mean the addition of the solution to the activated carbon or the addition of the activated carbon to the solution. In one embodiment, the addition of the solution to the activated carbon is carried out by passing the solution through a column or cartridge containing the activated carbon, and optionally, the flow of the solution through the column is facilitated by the use of a pump.

[0035] The phrase "one or more times" can include one or more contacting steps required to reduce the concentration of gadolinium ions to the desired level. Ideally, the number of times should be small.

[0036] The term "separation" refers to the physical removal of activated carbon from the solution. In one embodiment, the separation is carried out by filtration. In certain embodiments, the separation is carried out after each contact step. When the activated carbon is contained in a column, the separation is automatically achieved as the solution exits through the column. Nevertheless, when the activated carbon is contained in a column, the method of the present invention may include a separate separation step, whereby fine particles of activated carbon that may be present are removed. A "pharmaceutical formulation" can be understood to be a composition of a Gd-chelate or a salt or solvate thereof with a biocompatible carrier in a form suitable for mammalian administration. A "biocompatible carrier" is a fluid, particularly a liquid, in which the Gd-chelate is dissolved and as a result the resulting composition is physiologically tolerated, i.e., can be administered to the body of a mammal without toxicity or undue discomfort. The phrase "in a form suitable for mammalian administration" means a composition that is sterile, pyrogen-free, contains no compounds that cause toxicity or adverse effects, and is formulated at a biocompatible pH. Such a composition does not contain fine particles that may pose a risk of causing embolism in vivo and is formulated so that no precipitation occurs upon contact with biological fluids (e.g., blood). Such a composition also contains only biologically compatible excipients and is preferably isotonic.

[0037] The pharmaceutical preparation is suitable for use as an "MRI contrast agent", i.e., for performing MRI of the body of humans and non-human animals. The pharmaceutical preparation contains one or more pharmaceutically acceptable excipients. These preferably do not interfere with the manufacture, storage or use of the final composition. Non-limiting examples of suitable pharmaceutically acceptable excipients include buffers, stabilizers, antioxidants, osmolality adjusters, pH adjusters, excess free chelates and weak complexes of physiologically tolerated ions. These and other suitable excipients are well known to those skilled in the art and are further described, for example, in WO 90 / 03804, EP 0463644, EP 0258616 and US 5876695, the contents of which are incorporated herein by reference. In one embodiment, the pharmaceutical preparation of the present invention is in a form suitable for parenteral administration, such as injection. Thus, the pharmaceutical preparation can be formulated for administration using physiologically acceptable excipients in a manner that is completely within the skill of the art. For example, the Gd-chelate may be suspended or dissolved in an aqueous medium, optionally with the addition of a pharmaceutically acceptable excipient, and then the resulting solution or suspension may be sterilized.

[0038] A non-limiting example of a suitable buffer is tromethamine hydrochloride.

[0039] The term "excess free chelate" (which may also be referred to as "excess chelate" or "free ligand") is defined as any compound capable of sequestering free gadolinium ions. The presence of excess free chelate ensures that free gadolinium is not formed during the guaranteed shelf life of the product. The decomposition of gadolinium-containing ligands can, in principle, result in free gadolinium, and the excess free chelate complexes the liberated gadolinium ions, ensuring zero concentration of free Gd. Furthermore, it is known that there is a correlation between the amount of excess free chelate in a paramagnetic chelate formulation and the amount of paramagnetic metal deposited in an animal model (Sieber 2008 J Mag Res Imaging; 27(5): 955-62). The amount of excess free chelate is selected that can act as a gadolinium scavenger to reduce or prevent the release of gadolinium from the formulation in vivo during its shelf life and after injection. The optimal amount of free chelate results in a pharmaceutical formulation having suitable physicochemical properties (i.e., viscosity, solubility, and osmolality) and avoiding toxicological effects such as zinc depletion when there is too much free chelate. In one embodiment, the excess free chelate is as defined above for "chelates in non-complexed form". In one embodiment of the present invention, the excess free chelate is DOTA in non-complexed form. When DOTA is used as the excess free chelate, in one embodiment, it is present in the range of 0.002 to 0.4 mol / mol%.

