LABELING PRECURSORS WITH SQUARIC ACID COUPLING

Abstract

The invention relates to a marking precursor incorporating a chelator or fluorination group for radiolabelling with .sup.44Sc, .sup.47Sc, .sup.55Co, .sup.62Cu, .sup.64Cu, .sup.67Cu, .sup.66Ga, .sup.67Ga, .sup.68Ga, .sup.89Zr, .sup.86Y, .sup.90Y, .sup.90Nb, .sup.99mTc, .sup.111In, .sup.135Sm, .sup.140Pr, .sup.159Gd, .sup.149Tb, .sup.160Tb, .sup.161Tb, .sup.165Er, .sup.166Dy, .sup.166Ho, .sup.175Yb, .sup.177Lu, .sup.186Re, .sup.188Re, .sup.213Bi and .sup.225Ac or with .sup.18F, .sup.131I or .sup.211At, and one or two biological targeting vectors which are coupled to the chelator or fluorinating group via one or more squaric acid groups.

Claims

1. A labeling precursor for a radiopharmaceutical whose structure (A) comprises: (A)=TV.sub.1-S.sub.2-QS-L.sub.2-Ch-L.sub.1-QS-S.sub.1-TV.sub.1 wherein Ch is a chelator, TV.sub.1 is a targeting vector, QS is a squaric acid residue, L.sub.1and L.sub.2 are linkers, and S.sub.1 and S.sub.2 are spacers; the chelator is formed from a compound of formula (B) ##STR00026## the targeting vector is a fibroblast activation protein inhibitor (FAPi); QS is a squaric acid residue: ##STR00027## L.sub.1forms an amide residue; L.sub.2 is —(CH.sub.2).sub.mNH— with m=1 through 10; and S.sub.1 and S.sub.2 are independently selected from —(CH2).sub.nNH— with n=1 through 10.

2. The labeling precursor according to claim 1, wherein S.sub.1 and S.sub.2 are both —(CH.sub.2).sub.nNH— with n=4.

3. The labeling precursor according to claim 1, wherein L.sub.1 is —NH(CH.sub.2).sub.mNH with m=2 and L.sub.2 is —(CH.sub.2).sub.mNH with m=2

4. The labeling precursor according to claim 1, wherein the chelator has been modified to form a compound of formula (C): ##STR00028##

5. The labeling precursor according to claim 1, wherein the FAPi is a residue of the compound (D): ##STR00029##

6. The labeling precursor according to claim 1, wherein the squaric acid residue is a squaric acid diester residue.

7. The labeling precursor according to claim 1, wherein the labeling precursor is a compound of the formula (E): ##STR00030##

8. The labeling precursor according to claim 7, wherein the precursor further comprises a radioactive isotope.

9. The labeling precursor according to claim 8, wherein the radioactive isotope is selected from .sup.44Sc, .sup.47Sc, .sup.55Co, .sup.62Cu, .sup.64Cu, .sup.67Cu, .sup.66Ga, .sup.67Ga, .sup.68Ga, .sup.89Zr, .sup.86Y, .sup.90Y, .sup.90Nb, .sup.99mTc, .sup.111In, .sup.135Sm, .sup.140Pr, .sup.159Gd, .sup.149Tb, .sup.160Tb, .sup.161Tb, .sup.165Er, .sup.166Dy, .sup.166Ho, .sup.175Yb, .sup.177Lu, .sup.186Re, .sup.188Re, .sup.213Bi and .sup.225Ac.

10. The labeling precursor according to claim 8, wherein the radioactive isotope is .sup.68Ga or .sup.177Lu.

11. A method for preparing a labeling precursor for a radiopharmaceutical comprising the steps of (i) conjugating a chelator, Ch, with a linkers L.sub.1 and L.sub.2 to form a precursor P.sub.1=L.sub.2-Ch-L.sub.1; (ii) conjugating a targeting vector, TV.sub.1, with a spacer, S.sub.1, and squaric acid, QS, to form a precursor P.sub.2=TV.sub.1-S.sub.1-QS; (iii) conjugating a targeting vector, TV2, with a spacer, S2, and squaric acid, QS, to form a precursor P.sub.3=TV.sub.2-S.sub.2-QS; (iv) conjugating precursors P1, P2 and P3 to form a labeling precursor of the structure TV.sub.2-S.sub.2-QS-L.sub.2-Ch-L.sub.1-QS-S.sub.1-TV.sub.1, wherein TV.sub.1=TV.sub.2 and S.sub.1=S.sub.2.

12. The method according to claim 11, wherein the chelator is based on (2-(1,4,7,10-tetraazacyclododecne-4,7,10)-pentanedioic acid (DOTA).

13. The method according to claim 11, wherein the targeting vector, TV.sub.1 and TV.sub.2, is a FAPi.

14. The method according to claim 13, wherein the FAPi targeting vector is a residue of the compound (D): ##STR00031##

15. The method according to claim 11, wherein L.sub.1 is —NH(CH.sub.2).sub.mNH with m=2 and L.sub.2 is —(CH.sub.2).sub.mNH with m=2 and S.sub.1 and S.sub.2 are both —(CH.sub.2).sub.nNH— with n=4.

16. A method for preparing a labeling precursor for a radiopharmaceutical comprising the steps of (a) providing a compound of formula (I): ##STR00032## (b) adding a first linking group to the compound of formula (I) by reacting the compound of formula (I) with a compound of formula (II): ##STR00033## (c) deprotecting the pentane dioic acid group of the compound formed in step (b) to form a compound of formula (III): ##STR00034## (d) adding a second linking group to the deprotected compound of formula (III) by reacting the deprotected compound of formula (III) with ethylenediamine to form a bi-linked compound of formula (IV): ##STR00035## (e) deprotecting the bi-linked compound of formula (IV) to form the bi-linked chelator of formula (V): ##STR00036## (f) reacting a butyl amine spaced targeting vector of the formula (VI) with squaric acid to form a compound of the formula (VII): ##STR00037## (g) reacting the squaric acid-modified targeting vector of formula (VII) with the bi-linked chelator of formula (V) to form the labeling precursor of formula (VII): ##STR00038##

17. A method of diagnosing and/or treating cancer comprising administering a radiopharmaceutical comprising a radioactive isotope and a compound of formula (E) to diagnose and/or treat cancer expressing FAP ##STR00039##

18. The method of theranostics according to claim 17, wherein the radioactive isotope is selected from .sup.44Sc, .sup.47Sc, .sup.55Co, .sup.62Cu, .sup.64Cu, .sup.67Cu, .sup.66Ga, .sup.67Ga, .sup.68Ga, .sup.89Zr, .sup.86Y, .sup.90Y, .sup.90Nb, .sup.99mTc, .sup.111In, .sup.135Sm, .sup.140Pr, .sup.159Gd, .sup.149Tb, .sup.160Tb, .sup.161Tb, .sup.165Er, .sup.166Dy, .sup.166Ho, .sup.175Yb, .sup.177Lu, .sup.186Re, .sup.188Re, .sup.213Bi and .sup.225Ac.

