METAL COMPLEX FORMULATIONS

Abstract

The present invention relates to a method of preparation of formulations of lanthanide metal complexes of macrocyclic chelators which further comprise a small excess of free chelator. The method uses a solid phase-bound scavenger chelator to remove excess lanthanide metal ions, prior to the addition of a defined excess chelator. Also provided is a method of preparation of MRI contrast agents, together with solid-phase bound chelator meglumine salts useful in the methods.

Claims

1. A method of preparation of a liquid pharmaceutical formulation, said formulation comprising a metal complex of a lanthanide metal with a macrocyclic chelator, together with said chelator in uncomplexed form in an amount in the range 0.002 and 0.4 mol/mol % of said metal complex, said method comprising: (i) complexing said chelator with an excess of said lanthanide metal in a suitable solvent, to give a first solution of said metal complex containing excess lanthanide; (ii) removing the excess lanthanide from the first solution of step (i) by contacting said solution one or more times with a scavenger resin, whereby the excess lanthanide is complexed to said scavenger resin; (iii) separating the solid phase from the first solution of step (ii), to give a second solution which comprises said metal complex free from excess lanthanide; (iv) adding said chelator in uncomplexed form in the range 0.002 and 0.4 mol/mol % to said second solution from step (iii) to give said liquid pharmaceutical formulation; wherein said chelator in uncomplexed form is free of coordinated metal ions.

2. The method of claim 1, wherein the excess of lanthanide metal of step (i) is 0.001 to 5 mol/mol %.

3. The method of claim 1, wherein the chelator in uncomplexed form is in an amount in the range 0.025 and 0.25 mol/mol.

4. The method of claim 1, wherein the chelator in uncomplexed form is free of lanthanide, calcium, zinc and magnesium ions.

5. The method of claim 1 wherein the lanthanide metal is gadolinium.

6. The method of claim 1, wherein the macrocyclic chelator comprises DOTA, NOTA, DO3A, BT-DO3A, HP-DO3A and PCTA.

7. The method of claim 6, wherein the macrocyclic chelator comprises DOTA.

8. The method of claim 1, wherein the scavenger resin is a solid phase bound scavenger chelator.

9. The method of claim 8, wherein the scavenger chelator comprises iminodiacetic acid, EDTA or DTPA.

10. The method of claim 9, wherein the scavenger chelator comprises iminodiacetic acid.

11. The method of claim 1 wherein the excess lanthanide of step (i) displaces any coordinated impurity metal(s) from said chelator, wherein each said impurity metal has a lower formation constant with said macrocyclic chelator than said lanthanide.

12. The method of claim 1, wherein the lanthanide metal is gadolinium and the macrocyclic chelator comprises DOTA.

13. The method of claim 12, wherein the gadolinium-DOTA complex comprises the meglumine salt of gadolinium-DOTA.

14. The method of claim 13, wherein the scavenger resin is a solid-phase bound scavenger chelator present as the meglumine salt of said scavenging chelator.

15. The method of claim 14, wherein the scavenger chelator comprises iminodiacetic acid.

16. The method of claim 1, wherein the complexation of step (i) is completed by adjusting the pH 4.5 to 5.5 using meglumine.

17. A method of preparation of an MRI contrast agent, the method comprising: (a) carrying out the method of claim 1 to obtain the liquid pharmaceutical formulation as defined therein; (b) optionally diluting the liquid pharmaceutical formulation from step (a) with a biocompatible carrier; (c) dispensing the formulation from step (b) into pharmaceutically acceptable containers or syringes to give dispensed containers or syringes; (d) either carrying out steps (a)-(c) under aseptic manufacturing conditions, or terminal sterilisation of the dispensed containers or syringes from step (c), to give the MRI contrast agent in said pharmaceutically acceptable containers or syringes in a form suitable for mammalian administration.

18. The method of claim 17, wherein terminal sterilisation is used.

19. A solid-phase bound scavenger chelator, wherein the solid-phase bound scavenger chelator is present as the meglumine salt of said scavenger chelator.

20. The scavenger chelator of claim 19, wherein the scavenger chelator comprises iminodiacetic acid.

21. (canceled)

Description

DESCRIPTION OF THE FIGURES

[0083] FIG. 1 shows that gadolinium ions are replaced with either sodium (Na-Chelex) or megluminium (M.sup.eg-Chelex) ions, and the chloride ion content is unaffected by treatment of a gadolinium chloride reference solution with the Chelex resins.

