SYNTHESIS OF A RADIOACTIVE AGENT COMPOSITION

Abstract

The present invention relates to a method for the synthesis of a radioactive agent composition comprising at least a purification step carried out in the presence of an antioxidant, to the composition obtained by this method comprising radioactive agent and excipient, and to the method for preventing radiolysis of radioactive agent composition comprising the synthesis of said radioactive agent according to the method of the invention.

Claims

1. A method for the synthesis of a radioactive agent composition comprising at least a purification step carried out in the presence of an antioxidant.

2. The method according to claim 1 for which the radioactive agent is a halogen-labeled agent, preferably a fluoro-labeled agent.

3. The method according to claim 1 for which the radioactive agent is [18F]-fluoroestradiol (FES).

4. The method according to claim 1 comprising the following steps: i) Radioelement synthesis from 18-oxygen enriched water in order to get .sup.18F.sup.; ii) Radiolabeling of FES precursor with .sup.18F.sup. obtained at step i); iii) Purification of crude FES obtained at step ii) in the presence of an antioxidant.

5. The method according to claim 1 further comprising the step of formulating purified radioactive agent obtained after the purification step with excipient.

6. The method according to claim 5 for which the formulation step is carried out in the presence of an antioxidant.

7. The method according to claim 4 for which the radiolabeling step is carried out in the presence of an antioxidant.

8. The method according to claim 1 for which the antioxidant is chosen amongst ascorbic acid, polyphenols, glutathione, tocopherol, caffeic acid, alkali metal salts or alkaline earth metal salts of ascorbic acid.

9. The method according to claim 1 for which the antioxidant is chosen amongst ascorbic acid, alkali metal salts or alkaline earth metal salts of ascorbic acid.

10. The method according to claim 1 for which the antioxidant is sodium ascorbate.

11. The method according to claim 1 for which antioxidant is added during the synthesis in an amount at least equal to 0.1% m/v, preferably an amount comprised between 0.45% and 0.55% m/v.

12. Composition obtained according to the method of claim 1 comprising radioactive agent and excipient, the excipient comprising, antioxidant, sodium chloride and between 3 to 15% v/v of ethanol.

13. Composition according to claim 12 characterized in that the excipient comprises: from 0.4 to 0.5% m/v of sodium ascorbate; from 0.8 to 1.0wt % m/v of sodium chloride; from 3 to 15%, preferably between 3 to 10% v/v ethanol.

14. Composition according to claim 12 characterized in that the pH is comprised between 4.5 and 8.5 preferably between 4 and 8.

15. Method for preventing radiolysis of radioactive agent composition comprising the synthesis of said radioactive agent according to the method of claim 1.

Description

[0118] FIG. 1 is a HPLC chromatogram giving the concentration with reference to the retention time of crude [.sup.18F]FES synthesized without an antioxidant.

[0119] FIG. 2 is a HPLC chromatogram giving the concentration with reference to the retention time of crude [.sup.18F]FES synthesized in the presence of sodium ascorbate.

EXAMPLES

[0120] Abbreviates:

[0121] [.sup.18F]FES: [.sup.18F] Fluoroestradiol

[0122] Precursor: 3-O-methoxymethyl-16,17-O-sulfuryl-16-epiestriol

Example 1 (Comparative)

Synthesis of 1.SUP.18.F1FES without Adding of Antioxidant, Evaluation of the Influence of the Quantity of 18-Fluorine

[0123] [.sup.18F]fluoroestradiol was prepared on two different automatic apparatus, Neptis of ORA company or All-In-One of TRASIS company. The skilled person knows how to operate such a cassette-synthetizer in order to carry out the [.sup.18F]FES synthesis.

[0124] 18-Fluorine is prepared from .sup.18O(p,n).sup.18F reaction in a cyclotron by irradiation with protons of energy comprised between 14 and 18 MeV.

