WO2013037957A1 - Method for purifying contrast media - Google Patents

Abstract

The present invention relates to a method for purifying a gallium Ga68-radiolabeled contrast medium including a gallium Ga68-radiolabeled chelate vectorized by a folate or folate-derivative targeting ligand, the method including the following consecutive steps: preparing a solution of the chelate vectorized by a folate or folate-derivative targeting ligand that is not radiolabeled; radiolabeling the vectorized chelate with Ga68 in a complexing solution in order to obtain a radiolabeled, vectorized chelate solution; purifying the resulting solution by using a purification means to remove at least one radiolabeled impurity that includes a radiolabeled chelate vectorized by a folate oxidation residue, and simultaneously removing the free or colloidal gallium Ga68 and the traces of ⁶⁸Ge; and recovering the purified solution containing the gallium Ga68-radiolabeled chelate vectorized by a folate or folate-derivative targeting ligand, and having a purity of at least 95%.

Description

 PROCESS FOR PURIFYING CONTRAST PRODUCTS

 The invention relates to the purification of products for PET medical imaging (positron emission tomography), and in particular of products containing a radionuclide for PET gallium 68 imaging. The invention relates in particular to products derived from folic acid radiolabeled with gallium.

 The document WO 2007/042504 in the name of the applicant explains in detail the interest of the PET imaging, in particular gallium 68 (Ga68) very advantageous because not requiring the use near or within the hospital. radionuclide production equipment (cyclotron) very bulky and very expensive.

 The Ga68 produced by a small dedicated generator is coupled to a vectorized chelate (indifferently called cold kit in the present application) not yet radiolabeled, the coordination reaction (complexation of the radionuclide by the cold kit) providing a radiolabeled vectorized chelate (indifferently called vector chelate complexed in the present application) to Ga68 and which is administered to the patient for PET imaging.

 More specifically, the vectorized chelate comprises a targeting part (indifferently called targeting agent, targeting ligand or biovector in the present application) of a specific biological target (cellular receptor for example), in particular of a pathological zone of diagnostic interest, this targeting portion being typically connected by a chemical bond (covalent bond by any suitable linker group) to the chelate representing the signal portion. This chelate is capable of complexing the radionuclide, in particular Ga68, and many macrocyclic chelates are used, in particular of DOTA, NOTE, PCTA type.

 More precisely, the solution of gallium (Ga68 radioactive), eluate of the gallium generator, is mixed in a dedicated and protected area of the hospital, zone designated radiopharmacy, with a vectorized chelate solution prepared in advance (the cold kit ) supplied by the contrast manufacturer.

Advantageously, the mixing is done in an automaton in which are introduced on the one hand the dose of Ga68 eluate generator and secondly the dose of chelate vectorized (not yet radiolabeled by Ga68). Given the short lifetime of the radionuclide (68 minutes for gallium 68) in clinical practice, it is still sought to improve the conditions of preparation of the radiolabeled contrast agent, and in particular to obtain a very fast and complex complexation. simple. In addition, the level of purity of the gallium radiolabeled vectorized chelate must be very high to be injectable in humans for diagnostic imaging. The target purity level is substantially at least 95%, and preferably at least 97% or 98%.

 WO 2007/042504 describes the preparation of numerous gallium Ga68-labeled vectorized chelates, especially compounds whose targeting ligand is a peptide or a derivative of folic acid. The applicant seeks in particular to obtain compounds FOLATE-NOTE, FOLATE PCTA and HOPO-FOLATE. The FOLATE-NOTA derivatives are in particular described in the CIP No. 13 / 205,352.

 For those skilled in radiopharmacy, it is known to purify the Ga68 eluate at the outlet of the gallium generator, any impurities of the generator, to maximize the complexation yield. For example, the document WO2006056395 describes the purification using a column intended to purify the Ga68 eluate produced by the gallium generator, the impurities being for example TiO 2 and the parent Ge68 radionuclide from which the Ga68 is derived. It is a question of purifying the Ga68 before its complexation by the vectorized chelate.

 It is also known to remove from Ga68 radiolabeled vector chelate solution gallium which has not reacted and remains free in solution (Ga68 impurity of the order of 1%), in order not to inject this radioactive free Ga68. to the patient. Thus, according to the literature associated with DOTATOC-Ga68 (octreotide), a human clinical product whose ligand is a peptide, Ga68 is removed by chromatography techniques such as silica columns, as described in Decristoforo et al. , Nuclear Medicine Communications, 2007, Vol 28, No. 11, pages 870-875 and Bauwens et al, Nuclear Medicine Communications, 2010, Vol 31, No. 8, pages 753-758.

Columns of hydrophobic silica grafted with a C 8 alkyl (octadecyl) group such as Sep Pak® Cl 8 from Waters or with a C 8 (octyl) alkyl group appear quite satisfactory for the usual purification of Ga68 radiolabelled products. . It is recalled that known extraction techniques for the purification of Ga68 radiolabelled products are in particular solid phase extraction columns. Solid phase extraction is a chromatographic sharing technique consisting of passing the solution to be purified through a single-use cartridge containing the absorbent (stationary phase), in the form of porous silica particles, functionalized on their surface with groups hydrophobic usually C8 (octyl) or Cl 8 (octadecyl). These absorbents are usually wetted with an organic polar solvent to solubilize the alkyl chains and thereby increase the solute retention area.

 The Applicant specifically working on gallium Ga68 radiolabelled products comprising a chelate, particularly the NOTA, vectorized by a targeting ligand derived from folate, has unexpectedly found using known purification means such as the Sep Pak ® column. Cl 8 de Waters, a purity only of the order of 90 to 92% of the radiolabeled vectorized chelate solution obtained after complexation. This purity is satisfactory for use in medical research, but prevents or at least poses a substantial problem for administering the product to humans.

 The applicant therefore had to solve several new technical problems, unknown to the prior art to his knowledge, in the case of Ga68 complexation of products comprising a chelate vectorized by a folate or its derivatives, in particular when the chelate is a NOTE.