[0040] "Physiologically tolerated ions" can, in one embodiment, be selected from calcium salts or sodium salts such as, for example, calcium chloride, calcium ascorbate, calcium gluconate, or calcium lactate.

[0041] The parenterally administrable form should be sterile and free from pharmaceutically unacceptable agents and should have a low osmolality to minimize irritation or other adverse effects upon administration and thus the pharmaceutical composition should be isotonic or slightly hypertonic. Non-limiting examples of suitable vehicles include aqueous vehicles customarily used for the administration of parenteral solutions such as sodium chloride injection, Ringer's injection, dextrose injection, dextrose and sodium chloride injection, lactated Ringer's injection as well as other solutions as described in Remington's Pharmaceutical Sciences, 22 nd Edition (2006 Lippincott Williams & Wilkins) and The National Formulary (https: / / books.google.com / books?id=O3qixPEMwssC&q=THE+NATIONAL+FORMULARY&dq=THE+NATIONAL+FORMULARY&hl=en&sa=X&ved=0CC8Q6AEwAGoVChMImfPHrdTqyAIVJfNyCh1RJw_E).

[0042] For the pharmaceutical composition of the present invention to be administered parenterally, i.e., by injection, its preparation further includes steps involving the removal of organic solvents and the addition of optional additional components such as biocompatible buffers and excipients or buffers. For parenteral administration, it is also necessary to perform steps to ensure that the pharmaceutical composition is sterile and pyrogen-free. Sterility can be achieved using "aseptic manufacturing conditions", i.e., sterility is maintained throughout the manufacturing process. Alternatively, "terminal sterilization" can be used, i.e., the final step to ensure the sterility of the product is carried out. A "pharmaceutically acceptable container or syringe" preferably ensures patient safety, the effectiveness of the pharmaceutical formulation throughout the intended shelf life, the uniformity of the pharmaceutical formulation across different production lots, control of the potential for migration of packaging components into the pharmaceutical formulation, control of the degradation of the pharmaceutical formulation by oxygen, moisture, heat, etc., prevention of microbial contamination, sterility, etc. Suitable containers and syringes can be made from pharmaceutically acceptable glass or plastic. An exemplary plastic bottle is Pluspak (trademark).

[0043] The term "ambient temperature" as used herein can be interpreted to mean any temperature between about 18 and 30 °C.

[0044] In one embodiment, the target [Gd 遊離 is in the range of 0.1 to 0.9 mM, in one embodiment 0.2 to 0.85 mM, and in another embodiment 0.32 to 0.83 mM. In one embodiment, the concentration of free gadolinium ions in the product after contact with the activated carbon endpoint is 1.8 μg / mL or less.

[0045] In one embodiment, the Gd-chelate is selected from gadoteric acid (Dotarem), gadodiamide (Omniscan), gadobenic acid (MultiHance), gadopentetic acid (Magnevist), gadoteridol (ProHance), gadofosveset (Ablavar, formerly Vasovist), gadoxetate (Eovist or Primovist), and gadobutrol (Gadavist).

[0046] In one embodiment, the chelate is a macrocyclic chelate. In one embodiment, the macrocyclic chelate is DOTA. In one embodiment, the Gd-chelate is gadoteric acid. In one embodiment, the Gd-chelate is meglumine gadoterate.

[0047] In one embodiment, the excess gadolinium in step (i) is from 0.001 to 5 mol / mol%.

[0048] In one embodiment, after the complexation step (i) and before the removal step (ii), the pH is adjusted to 4.5 to 7.0, for example 4.5 to 6.5.

[0049] In one embodiment, the Gd-chelate is meglumine gadoterate and the pH is adjusted using meglumine.

[0050] In one embodiment, the amount of activated carbon per milliliter of the first solution is 200 - 400 mg / ml, in one embodiment 100 - 200 mg / ml, and in another embodiment 10 - 20 mg / ml.

[0051] In one embodiment, the activated carbon is in the form of powder or particles, or it may be shaped or incorporated into other forms, such as pellets, disks or meshes. When the activated carbon is shaped into other forms, it may be bound together by a binder, such as cellulose.