[0125] The 18-Fluorine preparation reaction is a classical reaction well-known by the skilled person. Enriched water of CIL, ROTEM or ORPHACHEM companies is used.

[0126] From 37 to 450 GBq of 18-Fluorine (equivalent to approximately 10 to 100 ng) previously formed is fixed on a polymeric and carbonated ion-exchange resin. The ion-exchange resin is then eluted by 0.4 to 1 mL of a solution of tetrabutylammonium hydrogenocarbonate with an eluent flow equal to 10 mL/min.

[0127] Eluate is transferred into the reactor and dry-evaporated at 95 C. under dried nitrogen. Acetonitrile is added into the reactor. At the end of this step, the temperature is lowered to a temperature comprised between 70 and 80 C.

[0128] From 0.5 to 10 mg of precursor in solution in acetonitrile is added and the temperature of the reactor is heated to 130 C. during 10 minutes for radiolabeling. Acetonitrile is partly evaporated during 90 seconds under 90 C.

[0129] Hydrolysis of the compound is carried out with a diluted solution of sulfuric acid in ethanol during 5 minutes at 110 C.

[0130] After hydrolysis, the reactive media is solubilized in water and fixed on a polymeric reversed-phase cartridge. Unreacted fluorides, solvents, and polar compounds (tetrabutylammonium, carbonate, sulfates, methoxy-methyl) are eliminated by the washing of the cartridge with water, then cartridge is eluted with acetonitrile.

[0131] Compound obtained exiting the reversed-phase cartridge is purified in High Pressure Liquid Chromatography (HPLC). The HPLC is characterized by a semi-preparative pump, a silica C8 to C18 column at a temperature comprised between 15 and 25 C.

[0132] Eluant is a mixture of purified water/acetonitrile/ethanol (55/40/5). Eluant flow is comprised between 2 and 5 mL/min.

[0133] The totality of the [.sup.18F]FES peak (from 2 to 8 mL) is collected and diluted in water, before to be fixed on a reversed-phase cartridge, identical to the previous one.

[0134] Reversed-phase cartridge is washed with 20 mL of water, and then elution with ethanol is carried out to collect [.sup.18F]FES solution which is diluted with isotonic injectable 0.9% m/v sodium chloride solution. [.sup.18F]FES stock solution is obtained.

[0135] Radiochemical purity of the [.sup.18F]FES stock solution is measured.

[0136] Several batches with different quantity of 18-Fluorine (QMA, GBq) have been evaluated. Quantity of [.sup.18F]FES obtained, decay corrected molar yield and radiochemical purity at the end of the synthesis are measured and/or calculated and given in Table 1.

[0137] The decay corrected molar yield is the [.sup.18F]FES molar yield at the end of the synthesis corrected by a decay factor, corresponding to the decay of 18-Fluorine used for the synthesis. Decay factor depends on the length of the synthesis.

TABLE-US-00001 TABLE 1 [.sup.18F]FES obtained, decay corrected molar yield and radiochemical purity at the end of the synthesis without antioxidant. Decay Quantity Quantity corrected Radio- of 18- of [.sup.18F]FES molar chemical Fluorine obtained yield purity Batch (GBq) (GBq) (%) (%) 1 153.6 41.1 43.2 98.5 2 180.8 45.8 40.2 99.3 3 219.2 61.2 43.7 98.3 4 238.0 48.8 32.1 98.9 5 246.0 53.4 33.8 98.4 6 257.8 57.1 34.9 97.2 7 274.0 44 25.1 97.0 8 280.8 43.3 26.1 96.0 9 282 48.0 29.1 95.9 10 480 59.1 19.3 93.0

[0138] These results show that when the quantity of 18-Fluorine used for the synthesis of [.sup.18F]FES increases, the quantity of [.sup.18F]FES obtained does not equally increase and thus the decay corrected molar yield of [.sup.18F]FES decreases. This shows that the industrially-scale production of [.sup.18F]FES without anti-oxidant is difficult because of the degradation (radiolysis) of [.sup.18F]FES when produced in high quantity.