The usual columns, in particular SEP Pak® Cl 8 used for example for DOTATOC as indicated in the prior art, are unsatisfactory for obtaining the good radiolabelled product and for separating it from free or colloidal gallium 68 Ga as well as residues of 68 Ge. The complexation of the chelate, in particular NOTA, vectorized by a folate or its derivatives under the conditions of complexation of gallium (complexation in buffer solution, for example acetate buffer, with heating or at room temperature) is accompanied, although the vectorized chelate before radiolabeling is of high purity, the appearance of an impurity forming in the complexation reaction medium in large proportions, of the order of 5 to 8%. After careful study, the plaintiff was able to identify this impurity. This impurity comprises an oxidative cleavage residue of the chelate, in particular NOTA, vectorized by a folate or its derivatives, more specifically an N- (4-aminobenzoyl) -L-glutamic-NOTE compound in the case where the complex is a NOTE, which also complexes the Ga68. This impurity is therefore a radiolabeled chelate vectorized by a folate deprived of its pteridine part. The folate deprived of its pteridine part is designated FOLATEoxy in the application. The radiolabeled chelate is vectorized by a folate oxidation residue, that is to say by FOLATEoxy.

 It is necessary to eliminate this impurity together with the elimination of gallium free or colloidal and residues of 68 germanium because due to this oxidative cleavage, the folate can no longer fulfill its target function within the body satisfactorily. and the purity profile of the product administered to the patient should be known and controlled as much as possible to avoid any clinical risk. In particular, the pharmaceutical use recommends purities greater than 93%.

 Moreover, the applicant has realized that the chelates, such as the NOTE, radiolabeled and vectorized by folate are not sufficiently retained by the conventional purification columns, which leads to a major loss of the radiolabelled product, the order of 50%. Consequently, the dose of radioactivity (in Mbq) of the radiolabelled product purified with the usual purification means of the prior art is not sufficient for PET diagnostic imaging, which makes the product concretely ineffective in the man.

The non-retention of the radiolabeled chelates vectorized by a folate or derived by the conventional purification columns, type Sep Pack® Cl 8 from Waters, was unexpected: folic acid and its derivatives are known to those skilled in the art as a compound very hydrophobic (hydrophobicity is associated in particular with the interactions Pi of aromatic rings, and with the lightly charged character of the molecule, it is besides known that this hydrophobicity can generate aggregates between the molecules because of the interactions between cycles Pi of the molecules ). There was no reason to use even more hydrophobic columns; the chelates vectorized by a folate or derivative of the applicant when the chelates are NOTA have a still greater hydrophobicity compared to that of the chelates which are not NOTA and which have only one free charge (with respect to the DOTA -TOC, the modification on the chelate side leads to a neutral complex for this part of the molecule), hence an even greater hydrophobicity;

 the chelates vectorized by a folate or derivative, in particular when the chelate is a NOTE, of the applicant being retained on the conventional Sep Pack® Cl 8 analysis columns, there was no reason that they should be not satisfactorily on the purification columns under the conditions of use of products radiolabeled with Ga68 (with DOTA-TOC or DOTA AMBA compounds in particular as reference).

 The applicant was thus surprised to find that these conventional hydrophobic silica columns grafted C 18 are not sufficient to purify the solution of radiolabeled chelates by Ga68 vectorized with a folate or derivative, especially when the chelate is a NOTE.

 The requester identified columns:

 the nature of which makes it possible to selectively separate the impurity from the good product, the oxidation product of folate (folate less pteridine = FOLATEoxy) having a polarity different from that of the non-oxidized folate and thus it is the same for the vectorized chelate by FOLATEoxy and chelate vectorized by folate;

having a high amount and hydrophobicity of the stationary phase to capture sufficient radiolabeled folate vectorized chelate, particularly in the case where the chelate is a NOTE, to have a dose of at least 150 MBq.

 The applicant has found that hydrophobic columns, in particular Sep Pack® tC 18 900 mg of Waters, which are very hydrophobic silica columns grafted with a C18 alkyl group and whose silanol functions are protected, having the characteristics following:

 particle size: 37-55 μιη

 - pore size of the order 125 A °

 - carbon percentage: 17%.

were particularly useful for purifying the radiolabeled chelate vectorized by a folate or derivative, especially when the chelate is a NOTE or derivative.

 It is understood that other columns than the Sep Pack® tC18 columns of Waters are usable (for example companies Waters, Millipore, Agilent, Phenomenex) insofar as they have the analogous or superior properties including hydrophobicity. The principle is to use means of partition chromatography, stationary phase / nature of the eluent, to selectively obtain the right product and the impurity. For example, it is possible to use particle sizes of 55 to 105 μηι.

 It is pointed out that the prior art of the purification of gallium-68-labeled complexes does not describe, to the applicant's knowledge, purification processes involving problems due to the nature of the biovector of the vectorized chelate for gallium complexation and in particular to folate compounds.

 The present invention thus relates to a method for purifying a gallium Ga68-labeled contrast material comprising a gallium Ga68 radiolabeled chelate vectorized by a folate or folate-derived targeting ligand, the method comprising the following successive steps:

 a) preparing a solution of the chelate vectorized by a folate targeting ligand or non-radiolabelled folate derivative;

 b) Ga68 radiolabeling of the complexing solution vectorized chelate to obtain a radiolabelled vector chelate solution;

 c) purifying the resulting solution by removing with the aid of means for purifying at least one radio labeled impurity which comprises a Ga68 radiolabeled chelate chelator vectorized by a folate oxidation residue;

 d) recovering the purified solution containing the gallium Ga68 radiolabeled chelate vectorized by a folate or folate-derived targeting ligand with a purity of at least 95%.

 For the purposes of the present invention, the term "folate or folate-derived targeting ligand" means folic acid and its derivatives, in particular described in the CIP No. 13 / 205,352, that is to say capable of targeting the folate receptor.

Advantageously, the folate or folate-derived targeting ligand has the following general formula (A):

u (B) suivante:

u (B) next:

and their tautomers

in which:

 represents the binding site of the folate targeting ligand or folate derivative to the chelate, directly or via a chemical bond;

Gi is selected from the group consisting of: a halogen atom, R _f 2, OR _f 2, SR _f 3 and NR R _f 5, preferably Gl is selected from NH 2 and OH, more preferably Gl is OH;

G ₂ is selected from the group consisting of: a halogen atom, R _f 2, OR _f 2, SR _f 3 and NR _{f 4} R _f 5, more preferably G ₂ is NH ₂ ;

G ₃ represents a divalent group selected from the group consisting of - (R _f 6 ') C = and - N = and G ₄ represents a divalent group selected from the group consisting of - (R _f 6') C- and -N - or

G ₃ represents a divalent group selected from the group consisting of - (R _f 6 ') C- and - N- and G ₄ represents a divalent group selected from the group consisting of - (R _f 6') C = and -N = or G ₃ and G ₄ independently represent a divalent group selected from the group consisting of - (R _f δ ') C (R _f 7') - and -N (R _f 4 ') -;

 Advantageously, G3 is -N = (folic acid) or -CH- (compounds described hereinafter: CB3717, raltitrexed, MAI) when the ring comprising G3 is aromatic, and G3 is -NH- or -CH2- (compounds described herein after: AG-2034, lometrexol) when the nucleus comprising G3 is nonaromatic.