[0084] FIG. 2 shows that the same gadolinium removal procedure of the invention is effective when used on a mixture of Gd-DOTA/excess gadolinium. FIG. 2 also demonstrates that chelex is unable to remove gadolinium from Gd-DOTA, as no free DOTA is formed.

[0085] The invention is illustrated by the non-limiting Examples detailed below. Example 1 provides the preparation of a meglumine scavenger chelator resin according to the invention. Example 2 shows that two different Chelex resins successfully remove gadolinium ions from a reference solution of GdCl.sub.3. The sodium form of the resin is shown to increase the sodium content of the solution and the megluminium form of the resin is shown to increase the megluminium content of the solution.

[0086] Example 3 shows that the two different Chelex resins of Example 2 successfully remove gadolinium ions from a composition containing the Gd-DOTA complex with excess free gadolinium. Example 3 also demonstrates that the Chelex resin is unable to remove Gd.sup.3+ from the Gd-DOTA complex, because no free DOTA is present in the chromatogram (FIG. 2).

[0087] Example 4 provides a HPLC-CAD method capable of analysing Gd-DOTA, free DOTA and meglumine in a mixture of such components.

[0088] Example 5 provides the synthesis of a Gd-DOTA complex formulation containing excess DOTA according to the invention.

[0089] Example 6 provides a method for the megluminization of a scavenger resin, according to the invention.

ABBREVIATIONS

[0090] BT-DO3A: 10-(2,3-dihydroxy-1-hydroxymethylpropyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid;

[0091] Cyclen: 1,4,7,10-tetraazacyclododecane;

[0092] DO3A: 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid;

[0093] DOTA: 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid;

[0094] DTPA: diethylenetriamine-pentaaacetic acid;

[0095] EDTA: ethylenediamine-tetraacetic acid;

[0096] GMP: Good Manufacturing Practice;

[0097] HP-DO3A: 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid-10-(2-hydroxypropyl);

[0098] HPLC: High Performance Liquid Chromatography;

[0099] HPLC-CAD: HPLC Charged Aerosol Detector;

[0100] ICP-AES: Inductively Coupled Plasma Atomic Emission Spectroscopy

[0101] ICP-MS: Inductively Coupled Plasma Mass Spectrometry;

[0102] MeCN: Acetonitrile;

[0103] min: minutes;

[0104] MRI: Magnetic Resonance Imaging;

[0105] NOTA: 1,4,7-Triazacyclononane-1,4,7-triacetic acid;

[0106] PCTA: 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1,11,13-triene-3,6,9,-triacetic acid;

[0107] WFI: water for injection.

EXAMPLE 1

Preparation of Megluminized Chelex® Resin (“Meg-Chelex”)

[0108] Chelex-100 resin (Sigma-Aldrich; 100 g) on a sintered glass filter was treated with 1M HCl (1 L) in 4 portions over 4 h. The resin was then washed with water until the eluent was pH 6.5, and a solution of meglumine (10 g) in water (400 mL) was equilibrated with the resin over a period of 1 h. The resin was again washed with water to pH 8, and then filtered and dried under vacuum for a minute to give the moist resin, which is used in this form (“M.sup.eg-Chelex”).

EXAMPLE 2

Removal of Gadolinium Ions Using Chelex® Resin

[0109] A gadolinium chloride reference solution was treated with either standard Chelex (sodium ion form; “Na-Chelex” or megluminized Chelex (Example 1; “M.sup.eg-Chelex”):

[0110] To each moist Chelex (Na or meglumine) resin (0.5 g) was added 5 mL of a GdCl.sub.3 reference solution (1 mg/mL). The suspension was then left on a shaking table overnight at 30° C. HPLC-CAD analysis (using the method of Example 4) of the suspensions indicated that there was no sodium contamination of the gadolinium solution treated with M.sup.eg-Chelex, whereas the solution treated with Na-Chelex had a much higher sodium ion concentration. Arsenazo dye testing indicated no free gadolinium in either solution (the limit of detection using this method is 8 ppm). The results are shown in FIG. 1.

