2-alkoxy-6-[18F]fluoronicotinoyl substituted lys-c(O)-glu derivatives as efficient probes for imaging of PSMA expressing tissues

Abstract

6-[.sup.18F]Fluoro-2-alkoxynicotinoyl substituted Lys-C(O)-Glu derivatives were identified as efficient imaging probes for PSMA expressing tissues in comparison to other known PSMA specific ligands like [.sup.18F]DCFPyL, [.sup.68Ga]HBED-CC-PSMA, [.sup.18F]PSMA-1007 and [Al.sup.18F]HBED-CC-PSMA. Unexpectedly, the 6-[.sup.18F]fluoro-2-alkoxy and 6-[.sup.18F]fluoro-4-alkoxy substituted analogs showed significant differences in accumulation in PSMA expressing prostate tumor cells. Whereas the 2-alkoxy derivative showed cellular uptake values higher than [.sup.18F]DCFPyL, the cellular uptake of the corresponding 4-alkoxy substituted derivative was significantly lower. Furthermore, in vivo PET studies with 2-alkoxy-substituted probes demonstrated excellent visualization of PSMA positive ganglia with extremely high target to background ratio. In contrast, the 4-alkoxy substituted derivatives showed less favorable biodistribution with significantly lower uptake in PSMA positive tissues. Especially, the .sup.18F-labeled 2-methoxy derivate ((2S)-2-({[(1S)-1-carboxy-5-[(6-[.sup.18F]fluoro-2-methoxypyridin-3-yl)formamido]pentyl]carbamoyl}-amino)pentanedioic acid) demonstrated exceptional clinical efficiency in detecting small PCa lesions, including those which could not be visualized with [.sup.68Ga]HBED-CC-PSMA representing currently the gold standard for the diagnosis of recurrent PCa. Furthermore, this probe is easily accessible on a preparative scale in commercially available automated synthesis modules like GE FASTlab and TRACERlab FX N Pro. Consequently, the novel probe is a valuable tool for the visualization of ganglia and reendothelialization as well as for the diagnosis of glioma, neuropathic pain and atherosclerotic plaques.

Claims

1. A compound of formula (I): ##STR00005## wherein R is C.sub.1-C.sub.10 substituted or unsubstituted alkyl, or C.sub.5-C.sub.12 unsubstituted or substituted aryl or heteroaryl.

2. The compound of formula (I) according to claim 1 wherein R is C1-C4 substituted or unsubstituted alkyl.

3. The compound of formula (I) according to claim 1 wherein R is C1-C3 substituted or unsubstituted alkyl.

4. The compound of formula (I) according to claim 1 wherein R is methyl.

5. A method for imaging of a PSMA-positive organ or tissue or both in a subject, comprising administering to said subject the compound of formula (I) according to claim 1 and obtaining and image of said organ or tissue or both.

6. The method according to claim 5, wherein said subject has a pathological condition that is selected from the group consisting of cancer, prostate cancer, re-endothelialization, neuropathic pain and atherosclerosis.

7. A method for staging a pathological or physiological condition associated with one or more PSMA-positive organs or tissues or both of a subject, comprising administering to said subject the compound of formula (I) according to claim 1 and staging said pathological or physiological condition.

8. The method according to claim 7, wherein said subject has a pathological condition that is selected from the group consisting of cancer, prostate cancer, reendothelialization, neuropathic pain and atherosclerosis.

9. A method of making a compound of formula (I) according to claim 1 from a compound of formula II and Lys-C(O)-Glu comprising: ##STR00006## Y is Me.sub.3N.sup.+Z.sup.− or ##STR00007## Z.sup.− is CF.sub.3SO.sub.3 or CF.sub.3CO.sub.2 R is C.sub.1-C.sub.10 substituted or unsubstituted alkyl, or C.sub.5-C.sub.12 unsubstituted or substituted aryl or heteroaryl, a) providing an aqueous solution of [.sup.18F]fluoride; b) loading of [.sup.18F]fluoride onto an anion exchange resin; c) washing the anion exchange resin; d) drying the resin with flow of air or inert gas; e) elution of [.sup.18F]fluoride with a solution of a compound of formula (II) in a polar aprotic solvent; f) if the elution was carried out by a C.sub.2-C.sub.6 alcohol as the solvent, then diluting the reaction mixture with a polar aprotic solvent; g) heating the resulting solution at 30-70° C. for 1-30 min which furnishes a crude of a compound of formula [.sup.18F]III; ##STR00008## wherein R is as defined for formula II, h) purification of the compound of formula [.sup.18F]III reversed phase solid phase extraction (RP SPE) as follows: dilution of the above mixture with H.sub.2O, loading the resulting solution on a RP SPE cartridge, washing the cartridge with H.sub.2O, elution of the purified compound of formula [.sup.18F]III with a C.sub.2-C.sub.6 alcohol; i) elution of the purified compound of formula [.sup.18F]III directly to a solution of Lys-C(O)-Glu and a base in an anhydrous C.sub.2-C.sub.6 alcohol; j) heating the resulting solution at 30-70° C. for 1-30 min; k) purification of the resultant crude compound of formula I by RP SPE or alternatively RP HPLC; and l) optionally formulation.