 Advantageously, G4 is -CH- or -C (CH3) - when the ring comprising G3 is aromatic, and -CH2- or -CH (CH3) - when the ring comprising G3 is non-aromatic.

 Advantageously G3 represents a divalent group selected from the group consisting of - (Rf6 ') C = and -N =, and G4 represents a divalent group selected from the group consisting of - (Rf6') C- and -N-. More preferably G4 is - (Rf6 ') C-.

 More preferably G3 is -N = and G4 is-(Rf6 ') C-, still more preferably G4 is -CH-.

 In another advantageous embodiment, G3 represents - (Rf6 ') C =, advantageously -CH = and G4 represents- (Rf6') C- still more advantageously G4 is -CH-.

G ₅ is absent (pemetrexed compound) or is selected from - (R _f 6 ') C =, - N =, - (R _f 6') C (R _f 7 ') - and -N (R _f 4') - more advantageously G ₅ is chosen from - (R _f 6 ') C = and -

N =;

 J is a 5- or 6-membered aryl or heteroaryl group, preferably J is a phenyl group.

_O G is N or C (compound described below: 3-deaza-ICI-198.583), advantageously G6 is N;

K ₁ and K ₂ are independently selected from the group consisting of -C (Z _f ) -, -C (Z _f ) O-, -OC (Z _f ) -, -N (Rf 4 ") -, -C (Zf) -N (R f 4), -N (R f 4 ") - C (Z _f) -0-C (Z _f) -N (R f 4") -, - N (R f 4 ") - C (Z _f) -0- , N (R f 4 ") - C (Zf) -N (R _f 5") -, -O-, -S-, -S (O) -, -S (0) ₂ -, - N (R 4 _Î ") S (O) ₂ -, -C (R _f 6") (R _f 7 ") -, -N ( ^C≡CH ) -, -N (CH ₂ -C ^≡CH ) -, alkyl in the form of and C ₁₂ alkoxy-Cl _{2; f} wherein Z is O or S; preferably is Ki - N (R f 4 ") - or -C (TER") (R _f 7 ") - with R f 4", Rf6 _"f and R 7" is H; preferably K ₁ is -N (R _f ") - more advantageously -NH-; Advantageously K ₂ is -C (Z _f ) -, more advantageously -CO.

R _f 2, R _f 3, R _f 4, Rf 4 ', R _f 4 ", R _f 5, R _f 5", R _f 6 "and R _f 7" are independently selected from the group consisting of: H, halogen atom, C 1 -C alkyl, alkoxy

C ₁ -C ₁₂ alkanoyl, C ₁ -C _12, alkenyl C ₂ -C ₁₂ alkynyl, C ₂ -C ₁₂ alkoxy (Ci -C ₂₎ alkoxycarbonyl, and (alkylamino C ₁ -C ₁₂₎ alkoxycarbonyl ; advantageously R _f 4 ", R _f 6" and R _f 7 "are H

R _f 6 and R _f 7 'are independently selected from the group consisting of: H, halogen, C ₁ -C ₁₂ alkoxy and C ₁ -C ₁₂ alkyl; or R _f 6 'and R _f 7' together form

= 0; advantageously Re and R7 are both H

R _O and R ₇ are independently selected from the group consisting of: H and C ₁ -C ₁₂

 Lf is a divalent chemical linkage, including, where appropriate, a naturally occurring amino acid or a natural polyamino acid, such as for example glutamine (Gin), bound to

K2 by its alpha-amino group via an amide bond; Advantageously Lf is glutamine.

 p, r and s are independently 0 or 1 and

 x is an integer of 1 to 5, advantageously 1.

 Advantageously, the targeting ligand folate or folate derivative has the general formula (A).

 Formulas (A) and (B) include their tautomeric forms, for example for compounds in which Gi is OH, SH or NH.

Advantageously in this case, the tautomeric forms of the compounds of formula (A) and (B) are as follows: Tautomeric form of (A):

Shape tautomèr

dans lesquelles G₂-G5, Re, R7, i, K₂, Lf, J, s, p, r et x sont tels que définis ci-dessus, Gi représente O, S or N et Ge représente CH or NH, avantageusement Gi représente O, avantageusement Ge représente NH.

in which G ₂ -G 5, Re, R 7, I, K ₂ , Lf, J, s, p, r and x are as defined above, Gi is O, S or N and Ge is CH or NH, advantageously Gi represents O, advantageously Ge represents NH.

Advantageously when at least one of the groups K ₁ , K ₂ , R _f 1, R _f 2, R _f 3, R _f 4, R _f 4 ^! R _f 4 ", R _f 5, R _f 5", R _f 6, R _f 7 ", R _f 6, R _f 7, R _f 6 'and R _f 7' include an alkyl, alkoxy, alkylamino group, alkanoyl, alkenyl, alkynyl, alkoxycarbonyl or alkylaminocarbonyl, the group preferably contains 1 to 6 carbon atoms (C 1 -C e), more preferably 1 to 4 carbon atoms (C 1 -C 4).

Advantageous folate or folate-derived targeting ligands include the following folate derivatives and their tautomeric forms

 at)

wherein * represents the binding site of the folate targeting ligand or folate derivative to the chelate, directly or via a chemical linkage.

 R1 R2 R3 R1 R2 R3

MTX NH ₂ N CH ₃ 2-dAMT HNH

2-dMTX HN CH ₃ 2-CH ₃ -AMT CH ₃ NH

2-CH ₃ -MTX CH ₃ N CH ₃ Edatrexate NH ₂ CC ₂ H ₅

AMT NH ₂ NH

dans lesquelles J est tel que défini ci-dessus.

in which J is as defined above.