19. The method of theranostics according to claim 17, wherein the method is a method of diagnosing the radioactive isotope is .sup.68Ga or the method is a method of treatment and the radioactive isotope is .sup.177Lu.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0024] FIG. 1 illustrates the chemical structures of PSMA inhibitors;

[0025] FIG. 2 illustrates the chemical structure of labeling precursor PSMA-11;

[0026] FIG. 3 illustrates the chemical structure of the labeling precursor PSMA-617;

[0027] FIG. 4 illustrates the chemical structure of DOTA-conjugated FAP labeling precursor;

[0028] FIG. 5 illustrates the chemical structure of the tracer DOTA zoledronate (left) and NODAGA zolendronate (right);

[0029] FIG. 6A illustrates the chemical structures of chelators used in the invention;

[0030] FIG. 6B illustrates the chemical structures of chelators used in the invention;

[0031] FIG. 6C illustrates the chemical structures of chelators used in the invention

[0032] FIG. 7 illustrates the synthesis schema for QS-KuE precursor;

[0033] FIG. 8 illustrates the coupling schema of QS-KuE precursor to DOTA;

[0034] FIG. 9A illustrates the chemical structure of labeling precursor NOTA.QS.PSMA;

[0035] FIG. 9B illustrates the chemical structure of labeling precursors AAZTA.QS.PSMA and DATA.QS.PSMA;

[0036] FIG. 10 illustrates the chemical structure of squaric acid-conjugated PSMA-labeling precursor for radiohalides;

[0037] FIG. 11 illustrates the chemical formula of squaric acid-conjugated .sup.18F-radiotracer for PSMA before cleavage of tert-butyl protecting groups;

[0038] FIG. 12 illustrates the chemical formula of squaric acid-conjugated PSMA-labeling precursors for .sup.99mTc;

[0039] FIG. 13 illustrates a synthesis schema for FAP-labeling precursor;

[0040] FIG. 14 illustrates the chemical structures of FAP-labeling precursors with squaric acid-coupling;

[0041] FIG. 15 illustrates the chemical structure associated with coordination by AAZTA.QS;

[0042] FIG. 16 illustrates the chemical formula of dimeric labeling precursors;

[0043] FIG. 17 illustrates the synthesis schema of DOA2 with two amine groups;

[0044] FIG. 18 illustrates the synthesis schema of KuE-QS;

[0045] FIG. 19 illustrates the synthesis schema of FAPI-QS;

[0046] FIG. 20 illustrates the chemical formula for the synthesis of dimers;

[0047] FIG. 21A reproduces PET images after injection of inventive tracer .sup.68Ga-DOTA.QS.PSMA;

[0048] FIG. 21B reproduces PET images after injection of inventive tracer .sup.68Ga-DOTA.QS.PSMA;

[0049] FIG. 22 reproduces PET images of strong tracer accumulation in the tumor;

[0050] FIG. 23 is a graphical illustration of the organ distributions with various inventive radiotracers;

[0051] FIG. 24 illustrates the synthesis schema of NODAGA.QS.PAM;

[0052] FIG. 25A reproduces PET images of rats for injected tracers .sup.68Ga-NOTA.QS.PAM and .sup.68Ga-DOTA.sup.Zol;

[0053] FIG. 25B reproduces PET images of rats for injected tracers .sup.68Ga-NOTA.QS.PAM and .sup.68Ga-DOTA.sup.Zol;

[0054] FIG. 26 is a bar graph illustrating the uptake values for .sup.68Ga-NOTA.QS.PAM and .sup.68Ga-DOTA.sup.Zol in different organs;

[0055] FIG. 27 graphically illustrates the radioactive labeling of compounds with .sup.68Ga measured by radio-DC;

[0056] FIG. 28 graphically illustrate the radioactive labeling of compounds with .sup.68Ga measured by radio-HPLC;

[0057] FIG. 29 graphically illustrates stability tests of compounds with .sup.68Ga measured by HPLC;

[0058] FIG. 30 graphically illustrates ex vivo results of three compounds each labeled with .sup.68Ga;

[0059] FIG. 31A illustrates the first portion of the synthesis schema of [.sup.68Ga]Ga-TRAP.QS.PSMA where: a) is DIPEA, Triphosgene, DCM, 0° C., 4 h; b) is H-Lys(tBoc)-2CT-Polystyrol-solid phase, DCM, RT, 16 h; c) is TFA, RT, 71%; and d) is Dimethyl Squarate, Phosphate buffer (pH=7), RT, 24 h 85%;

[0060] FIG. 31B illustrates the second portion of the synthesis schema of [.sup.68Ga]Ga-TRAP.QS.PSMA where: e) is Phosphate buffer pH=9, RT, 24 h, 20%;

[0061] FIG. 32 graphically illustrates the radioactive labeling of compounds with [.sup.68Ga]Ga-TRAP.QS.PSMA measured by radio-DC;

[0062] FIG. 33 graphically illustrate the radioactive labeling of compounds with [.sup.68Ga]Ga-TRAP.QS.PSMA measured by radio-HPLC;

[0063] FIG. 34 graphically illustrates stability tests with [.sup.68Ga]Ga-TRAP.QS.PSMA;

[0064] FIG. 35 reproduces images of in vivo investigation with [.sup.68Ga]Ga-TRAP.QS.PSMA;

[0065] FIG. 36 graphically illustrates ex vivo results of [.sup.68Ga]Ga-TRAP.QS.PSMA;

[0066] FIG. 37A is the first portion of a synthesis schema for a DATA.QS.PSMA compound;

[0067] FIG. 37B is the second portion of a synthesis schema for a DATA.QS.PSMA compound;

[0068] FIG. 38 is a graphical illustration of the radiolabeling kinetics of [.sup.68Ga]Ga-DATA.SA.KuE;

[0069] FIG. 39 is a graphical illustration of the in vitro stability of [.sup.68Ga]Ga-DATA.SA.KuE;

[0070] FIG. 40 reproduces MIP images of [.sup.68Ga]Ga-DATA.QS.PSMA in the tumor and associated time/activity curves;

[0071] FIG. 41 is a graphical illustration of an ex vivo investigation;

[0072] FIG. 42 is a graphical illustration of an ex vivo investigation;

[0073] FIG. 43 is a graphical illustration of an ex vivo investigation;

[0074] FIG. 44 is the synthesis schema of an AAZTA.SA.PSMA compound;

[0075] FIG. 45 is a graphical illustration of the radiolabeling kinetics of a [.sup.44Sc]Sc-AAZTA.QS.PSMA compound;

[0076] FIG. 46 is a graphical illustration of the stability of [.sup.44Sc]Sc-AAZTA.QS.PSMA compound;

[0077] FIG. 47 is a graphical illustration of an ex vivo investigation of [.sup.44Sc]Sc-AAZTA.SA.KuE compounds;

[0078] FIG. 48 reproduces images of in vivo investigation with [.sup.44Sc]Sc-AAZTA.QS.PSMA;

[0079] FIG. 49 reproduces images of an in vivo investigation with [.sup.44Sc]Sc-AAZTA.QS.PSMA;

[0080] FIG. 50 illustrates chemical structures of compounds for .sup.18F-radiotracers;

[0081] FIG. 51 illustrates a reaction synthesis of DATA.sup.5m.SA.FAPi;

[0082] FIG. 52 is a graphical illustration of [.sup.68Ga]Ga-DOTA.SA.FAPi labeling efficacy;

[0083] FIG. 53 is a graphical illustration of the radiolabeling kinetics [.sup.68Ga]Ga-DOTA.SA.FAPi;

[0084] FIG. 54 reproduces an image of in vivo investigation with [.sup.68Ga]Ga-DOTA.SA.FAPi; and

[0085] FIG. 55 graphically illustrates the ex vivo results of [.sup.68Ga]Ga-DOTA.SA.FAPi.

