Method for the manufacture of highly purified 68Ge material for radiopharmaceutical purposes

Abstract

A method for the manufacture of highly purified .sup.68Ge material for radiopharmaceutical purposes. The invention particularly concerns the production of .sup.68Ge-API (API=Active Pharmaceutical Ingredient) solution complying with the Guidelines for good manufacturing practices (GMP). Starting material for the method of the present invention can be a .sup.68Ge stock solution of commercial or other origin as raw material. Such .sup.68Ge containing raw solutions are purified from potential metal and organic impurities originating from production processes. The radiochemical method disclosed is based on a twofold separation of .sup.68Ge from organic and metallic impurities with two different adsorbent materials. During the first separation phase .sup.68Ge is purified from both organic and metallic impurities by adsorption in germanium tetrachloride form, after which hydrolyzed .sup.68Ge is purified from remaining metallic impurities by cation exchange. The final .sup.68Ge-API-product e.g. fulfills the regulatory requirements for specifications of the GMP production of .sup.68Ge/.sup.68Ga generators.

Claims

1-10. (canceled)

11. A method for the manufacture of highly purified .sup.68Ge material for radiopharmaceutical purposes, characterized by (a) adjusting a .sup.68Ge-containing solution containing organic and metallic impurities to a HCl concentration of 6.5 to 12 M in order to convert the .sup.68Ge contained in the solution, to a .sup.68GeCl.sub.4-containing material; (b) loading the solution comprising the .sup.68GeCl.sub.4-containing material obtained in step (a) to a resin matrix, wherein said resin matrix is a hydrophilic, macroporous, acrylic ester polymeric resin; (c) eluting said resin matrix with water in order to hydrolyze the .sup.68GeCl.sub.4-containing material and to release .sup.68Ge essentially in germanic acid form [.sup.68Ge(OH).sub.4] from the .sup.68GeCl.sub.4-containing material which was adsorbed to the resin matrix in step (b); (d) adjusting an eluate solution containing .sup.68Ge obtained in step (c) to an HCl concentration <1M; and (e) loading said adjusted eluate solution of step (d), containing .sup.68Ge essentially in the form of .sup.68Ge(OH).sub.4 to a cation exchange resin, wherein metal ion impurities are essentially quantitatively retained whereas the final .sup.68Ge-containing product being essentially free of organic and metallic impurities, elutes through.

12. The method according to claim 11, characterized in that the organic impurities are selected from the group consisting of organic solvents, linear and branched C.sub.6 to C.sub.12 alkanes, in particular n-heptane; halogenated C.sub.1 to C.sub.3 alkanes, in particular CCl.sub.4, and organic dyes, particularly sudan dyes.

13. The method according to claim 11, characterized in that the metallic impurities are selected from the group consisting of Fe, Ni, Cu, Zn, Ga, Nb, and Pb.

14. The method according to claim 11, characterized in that the .sup.68Ge-containing solution in step (a) is adjusted to an HCl concentration of 7.5 M.

15. The method according to claim 11, characterized in that the resin matrix of step (b) is equilibrated with the same HCl concentration to which the .sup.68Ge-containing solution in step (a) is adjusted to.

16. The method according to claim 11, characterized in that the resin matrix of step (b) has a pore size of appr. 25 nm and/or a surface area of appr. 500 m.sup.2/g.

17. The method according to claim 11, characterized in that the cation exchange resin in step (e) belongs to the group of strong cation exchange resins.

18. The method according to claim 11, characterized in that the impurities in the final .sup.68Ge product of step (e) exhibit at least the purification factors as shown in the following table (Metals determined with inductively coupled plasma mass spectrometry, ICP-MS): TABLE-US-00005 Metal Purification Factor Fe  5 200 Ni 33 000 Cu 100 000  Zn  2 900 Ga 500 000  Nb   250 Pb 25 000

19. The method according to claim 11, characterized in that the molarity of HCl of the final .sup.68Ge-containing product is 0.1 to 0.3 M, in particular 0.2 M.

20. The method according to claim 11, characterized in that the yield for .sup.68Ge is at least appr. 97%.

Description

[0063] Further features and advantages of the present invention will become evident from the description of an illustrative example of the present invention and the description of the drawings.

[0064] FIG. 1 is a flow chart showing .sup.68Ge-purification process of the present invention schematically;

[0065] FIG. 2 is a diagram showing .sup.68Ge activity in eluate fractions in different steps of the purification procedure; and

[0066] FIG. 3 shows an exemplified arrangement of a column packed with the resin matrix as a first column.

EXAMPLE I

Purification of .SUP.68.Ge-solutions

[0067] In order to obtain .sup.68Ge in controlled chemical environment free from metallic and organic impurities usable as .sup.68Ge-API, a two-step purification procedure has been developed. The concept is based on the use of two columns with different functionalities in order to

[0068] 1) adsorb and isolate .sup.68Ge on the first column material (Column I) for the removal of original solution, metal impurities and organic impurities,

[0069] 2) to elute .sup.68Ge through the second column material (Column II) for the deep purification of remaining metal impurities by cation exchange process.