 Glu = glutamic acid

 wherein * represents the binding site of the folate targeting ligand or folate derivative to the chelate, directly or via a chemical linkage.

Advantageously, the folate or folate-derived targeting ligand has the following formula (a1) or (a2)

 (A2)

in which * represents the binding site of the folate targeting ligand or folate derivative to the chelate, directly or via a chemical linkage

and their tautomeric forms.

 The folate or folate derivative targeting ligands include the following derivatives: pteropolyglutamic acid, pteridines capable of targeting the folate receptor (tetrahydropterins, tetrahydrofolates, dihydrofolates in particular).

 The folate-derived targeting ligands also include the following compounds: aminopterin, amethopterin (methotrexate), N-methylfolate, 2-deaminohydroxyfolate; and their deaza derivatives such as 1-deazamethopterin or 3-deazamethopterin, and 3 ', 5'-dichloro-4-amino-4-deoxy-N-methylpteroylglutamic acid (dichloro methotrexate).

The folate-derived targeting ligands also include the deaza or dideaza compounds. The terms "deaza" and "dideaza" refer to known derivatives of folic acid, which do not have nitrogen atoms G ₃ , G ₅ , Ge. For example, the deaza derivatives include the derivatives 1-deaza, 3-deaza, 5-deaza, 8-deaza and 10-deaza.

In one embodiment, the chelate is a NOTE or derived from the NOTE. The NOTA or derivatives of the NOTE are well known to those skilled in the art and are in particular described in the CIP No. 13 / 205,352.

 These NOTA or derivatives are capable of complexing gallium Ga68. They have a NOTA skeleton or derivatives such as NET A, TACN-HP and NODAGA.

NOTE is in particular chosen from:

 - NOTE where * represents the binding site between the NOTA molecule and the folate or folate-derived targeting ligand directly or via a chemical linkage.

- NODA-GA in which * represents the binding site between the molecule NOTA and the targeting ligand folate or folate derivative directly or via a chemical bond.

and any NOTA derivative capable of complexing Ga68, especially that having the following formula in which * represents the binding site between the molecule NOTE and the folate or folate-derived targeting ligand directly or via a chemical bond

By extension, NOTA includes NETA chelates capable of complexing Ga68 with comparable complexation rates. Advantageously, the NOTE or derivative of the NOTE has the following general formula (II):

dans laquelle m est un nombre entier entre 0 et 10, avantageusement entre 1 et 5, encore plus avantageusement de 2 et X₂ représente une fonction de liaison entre la molécule NOTA et le ligand de ciblage folate ou dérivé du folate directement ou par l'intermédiaire d'un lien chimique. Avantageusement X₂ est choisi dans le groupe constitué par -CONH-, -COO-, -NHCO-, -NH-, -CO- et -OCO-. Plus avantageusement X₂ représente le groupe - CONH- ou -NH, Encore plus avantageusement le groupe -CONH.

in which m is an integer between 0 and 10, advantageously between 1 and 5, still more preferably 2 and X ₂ represents a binding function between the molecule NOTA and the targeting ligand folate or derived from folate directly or by the intermediate of a chemical bond. Advantageously X ₂ is selected from the group consisting of -CONH-, -COO-, -NHCO-, -NH-, -CO- and -OCO-. More preferably, X ₂ is -CONH- or -NH, still more preferably -CONH.

 More advantageously, when the NOTE is complexed (or radiolabelled) with Ga68, the NOTE thus has the following formula III

wherein m and X ₂ are as defined above. More preferably, the NOTE has the following formula (IV):

wherein * represents the binding site between the NOTA molecule and the folate or folate-derived targeting ligand directly or via a chemical linkage.

 More preferably, when NOTA is radiolabeled with Ga68, NOTE thus has the following formula V:

wherein * represents the binding site between the NOTA molecule and the folate or folate-derived targeting ligand directly or via a chemical linkage.

 In a particular embodiment, the folate or folate-derived targeting ligand is linked to the chelate via a chemical linkage. This link is in particular defined in the CIP n ° 13 / 205,352 under the name of LINKER. It is a link that can react with at least one functional group of the folate or derivative targeting ligand and with at least one functional group of the chelate such as the NOTE.

 Advantageously, the chemical bond is chosen from:

 a.1) - a single link;

- - (CH ₂ ) _n -, - (CH ₂ ) _n CO-, - (CH ₂ ) _n NHCO-, - (CH ₂ ) _n CONH- - (CH ₂ ) _n CONH (CH ₂ ) _n , - ( CH ₂ ) _n phenylNH-, - (CH ₂ ) _n NH-, -NH (CH ₂ ) _n NH-, - (CH ₂ ) _n phenyl-, and -NH (CH ₂ ) _n - with n = l-20 ;

- (CH ₂ CH ₂ 0) _q (CH ₂ ) _r CO-, (CH ₂ CH ₂ 0) _q (CH ₂ ) _n NH-CO-, - (CH ₂ CH ₂ 0) _q (CH ₂ ) r- (CH ₂ CH ₂ 0) _q (CH ₂ ) _n NH- with q = 1-10 and r = 2-10;

- - (CH ₂ ) _n -CONH-PEG-,,

(CH2) n

 PEG- (CH2) n

 NOT

 Where * represents the chelate binding site, with n = 1 to 5;

-CO-CH ₂ -O- (CH ₂ ) _n -O- (CH ₂ ) _p -O-CH ₂ -CO-, -CO- (CH ₂ ) _n -C0 ₂ - (CH ₂ ) _p -OCO - (CH ₂ ) _q -CO-, -CO-CH (OH) -CH (OH) -CO-; CO- (CH ₂ ) _n -CO-; -CO-CH ₂ -O- (CH ₂ ) _n -O- (CH ₂ ) _p -O-CH ₂ -, -CO- (CH ₂ ) _n -C0 ₂ - (CH ₂ ) _p -OCO- (CH) ₂ ) _q -, -CO-CH (OH) -CH (OH) - and -CO- (CH ₂ ) _n -, with n = 1-20, p = 1-20 and q = 1-20;

