Efficient synthesis of chelators for nuclear imaging and radiotherapy: compositions and applications
Novel methods of synthesis of chelator-targeting ligand conjugates, compositions comprising such conjugates, and therapeutic and diagnostic applications of such conjugates are disclosed. The compositions include chelator-targeting ligand conjugates optionally chelated to one or more metal ions. Methods of synthesizing these compositions in high purity are also presented. Also disclosed are methods of imaging, treating and diagnosing disease in a subject using these novel compositions, such as methods of imaging a tumor within a subject and methods of diagnosing myocardial ischemia.
1. A method of synthesizing a chelator-targeting ligand conjugate, comprising:
(a) conjugating, in an organic medium, a protected ethylenedicysteine of the following formula:
to at least one unprotected glucosamine, wherein:
A and D are each a protected thiol;
B and C are each a tertiary amine, wherein the tertiary amine is a protected secondary amine;
and the conjugation is via an amide bond formed between a COOH group of the protected ethylenedicysteine and the amino group of the unprotected glucosamine to form a protected ethylenedicysteine glucosamine; and
(b) removing each protecting group, in one or more steps, from the protected ethylenedicysteine glucosamine to form a chelator-targeting ligand conjugate, wherein the chelator-targeting ligand conjugate is ethylenedicysteine glucosamine (EC-G), wherein the purity of the chelator-targeting ligand conjugate is between about 80% (w/w) and about 99.9% (w/w), as measured by HPLC using ELSD detection.
2. The method of claim 1 , wherein the organic medium comprises a polar solvent.
3. The method of claim 1 , wherein the organic medium is dimethylformamide, dimethylsulfoxide, dioxane, methanol, ethanol, hexane, methylene chloride, acetonitrile, tetrahydrofuran, or a mixture thereof.
4. The method of claim 1 , further comprising at least one purification step, wherein the purification step is silica gel column chromatography, HPLC, or a combination thereof.
5. The method of claim 4 , wherein the purity of the chelator-targeting ligand conjugate is between about 85% (w/w) and about 99.9% (w/w), as measured by HPLC using ELSD detection.
6. The method of claim 5 , wherein the purity of the chelator-targeting ligand conjugate is between about 90% (w/w) and about 99.9% (w/w), as measured by HPLC using ELSD detection.
7. The method of claim 1 , further comprising chelating a metal ion to the chelator-targeting ligand conjugate to generate a metal ion labeled-chelator-targeting ligand conjugate.
8. The method of claim 7 , wherein the purity of the metal ion labeled-chelator-targeting ligand conjugate is between about 80% w/w and about 99.9% w/w, as measured by HPLC using ELSD detection.
9. The method of claim 8 , wherein the purity of the metal ion labeled-chelator-targeting ligand conjugate is between about 85% w/w and about 99.9% w/w, as measured by HPLC using ELSD detection.
10. The method of claim 9 , wherein the purity of the metal ion labeled-chelator-targeting ligand conjugate is between about 90% w/w and about 99.9% w/w, as measured by HPLC using ELSD detection.
11. The method of claim 7 , wherein the metal ion is selected from the group consisting of a technetium ion, a copper ion, an indium ion, a thallium ion, a gallium ion, an arsenic ion, a rhenium ion, a holmium ion, a yttrium ion, a samarium ion, a selenium ion, a strontium ion, a gadolinium ion, a bismuth ion, an iron ion, a manganese ion, a lutecium ion, a cobalt ion, a platinum ion, a calcium ion and a rhodium ion.
12. The method of claim 7 , wherein the metal ion is 187 Re, 99m Tc, platinum, or 188 Re.
13. The method of claim 7 , wherein the metal ion is a radionuclide.
14. The method of claim 13 , wherein the radionuclide is selected from the group consisting of 99m Tc, 188 Re, 186 Re, 153 Sm, 166 Ho, 90 Y, 89 Sr, 67 Ga, 68 Ga, 111 In, 183 Gd, 59 Fe, 225 Ac, 212 Bi, 211 At, 45 Ti, 60 Cu, 61 Cu, 67 Cu, 64 Cu and 62 Cu.
15. The method of claim 14 , further comprising the addition of a reducing agent.
16. The method of claim 1 , wherein the protected thiol is protected using a thiol protecting agent selected from a group consisting of an alkyl halide, a benzyl halide, a benzoyl halide, a sulfonyl halide, benzhydrol, a triphenylmethyl halide, a methoxytriphenylmethyl halide and cysteine.
17. The method of claim 1 , wherein the protected tertiary amine is protected using an amine protecting agent selected from the group consisting of benzylchloroformate, p-nitro-chlorobenzylformate, ethylchloroformate, di-tert-butyl-dicarbonate, triphenylmethyl chloride and methoxytriphenylmethyl chloride.
18. The method of claim 1 , wherein the protected ethylenedicysteine glucosamine is EC-Benzhydrol-Cbz-Glucosamine.