[0070] In the present example, a resin matrix which is a hydrophilic, macroporous acrylic ester polymeric resin (Pre-Filter resin, EICHROM, USA, pore size approx. 25 nm and a surface area of approx. 500 m.sup.2/g and a high capacity for various organic compounds) is used as a first column material and a resin with strong cation exchange capabilities [i.e. a strong cation exchange resin] (AG® MP50 resin, Biorad, USA) is used as the second column material.

[0071] In the first part of the procedure, the acid molarity of the original .sup.68Ge solution is adjusted to concentrated hydrochloric acid (7.5 M HCl). Under this condition tetravalent germanium is selectively adsorbed on the Column I. Application of high concentrated HCl solution further is an important factor with respect to removal of bacterial endotoxins and/or elimination of any bacterial or microbial activity. After the purification procedure .sup.68Ge is quantitatively separated from the original solution and obtained in chemically controlled and pure solution.

[0072] The general scheme of the method for the manufacture of highly purified .sup.68Ge material for radiopharmaceutical purposes is presented in FIG. 1. As mentioned above, the first column (Column I) contains Pre-Filter resin from EICHROM, USA), which consists of an uncoated inert polymeric acrylic ester material as described above. The second column (Column II) contains a strong cation exchange resin AG®MP-50 (Biorad, USA). The purification system has been proven for the behavior of .sup.68Ge, as well as purification factors for selected metals Fe, Ni, Cu, Zn, Ga, Nb and Pb have been determined.

[0073] The role of Column I in the method in accordance with the present invention is a selective adsorption of tetravalent .sup.68Ge on the column resin material from the original solution adjusted to 7.5 M HCl. Without being bound to the mechanism described in the following, it appears that in high HCl concentration GeCl.sub.4 is adsorbed by the used Pre-Filter resin as germanium tetrachloride (GeCl.sub.4) together with organic and metallic impurities via non-polar binding. Subsequently, tetravalent germanium can be eluted with pure water or low concentrated acid, while organic and metallic impurities remain on column I.

[0074] Most of metallic cations have strong adsorption on strong cation exchange resins in dilute HCl concentrations ([HCl]<1 M), while adsorption of germanium, which is in the chemical form of germanic acid (Ge(OH.sub.4)), in these conditions is negligible. The use of the second column in the method is based on this difference in chemical properties. .sup.68Ge being eluted from Pre-Filter resin-Column I, is further reformulated with water to an HCl concentration of 0.3 M. Under these conditions metal impurities are selectively removed by the cation exchange column (Column II) while .sup.68Ge elutes through. With small volume of water the cation exchange column II is further rinsed in order to elute .sup.68Ge quantitatively.

[0075] In the first column, .sup.68Ge retains in Column I as .sup.68GeCl.sub.4. Additionally, organic and metallic impurities retain in Column I.

[0076] The .sup.68GeCl.sub.4 being adsorbed to the surface of column I is hydrolyzed and eluted as .sup.68Ge with 1.5 mL of H.sub.2O. The eluate then is diluted with 8.5 mL of H.sub.2O.

Column II is rinsed with 1+1 mL H.sub.2O.

[0077] Impurity metals quantitatively retain in Column II in dilute HCl, however, the desired .sup.68Ge does not retain and elutes through as GMP grade .sup.68Ge-API.

EXAMPLE II

Purification of 68Ge from Selected Metal Ions

[0078] For testing the ability of the method in accordance with the invention to remove even tiny amounts of metals, in the procedure selected metals Fe, Ni, Cu, Zn, Ga, Nb and Pb, 100 μg each, were added to a .sup.68Ge solution (ITG), which was mixed with concentrated HCl (30%, Suprapur quality) solution so that the final HCl concentration was 7.5 M. The solution was equilibrated for minimum of 20 minutes. Column I was pre-rinsed with 5+5 mL of 7.5 M HCl for equilibration. The .sup.68Ge solution was eluted through Column I, which was subsequently rinsed with 5+5 mL of 7.5 M HCl in order to further remove impurities. During this step also the microbiological impurities were inactivated and eluted from the column. For the hydrolysis and removal of .sup.68Ge, Column I was first eluted with 0.5 mL of H.sub.2O in order to decrease the HCl content in the column, after which .sup.68Ge-containing fraction was eluted with 3×0.5 mL of H.sub.2O. This was followed by an additional 5 mL elution with H.sub.2O. The .sup.68Ge-containing eluate fraction was diluted to 10 mL with H.sub.2O in order to decrease the molarity of HCl to 0.25 M. The diluted eluate was eluted through the Column II, which had been pre-rinsed with 5+5 mL of 0.25 M HCl. After eluting the sample, the column was rinsed with 2×1 mL of H.sub.2O for quantitative rinsing of .sup.68Ge from the Column II. All the eluates were measured with HPGe gamma spectrometer. The activities and results are shown in Table 1 below and in FIG. 2.