[0139] Moreover, the radiochemical purity of the different batches decreases when the quantity of 18-Fluorine used for the synthesis increases.

Example 2 (Comparative)

Synthesis of [.SUP.18.F]FES with Antioxidant During Purification Steps, without Adding of Antioxidant in the Final Product, Evaluation of the Radiochemical Purity During Storage

[0140] The beginning of the synthesis (radioelement synthesis and radiolabeling steps) is identical to the one of example 1, except that the quantity of 18-Fluorine is equal to 250 GBq.

[0141] After hydrolysis, the reactive media is solubilized in an aqueous 0.5% m/v sodium ascorbate solution and fixed on a polymeric reversed-phase cartridge. Unreacted fluorides, solvents, and polar compounds (tetrabutylammonium, carbonate, sulfates, methoxy-methyl) are eliminated by the washing of the cartridge with an aqueous solution of sodium ascorbate. Then, the cartridge is eluted with acetonitrile.

[0142] Compound obtained exiting the reversed-phase cartridge is purified in High Pressure Liquid Chromatography (HPLC). The HPLC is characterized by a semi-preparative pump, a silica C8 to C18 column at a temperature comprised between 15 and 25 C.

[0143] Eluent is a solution of 0.5% m/v sodium ascorbate in purified water/acetonitrile/ethanol (55/40/5). Eluent flow is comprised between 2 and 5 mL/min.

[0144] The totality of the [.sup.18F]FES peak (from 2 to 10 mL) is collected and diluted in a 0.5% m/v aqueous sodium ascorbate solution, before to be extracted on a reversed-phase cartridge, identical to the previous one.

[0145] Reversed-phase cartridge is washed with 20 mL of a 0.5% m/v aqueous sodium ascorbate solution, and then eluted with ethanol. Then, [.sup.18F]FES solution collected is diluted with isotonic injectable 0.9% m/v sodium chloride solution. [.sup.18F]FES stock solution is obtained.

[0146] Radiochemical purity at the end of the synthesis, and after 4, 8 and 10 hours of storage is measured and given in table 2.

TABLE-US-00002 TABLE 2 Influence of the length of the storage on radiochemical purity, when synthesis is carried out without antioxidant. Time of storage Radio-chemical purity (hours) (%) 0 99.3 4 95 8 93 10 92

[0147] This table shows that the radiochemical purity decreases when the storage length increases. After 10 hours of storage, the radiochemical purity of [.sup.18F]FES when synthesized without antioxidant is decreased by 7.3%.

[0148] The chromatogram of purification of the crude [.sup.18F]FES is given in FIG. 1.

[0149] This figure gives the concentration of the different compounds with reference to the retention time. When no antioxidant is added during the synthesis, the impurities peak is wide and big.

[0150] This means that after purification, the crude [.sup.18F]FES comprises lots of impurities (radioactive or synthesis by-products), and the [.sup.18F]FES yield is lowered.

Example 3

Synthesis of [.SUP.18.F]FES in the Presence of Antioxidant (Sodium Ascorbate), Evaluation of the Influence of the Quantity of 18-Fluorine

[0151] Steps of radioelement synthesis and radiolabeling are identical to the one of example 1.

[0152] After hydrolysis, the reactive media is solubilized in an aqueous 0.5% m/v sodium ascorbate solution and fixed on a polymeric reversed-phase cartridge. Unreacted fluorides, solvents, and polar compounds (tetrabutylammonium, carbonate, sulfates, methoxy-methyl) are eliminated by the washing of the cartridge with an aqueous solution of sodium ascorbate. Then, the cartridge is eluted with acetonitrile.

[0153] Compound obtained exiting the reversed-phase cartridge is purified in High Pressure Liquid Chromatography (HPLC). The HPLC is characterized by a semi-preparative pump, a silica C8 to C18 column at a temperature comprised between 15 and 25 C.