EXAMPLE 3

Removal of Gadolinium Ions from a Gd-DOTA/Excess DOTA Preparation Using Chelex® Resin

[0111] A Gd-DOTA-meglumine reaction mixture (concentration ˜380 mg/mL) containing a known excess of free gadolinium (160 μg/mL) was treated with standard (Na-Chelex) or megluminized (M.sup.eg-Chelex) Chelex:

[0112] To 0.5 g of the moist Chelex resin (Na-Chelex or M.sup.eg-Chelex; Example 1), was added a 5 mL aliquot of the above Gd-DOTA-meglumine/free Gd mixture. The suspension was left on a shaking table overnight at 30° C.

[0113] HPLC-CAD analysis (using the method of Example 4) of the resulting suspensions indicated no additional sodium contamination (DOTA containing some sodium ions was used) of M.sup.eg-Chelex treated gadolinium solution, whereas Na-Chelex treated solution had increased levels of sodium. Arsenazo dye testing indicated no free gadolinium in either solution. The meglumine concentration in the M.sup.eg-Chelex treated reaction mixture was slightly increased, indicative of gadolinium exchange. The results are shown in FIG. 2.

EXAMPLE 4

HPLC-CAD Method: DOTA Determination in GdDOTA-Meglumine Solution

[0114] Detector: ESA Corona, Charged Aerosol Detector;

[0115] Column: SeQuant ZIC-pHILIC (5 μm, 150*4.6 mm).

[0116] Sample preparation: to 20 μL (ca 0.5M) reaction mixture was added Zn(OAc)2 (10 μg/mL) then water (270 μL) followed by MeCN (700 μL)*.

[0117] Injection volume: 20 μL;

[0118] Mobile phase: 100 mM ammonium acetate (A), Acetonitrile (B).

[0119] The column was conditioned with an initial composition (of 15:85 A:B) at a flow rate of 1 mL/min for at least five minutes prior to sample injection.

[0120] Gradient:

TABLE-US-00002 Flow Rate Time (min) (mL/min) % A % B Curve 1. initial 1.00 15.0 85.0 2. 50.00 1.00 33.0 66.0 6 [0121] where curve 6 refers to a linear gradient.

[0122] The following retention times were observed:

TABLE-US-00003 Retention time (min) Meglumine 21.3 GdDOTA 23.2 ZnDOTA*  28.1. *DOTA was analysed indirectly as the ZnDOTA complex.

EXAMPLE 5

Preparation of a Gd-DOTA Complex Formulation Containing Excess DOTA

[0123] DOTA (211 kg) was dissolved in boiling water (1600 kg) and Gd2O3 was added (94.8 kg). The temperature was set to 70° C. and the slurry was stirred over-night. The presence of free gadolinium ions (1390 ug/g) in the solution was determined by colorimetric titration.

[0124] The temperature was adjusted to 50° C. and meglumine was added to achieve pH 5.5 in the solution. Initially 94.8 kg meglumine was added and the final adjustment of the pH was made with an aqueous solution of meglumine (1.5 M).

[0125] Scavenger resin (Puropack C150, 50 L, preconditioned according to example 6) was placed in a column. The GdDOTA solution was pumped through the column at a flow rate sufficient to pass the entire volume of solution in 2 h. The concentration of free gadolinium (45 ug/ml) was determined using colorimetric titration. The ion exchange of the GdDOTA solution was continued with one more passage through the column to establish a level of free gadolinium below detection limit by colorimetric titration (4 ug/g), to give a GdDOTA-meglumine solution.

[0126] An aliquot of the purified GdDOTA-meglumine complexation mixture was treated to an additional process step: The concentration of GdDOTA was determined by IR measurement and together with a weight measurement of the solution, the total amount of GdDOTA was determined to be 269.8 kg. Free DOTA (2.79 litre of 101.1g/mL solution; total of 307.6g) was then added.

[0127] Then Meglumine solution (1 M) was added in small portions until a pH of 7.2 was obtained. The weight was reduced to 630 kg by distillation in vacuo (140° C.). The solution was kept at 40° C. for 10 h. The concentration of GdDOTA was determined to 1.06M, and the amount of free DOTA was determined to 537 ug/mL.

EXAMPLE 6

Preparation of Megluminized Puropack C150® Resin (“M.SUP.eg.-PPC”).

[0128] Puropack C150 resin was conditioned to proton form according to standard procedures. The resin was rinsed with water until neutral water was eluted from the resin bed.

[0129] A solution of meglumine (400 g/kg resin) was cycled through the resin bed for 10h and the resin was again rinsed to neutral pH with water.