[0052] In one embodiment, the activated carbon is in the form of particles.

[0053] In one embodiment, the activated carbon is packed into a column or cartridge. In this embodiment, the activated carbon can be in any of the forms described herein. Optionally, the activated carbon is supported by a scaffold within the column, which may be useful for the activated carbon shaped or incorporated into the above forms.

[0054] In one embodiment, when activated carbon is contained in the column, the column is a housing in which the activated carbon exists as one or more stationary disks made of activated carbon aggregated by a cellulose binder.

[0055] In one embodiment, step (ii) is performed at ambient temperature.

[0056] For the preparation of a liquid pharmaceutical formulation comprising a Gd-chelate together with the chelate in non-complexed form according to one aspect of the present invention, the Gd-chelate is Gd-DOTA, the chelate is DOTA, and the non-complexed form of the DOTA is in an amount in the range of 0.002 to 0.4 mol / mol% of the Gd-DOTA. In one embodiment, the non-complexed form of DOTA is in an amount in the range of 0.025 to 0.25 mol / mol%.

[0057] In one embodiment, the non-complexed form of DOTA does not contain coordinated gadolinium ions and contains less than 50 ppm of M, where M is a metal ion selected from calcium, magnesium and zinc, or a mixture thereof.

[0058] As described in Example 2 below, to study the removal of free gadolinium ions, a meglumine Gd-DOTA liquid bulk solution was diluted to 0.5 M (with respect to Gd-DOTA) using water, and subsequently gadolinium ions (gadolinium chloride) were added to form a gadolinium-spiked meglumine Gd-DOTA solution. The resulting solution was theoretically 0.5 M (with respect to [Gd-DOTA]), and the concentration of excess free gadolinium ions was determined to be 1.4 mM by spectroscopic analysis.

[0059]

Chemical formula

[0060] Scheme 1. Gadolinium spike complexation. During the addition of gadolinium ions to the Gd-DOTA solution (Scheme 1 above), the pH decreases from 7.3 to 4.8. This decrease in pH ensures that the spiked gadolinium ions are in the form of free ions, because gadolinium ions form hydroxide ions and hydrolysis species at pH values above 6 (Figure 1), which are known to ultimately form insoluble gadolinium hydroxide; Gd(OH)3.

[0061] To ensure that insoluble gadolinium hydroxide is not formed in the spiked meglumine Gd-DOTA solution during the experiment, the pH was increased gradually, aliquots were extracted at gradually increasing pH, and left to stand for >72 hours before analysis of the free gadolinium content. As can be seen in Figure 2, the free gadolinium concentration does not decrease within the pH range appropriate for the activated carbon experiment. In addition, as reported by Djurdevic et al (Acta. Chim. Slov. 2010, 386-397), the gadolinium concentration [Gd] only decreases slightly at pH close to 7, indicating that the tendency to form insoluble complexes is lower in 0.5M Gd-DOTA solution than in aqueous solution (Figure 1).

[0062] The above-described Gd-spiked Gd-DOTA samples were subjected to activated carbon treatment, and the amount of residual free Gd was determined using spectrophotometry. Figure 3 compares the [Gd] 遊離 of the spiked Gd-DOTA solution before activated carbon treatment (NT; untreated) with the solutions treated with 0.01 - 0.2 g / mL of activated carbon after contact times of 10 and 50 minutes. The data show that as little as 0.02 g / mL of activated carbon is able to reduce the concentration of free gadolinium from 1.4 mM to approximately 0.02 mM. The 0.01 g / mL sample shows a lower [Gd] after 50 minutes compared to 10 minutes, and it is unclear whether the system had reached equilibrium at this point or whether further adsorption was possible. The remaining samples (>0.01 g / mL) had reached equilibrium after the initial time point and showed an excessive activated carbon loading.