- -NH- (CH ₂ ) n-CO; -NH-CH ₂ - (CH ₂ -O-CH ₂ ) n -CO- and -NH-CH ₂ - (CH ₂ -O-CH ₂ ) n- with n = 1 to 10; a.2) -P1-1-P2 with PI and P2 identical or different are selected from O, S, NH, nothing, CO ₂ , NHCO, CONH, NHCONH, NHCSNH, SO ₂ NH-, NHS0 ₂ - and squarate with 1 = alkyl, alkoxyalkyl, polyalkoxyalkyl (PEG), alkyl interrupted by one or more squarates or by one or more aryls, alkenyls, alkynyls, alkyls which are interrupted by one or more groups selected from -NH-, -O-, -CO -, - NH (CO) -, - (CO) NH-, -O (CO) -, or - (OC) O-

More advantageously, the chemical bond is chosen from:

- (CH ₂ ) _n- , - (CH ₂ ) _n CO-, - (CH ₂ ) _n NHCO-, (CH ₂ ) _n CONH-, - (CH ₂ ) _n phenylNH-, in particular - (CH ₂ ) _2- phenylNH-, - (CH ₂ ) _n NH-, in particular - (CH ₂ ) ₃ NH-, -NH (CH ₂ ) _n NH- in particular NH (CH ₂ ) ₂ NH or NH (CH ₂ ) ₃ NH, - (CH ₂ ) _n phenyl-, in particular - (CH ₂ ) ₂ phenyl and - NH (CH ₂ ) _n -, in particular NH (CH ₂ ) _2- or NH (CH ₂ ) ₃ , with n = 1-20, advantageously n = 2 to 10, - (CH ₂ ) _n -CONH-PEG-,,

dans laquelle * représente le site de liaison au chélate, avec n=l à 5 et avantageusement n=4 ou 5.

in which * represents the chelate binding site, with n = 1 to 5 and advantageously n = 4 or 5.

Even more advantageously, the chemical bond is chosen from - (CH ₂ ) _n -, - (CH ₂ ) _n CO-, - (CH ₂ ) _n NHCO-, (CH ₂ ) _n CONH- - (CH ₂ ) _n phenylNH- in particular - (CH ₂ ) ₂ phenylNH-, - (CH ₂ ) _n NH- in particular - (CH ₂ ) ₃ NH-, -NH (CH ₂ ) _n NH- in particular NH (CH ₂ ) ₂ NH or NH (CH ₂ ) ₃ NH, - (CH ₂ ) _n phenyl-, in particular - (CH ₂ ) ₂ phenyl and - NH (CH ₂ ) _n - in particular NH (CH ₂ ) ₂ - or NH (CH ₂ ) ₃ -, with n = 1-20, advantageously n = 2 to 10.

Even more advantageously, the chemical bond is - (CH ₂ ) _n -, with n = 1-20, advantageously n = 2 to 10, in particular 2. this type of chemical bond is particularly advantageous since it is easier to couple the targeting ligand folate or folate derivative with a chelate such as NOTE using - (CH ₂ ) _n -.

Advantageously, in the context of the present invention, the folate or FOLATEoxy oxidation residue has the following formula

dans laquelle * représente le site de liaison du FOLATEoxy au chélate.

in which * represents the binding site of FOLATEoxy to the chelate.

 In a particular embodiment, the chelate vectorized by a folate targeting ligand or non-radiolabeled folate derivative according to the invention is chosen from the compounds of the following general formula:

Compound 2 'is particularly advantageous.

These compounds, when complexed (radiolabeled) by Ga68, have the following formula:

 Compound 2 is particularly advantageous.

 In this case, the radiolabeled impurities obtained following the oxidation of the folate derivatives and thus vectorized by FOLATEoxy have the following formulas:

 In a particular embodiment, the purification means of step c) is a solid phase extraction column whose stationary phase is hydrophobic and neutral.

A column is used to selectively fix only the right product (radiolabeled chelate vectorized by the folate targeting ligand or derivative) or only the impurity because of their difference in affinity for the hydrophobic column. It is also possible to graft the right product and the impurity, then selectively elute one and / or the other.

 In an advantageous embodiment, the purification means of step c) is a solid phase extraction column whose stationary phase is hydrophobic and neutral with a carbon content of at least 15%, advantageously from minus 17%, advantageously between 15 and 17%, still more advantageously 17% and in that step c) consists of:

cl) the selective binding on this column of the radiolabeled chelate vectorized by the folate or derivative targeting ligand and the elimination of the impurity and

c2) eluting with a suitable polar solvent the radiolabeled chelate vectorized by the folate targeting ligand or derivative attached to the column.

 Advantageously, the appropriate solvent for the elution used in step c2) is a mixture of water and ethanol, advantageously the mixture contains between 10 and 50% of ethanol.

 In particular use is made of columns whose carbon content is quite high, of the order of at least 15%), advantageously at least 17%, in particular between 15 and 17%, which is correlated with a high hydrophobicity, a particle size advantageously having 55-105 μιη, preferably 30-60 μιη, in particular 37-55 μιη, and a pore size advantageously of 100 -150 Å. In particular, 900mg / l, 4ml columns are used as detailed in the examples.

 Advantageously, the preferred columns are columns with stationary silica phase. Because of the difference in polarity (hydrophobicity) between the good product (radiolabeled chelate vectorized by the folate or derivative targeting ligand) and the impurity, the elution with a suitable solvent (water / ethanol mixture for example) makes it possible to obtain the right product with a very high purity yield (at least 93%). Other columns with high hydrophobicity are of interest such as polymer columns of the type of resin columns with divinylbenzene, vinylpyrrolidone compounds, their derivatives and combinations thereof.

According to variants, it is possible to use columns that perform less well in terms of hydrophobicity, by using mechanical means intended in particular to increase the contact time of the solution with the stationary phase. Such variations are conceivable if they comply with good radiopharmacy practices while enabling the desired high level of purity to be attained (at least 93%), but they are less advantageous for reliably and reproducibly producing products with a high degree of purity. purity, especially in practice the complexation and purification are performed in automata to limit the intervention and exposure of operators to radiolabelled products.

 Advantageously, the optional free residual Ga68 is also removed by the purification means of step c).

 In another embodiment, it may be eliminated during step b), and therefore before step c) or in a subsequent step.

 Advantageously, the charge of the column is at least 600 mg of stationary phase, preferably at least 900 mg.

Advantageously, the silica is grafted with an alkyl group, in particular with C ₁₈ . Advantageously, the silanol groups of the silica are protected. Even more advantageously, the silica is grafted with an octadecyl group and its silanol functions are protected.