DETAILED DESCRIPTION OF ADVANTAGEOUS INVENTIVE EMBODIMENTS

[0086] This object is achieved by a labeling precursor of structure (A), (B), (C), (D), (E), (F), (G), (H), (I), (J), (K) or (L) with

[0087] (A)=Ch-L.sub.1-QS-TV.sub.1,

[0088] (B)=Ch-L.sub.1-QS-S.sub.1-TV.sub.1,

[0089] (C)=Ch-L.sub.1-QS-S.sub.1-QS-TV.sub.1,

[0090] (D)=Ch-L.sub.1-QS-S.sub.2-QS-S.sub.1-TV.sub.1,

[0091] (E)=TV.sub.2-QS-L.sub.2-Ch-L.sub.1-QS-TV.sub.1,

[0092] (F)=TV.sub.2-S.sub.3-QS-L.sub.2-Ch-L.sub.1-QS-S.sub.1-TV.sub.1,

[0093] (G)=TV.sub.2-QS-S.sub.4-QS-L.sub.2-Ch-L.sub.1-QS-S.sub.2-QS-TV.sub.1,

[0094] (H)=TV.sub.2-S.sub.3-QS-S.sub.4-QS-L.sub.2-Ch-L.sub.1-QS-S.sub.2-QS-S.sub.1-TV.sub.1,

[0095] (I)=Fg-L.sub.1-QS-TV.sub.1,

[0096] (J)=Fg-L.sub.1-QS-S.sub.1-TV.sub.1,

[0097] (K)=Fg-L.sub.1-QS-S.sub.2-QS-TV.sub.1,

[0098] (L)=Fg-L.sub.1-QS-S.sub.2-QS-S.sub.1-TV.sub.1;

comprising a chelator Ch, selected from the group comprising EDTA (ethylenediamine-tetraacetate), EDTMP (diethylenetriaminepenta(methylenephosphonic acid)), DTPA (diethylenetriaminepentacetate) and its derivatives, DOTA (dodeca-1,4,7,10-tetraamine-tetraacetate), DOTAGA (2-(1,4,7,10-tetraazacyclododecane-4,7,10)-pentanedioic acid) and other DOTA derivatives, TRITA (Trideca-1,4,7,10-tetraamine-tetraacetate), TETA (tetradeca-1,4,8,11-tetraamine-tetraacetate) and its derivatives, NOTA (Nona-1,4,7-triamine-triacetate) and its derivatives such as NOTAGA (1,4,7-triazacyclononane,1-glutaric acid,4,7-acetate), NOPO (1,4,7-triazacyclononane-1,4-bis[methylene(hydroxymethyl)phosphinic acid]-7-[methylene(2-carboxyethyl)phosphinic acid]), PEPA (pentadeca-1,4,7,10,13-pentaamine pentaacetate), HEHA (hexadeca-1,4,7,10,13,16-hexaamine-hexaacetate) and its derivatives, HBED (Hydroxybenzyl-ethylene-diamine) and its derivatives, DEDPA and its derivatives, such as H.sub.2DEDPA (1,2-[[6-(carboxylate)pyridin-2-yl]methylamine]ethane), DFO (deferoxamine) and its derivatives, Trishydroxypyridinone (THP) and its derivatives such as YM103, TRAP (Triazacyclononane phosphinic acid), TEAP (Tetraazycyclodecane phosphinic acid) and its derivatives, AAZTA (6-Amino-6-methylperhydro-1,4-diazepine-N,N,N′,N′-tetraacetate) and derivatives such as DATA ((6-pentanoic acid)-6-(amino)methyl-1,4-diazepine triacetate); SarAr (1-N-(4-aminobenzyl)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]-eicosan-1,8-diamine) and salts thereof, aminothiols and their derivatives of the type

##STR00001## ##STR00002##

or [0099] a fluorination group Fg selected from the group comprising

##STR00003## ##STR00004## [0100] one or two linkers L.sub.1 and L.sub.2, which are selected independently of one another from the group comprising —(CH.sub.2).sub.m—, —(CH.sub.2CH.sub.2O).sub.m— and —(CH.sub.2).sub.mNH— with m=1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, residues of amide, carboxamide, phosphinate, alkyl, triazole, thiourea, ethylene and maleimide; [0101] one or more squaric acid residues QS

##STR00005## [0102] optionally one, two, three or four spacers S.sub.j with 1≤j≤4, which are selected independently of one another from the group comprising —(CH.sub.2).sub.n—, —(CH.sub.2)—CH(COOH)—NH—, —(CH.sub.2CH.sub.2O).sub.n— and —(CH.sub.2).sub.nNH— with n=1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, residues of amide, carboxamide, phosphinate, alkyl, triazole, thiourea, ethylene and maleimide; and [0103] one or two targeting vectors TV.sub.1 and TV.sub.2, which are selected independently of one another from the group comprising residues of compounds of the structure [1] to [41] with

##STR00006## ##STR00007## ##STR00008## ##STR00009## ##STR00010## ##STR00011## ##STR00012## ##STR00013##

where Y is a protective group and X′═Cl, Br or I and the dashed bond of the targeting vectors [1]-[41] denotes a binding site with a leaving group.

[0104] Advantageous embodiments of the labeling precursors according to the invention are characterized in that [0105] the labeling precursor contains exactly one targeting vector TV.sub.1; [0106] the labeling precursor contains two targeting vectors TV.sub.1 and TV.sub.2 with TV.sub.1≠TV.sub.2 which are different from one another; [0107] the labeling precursor contains two equal targeting vectors TV.sub.1 and TV.sub.2 with TV.sub.1=TV.sub.2; [0108] the protective group Y is selected from the group comprising tert-butyloxycarbonyl (tert-butyl), trialkylsilyl groups, trimethylsilyl (—Si(CH.sub.3).sub.3), triethylsilyl (—Si(CH.sub.2CH.sub.3).sub.3), isopropyldimethylsilyl (—Si(CH.sub.3).sub.2C(CH.sub.3).sub.2), tert-butyldimethylsilyl (—Si(CH.sub.3).sub.2C(CH.sub.3).sub.3) and tert-butoxydimethylsilyl (—Si(CH.sub.3).sub.2OC(CH.sub.3).sub.3); [0109] the linkers L.sub.1 and L.sub.2 are equal (L.sub.1=L.sub.2); [0110] the linkers L.sub.1 and L.sub.2 are different from one another (L.sub.1≠L.sub.2); [0111] the spacers S.sub.1 and S.sub.3 are equal (S.sub.1=S.sub.3); [0112] the spacers S.sub.1 and S.sub.3 are different from one another (S.sub.1≠S.sub.3); [0113] the spacers S.sub.2 and S.sub.4 are equal (S.sub.2=S.sub.4); and/or [0114] the spacers S.sub.2 and S.sub.4 are different from one another (S.sub.2≠S.sub.4).

[0115] The labeling precursor according to the invention wherein the chelator Ch or the fluorination group Fg is intended for labeling with a radioisotope selected from the group comprising .sup.44Sc, .sup.47Sc, .sup.55Co, .sup.62Cu, .sup.64Cu, .sup.67Cu, .sup.66Ga, .sup.67Ga, .sup.68Ga, .sup.89Zr, .sup.86Y, .sup.90Y, .sup.90Nb, .sup.99mTc, .sup.111In, .sup.135Sm, .sup.140Pr, .sup.159Gd, .sup.149Tb, .sup.160Tb, .sup.161Tb, .sup.165Er, .sup.166Dy, .sup.166Ho, .sup.175Yb, .sup.177Lu, .sup.186Re, .sup.188Re, .sup.213Bi and .sup.225Ac, respectively with .sup.18F, .sup.131I or .sup.211At.

[0116] Accordingly, the invention further relates to radiotracer compounds containing one of the labeling precursors described above which comprise [0117] a chelator Ch and a complexed radioisotope selected from the group comprising .sup.44Sc, .sup.47Sc, .sup.55Co, .sup.62Cu, .sup.64Cu, .sup.67Cu, .sup.66Ga, .sup.67Ga, .sup.68Ga, .sup.89Zr, .sup.86Y, .sup.90Y, .sup.90Nb, .sup.99mTc, .sup.111In, .sup.135Sm, .sup.140Pr, .sup.159Gd, .sup.149Tb, .sup.160Tb, .sup.161Tb, .sup.165Er, .sup.166Dy, .sup.166Ho, .sup.175Yb, .sup.177Lu, .sup.186Re, .sup.188Re, .sup.213Bi and .sup.225Ac, or [0118] a fluorination group Fg and a covalently bound radioisotope .sup.18F, .sup.131I or .sup.211At or a covalently bound group containing .sup.18F, .sup.131I or .sup.211At, in particular —CF.sub.2.sup.18F (trifluoromethyl).

[0119] The invention also relates to the use of the labeling precursors described above for the production of a radiopharmaceutical.