[0063] As is evident from Fig. 3, there is no possibility of further reducing the concentration of free gadolinium by adding more activated carbon, and 0.02 mM may be an overestimation due to background interference in spectrophotometry. The reference sample (Ref) of meglumine Gd-DOTA solution after dilution with water but before gadolinium addition shows that there is some minor spectrophotometric background interference actually present. Note that the reference solution contains a slight excess of DOTA, which may have some minor detrimental effects on the background interference. Therefore, the concentration of free gadolinium is quite likely to be lower than the 0.02 - 0.01 mM indicated by this method. Nevertheless, a gadolinium ion concentration of 0.01 mM is still acceptable for the production of meglumine gadoterate because the subsequent DOTA addition (within the range of 0.35 - 0.87 mM) is still considered to be virtually quantitative.

[0064] As can be seen from Fig. 3, the pH is slightly affected by the activated carbon treatment but still remains within a range that is fully acceptable with respect to the process requirements and the solubility of gadolinium ions (Fig. 2).

[0065] The HPLC-CAD-MS analysis of the activated carbon-treated samples shows that no new compounds are formed due to decomposition or chemical incompatibility (as shown in Fig. 4). No new peaks were observed other than trace impurities introduced by the activated carbon (small amounts of sodium and unidentified impurities) or trace impurities introduced by the spiking operation (chloride ions).

[0066] The specific examples presented herein relate to meglumine Gd-DOTA, but these data support the application of the present invention for the effective removal of free gadolinium ions from various different solutions containing Gd-chelates.

[0067] This specification discloses the present invention and uses examples to enable those skilled in the art to practice the present invention, including practicing any incorporated methods. The patentable scope of the present invention is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the language of the claims or if they include equivalent structural elements that have non-substantive differences from the language of the claims. All patents and patent applications described herein are hereby incorporated by reference in their entirety as if individually incorporated.

[0068] Brief Description of the Embodiments Example 1 is a comparative example that describes a known method for removing free Gd ions from meglumine Gd-DOTA solution.

[0069] Example 2 is the method of the present invention for removing free Gd ions from meglumine Gd-DOTA solution.

[0070] List of Abbreviations Used in the Examples CAD Charged Particle Detector DAD Diode Array Detector DIW Deionized Water HPLC High Performance Liquid Chromatography MeCN Acetonitrile OAc Acetate RT Room Temperature TOF Time of Flight UPLC Ultra Performance Liquid Chromatography

Examples

[0071] [Comparative Example 1] Removal of Gd ions from meglumine Gd-DOTA solution according to the prior art method. DOTA (211 kg) was dissolved in boiling water (1600 kg), and Gd2O3 was added (94.8 kg). The temperature was set at 70 °C, and the slurry was stirred overnight. The presence of free gadolinium ions (1390 ug / g) in the solution was determined by colorimetric titration.

[0072] The temperature was adjusted to 50 °C, and meglumine was added to achieve a pH of 5.5 in the solution. First, 94.8 kg of meglumine was added, and the final pH adjustment was performed with an aqueous solution of meglumine (1.5 M).

[0073] The scavenger resin (Puropack C150, 50 L) was conditioned to the proton form according to standard procedures. The resin was rinsed with water until neutral water eluted from the resin bed. A solution of meglumine (400 g / kg resin) was circulated through the resin bed for 10 hours, and the resin was rinsed again with water to a neutral pH.

[0074] The megluminized resin was placed in a column, and the Gd-DOTA solution was pumped through the column at a flow rate sufficient to pass the entire volume of the solution in 2 hours. The concentration of free gadolinium (45 ug / ml) was determined using colorimetric spectrophotometry. To establish a level of free gadolinium (4 ug / g) below the detection limit by colorimetric titration, the solution was passed through the column one more time to continue the ion exchange of the meglumine Gd-DOTA solution and obtain a Gd-DOTA-meglumine solution.

[0075] [Example 2] Removal of Gd ions from a meglumine Gd-DOTA solution using the method of the present invention. A 0.44 M GdCl3 solution was prepared from 1.86 g of GdCl3 hexahydrate dissolved in 10 mL of deionized water. The concentration of gadolinium ([Gd]) was determined using spectrophotometry.