Advantageously, the grafted silica has the formula SiCi ₈ H ₃₇ .

 Preferably, a hydrophobic column, in particular Sep Pack® tC18 900 mg of Waters, having the following characteristics:

silica grafted with a C ₁₈ alkyl group of formula SiOCi ₈ H ₃₇ , the silanol groups of which are protected.

 particle size: 37-55 μιη

 - pore size of the order 125 A °

- carbon percentage: 17%.

 The applicant has had both to increase the retention capacity and hydrophobicity of the column used.

Advantageously, the tC18 columns are not efficient enough for the retention capacities corresponding to a load, in particular of the order of 145 to 300 mg; under the conditions of complexation described and with the volumes of solution radiolabeled at purify, it is necessary to use tC18 columns with a load of at least 600 mg, very advantageously of the order of 900 mg.

 The steps a) and b) preparation and radiolabeling are well known to those skilled in the art and in particular are described in the application WO 2007/042504.

 Advantageously, the extraction column is rinsed before use in the process according to the invention, advantageously by the eluting solvent, in particular with ethanol and then with water.

 The invention is illustrated with the aid of the following figures and nonlimiting examples. Description of the figures:

FIG. 1 represents the medium before purification (Satin detector) and FIG. 2 the medium after purification using the 900 mg SepPack tC18 column (WAT 036800) according to Example 3.

Example 1 Synthesis of [Folate Dideaza-NODAGA-Ga68]

Etape 1 :

Step 1 :

0.5 g of intermediate 2 is dissolved in 20 ml of CH ₃ CN in the presence of 0.6 g of K ₂ CO ₃ . A suspension of the brominated derivative (Int.1) in 20 ml of CH ₃ CN is added thereto. The reaction medium is maintained under reflux, under argon, with vigorous stirring, for 18 h. After cooling to room temperature, the reaction medium is filtered. The insoluble material is taken up in 20 ml of water and filtered. The filtrate is evaporated under pressure. The residue obtained is taken up in Et ₂ 0 and is then filtered. 1.2 g of product is obtained. [M + H] + = 423.16

 2nd step:

0.6 g of the intermediate obtained in the previous step (Int 3) is suspended in 2.4 ml of ethanol. The dissolution is complete after the addition of 6 ml of 1 M NaOH. The reaction medium is stirred for 1 h 30 at 70 ° C. After returning to ambient temperature, the medium is brought to pH 1 by addition of 6N HCl. The suspension obtained is filtered and then washed with water and then with ethanol. After drying, 0.35 g of product is obtained (yield = 80%). [M + H] ⁺ = 311.10

 Step 3:

Int.4 (1.8 mmol) and Int.5 (1.8 mmol) are dissolved in DMF at room temperature under anhydrous conditions (CaCl ₂ ). 1.4 eq of HOBT (2.5 mmol) then 1.4 eq of EDCI (2.5 mmol) are added to the reaction medium. After reaction overnight at room temperature, the reaction medium is precipitated from 250 ml of water. After filtration, the residue is washed with water and then dried under vacuum; 0.85 g of yellow crystals are obtained with a yield of 81%. [M + H] + = 638.30

 Step 4:

0.266 mmol of the intermediate obtained in the previous step (Int 6) is dissolved in 1.8 ml of TFA. The reaction medium is left at room temperature for 1 h and is then evaporated. The product is obtained by crystallization of 25 ml of Et ₂ 0. 180 mg of yellow crystals are obtained, which are purified in a column open on RP2 silica, the elution being carried out with water (TFA 0, 05%) / CH ₃ CN. After lyophilization, 50 mg of white product are obtained (yield 31%). BP: [M + H] ⁺ = 482.22, [M + 2H] ²⁺ = 241.68 Step 5

 Formation of the activated ester:

After 75 mg of NODAGA (tBu) ₃ (Int 8) were dissolved in 2 ml of CH ₂ Cl ₂ , 15 mg (1 eq) of NHS and then 28 mg (1 eq) of DCC were added. After reaction for one and a half hours at room temperature, the DCU formed is filtered through Whatman paper and the filtrate is concentrated to a final volume of approximately 0.5 ml.

 amidation:

50 mg of the intermediate obtained in the previous step (Int 7) are dissolved in 2.5 ml of DMSO in the presence of 2 eq of NEt ₃ (40 μl). The activated ester, dissolved in CH ₂ Cl _2, is added. After reaction for 1H, the reaction medium is precipitated from 25 ml of Et ₂ O. The product obtained is purified by flash chromatography (Merck SVF D26-R18 25-40 μιη -31 g silica cartridge), after having was solubilized in 50/50 (aqueous eluent phase (TFA pH 2.8) / CH ₃ CN). After lyophilization, 24 mg of white crystals are obtained (yield 28.4%). BP: [M + H] ⁺ = 1007.5, [M + 2H] ²⁺ = 504.44

 Step 6

24 mg of the intermediate obtained in the previous step (Int 9) are solubilized in 1 ml of TFA. After reaction for 6 h at room temperature, the reaction medium is evaporated and taken up in 25 ml of Et ₂ 0. 10 mg of crystals are obtained.

 Step 7

20 μl of an aqueous solution of 1 mg / ml of compound obtained in step 6 (compound) and 1 ml of 0.1M sodium lactate buffer pH3.9 are introduced into a reaction vial. 400 μl of a ⁶⁸ GaCl _{3 solution} in a mixture of 0.02M HCl / acetone are then added. The reaction medium is incubated at room temperature for 15 min. The reaction flask is washed with 6 ml of water and the reaction medium is transferred to a C-18 column which has been preconditioned with 1 ml of ethanol and 1 ml of ultrapure water. The final product is eluted from the cartridge with 1 ml of a 50% ethanol / water solution.

 The final product (compound 1) is passed through a 0.22μιη Millipore filter and is diluted with 0.9% NaCl to 6 ml.