[0154] Eluant is a solution of 0.5% m/v sodium ascorbate in purified water/acetonitrile/ethanol (55/40/5). Eluant flow is equal comprised between 2 and 5 mL/min.

[0155] The totality of the [.sup.18F]FES peak (from 2 to 10 mL) is collected and diluted in a 0.5% m/v aqueous sodium ascorbate solution, before to be fixed on a reversed-phase cartridge, identical to the previous one.

[0156] Reversed-phase cartridge is washed with 20 mL of a 0.5% m/v aqueous sodium ascorbate solution, and then eluted with ethanol. Then, [.sup.18F]FES solution collected is diluted with isotonic injectable 0.9% m/v sodium chloride solution containing 0.45% m/v sodium ascorbate. [.sup.18F]FES stock solution is obtained.

[0157] Radiochemical purity of the [.sup.18F]FES stock solution is measured.

[0158] Several batches with different quantity of 18-Fluorine (QMA, GBq) have been evaluated. Decay corrected molar yield and radiochemical purity at the end of the synthesis are calculated and given in Table 3.

TABLE-US-00003 TABLE 3 quantity of 18-Fluorine (QMA, GBq), decay corrected molar yield and radiochemical purity calculated at the end of the synthesis when carried in the presence of sodium ascorbate. Decay Radio- Quantity Quantity corrected Radio- chemical of 18- of [.sup.18F]FES molar chemical purity after Batch Fluorine obtained yield purity 10 h storage number (GBq) (GBq) (%) (%) (%) 1 79 46.7 86.4 98.8 98.0 2 99 16.6 68.8 99.5 99.0 3 164 78.4 69.8 98.0 96.7 4 195 98.9 74.1 97.5 97.1

[0159] The decay corrected molar yield of [.sup.18F]FES obtained at the end of reaction when sodium ascorbate is added during all the synthesis step from purification to formulation, is much higher than when the synthesis occurs without antioxidant.

[0160] Moreover, this table shows that high quantity of [.sup.18F]FES may be synthesized with a high yield. Indeed, when compared to table 1, when there is not antioxidant, for the same quantity of 18-Fluorine used, the decay molar yield is doubled.

Example 4

Synthesis of [.SUP.18.F]FES in the Presence of Antioxidant (Sodium Ascorbate), Evaluation of the Radiochemical Purity During Storage

[0161] The synthesis is identical to the one of example 3, except that the quantity of 18-Fluorine is equal to 164 GBq.

[0162] Radiochemical purity at the end of the synthesis, and after 5 and 10 hours of storage is measured and given in table 4.

TABLE-US-00004 TABLE 4 Influence of the length of the storage on radiochemical purity, when synthesis is carried out in the presence of sodium ascorbate. Time of storage Radio-chemical purity (hours) (%) 0 98.0 5 96.8 10 96.7

[0163] This table shows that the radiochemical purity decreases much less faster when the storage length increases. After 10 hours of storage, the radiochemical purity of [.sup.18F]FES when synthesized in the presence of sodium ascorbate is decreased by 1.3% (compared to 7.3% when the synthesis is carried out without sodium ascorbate).

Example 5

Synthesis of [.SUP.18.F]FES in the Presence of Sodium Ascorbate, Purification Chromatogram

[0164] The synthesis is identical to the one of example 3, except that the quantity of 18-Fluorine is equal to 260 GBq.

[0165] The chromatogram of purification of the crude [.sup.18F]FES obtained when synthesized in the presence of sodium ascorbate is given in FIG. 2.

[0166] This figure gives the concentration of the different compounds with reference to the retention time. When sodium ascorbate is added during the synthesis, the impurities and degradation products peak is almost nonexistent.

[0167] This means that after purification, the crude FE[.sup.18F]FES does not comprise as much impurities as when no antioxidant is added during the synthesis and the final yield and the final radiochemical purity are enhanced.