[0120] In an advantageous embodiment, the labeling precursors described above are used for the production of a radiopharmaceutical labeled with .sup.44Sc, .sup.47Sc, .sup.55Co, .sup.62Cu, .sup.64Cu, .sup.67Cu, .sup.66Ga, .sup.67Ga, .sup.68Ga, .sup.89Zr, .sup.86Y, .sup.90Y, .sup.90Nb, .sup.99mTc, .sup.111In, .sup.135Sm, .sup.140Pr, .sup.159Gd, .sup.149Tb, .sup.160Tb, .sup.161Tb, .sup.165Er, .sup.166Dy, .sup.166Ho, .sup.175Yb, .sup.177Lu, .sup.186Re, .sup.188Re, .sup.213Bi, .sup.225Ac, .sup.18F, .sup.131I or .sup.211At.

[0121] In an advantageous embodiment, the labeling precursors described above are used for the production of a radiopharmaceutical for positron emission tomography (PET) imaging diagnostics.

[0122] In an advantageous embodiment, the labeling precursors described above are used for the production of a radiopharmaceutical for single-photon emission computed tomography (SPECT) imaging diagnostics.

[0123] In an advantageous embodiment, the labeling precursors described above are used for the production of a radiopharmaceutical for the treatment of cancerous tumors.

[0124] A further object of the present invention is to provide a simple and efficient method for the synthesis of labeling precursors for the diagnosis and theranostics of cancer tumors expressing PSMA and/or FAP.

[0125] This object is achieved by a method comprising the steps of [0126] conjugating a chelator Ch or a fluorination group Fg with a linker L.sub.1 to form a precursor P.sub.1=Ch-L.sub.1 or P.sub.1=Fg-L.sub.1 or conjugation of a chelator Ch or a fluorination group Fg with a linker L.sub.1 and squaric acid QS to form a precursor P.sub.2=Ch-L.sub.1-QS or P.sub.2=Fg-L.sub.1-QS or conjugation of a chelator Ch with linkers L.sub.1 and L.sub.2 to form a precursor P.sub.3=L.sub.2-Ch-L.sub.1 or conjugation of a chelator Ch with linkers L.sub.1, L.sub.2 and squaric acid QS to form a precursor P.sub.4=QS-L.sub.2-Ch-L.sub.1-QS; [0127] optionally, conjugation of a targeting vector TV.sub.1 with squaric acid QS to form a precursor P.sub.5=TV.sub.1-QS or conjugation of a targeting vector TV.sub.1 with squaric acid QS and a spacer S.sub.2 to form a precursor P.sub.6=TV.sub.1-QS-S.sub.2 or conjugation of a targeting vector TV.sub.1 with a spacer S.sub.1 to form a precursor P.sub.7=TV.sub.1-S.sub.1 or conjugation of a targeting vector TV.sub.1 with a spacer S.sub.1 and squaric acid QS to form a precursor P.sub.8=TV.sub.1-S.sub.1-QS or conjugation of a targeting vector TV.sub.1 with a spacer S.sub.1, squaric acid QS and a spacer S.sub.2 to form a precursor P.sub.9=TV.sub.1-S.sub.1-QS-S.sub.2; [0128] optionally, conjugation of a targeting vector TV.sub.2 with squaric acid QS to form a precursor P.sub.10=TV.sub.2-QS or conjugation of a targeting vector TV.sub.2 with squaric acid QS and a spacer S.sub.4 to form a precursor P.sub.11=TV.sub.2-QS-S.sub.4 or conjugation of a targeting vector TV.sub.2 with a spacer S.sub.3 to form a precursor P.sub.12=TV.sub.2-S.sub.3 or conjugation of a targeting vector TV.sub.2 with a spacer S.sub.3 and squaric acid QS to form a precursor P.sub.13=TV.sub.2-S.sub.3-QS or conjugation of a targeting vector TV.sub.2 with a Spacer S.sub.3, squaric acid QS and a spacer S.sub.4 to form a precursor P.sub.14=TV.sub.2-S.sub.3-QS-S.sub.4; [0129] conjugation of a targeting vector TV.sub.1 with the precursor P.sub.2 or conjugation of the precursors P.sub.1 and P.sub.5 to form a labeling precursor of the structure Ch-L.sub.1-QS-TV.sub.1 or Fg-L.sub.1-QS-TV.sub.1 or conjugation of precursors P.sub.1 and P.sub.8 or P.sub.2 and P.sub.7 to form a labeling precursor of the structure Ch-L.sub.1-QS-S.sub.1-TV.sub.1 or Fg-L.sub.1-QS-S.sub.1-TV.sub.1 or conjugation of precursors P.sub.2 and P.sub.9 to form a labeling precursor of the structure Ch-L.sub.1-QS-S.sub.2-QS-S.sub.1-TV.sub.1 or Fg-L.sub.1-QS-S.sub.2-QS-S.sub.1-TV.sub.1; or [0130] conjugation of the precursors P.sub.3, P.sub.5 and P.sub.10 to form a labeling precursor of the structure TV.sub.2-QS-L.sub.2-Ch-L.sub.1-QS-TV.sub.1 or conjugation of precursors P.sub.3, P.sub.8 and P.sub.13 or P.sub.4, P.sub.7 and P.sub.12 to form a labeling precursor of structure TV.sub.2-S.sub.3-QS-L.sub.2-Ch-L.sub.1-QS-S.sub.1-TV.sub.1 or conjugation of precursors P.sub.4, P.sub.6 and P.sub.11 to form a labeling precursor of structure TV.sub.2-QS-S.sub.4-QS-L.sub.2-Ch-L.sub.1-QS-S.sub.2-QS-TV.sub.1 or conjugation of the precursors P.sub.4, P.sub.9 and P.sub.14 to form a labeling precursor of the structure TV.sub.2-S.sub.3-QS-S.sub.4-QS-L.sub.2-Ch-L.sub.1-QS-S.sub.2-QS-S.sub.1TV.sub.1;
wherein [0131] the chelator Ch is selected from the group comprising from the group comprising EDTA (ethylenediaminetetraacetate), EDTMP (diethylenetriaminepenta(methylene phosphonic acid)), DTPA (diethylenetriaminepentacetate) and its derivatives, DOTA (dodeca-1,4,7,10-tetraaminetetraacetate) , DOTAGA (2-(1,4,7,10-tetraazacyclododecane-4,7,10)-pentanedioic acid) and other DOTA derivatives, TRITA (Trideca-1,4,7,10-tetraamine-tetraacetate), TETA (tetradeca-1,4,8,11-tetraamine-tetraacetate) and its derivatives, NOTA (Nona-1,4,7-triamine-triacetate) and its derivatives such as NOTAGA (1,4,7-triazacyclononane,1-glutaric acid,4,7-acetate), NOPO (1,4,7-triazacyclononane-1,4-bis[methylene(hydroxymethyl)phosphinic acid]-7-[methylene(2-carboxyethyl)phosphinic acid]), PEPA (pentadeca-1,4,7,10,13-pentaamine pentaacetate), HEHA (hexadeca-1,4,7,10,13,16-hexaamine-hexaacetate) and its derivatives, HBED (Hydroxybenzyl-ethylene-diamine) and its derivatives, DEDPA and its derivatives, such as H.sub.2DEDPA (1,2-[[6-(carboxylate)pyridin-2-yl]methylamine]ethane), DFO (deferoxamine) and its derivatives, Trishydroxypyridinone (THP) and its derivatives such as YM103, TRAP (Triazacyclononane phosphinic acid), TEAP (Tetraazycyclodecane phosphinic acid) and its derivatives, AAZTA (6-Amino-6-methylperhydro-1,4-diazepine-N,N,N′,N′-tetraacetate) and derivatives such as DATA ((6-pentanoic acid)-6-(amino)methyl-1,4-diazepine triacetate); SarAr (1-N-(4-aminobenzyl)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]-eicosan-1,8-diamine) and salts thereof, aminothiols and their derivatives of the type

##STR00014## ##STR00015## [0132] the fluorination group Fg is selected from the group comprising

##STR00016## ##STR00017## [0133] the linkers L.sub.1 and L.sub.2 are selected independently of one another from the group comprising —(CH.sub.2).sub.m—, —(CH.sub.2CH.sub.2O).sub.m— and —(CH.sub.2).sub.mNH— with m=1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, residues of amide, carboxamide, phosphinate, alkyl, triazole, thiourea, ethylene and maleimide; [0134] the spacers S.sub.j with 1≤j≤4 are selected independently of one another from the group comprising —(CH.sub.2).sub.n—, —(CH.sub.2)—CH(COOH)—NH—, —(CH.sub.2CH.sub.2O).sub.n— and —(CH.sub.2).sub.n—NH— with n=1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, residues of amide, carboxamide, phosphinate, alkyl, triazole, thiourea, ethylene and maleimide; and [0135] the targeting vectors TV.sub.1 and TV.sub.2 are selected independently of one another from the group comprising compounds of the structure [1] to [41] with

##STR00018## ##STR00019## ##STR00020## ##STR00021## ##STR00022## ##STR00023## ##STR00024## ##STR00025## [0136] where Y is a protective group and X′═Cl, Br or I and the dashed linkage of the targeting vectors [1]-[41] denotes a binding site with a leaving group.