10. A method of making a compound of formula (I) according to claim 1 from a compound of formula (IV) comprising: ##STR00009## wherein Y is Me.sub.3N.sup.+Z.sup.− or ##STR00010## Z.sup.− is CF.sub.3SO.sub.3 or CF.sub.3CO.sub.2 R is C.sub.1-C.sub.10 substituted or unsubstituted alkyl, or C.sub.5-C.sub.12 unsubstituted or substituted aryl or heteroaryl, a) providing an aqueous solution of [.sup.18F]fluoride; b) loading of [.sup.18F]fluoride onto an anion exchange resin; c) washing the anion exchange resin; d) drying the resin with flow of air or inert gas; e) eluting [.sup.18F]fluoride with a solution of a compound of formula (IV) in a C.sub.2-C.sub.6 alcohol; f) evaporation of volatiles; g) dissolution of the residue in a polar aprotic solvent; h) heating of the resulting solution at 40-130° C. for 2-30 min; i) addition of 85% H.sub.3PO.sub.4 or 10 M HCl to a solution of a resultant crude compound of formula [.sup.18F]V; ##STR00011## wherein R is as defined for the compound of formula (IV), j) heating of the resulting mixture at 40-130° C. for 2-30 min; k) dilution of the reaction mixture and adjustment of the pH to 2.0-2.5 with an aqueous solution of a base; l) RP HPLC purification by H.sub.3PO.sub.4 in aqueous EtOH as an eluent; m) dilution with isotonic saline, adjustment of the pH with a base; and n) sterile filtration.

11. A kit or a cassette system for preparing a compound of formula (I) according to claim 1, said kit or a cassette system comprises (i) an anion exchange column; (ii) a reaction vessel; (iii) vials containing aliquots eluents; (iv) a vial containing an aliquot of a compound of formula II or IV ##STR00012## wherein Y is Me.sub.3N.sup.+Z.sup.− or ##STR00013## Z.sup.− is CF.sub.3SO.sub.3 or CF.sub.3CO.sub.2 R is C.sub.1-C.sub.10 substituted or unsubstituted alkyl, or C5-C12 unsubstituted or substituted aryl or heteroaryl; (v) reagent vials wherein each reagent vial contains an aliquot of a reagent; (vi) optionally, one or more SPE columns for purification; (vii) optionally, a HPLC column for purification and, (viii) cleaning material for said reaction vessel and said SPE columns.

12. A pharmaceutical composition containing at least one compound of formula (I) according to claim 1 together with at least one pharmaceutically acceptable solvent, ingredient and/or diluent.

13. A method for imaging prostate cancer cells or prostate cancerous tissue, comprising administering to said prostate cancer cells or prostate cancerous tissue the pharmaceutical composition according to claim 12 and obtaining and image of said prostate cancer cells or prostate cancerous tissue.

14. A method of making a compound of formula (I) according to claim 1 from a compound of formula II and Lys-C(O)-Glu comprising: ##STR00014## wherein Y is Me.sub.3N.sup.+Z.sup.− or ##STR00015## Z.sup.− is CF.sub.3SO.sub.3 or CF.sub.3CO.sub.2 R is C.sub.1-C.sub.10 substituted or unsubstituted alkyl, or C.sub.5-C.sub.12 unsubstituted or substituted aryl or heteroaryl, a) providing an aqueous solution of [.sup.18F]fluoride; b) loading of [.sup.18F]fluoride onto an anion exchange resin; c) washing the anion exchange resin; d) drying the resin with flow of air or inert gas; e) elution of [.sup.18F]fluoride with a solution of a compound of formula (II) in a polar aprotic solvent; f) if the elution was carried out by a C.sub.2-C.sub.6 alcohol as solvent diluting the reaction mixture with a polar aprotic solvent; g) heating of the resulting solution at 30-70° C. for 1-30 min which furnishes a crude of a compound of formula [.sup.18F]III; ##STR00016## wherein R is as defined for formula II, h) purification of the compound of formula [.sup.18F]III by reversed phase solid phase extraction (RP SPE) as follows: dilution of the resultant mixture with H.sub.2O, loading the resulting solution on a RP SPE cartridge, washing the cartridge with H.sub.2O, elution of the purified compound of formula [.sup.18F]III with C.sub.2-C.sub.6 alcohol; i) elution of the compound of formula [.sup.18F]III directly to a solution of Lys-C(O)-Glu and a base in an anhydrous C.sub.2-C.sub.6 alcohol; j) heating the resulting solution at 30-70° C. for 1-30 min; k) purification of the resultant crude compound of formula I by RP SPE or alternatively RP HPLC; and and wherein the method does not comprise an evaporation step; and/or a deprotection step; and/or a neutralization step.