A similar procedure is used for acetate, HEPES, lactate, succinate, phosphate, maleate, malate buffers. Example 2 Synthesis of [folate-NODAGA-Ga68:

 Step 1: Compound of formula

20 g (91.7 mmol) of Boc ₂ 0 were dissolved in 40ml of CH ₂ C1 _2. Then a solution of 22 g (366.6 mmol) of diaminoethane in 200 ml of CH ₂ C1 ₂ is added dropwise. The reaction medium is stirred at room temperature for 2 hours. First, the product is purified by extraction with water. The organic phase is dried over Na ₂ SO ₄ and filtered. Then it is purified by flash chromatography on silica with a CH ₂ Cl ₂ / methanol gradient. 4g of an oil are obtained, m / z = 161 (ES +)

Step 2: Compound of formula

10.27 g (24 mmol) of Fmoc-Glu-OtBu are dissolved in 300 ml of CH ₂ C1 ₂ . 2.8 g of NHS and 4.98 g of DCC are introduced. After 45 minutes, the reaction mixture is filtered and added dropwise into a solution of 3.869 g of product obtained in step 1 dissolved in 50 ml of CH ₂ C1 ₂ . After 2 hours at room temperature the product is first purified by extraction with water. The organic phase is dried over Na ₂ SO ₄ and filtered. Then it is purified by flash chromatography on silica with a CH ₂ Cl ₂ / acetone gradient. 7g of the product are obtained, m / z = 568 (ES +)

Etape 3 : Composé de formule

Step 3: Compound of formula

6.5 g (11.4 mmol) of the product obtained in step 2 are dissolved in 91 ml of acetonitrile. A solution of 19.5 ml of piperidine in 78 ml of acetonitrile is added dropwise. After 2 hours at room temperature under an argon atmosphere, the reaction mixture is evaporated and purified by flash chromatography on silica with a CH ₂ Cl ₂ / methanol gradient. 3.65g of an oil are obtained, m / z = 346 (ES +)

 Step 4: Compound of formula

3.3 g (10.5 mmol) of pteroic acid and 3.65 g of the product obtained in step 3 are dissolved in 335 ml of DMSO under argon. 3.038g of EDCI and 1g of HOBT are added. The reaction mixture is heated at 40 ° C overnight and precipitated in water. The residue is filtered and washed with water first and then ₂₀ g of red powder are obtained, m / z = 640 (ES +).

 Step 5: Compound of formula

6 g (9.3 mmol) of the product obtained in step 4 are dissolved in 74 ml of TFA. After 1 hour at room temperature, the reaction mixture is precipitated in 800 ml. Et20. After filtration, 4.5 g of yellow powder are obtained, m / z = 484 (ES +)

 Step 6: Compound of formula

By applying the same procedure as that described in step 5 of Example 1 starting from:

 85 mg of the product obtained in step 5 of Example 2 and

- 75mg of NOTAGA (tBu) ₃

 15mg of product are obtained, m / z (ES +) = 1009

 Step 7: Compound of formula (NODAGA-folate compound) (compound 2 '):

By applying the same procedure as that described in step 6 of Example 1 starting from 20 mg of the product obtained in step 6 of Example 2

4 mg of product are obtained, m / z (ES +) = 841 Step 8: Compound of formula (compound NODAGA-folate-Ga68) (compound 2):

20 μl of an aqueous solution of 1 mg / ml of the compound obtained in step 7 and 1 ml of buffer (in particular 0.5 M sodium acetate pH 3.5 to 4 or other buffers such as lactate buffer or succinate 0, 1M) are introduced into a reaction flask. 400 μl of a ⁶⁸ GaCl _{3 solution} in a 0.02 M HCl / acetone mixture are then added. The reaction mixture is incubated at room temperature for 15 minutes. The reaction flask is washed with 6 ml of water

 The final product is passed through a Millipore 0.22μιη filter and is diluted with 0.9% NaCl to 6 ml.

EXAMPLE 3 Purification of Fo-Late NOD AG A-Ga68 and Folate Dideaza NODAGA

Ga68

 The reaction medium is diluted with 3 ml of water and then fixed on the 900 mg column of SepPack tC18 (WAT 036800) using a syringe. The reactor is rinsed with 2ml of water which are also placed on the column. After 2 to 5 minutes, the impurities are recovered. 1 ml of 50% EtOH water is added which makes it possible to recover in 2 minutes the product which is filtered at the same time on a Millipore filter of 0.22 μm at the outlet of the column.

 It is adjusted with 0.9% NaCl to be finally 10% EtOH.

 The results are shown in Figures 1 (before purification) and 2 (after purification).

Claims

A method for purifying a gallium Ga68-labeled contrast material comprising a gallium Ga68 radiolabeled chelate vectorized by a folate or folate-derived targeting ligand, the method comprising the following successive steps:  a) preparation of a solution of the chelate vectorized by a targeting ligand folate or non-radiolabelled folate derivative  b) Radiolabeling with Ga68 of the Vectorized Chelate in Complexation Solution to Obtain a Radiolabeled Vectorized Chelate Solution  c) purification of the solution obtained, by elimination using purification means of at least one radio-labeled impurity which comprises a radiolabeled chelate vectorized by a folate oxidation residue and simultaneous elimination of free gallium 68Ga or colloidal and traces of 68 Ge  d) recovering the purified solution containing the gallium Ga68 radiolabeled chelate vectorized by a folate or folate-derived targeting ligand with a purity of at least 95%,  characterized in that the purification means of step c) is a solid phase extraction column whose stationary phase is hydrophobic and neutral with a carbon content of at least 15% and in that step c ) consists of  cl) selective attachment to this column of the radiolabeled vector chelate and removal of the impurity and  c2) eluting with a suitable polar solvent radiolabeled vectorized chelate attached to the column. 2. Purification process according to claim 1 characterized in that the targeting ligand folate or folate derivative has the following general formula (A):