[0137] Advantageous embodiments of the method according to the invention are characterized in that [0138] the targeting vectors TV.sub.1 and TV.sub.2 are different from one another (TV.sub.1≠TV.sub.2); [0139] the targeting vectors TV.sub.1 and TV.sub.2 are equal (TV.sub.1=TV.sub.2); [0140] the protective group Y is selected from the group comprising tert-butyloxycarbonyl (tert-butyl), trialkylsilyl groups, trimethylsilyl (—Si(CH.sub.3).sub.3), triethylsilyl (—Si(CH.sub.2CH.sub.3).sub.3), isopropyldimethylsilyl (—Si(CH.sub.3).sub.2C(CH.sub.3).sub.2), tert-butyldimethylsilyl (—Si(CH.sub.3).sub.2C(CH.sub.3).sub.3) and tert-butoxydimethylsilyl (—Si(CH.sub.3).sub.2OC(CH.sub.3).sub.3); [0141] the linkers L.sub.1 and L.sub.2 are equal (L.sub.1=L.sub.2); [0142] the linkers L.sub.1 and L.sub.2 are different from one another (L.sub.1≠L.sub.2); [0143] the spacers S.sub.1 and S.sub.3 are equal (S.sub.1=S.sub.3); [0144] the spacers S.sub.1 and S.sub.3 are different from one another (S.sub.1≠S.sub.3); [0145] the spacers S.sub.2 and S.sub.4 are equal (S.sub.2=S.sub.4); and/or [0146] the spacers S.sub.2 and S.sub.4 are different from one another (S.sub.2≠S.sub.4).

[0147] The fluorination group Fg comprises a leaving group X for labeling with one of the radioisotopes .sup.18F, .sup.131I or .sup.211At. The leaving group X is equal to a residue of bromine (Br), chlorine (Cl), iodine (I), tosyl (—SO.sub.2—C.sub.6H.sub.4—CH.sub.3; abbreviated “Ts”), nosylate or Nitrobenzenesulfonate (—OSO.sub.2—C.sub.6H.sub.4—NO.sub.2; abbreviated “Nos”), 2-(N-Morpholino) ethanesulfonic acid (—SO.sub.3—(CH.sub.2).sub.2—N(CH.sub.2).sub.4O; abbreviated “MES”), triflate or Trifluoro-methanesulfonyl (—SO.sub.2CF.sub.3; abbreviated “Tf”) or nonaflate (—OSO.sub.2—C.sub.4F.sub.9; abbreviated “Non”).

[0148] In the context of the present invention, the following designations or abbreviations are used: [0149] PSMA . . . Prostate specific membrane antigen; [0150] FAP . . . Fibroblast activation protein; [0151] FPPS . . . Farnesyl pyrophosphate synthase; [0152] 2-PMPA . . . 2-Phosphonomethyl glutaric acid; [0153] KuE . . . L-lysine-urea-L-glutamate; [0154] DOTA.QS.PSMA . . . labeling precursors, in particular with the structural formula according to FIG. 8, comprising DOTA (Dodeca-1,4,7,10-tetraamine-tetraacetate) as a chelator, to which one or two PSMA targeting vectors with the structural formula [1], [2], [3] and/or [4] are coupled via one or two linkers, squaric acid groups and spacers; [0155] NOTA.QS.PSMA . . . labeling precursors, in particular with the structural formula according to FIG. 9, comprising NOTA (Nona-1,4,7-triamine triacetate) as a chelator, to which one or two PSMA targeting vectors with the structural formula [1], [2], [3] and/or [4] are coupled via one or two linkers, squaric acid groups and spacers; [0156] AAZTA.QS.PSMA . . . labeling precursors, in particular with structural formula according to FIG. 9, comprising AAZTA as a chelator, to which one or two PSMA targeting vectors with the structural formula [1], [2], [3] and/or [4] are coupled via one or two linkers, squaric acid groups and spacers; [0157] DATA.QS.PSMA . . . labeling precursors, in particular with structural formula according to FIG. 9, comprising DATA as a chelator, to which one or two PSMA targeting vectors with the structural formula [1], [2], [3] and/or [4] are coupled via one or two linkers, squaric acid groups and spacers; [0158] DOTAGA.QS.PSMA . . . labeling precursors, including DOTAGA (2-(1,4,7,10-Tetraazacyclo-dodecane-4,7,10) pentanedioic acid) as a chelator, to which one or two PSMA targeting vectors with the structural formula [1], [2], [3] and/or [4] are coupled via one or two linkers, squaric acid groups and spacers; [0159] NOTAGA.QS.PSMA . . . labeling precursor, comprising NOTAGA (1,4,7-triazacyclononane, 1-glutaric acid, 4,7-acetate) as a chelator, to which one or two PSMA targeting vectors with the structural formula [1], [2], [3] and/or [4] are coupled via one or two linkers, squaric acid groups and spacers;

[0160] TRAP.QS.PSMA . . . labeling precursors, comprising TRAP (triazacyclononanephosphinic acid) as a chelator, to which one or two PSMA targeting vectors with the structural formula [1], [2], [3] and/or [4] are coupled via one or two linkers, squaric acid groups and spacers;

[0161] NOTA.QS.PAM . . . labeling precursor, comprising NOTA as a chelator, to which one or two pamidronate targeting vectors according to structural formula [40] are coupled via one or two linkers, squaric acid groups and spacers.

[0162] Further abbreviations used in the context of the invention correspond to the above abbreviations, wherein another chelator, another fluorination group and/or another targeting vector—in particular a targeting vector for FAP according to the structural formulas [5] to [41]—is designated in an analogous manner by its respective abbreviation or acronym. For example, analogous derivatives that are used to target farnesyl pyrophosphate synthase (FPPS) in bone metastases are abbreviated as “PAM” for pamidronate and “ZOL” for zoledronate, depending on the type of bisphosphonate.

[0163] The labeling precursor according to the invention optionally comprises one or more spacers S.sub.j with 1≤j≤4, i.e. one spacer S.sub.1, two spacers S.sub.1 and S.sub.2, three spacers S.sub.1, S.sub.2 and S.sub.3 or four spacers S.sub.1, S.sub.2, S.sub.3 and S.sub.4.

[0164] In the structural formulas [1]-[41] of the targeting vectors, the bonds provided for conjugation with a squaric acid group or a spacer S.sub.1 or S.sub.2 of the labeling precursor according to the invention are shown in dashed lines. The group conjugated via the dashed bond is a leaving group which is split off when the targeting vector is coupled with the squaric acid group or the spacer S.sub.1 or S.sub.2.

[0165] The invention is explained in more detail below by reference to figures and examples.