15. A method of making a compound of formula (I) according to claim 1 from a compound of formula (IV) comprising: ##STR00017## wherein Y is Me.sub.3N.sup.+Z.sup.− or ##STR00018## Z.sup.− is CF.sub.3SO.sub.3 or CF.sub.3CO.sub.2 R is C.sub.1-C.sub.10 substituted or unsubstituted alkyl, or C.sub.5-C.sub.12 unsubstituted or substituted aryl or heteroaryl, a) providing an aqueous solution of [.sup.18F]fluoride; b) loading of [.sup.18F]fluoride onto an anion exchange resin; c) washing the anion exchange resin; d) drying the resin with flow of air or inert gas; e) eluting of [.sup.18F]fluoride with a solution of a compound of formula (IV) in a C.sub.2-C.sub.6 alcohol; g) dissolution of the residue in a polar aprotic solvent; h) heating of the resulting solution at 40-130° C. for 2-30 min; i) addition of 85% H.sub.3PO.sub.4 or 10 M HCl to a solution of a resultant crude compound of formula [.sup.18F]V; ##STR00019## wherein R is as defined for the compound of formula (IV), j) heating of the resulting mixture at 40-130° C. for 2-30 min; k) dilution of the reaction mixture and adjustment of the pH to 2.0-2.5 with an aqueous solution of a base; l) RP HPLC purification by H.sub.3PO.sub.4 in aqueous EtOH as an eluent; m) dilution with isotonic saline, adjustment of the pH with a base; and n) sterile filtration, and wherein the method does not comprise an evaporation step; and/or a deprotection step; and/or a neutralization step.

16. The compound of formula (I) according to claim 1 wherein R is allyl, propargyl, phenyl or pyridyl.

17. The method according to claim 9 of making a compound of formula (I) from a compound of formula II and Lys-C(O)-Glu comprising: ##STR00020## Y is Me.sub.3N.sup.+Z.sup.− or ##STR00021## Z.sup.− is CF.sub.3SO.sub.3 or CF.sub.3CO.sub.2 R is methyl, ethyl, propyl, butyl, allyl, propargyl, phenyl or pyridyl, a) providing an aqueous solution of [.sup.18F]fluoride; b) loading of [.sup.18F]fluoride onto an anion exchange resin; c) washing the anion exchange resin; d) drying the resin with flow of air or inert gas selected from the group consisting of He and Ar; e) elution of [.sup.18F]fluoride with a solution of a compound of formula (II) in a polar aprotic solvent selected from the group consisting of DMF, DMSO, MeCN and a C.sub.2-C.sub.6 alcohol or in a mixture thereof; f) If the elution was carried out by a C.sub.2-C.sub.6 alcohol as the solvent, then diluting the reaction mixture with a polar aprotic solvent selected from the group consisting of DMF, DMSO, MeCN, and aprotic solvent/C.sub.2-C.sub.6 alcohol mixture; g) heating the resulting solution at 40-50° C. for 2-7 min which furnishes a crude of a compound of formula [.sup.18F]III; ##STR00022## wherein R is as defined for formula II, h) purification of the compound of formula [.sup.18F]III by reversed phase solid phase extraction (RP SPE) as follows: dilution of the above mixture with H.sub.2O, loading the resulting solution on a RP SPE cartridge, washing the cartridge with H.sub.2O, elution of the purified compound of formula [.sup.18F]III with EtOH; i) elution of the purified compound of formula [.sup.18F]III directly to a solution of Lys-C(O)-Glu and a base selected from the group consisting of CsHCO.sub.3, RbHCO.sub.3, tetraalkylammonium phosphate, bicarbonate and carbonate in an anhydrous EtOH; j) heating the resulting solution at 40-50° C. for 2-7 min; k) purification of the resultant crude compound of formula I by RP SPE or alternatively RP HPLC; and l) optionally formulation.