or (B) following: and their tautomers in which:  represents the binding site of the folate targeting ligand or folate derivative to the chelate, directly or via a chemical bond; Gi is selected from the group consisting of: a halogen atom, R _f 2, OR _f 2, SR _f 3 and NR R _f 5; G ₂ is selected from the group consisting of: a halogen atom, R _f 2, OR _f 2, SR _f 3 and NR _{f 4} R _f 5; G ₃ represents a divalent group selected from the group consisting of - (R _f 6 ') C = and - N = and G ₄ represents a divalent group selected from the group consisting of - (R _f 6') C- and -N - or G ₃ represents a divalent group selected from the group consisting of - (R _f 6 ') C- and - N- and G ₄ represents a divalent group selected from the group consisting of - (R _f 6') C = and -N = or G ₃ and G ₄ independently represent a divalent group selected from the group consisting of - (R _f 6 ') C (R _f 7') - and -N (R _f 4 ') -; G ₅ is absent or is selected from - (Rf6 ') C = -N = - (Rf6') C (Rf7 ') - and -N (Rf4') -;  J is a 5- or 6-membered aryl or heteroaryl group; G _Ô is N or C; K ₁ and K ₂ are independently selected from the group consisting of -C (Z _f ) -, - C (Z _f) 0-, -OC (Z _f) -, -N (R f 4 ") -, -C (Zf) -N (R f 4), -N (R f 4") - C (Z _f) -0 -C (Zf) -N (R f 4 ") -, - N (R f 4") - C (Z _f) -0-, -N (R f 4 ") - C (Zf) -N (R _f 5") -, - O-, -S-, -S (O) -, -S (O) ₂ -, - N (R _f 4 ") S (O) ₂ -, -C (R _f 6") (R _f 7 " ) -, -N (C ^≡ CH) -, -N (CH ₂ -C ^≡ CH) -, alkyl in d- And C ₁₂ alkoxy-Cl _2; where Z _f is O or S; R _f 2, R _f 3, R _f 4, Rf 4 ', R _f 4 ", R _f 5, R _f 5", R _{f 0} "and R _f 7" are independently selected from the group consisting of: H, halogen, alkyl Ci-Cn alkoxy, Ci-Ci ₂ alkanoyl, Ci-Cn alkenyl, C ₂ -C ₁₂ alkynyl, C ₂ -C ₁₂ alkoxy (Ci -C ₂₎ alkoxycarbonyl, and (alkylamino-Ci ₂₎ carbonyl; R _f 'and R _f ' are independently selected from the group consisting of: H, halo, C1-C6 alkyl and C1-C6 alkoxy, or R _f 'and R _f ' together form = 0; R _O and R ₇ are independently selected from the group consisting of: H and alkyl Lf is a divalent chemical bond  p, r and s are independently 0 or 1 and  x is an integer from 1 to 5 Purification process according to any one of claims 1 or 2 characterized in that the chelate is a NOTE or derived from the NOTE.  Process according to Claim 3, characterized in that the NOTE or derivative of the NOTE has the following general formula (II):

wherein m is an integer from 0 to 10 and X ₂ represents a linking function between the NOTA molecule and the folate or folate-derived targeting ligand directly or via a chemical bond. Process according to Claim 4, characterized in that X ₂ is chosen from the group consisting of -CONH-, -COO-, -NHCO-, -NH-, -CO- and -OCO-. Process according to one of the preceding claims, characterized in that the folate or folate-derived targeting ligand is linked to the chelate via a chemical bond chosen from:  at. l) - a single link; - - (CH ₂ ) _n -, - (CH ₂ ) _n CO-, - (CH ₂ ) _n NHCO-, - (CH ₂ ) _n CONH- - (CH ₂ ) _n CONH (CH ₂ ) _n , - ( CH ₂ ) _n phenylNH-, - (CH ₂ ) _n NH-, -NH (CH ₂ ) _n NH-, - (CH ₂ ) _n phenyl-, and -NH (CH ₂ ) _n - with n = l-20 ; - (CH ₂ CH ₂ 0) _q (CH ₂ ) _r CO-, (CH ₂ CH ₂ 0) _q (CH ₂ ) _n NH-CO-, - (CH ₂ CH ₂ 0) _q (CH ₂ ) r, (CH ₂ CH ₂ 0) _q (CH ₂ ) _n NH- with q = 1-10 and r = 2-10; - - (CH ₂ ) _n -CONH-PEG-,,

 in which * represents the chelate binding site, with n = 1 to 5; -CO-CH ₂ -O- (CH ₂ ) _n -O- (CH ₂ ) _p -O-CH ₂ -CO-, -CO- (CH ₂ ) _n -C0 ₂ - (CH ₂ ) _p -OCO - (CH ₂ ) _q -CO-, -CO-CH (OH) -CH (OH) -CO-; C 0- (CH ₂ ) _n -CO-; -CO-CH ₂ -O- (CH ₂ ) _n -O- (CH ₂ ) _p -O-CH ₂ -, -CO- (CH ₂ ) _n -C0 ₂ - (CH ₂ ) _p -OCO- (CH) ₂ ) _q -, -CO- CH (OH) -CH (OH) - and -CO- (CH ₂ ) _n -, with n = 1-20, p = 1-20 and q = 1-20; - -NH- (CH ₂ ) n-CO; -NH-CH ₂ - (CH ₂ -O-CH ₂ ) n -CO- and -NH-CH ₂ - (CH ₂ -O-CH ₂ ) n- with n = 1 to 10; a.2) -P1-1-P2 with PI and P2 identical or different are selected from O, S, NH, nothing, CO ₂ , NHCO, CONH, NHCONH, NHCSNH, SO ₂ NH-, NHS0 ₂ - and squarate with 1 = alkyl, alkoxyalkyl, polyalkoxyalkyl (PEG), alkyl interrupted by one or more squarates or by one or more aryls, alkenyls, alkynyls, alkyls which are interrupted by one or more groups selected from -NH-, -O-, -CO -, - NH (CO) -, - (CO) NH-, -O (CO) -, or - (OC) O-.  Process according to any one of Claims 2 to 6, characterized in that the folate oxidation residue has the following formula:

 in which * represents the binding site of FOLATEoxy to the chelate.  8. Process according to any one of the preceding claims, characterized in that the chelate vectorized by a folate targeting ligand or non-radiolabelled folate derivative is chosen from the compounds of the following general formula:

2 'and

 Γ  9. Method according to one of claims 1 to 8, characterized in that the stationary phase is a hydrophobic silica whose carbon content is at least 15%, the particle size between 30 and 60 μηι and the size of pores between 100 and 150 Å.  10. Process according to claim 9, characterized in that the silica is grafted with an octadecyl group and its silanol functions are protected.  11. The method of claim 10 characterized in that the stationary phase is a hydrophobic silica whose carbon content is 17%, the particle size between 37 and 55 μηι and the pore size of 125 Å.  12. Method according to any one of claims 9 to 11 characterized in that the charge of the column is at least 600 mg of stationary phase, preferably at least 900 mg.  13. Method according to any one of claims 9 to 12 characterized in that the appropriate solvent for the elution used in step c2) is a mixture of water and ethanol.