[0166] FIG. 6 shows the structure of some of the chelators Ch used according to the invention. [0167] (FIG. 6: Chelators Used According to the Invention)

EXAMPLE 1

Synthesis Strategy for PSMA Labeling Precursors

[0168] In the synthesis of the labeling precursors according to the invention squaric acid diesters are preferably used. As a result, a large number of, in some cases very complex, labeling precursors can be synthesized using simple reaction processes. Squaric acid diesters are characterized by their selective reactivity with amines, so that no protective groups are required when coupling chelators, linkers, spacers and targeting vectors. In addition, the coupling can be controlled via the pH value.

[0169] First, a targeting vector for PSMA is synthesized (see FIG. 7) and, after purification in an aqueous medium at pH=7, reacted with squaric acid diester to form a prostethic group or a precursor for coupling with a chelator (see FIG. 8).

[0170] (FIG. 7: Synthesis Scheme for QS-KuE Precursor)

[0171] E. g. in the case of a targeting vector for PSMA, the PSMA inhibitor L-lysine-urea-L-glutamate (KuE) is synthesized by means of a known process. Thereby, lysine bound to a solid phase, in particular a polymer resin and protected with tertbutyloxycarbonyl (tert-butyl), is reacted with double-tert-butyl-protected glutamic acid. After activation of the protected glutamic acid by triphosgene and the coupling to the solid phase-bound lysine, L-lysine-urea-L-glutamate (KuE) is split off by TFA and at the same time fully deprotected. The product can then be separated from free lysine by means of semi-preparative HPLC. The lysine-related yield of the above reaction is greater than 50%.

[0172] (FIG. 8: Coupling of a QS-KuE Precursor to DOTA)

[0173] The QS-KuE precursor is conjugated in phosphate buffer at pH 9 with the chelator DOTA to form the labeling precursor DOTA.QS.PSMA.

[0174] For the radiolabeling of the PSMA labeling precursors, .sup.68Ga was eluted with 0.6 M HCl from an iThemba Ge/Ga generator and processed by means of aqueous ethanol elution over a cation exchange column. Radiolabeling takes place at pH values between 3.5 and 5.5 and temperatures between 25° C. and 95° C., depending on the chelator. The reaction progress was recorded by means of HPLC and IPTC in order to determine the kinetic parameters of the reaction.

EXAMPLE 2

Labeling Precursor NOTA.QS.PSMA. AAZTA QS.PSMA and DATA.QS.PSMA

[0175] Using a synthesis according to the strategy described in Example 1 with chelators NOTA, AAZTA and DATA instead of DOTA yields the precursors NOTA.QS.PSMA, AAZTA.QS.PSMA and DATA.QS.PSMA shown in FIG. 9. [0176] (FIG. 9: Labeling Precursors NOTA.QS.PSMA, AAZTA.QS.PSMA and DATA.QS.PSMA)

EXAMPLE 3

PSMA Labeling Precursors for Radiohalides

[0177] The PSMA labeling precursors shown in FIG. 10 for radiolabeling with halide isotopes such as .sup.18F and .sup.131I were prepared using slightly modified reactions according to the synthesis schema of FIG. 10 corresponding radiotracer labeled with .sup.18F is shown in FIG. 11.

[0178] (FIG. 10: Squaric Acid Conjugated PSMA Labeling Precursors for Radiohalides; FIG. 11: Squaric Acid-Conjugated .sup.18F-Radiotracer for PSMA Before Splitting Off the Cert-Butyl Protective Groups)

EXAMPLE 4

PSMA Labeling Precursor for .SUP.99m.Tc

[0179] By means of a synthesis according to the strategy described in Example 1, the PSMA labeling precursors shown in FIG. 12 for radiolabeling with the isotope .sup.99mTc were prepared. [0180] (FIG. 12: Squaric Acid Conjugated PSMA Labeling Precursors for .sup.99mTc with Aminothiol Based Chelators of the Type “N3S”)

EXAMPLE 5

Synthesis Strategy for FAP Labeling Precursors

[0181] (FIG. 13: Synthesis Strategy for FAP Labeling Precursors)

[0182] FIG. 14 shows two FAP labeling precursors which are prepared according to the synthesis strategy shown in FIG. 13.

[0183] (FIG. 14: FAP Labeling Precursors with Squaric Acid Coupling)

EXAMPLE 6

QS as a Complexation Helper

[0184] For clinical use it is very important that the complexation takes place efficiently at low temperature. Squaric acids complex free metals and can thus protect the chelator center against unspecific coordination. This effect could be observed in the radiolabeling of TRAP.QS at different temperatures. TRAP complexes quantitatively at room temperature. In contrast, an RCY value of only 50% was measured with TRAP.QS under the same conditions. If the temperature is increased, the labeling yield of TRAP.QS increases to quantitative values. This demonstrates the influence that squaric acid has on complexation. This effect illustrated in FIG. 15 enables the stable complexation of metals with a high coordination number, such as zirconium, by means of the AAZTA.QS chelator.

[0185] (FIG. 15: Coordination By Means of AAZTA.QS)

EXAMPLE 7

Dimeric Labeling Precursors Each with Two KuE and FAPI Targeting Vectors

[0186] (FIG. 16: Dimeric Labeling Precursors)

[0187] (i) Synthesis of the DO2A unit with two amine side groups:

[0188] (FIG. 17: Synthesis of DOA2 with Two Amine Groups)

[0189] (ii) Synthesis of the KuE-QS motif:

[0190] (FIG. 18: Synthesis of KuE-QS)

[0191] (iii) Synthesis of FAPI-QS, coupling of the 4,4-difluoroproline-quinoline-4-carboxylic acid motif with QS:

[0192] (FIG. 19: Synthesis of FAPI-QS)

[0193] (iv) Coupling of the DO2A unit with KuE-QS and respectively FAPI-QS:

[0194] (FIG. 20: Synthesis of Dimers)

EXAMPLE 8

.SUP.68.Ga-DOTA.OS.PSMA Preclinical Study

[0195] Using PET, preclinical comparative tests with radiotracers of type .sup.68Ga-DOTA.QS.PSMA, .sup.68Ga-PSMA-11 and .sup.68Ga-PSMA-617 were carried out on NMRInu/nu nude mice with an LNCaP tumor on the right hind leg. FIG. 21 shows PET images 60 min after injection of the tracer .sup.68Ga-DOTA.QS.PSMA according to the invention, partial images (A) and (B) showing the PET images of an unblocked tumor mouse and a tumor mouse blocked by means of co-injected 2-PMPA, respectively.

TABLE-US-00001 TABLE 1 Standardized intake values (SUV) of PSMA tracers SUV DOTA.QS.PSMA PSMA-11 PSMA-617 Tumor 0.73 1.16 0.73 Nieren 0.43 4.71 0.27 Leber 0.27 0.25 0.29

[0196] From the PET images depicted in FIG. 22 it can be seen that the tracer accumulates strongly in the tumor. From the PET data a standardized uptake value (SUV) of 0.73 in the tumor was determined for .sup.68Ga-DOTA.QS.PSMA. Biological distribution data ascertained by extraction of the organs and measurement of weight and activity show a slightly lower or equal tumor activity for .sup.68Ga-DOTA.QS.PSMA as for .sup.68Ga-PSMA-11 and .sup.68Ga-PSMA-617. In contrast, the off-target activity in the kidneys is significantly lower than for .sup.68Ga-PSMA-11.

[0197] Compared to other known radio tracers, the off-target enrichment of .sup.68Ga-DOTA.QS.PSMA is significantly reduced in kidney and liver. .sup.68Ga-DOTA.QS.PSMA has a high affinity for tumor tissue and improves the contrast and signal-to-noise ratio of imaging PET diagnosis of PCa primary tumors and especially PCa-affected lymph nodes in the pelvic area. The radiation exposure of the kidneys and neighboring organs is also reduced, which constitutes a significant advantage for theranostic treatment.

[0198] Analogous studies with .sup.64CuTRAP.QS.PSMA and .sup.68Ga-NOTAGA.QS.PSMA yielded comparable results. Furthermore, DOTA.QS.PSMA was labeled with .sup.177Lu and .sup.225Ac. First results on the radiological and physiological stability of these tracers indicate their suitability for theranostics.