[0076] A Gd-spiked (1.4 mM) meglumine Gd-DOTA solution was prepared from 50 mL of liquid bulk Clariscan™ meglumine Gd-DOTA, to which 0.6 mL of GdCl3 (0.44 M) was added and then diluted to 100 mL using DIW. The solution was then left to stand for >72 h before use in the experiment to allow complete complexation.

[0077] To 10 mL of Gd-spiked (1.8 mM) meglumine Gd-DOTA solution, 0.1, 0.2, 0.3, 0.4, 0.5, 1 or 2 g of activated carbon (mesh 100, Sigma Aldrich, 161551-175-D) was added. The suspension was placed in a shaking block and samples were taken after 10 and 50 min. All samples were filtered through an Acrodisc nylon membrane and analyzed for [Gd] and HPLC purity (pH was measured in the suspension).

[0078] HPLC analysis was performed on an Agilent Acquity UPLC system equipped with a diode array detector, Waters Premier TOF mass spectrometer and Dionex charged aerosol detector. Column: ZIC-pHILIC, 4.6×150 mm, 5 μm Mobile phase: A: 100 mM NH4OAc; B: MeCN, Flow rate: 1 mL / min Gradient: 15% A to 30% A (linear) over 40 min. Temperature: (room temperature) Detector: DAD (210~350 nm), CAD (500 pA) Injection: full loop injection (20 uL). HPLC sample preparation: To 380 μL of water, 10 μL of sample was added, followed by 10 μL of Cu(OAc)2 (10 mg / ml) and 600 μL of MeCN.

[0079] The concentration of free gadolinium was determined based on the difference in the visible spectra of free and complexed xylenol orange using a slightly modified published method (Barge, A; Contrast Media & Molecular Imaging, 2006, 184 - 8). The absorbance ratio at wavelengths 573 and 433 nm is proportional to [Gd] in the range from 0 to 0.1 mM (Figure 5). At higher ranges, the absorbance ratio deviates from linearity and shows a more complex relationship with [Gd]. Therefore, all measurement samples were diluted to fit within the calibration range of 0 - 0.1 mM.

[0080] A GdCl3 standard solution was prepared from GdCl3 hexahydrate and serially diluted using 50 mM HOAc buffer.

[0081] 50 mM HOAc was a buffer prepared by adding 0.72 mL of (concentrated) HOAc to 200 mL of deionized water, adjusting the pH to 5.9 using 1 M NaOH, and then diluting to 250 mL using deionized water.

[0082] A xylenol orange solution was prepared by dissolving 2 mg of xylenol orange in 100 mL of 50 mM HOAc (pH 5.9) buffer.

[0083] Sample preparation for spectrophotometry: 975 μL of xylenol orange solution was added to 25 μL of sample solution.

[0084] [Example 3] Industrial production of Gd - DOTA meglumine using the method of the present invention. DOTA (370 kg (range: 310 - 410 kg)) was dissolved in boiling water (2000 kg), and Gd2O3 (162.8 kg range: 135 - 190 kg)) was added. The temperature was set to 80 °C and stirred overnight. The presence of free gadolinium ions was determined by colorimetric titration.

[0085] The temperature was adjusted to 50 °C, and meglumine was added to achieve a pH of 5.7 (range 5.5 - 6.4). First, 160 kg (range 150 - 200 kg) of meglumine was added, and the final pH adjustment was performed with an aqueous solution of meglumine (1.5 M).

[0086] The temperature of the Gd - DOTA meglumine solution was further adjusted to 40 °C. Four modules of MCN activated carbon were arranged in series. The first three filter houses contained 1.01 kg of activated carbon, and the last one contained 2.7 kg of activated carbon. Before pumping the Gd - DOTA meglumine solution, the MCN activated carbon was pre - conditioned. The MCN activated carbon was rinsed with water until a conductivity of less than 10 μS / cm was reached. The GdDOTA solution was pumped through the quadruple activated carbon at a flow rate of 800 - 1000 liters / m 2 .h. The concentration of free gadolinium was determined using calorimetric titration. The GdDOTA solution after passing through the activated carbon established a free gadolinium level (1.8 μg / ml) below the detection limit by colorimetric titration, giving a Gd - DOTA meglumine solution.