[0079] In the quantitative analysis known amounts (100 μg) of each metal were applied in the purification system, and the eluates were measured by ICP-MS for the concentration of the selected metals, and purification factors for the metals were calculated. The results are collected in the Table 2 below.

EXAMPLE III

Selected Organic Compounds in the System

[0080] In the quantitative analysis known amounts (833 ppm) of organic compounds CCl.sub.4 and n-heptane were applied in the purification system, and the end product solution was sent to a certified analysis laboratory for the determination of concentrations of CCl.sub.4 and n-heptane. The concentrations were determined by gas chromatography (GC). The results are collected in Table 3 below. Neither CCl.sub.4 nor n-heptane was found within their detection limits.

[0081] Furthermore, in the quantitative analysis a known amount (0.8 ppm) of organic compound Sudan III was added to .sup.68Ge stock solution (ITG), which was applied in the purification system. The purified end product solution was analyzed by HPLC for the determination of concentration of Sudan III. The results are collected in Table 3 below.

Qualitative Analysis

[0082] In the qualitative analysis a known amount (0.8 ppm) of organic compound Sudan III was applied in the purification system. Following the purification process the end product was collected and visually analyzed. As Sudan III is a dye with red color the purification of the stained start solution can be visualized. In order to certify the visual observations photographs (not shown) were taken from the different analysis steps: start solution (a red color clearly was visible), column I for removal of organic compounds (FIG. 3), and end product (red color of the start solution no longer was seen with the bare eye).

Results

.SUP.68.Ge in the Column System

[0083] From the results determined with HPGe gamma spectrometer system and collected in Table 1 it can be seen that .sup.68Ge was eluted in 1.5 mL volume from the Pre-Filter resin column (Column I), and further eluted in diluted form and rinsed through the cation exchange column (Column II) for the final product. The yield of the separation process was 97.3% in 1.5+2 mL volume, and the molarity of HCl of the purified final product of .sup.68Ge-API was 0.2 M.

TABLE-US-00002 TABLE 1 Measured .sup.68Ge activity in eluate fractions and resins in different steps of the .sup.68Ge purification procedure. Metals Fe, Ni, Cu, Zn, Ga, Nb and Pb were added to the solution prior to purification; 100 μg of each metal. Activity Activity Volume in Solution in Solution Sample mL Bq % Load/Pre-filter resin 5 — — (column I) Rinse 1/Pre-filter resin 5 — — Rinse 2/Pre-filter resin 5 — — Eluate 1/Pre-filter + 0.5 — — AG MP-50 resins Eluate 2-4/Pre-filter + 1.5 10250 90.3  AG MP-50 resins Eluate 5/Pre-filter + 5 — — AG MP-50 resins Rinse 1/AG MP-50 resin 1 756.2 6.7 Rinse 2/AG MP-50 resin 1 34.9 0.3 Rinse 3/AG MP-50 resin 1 — — Rinse 4/AG MP-50 resin 1 — — Remains in resin/Pre- — 204.7 1.8 filter resin (column I) Remains in resin/AG — 99.8 0.9 MP-50 resin (column II) Total Bq: 11346

Purification of Selected Metals

[0084] From the results collected in Table 2 below it can be seen that purification factors for all of the selected metals were high. Nb, with oxidation state of +5, having thus differing chemical properties compared to the other selected metals, had a lower purification factor. The content of Cu in the purified eluate was lower than the limit of quantification of the ICP-MS instrument.

TABLE-US-00003 TABLE 2 Measured amounts and purification factors determined for selected metals in the final product after the .sup.68Ge purification procedure. Metals were determined with ICP-MS. Amount Added Amount Measured Purification Metal μg μg Factor Fe 100 0.019 5263 Ni 100 0.003 33333 Cu 100 <0.001 >100000 Zn 100 0.035 2857 Ga 100 0.0002 500000 Nb 100 0.393 254 Pb 100 0.004 25000

Purification of the Selected Organic Compounds

Quantitative Analysis

[0085] Based on the results collected in Table 3 below it can be seen that the .sup.68Ge purification process is efficient for all of the selected three organic compounds. All determined quantities in the final product after the purification procedure were below the determination limit of the applied analysis method.

TABLE-US-00004 TABLE 3 Determined quantities for selected organic compounds in the final product after the .sup.68Ge purification procedure. Measured Measured Measured Sample CCl.sub.4 n-heptane Sudan III Aliquot ppm ppm ppm 1 <d.l. <d.l. <d.l. 2 <d.l. <d.l. <d.l. 3 <d.l. <d.l. <d.l.

Qualitative Analysis

[0086] From the FIGS. 3-5 below it can be seen that the selected organic compound Sudan III is qualitatively removed by the Column I, and no remains of Sudan III can be observed in the final product.

[0087] Based on the results of the experiments it can be deduced that the developed novel radiochemical method is fully capable of purifying a .sup.68Ge-solution from metallic and organic impurities with very high purification factors, i.e. practically quantitatively, which then qualifies as pharmaceutically acceptable .sup.68Ge-API within the GMP-Guidelines.

LITERATURE

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