[0199] Due to the influence of the aromatic binding pocket of PSMA on the affinity of PSMA inhibitors, some importance is assigned to the lipophilicity of PSMA tracers. Studies indicate that an increased lipophilicity also promotes the intake or endocytosis of the tracer in tumor tissue.

[0200] Accordingly, the lipophilicity of the tracers TRAP.QS.PSMA and DOTA.QS.PSMA according to the invention was determined by means of the HPLC method by Donovan and Pescatore (S. F. Donovan, M. C. Pescatore, J. Chromatogr. A 2002, 952, 47-61). For this purpose, the retention time of TRAP.QS.PSMA, DOTA.QS.PSMA and some calibration standards with known lipophilicity were measured in an ODP-HPLC column with a methanol/water gradient at pH 7. The log D values for TRAP.QS.PSMA and DOTA.QS.PSMA determined by linear regression of the retention times are shown in Table 2 together with literature values for PSMA-11 and PSMA-617.

[0201] Since DOTA.QS.PSMA has no retention on the ODP-HPLC column, only a maximum value is given for log D. TRAP.QS.PSMA, PSMA-11 and PSMA-617 have comparable lipophilicity. Surprisingly, the uptake of TRAP.QS.PSMA in the kidneys is significantly reduced compared to PSMA-11 and PSMA-617. This observation cannot be explained by the slight differences in the respective log D values. Apparently, affinity and endocytosis is not only influenced by lipophilicity, but other interactions such as π-π stacking in the enzymatic binding pocket also play a role. Squaric acid appears advantageous because of its small size compared to phenyl. In contrast, DOTA.QS.PSMA shows a considerably higher lipophilicity in connection with an uptake in the kidneys comparable to PSMA-617.

TABLE-US-00002 TABLE 2 Lipophilicity of PSMA tracers Tracer logD [nM] TRAP.QS.PSMA −1.5 ± 0.5 DOTA.QS.PSMA ≤−3.5 PSMA-11 −1.7 ± 0.6 PSMA-617 −2.0 ± 0.3

[0202] In addition, PET was used to carry out preclinical ex vivo tests with the radiotracers of type [.sup.68Ga]Ga-DOTA.QS.PSMA, [.sup.68Ga]Ga-PSMA-11 and [.sup.68Ga] Ga-PSMA-617 on NMRInu/nu nude mice with an LNCap tumor. FIG. 23 shows the organ distributions of the corresponding compounds. The results obtained underline those obtained in the in vivo tests. Biological distribution data determined by extraction of the organs and measurement of weight and activity show that [.sup.68Ga]Ga-DOTA.QS.PSMA has a slightly lower or the same tumor activity as [.sup.68Ga]Ga-PSMA-11 and [.sup.68Ga]Ga-PSMA-617. In contrast, the off-target activity in the kidney is significantly lower than for [.sup.68 Ga]Ga-PSMA-11.

EXAMPLE 9

FPPS Tracer

[0203] Bisphosphonates such as alendronate, pamidronate and zoledronate (structural formula [39], [40] and [41] respectively) inhibit farnesyl pyrophosphate synthase (FPPS) and induce apoptosis in bone metastases.

[0204] For labeling bone metastases a squaric acid-coupled tracer NOTA.QS.PAM with chelator NOTA and targeting vector pamindronate (structural formula [40]) was synthesized in accord with the strategy described in Example 1. FIG. 24 illustrates the synthetic schema with reference to the NODAGA chelator.

[0205] (FIG. 24: Synthesis of NODAGA.QS.PAM)

[0206] The tracer NOTA.QS.PAM according to the invention and the clinically established reference tracer DOTA.sup.Zol were labeled with .sup.68Ga, injected into young healthy Wistar rats, followed by recording of PET scans at intervals of 5 min, 60 min and 120 min after injection.

[0207] FIG. 25 shows the corresponding PET images for the tracers .sup.68Ga-NOTA.QS.PAM and .sup.68Ga-DOTA.sup.Zol 120 min after injection. Both tracers show a specific uptake in bone regions with increased remodeling rate, especially in the epiphyses, which are still growing in young rats. In addition to the skeleton, the bladder shows increased activity and indicates preferential renal excretion. In contrast, retention in soft tissue is extremely low.

[0208] Compared to .sup.68Ga-DOTA.sup.Zol, the renal excretion of .sup.68Ga-NOTA.QS.PAM is slightly reduced. This observation is consistent with the renal excretion of PSMA tracers. This is the result of increased accumulation in the target tissue in association with accelerated renal excretion of free, non-specifically bound tracer. In terms of pharmacological kinetics, the inventive squaric acid-coupled tracers exhibit advantages over known tracers.

[0209] FIG. 26 shows the uptake values (SUV) for .sup.68Ga-NOTA.QS.PAM and .sup.68Ga-DOTA.sup.Zol in different organs at intervals of 5 min and 60 min after injection in the form of a bar graph. The organ distribution of the activity demonstrates that both tracers exhibit high uptake and retention in bone, whereby .sup.68Ga-NOTA.QS.PAM has a slightly higher femur SUV (SUV femur: .sup.68Ga-DOTA.sup.Zol=3.7±0.4; .sup.68Ga-NOTA.QS.PAM=4.5±0.2). Both tracers are characterized by renal excretion and low retention in the remaining tissue.

EXAMPLE 10

QS.PSMA

[0210] In order to elucidate the activity of QS, tests comparable to those for DOTA.QS.PSMA were carried out with NODAGA.QS.PSMA. FIGS. 27 and 28 show the radioactive labeling of the compounds with .sup.68Ga, respectively measured by radio-DC (FIG. 27) and radio-HPLC (FIG. 28). Yields of more than 95% are achieved.

[0211] Corresponding stability tests were carried out in human serum and in PBS buffer. The compounds show stabilities of more than 95% after 2 hours in PBS and HS. FIG. 29 shows the stability measured by HPLC.

[0212] In addition, the three compounds DOTAGA.QS.PSMA, NODAGA.QS.PSMA and TRAP.QS.PSMA were investigated in vivo and ex vivo. FIG. 30 shows the ex vivo results of the three compounds each labeled with .sup.68Ga. From FIG. 30 it can be seen that all three compounds accumulate in tumor tissue, with NODAGA.QS.PSMA showing low accumulation in the kidneys.

EXAMPLE 11

TRAP.QS.PSMA

[0213] FIG. 31a-b, 32-36 show the synthesis and measurement results for radiolabeling, stability and in vivo investigations of the radiotracer [.sup.68Ga]Ga-TRAP.QS.PSMA. The results are comparable to those of Examples 8 and 10. The in vivo studies were carried out with .sup.68Ga and .sup.64Cu. From the images it can be seen that, compared to Examples 8 and 10, the accumulation in the kidneys is increased for both radiotracers. This is due to the different lipophilicity of the radiotracers of Example 11 caused by long-chain linkers. The ex vivo comparison shows that compared to [.sup.68Ga]Ga-PSMA-11 the accumulation in tumor tissue is elevated and noticeably decreased in the kidneys.

EXAMPLE 12

[.SUP.68.Ga]Ga-DATA OS.PSMA

[0214] Further compounds according to the invention are those of the DATA.QS.PSMA type, the structure of which corresponds to the other compounds listed, with the DATA chelator enabling simpler and milder labeling. In the synthesis shown in FIG. 37, a yield of about 70% is achieved. In the case of radioactive labeling with .sup.68Ga, a yield of more than 95% is achieved (FIG. 38). As can be seen from FIG. 39, the compounds have high stability in both human serum (HS) and phosphate-buffered saline (PBS). In in vitro studies of the compound with LNCap cells, an IC.sub.50 value of 51.5 nM is obtained, which is comparable to PSMA-11 and PSMA-617 (Table 3).