[0087] Data generated from industrial production are shown in the following table.

[0088]

Table 1

Claims

1. The following steps: (i) Complexing a chelate and excess gadolinium in a suitable solvent to obtain a first solution containing a Gd-chelate and free gadolinium ions ([Gd 遊離 ]); (ii) removing [Gd 遊離 from the solution by contacting the first solution of step (i) with a certain amount of activated carbon one or more times; (iii) separating the activated carbon from the first solution of step (ii) to obtain a second solution containing the Gd-chelate and not containing excess 遊離 [Gd], A method comprising the same.

2. The method according to claim 1, wherein [Gd 遊離 in step (iii) of claim 1 is 1.8 μg / mL or less.

3. The method according to claim 1 or claim 2, wherein the Gd-chelate is selected from gadoteric acid, gadodiamide, gadobenic acid, gadopentetic acid, gadoteridol, gadofosveset, cadoxetamide, gadoxetic acid, and gadobutrol.

4. The method according to any one of claims 1 to 3, wherein the chelate is a macrocyclic chelate.

5. The method according to claim 4, wherein the macrocyclic chelate is DOTA.

6. The method according to any one of claims 1 to 5, wherein the Gd-chelate is gadoteric acid.

7. The method according to claim 6, wherein the Gd-chelate is meglumine gadoterate.

8. The method according to any one of claims 1 to 7, wherein the excess gadolinium in step (i) is from 0.001 to 5 mol / mol%.

9. The method according to any one of claims 1 to 8, wherein the pH is adjusted to 4.5 to 7.0 after the complexation step (i) and before the removal step (ii).

10. The method according to claim 9, wherein the Gd-chelate is meglumine gadoterate and the pH is adjusted using meglumine.

11. The method according to any one of claims 1 to 10, wherein the amount of activated carbon with respect to the first solution is 200 to 400 mg / ml.

12. The method according to any one of claims 1 to 11, wherein the activated carbon is in the form of particles, pellets, or mesh.

13. The method according to any one of claims 1 to 12, wherein the activated carbon is in the form of particles.

14. The method according to any one of claims 1 to 13, wherein the activated carbon is filled in a column or a cartridge.

15. The method according to any one of claims 1 to 14, wherein step (ii) is carried out at ambient temperature.

16. The following steps: (A) Performing the method according to any one of claims 1 to 15 to obtain a second solution according to any one of claims 1 to 15; (B) Adding a chelate in non-complexed form to the second solution from step (A) to obtain a liquid pharmaceutical formulation containing the Gd-chelate together with the chelate in non-complexed form. A method comprising the same.

17. The method according to claim 16, wherein the Gd-chelate is Gd-DOTA, the chelate is DOTA, and the non-complexed form of DOTA is in an amount in the range of 0.002 to 0.4 mol / mol% of the Gd-DOTA.

18. The method according to claim 17, wherein the non-complexed form of DOTA is in an amount in the range of 0.025 to 0.25 mol / mol%.

19. The method according to claim 17 or claim 18, wherein the non-complexed form of DOTA does not contain coordinated gadolinium ions and contains less than 50 ppm of M, and M is a metal ion selected from calcium, magnesium, and zinc, or a mixture thereof.

20. A method for preparing an MRI contrast agent, comprising: (a) performing the method according to any one of claims 16 to 19 to obtain a liquid pharmaceutical formulation according to any one of claims 16 to 19; (b) optionally diluting the liquid pharmaceutical formulation from step (a) with a biocompatible carrier; (c) dispensing the formulation from step (b) into a pharmaceutically acceptable container or syringe to obtain a dispensed container or syringe; (d) performing steps (a) to (c) under aseptic manufacturing conditions or performing final sterilization of the dispensed container or syringe from step (c) to obtain the MRI contrast agent in the pharmaceutically acceptable container or syringe in a form suitable for mammalian administration. A method comprising the steps of:

21. The method according to claim 20, wherein final sterilization is carried out.

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