18. The method according to claim 10 of making a compound of formula (I) from a compound of formula (IV) comprising: ##STR00023## wherein Y is Me.sub.3N.sup.+Z.sup.− or ##STR00024## Z.sup.− is CF.sub.3SO.sub.3 or CF.sub.3CO.sub.2 R is methyl, ethyl, propyl, butyl, allyl, propargyl, phenyl or pyridyl, a) providing an aqueous solution of [.sup.18F]fluoride; b) loading of [.sup.18F]fluoride onto an anion exchange resin; c) washing the anion exchange resin; d) drying the resin with flow of air or He or Ar; e) eluting [.sup.18F]fluoride with a solution of a compound of formula (IV) in MeOH; f) evaporation of volatiles; g) dissolution of the residue in a polar aprotic solvent selected from the group consisting of DMF, DMSO, and MeCN; h) heating of the resulting solution at 40-130° C. for 2-30 min; i) addition of 85% H.sub.3PO.sub.4 or 10 M HCl to a solution of a resultant crude compound of formula [.sup.18F]V; ##STR00025## wherein R is as defined for the compound of formula (IV), j) heating of the resulting mixture at 40-130° C. for 2-30 min; k) dilution of the reaction mixture and adjustment of the pH to 2.0-2.5 with an aqueous solution of a base selected from the group consisting of NaHCO.sub.3, Na.sub.2CO.sub.3, Et.sub.3N, NaOH, Na.sub.2HPO.sub.4 and Na.sub.3PO.sub.4; l) RP HPLC purification by H.sub.3PO.sub.4 in aqueous EtOH as an eluent; m) dilution with isotonic saline, adjustment of the pH with a base selected from the group consisting of NaHCO.sub.3, Na.sub.2CO.sub.3, NaOH, Na.sub.2HPO.sub.4 and Na.sub.3PO.sub.4; and n) sterile filtration.

19. The kit or a cassette system according to claim 11 for preparing a compound of formula (I), said kit or a cassette system comprises (i) an anion exchange column; (ii) a reaction vessel; (iii) vials containing aliquots eluents; (iv) a vial containing an aliquot of a compound of formula II or IV ##STR00026## wherein Y is Me.sub.3N.sup.+Z.sup.− or ##STR00027## Z.sup.− is CF.sub.3SO.sub.3 or CF.sub.3CO.sub.2 R is methyl, ethyl, propyl, butyl, allyl, propargyl, phenyl or pyridyl; (v) reagent vials wherein each reagent vial contains an aliquot of a reagent; (vi) optionally, one or more SPE columns for purification; (vii) optionally, a HPLC column for purification and, (viii) cleaning material for said reaction vessel and said SPE columns.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1: Structures of PSMA-specific PET-Ligands used in this study.

(2) FIG. 2: Preparation of the novel PSMA specific probes, [.sup.18F]1 and [.sup.18F]2.

(3) FIG. 3: Synthesis of precursors 8, 9 and 16 for radiolabeling.

(4) FIG. 4: Cellular uptake of 2-MeO— and 4-MeO-[.sup.18F]PSMA (A and B, respectively), and [.sup.18F]DCFPyL in PSMA.sup.+ LNCaP C4-2 and PSMA.sup.− prostate tumor cells. Data of cellular uptakes [.sup.18F]DCFPyL carried out in parallel with those of 2-MeO— and 4-MeO-[.sup.18F]PSMA are presented.

(5) FIG. 5: Uptake of different PSMA-specific tracers in healthy rats measured by PET. Conditions: PET scanner (Focus 220, Siemens); 57-71 MBq tracer was injected. PET scans started 60 min after injection and continued for 60 min. A: [.sup.18F]DCFPyL; B: [.sup.18F]DCFPyL+2-PMPA (23 mg/kg); C: 2-MeO-[.sup.18F]PSMA; D: 4-MeO-[.sup.18F]PSMA, E: [.sup.68Ga]Ga-PSMA-HBED-CC, F: [.sup.18F]AlF-PSMA-HBED-CC G: [.sup.18F]PSMA-1007 H: Shown sagittal section and list of abbreviations.

(6) FIG. 6: FIG. 6 is provided in FIGS. 6a and 6b. Left column: [.sup.68Ga]Ga-PSMA-HBED-CC PET-data, right column: 2-MeO-[.sup.18F]PMSA PET-data in the same patient. First row: Maximal intensity projections of the PET-data (darker black color reflects higher tracer uptake). Second row: Axial slices (caudal aspect) of the PET/CT fusion images (overlay of PET-data on the CT data). PET-tracer uptake displayed in “hot metal” (brighter yellow color reflects higher tracer uptake). Bl: Bladder, Bo: Bowel, K: Kidney, L: Liver, Sa: Salivary glands, Sp: Spleen, Tu: Suspected tumor, U: Ureter, R: Right side, L: Left side.

(7) FIG. 7: Layout of 2-MeO-[.sup.18F]PSMA synthesis on FX—N-Pro synthesis module.

(8) FIG. 8: Cassette for the production of [.sup.18F]1 on FASTab synthesis module (GE).

(9) FIG. 9: Production of [.sup.18F]1 on FASTab synthesis module (GE).