[0215] Furthermore, compounds of the type DATA.QS.PSMA were compared in vivo with PSMA-11 in the same animal model. The MIP images (FIG. 40) clearly show high accumulation of [.sup.68Ga]Ga-DATA.QS.PSMA in the tumor. The time/activity curves depicted in FIG. 40 also show that for [.sup.68Ga]Ga-DATA.QS.PSMA the excretion via the kidneys occurs significantly faster in the first hour than for [.sup.68Ga]-PSMA-11. The accumulation in tumor tissue is comparable.

TABLE-US-00003 TABLE 3 IC.sub.50 values of the unlabeled compounds Compound IC.sub.50 [nM] PSMA-11 26.1 ± 1.2 PSMA-617 15.1 DATA.QS.PSMA 51.1 ± 5.5

[0216] The results of ex vivo investigations (FIGS. 41-43) are in agreement with the in vivo observations. As can be seen from Table 4, the % ID/g values of the two compounds labeled with .sup.68Ga within the tumor are comparable, whereas for [.sup.68Ga]Ga-DATA.QS.PSMA the accumulation in the kidneys and the salivary glands is considerably reduced. Low accumulation in the salivary glands is very advantageous since the latter are exposed to an elevated dose and their function is considerably impaired in known methods for radiopharmaceutical treatment of prostate cancer. Blocking studies with 2-PMPA also show that the inventive compounds have an increased specificity for PSMA.

TABLE-US-00004 TABLE 4 Ex vivo activities .sup.68Ga.DATA.QS.PSMA .sup.68Ga.PSMA 11 % ID/g ± SD tumor 4.65 ± 0.58 5.51 ± 0.38 LN 0.35 ± 0.20 0.66 ± 0.10 salivary glands 0.19 ± 0.07 0.54 ± 0.11 lung 0.59 ± 0.27 0.74 ± 0.04 blood 0.50 ± 0.19 0.27 ± 0.03 heart 0.17 ± 0.06 0.17 ± 0.03 liver 0.21 ± 0.04 0.23 ± 0.04 spleen 0.54 ± 0.22 3.12 ± 0.39 kidney left 6.59 ± 2.45 36.66 ± 5.05  kidney right 6.23 ± 2.39 36.72 ± 4.33  small intestine 0.31 ± 0.12 0.50 ± 0.14 muscle 0.09 ± 0.05 0.11 ± 0.03 bone 0.15 ± 0.03 0.15 ± 0.04

EXAMPLE 13

[.SUP.44.Sc]Sc-AAZTA.QS.PSMA

[0217] Similar to DATA, the AAZTA chelator can also be labeled with radio nuclides such as .sup.44Sc and .sup.68Ga under mild conditions. In the instant example, the radioisotope .sup.44Sc is used and the properties of the radiotracer [.sup.44Sc]Sc-AAZTA.QS.PSMA are investigated. The synthesis shown in FIG. 44 was readily carried out with high yield. As shown in FIG. 45, a high yield is also obtained for radiolabeling. The stability of [.sup.44Sc]Sc-AAZTA.QS.PSMA exceeds 95% over a period of 24 hours (FIG. 46).

[0218] The radiotracer [.sup.44Sc]Sc-AAZTA.QS.PSMA was further examined in vivo in three mice, each carrying an LNCap tumor. In addition blocking tests were carried out on one of the mice. The ex vivo results shown in Table 5 and FIG. 47 show that the AAZTA derivatives labeled with .sup.44Sc are also highly accumulated within the tumor tissue. Furthermore, a large part of the activity in the tumor can be blocked with 2-PMPA. The same applies to the kidneys. These results are in agreement with corresponding in vivo studies. FIGS. 48 and 49 show the tumor activity 1 h after injection without blocking and 40 after injection (20 min static recording) with blocking by co-injection of 2-PMPA.

TABLE-US-00005 TABLE 5 Ex vivo activities % ID/g .sup.44Sc.AAZTA.QS.KuE (1) .sup.44Sc.AAZTA.QS.KuE (2) Block (+PMPA) tumor 14.73 14.14 0.53 LN 1.33 0.38 0.39 salivary glands 0.51 0.18 0.11 lung 1.31 0.59 0.06 blood 0.96 0.41 0.34 heart 0.41 0.14 0.11 liver 0.42 0.16 0.16 spleen 6.19 1.15 0.15 kindneys 119.86 42.76 7.97 small intestine 0.62 0.22 0.35 muscle 0.38 0.13 0.05 bone 0.46 0.29 0.10

EXAMPLE 14

Compounds for .SUP.18.F Labeling

[0219] For PET diagnosis with .sup.18F, various labeling precursors were synthesized and examined in vitro in LNCap cells. For several of the examined compounds, low IC.sub.50 values corresponding to PSMA-11 and PSMA-617 were observed. Three such compounds and their IC.sub.50 values are shown in FIG. 50.

[0220] (FIG. 50: Compounds for .sup.18F Radiotracers)

EXAMPLE 15

DOTA.FAPi and DATA.FAPi

[0221] The synthesis of DOTA.QS.FAPi shown in FIG. 51 is carried out analogously to Example 6 and comprises the steps: (a) Paraformaldehyde, MeOH, Amberlyst A21; (b) Pd /C, CH.sub.3COOH, abs. EtOH, K.sub.2CO.sub.3; (c) tert-butyl bromoacetate, MeCN, K.sub.2CO.sub.3; (d) formalin (37 wt %), CH.sub.3COOH, NaBH.sub.4, MeCN; (e) 1 M LiOH, 1,4-dioxane/H.sub.2O (2:1); (f) N-boc-Ethylenediamine, HATU, HOBt, DIPEA, MeCN; (g) (i) 80% TFA in DCM, (ii) 3,4-diethoxycyclobut-3-ene-1,2-dione, phosphate buffer pH 7, 1 M NaOH; (h) 3, phosphate buffer pH 9, 1 M NaOH.

[0222] (FIG. 51: Synthesis DATA.QS.FAPi)

[0223] Labeling with .sup.68Ga occurs rapidly and in high yield (FIGS. 52 and 53). The stability in human serum (HS) and NaCl solution is more than 98% over a period of 2 hours (Table 6).

TABLE-US-00006 TABLE 6 Stability in HS, EtOH and NaCl Medium time/min HS EtOH 0.9% NaCl 15 99.7 ± 0.3 99.6 ± 0.1 99.6 ± 0.2 30 99.8 ± 0.1 99.9 ± 0.1 99.9 ± 0.0 45 99.6 ± 0.4 99.9 ± 0.1 99.9 ± 0.1 60 99.2 ± 0.2 99.6 ± 0.2 99.6 ± 0.2 90 98.3 ± 0.2 99.6 ± 0.1 99.3 ± 0.1 120 98.8 ± 0.6 100.0 ± 0.1  99.4 ± 0.3

[0224] The FAP IC.sub.50 values were measured using Z-Gly-Pro-7-amino-4-methylcoumarin (AMC). The PREP IC.sub.50 values were determined using N-succinyl-Gly-Pro-AMC. The selectivity indices are comparable with literature values (Jansen et al. J Med Chem, 2014, 7, 3053). The measured values are shown in Table 7.

TABLE-US-00007 TABLE 7 IC.sub.50 values and selectivity indices Selectivity IC.sub.50 FAP IC.sub.50 PREP index (nM)* (μM) (FAP/PREP) DOTA.QS.FAPi - uncomplexed 0.9 ± 0.1 5.4 ± 0.3 6000 DOTA.QS.FAPi - natGa 1.4 ± 0.2 8.7 ± 0.9 6214 DOTA.QS.FAPi - natLu 0.8 ± 0.2 2.5 ± 0.4 3125 DATA.sup.5m.QS.FAPi - 0.8 ± 0.2 1.69 ± 0.09 2113 uncomplexed DATA5m.QS.FAPi - natGa 0.7 ± 0.1 4.7 ± 0.3 6714

[0225] In vivo as well as ex vivo examinations with [.sup.68Ga]Ga-DOTA.QS.FAPi in mice bearing colon cancer (HT29) show a high concentration in the tumor tissue (FIGS. 54 and 55).