Glycopeptides targeting tumor-associated fibroblast activation protein, radionuclide labels and applications thereof

Abstract

This invention relates to a class of FAP glycopeptides represented by Formula I, their radionuclide labels, and their applications. The FAP glycopeptides are obtained by modifying the linker portion forming the cyclic peptide based on the structure of the polypeptide FAP-2286, and further introducing monosaccharide or disaccharide molecules. After radionuclide labeling, the glycopeptides exhibit superior tumor uptake and lower liver uptake compared to FAP-2286, resulting in better imaging results. This is beneficial for obtaining candidate radionuclide therapeutic drugs with further research and development value, and ultimately for obtaining FAP-targeted cyclic peptide radiopharmaceuticals with independent intellectual property rights.

Description

A class of glycopeptides and radionuclide markers targeting tumor-associated fibroblast activation proteins and their applications Technical Field

[0001] This invention relates to the field of peptide technology that targets tumor-associated fibroblast activation protein (FAP), specifically to a class of FAP glycopeptides, their radionuclide labels, and their applications. Background Technology

[0002] The development of radiopharmaceuticals has become an important direction in new drug research and development both internationally and domestically, attracting the attention of numerous research institutions, enterprises, and the market. In particular, therapeutic radiopharmaceuticals targeting tumors, which can effectively diagnose and treat tumors with radionuclide therapy, represent a cutting-edge direction in current drug research. Examples include Lutathera (lutetium oxide octreotide), a radiolabeled peptide targeting the somatostatin receptor, and Pluvicto (formerly known as...), a radioactive small molecule targeting prostate-specific membrane antigen (PSMA). 177 Lu-PSMA-617 was also approved for marketing by the US FDA in 2018 and 2022, respectively.

[0003] Malignant tumors comprise both tumor cells and their surrounding microenvironment. The tumor microenvironment, also known as the tumor stroma, includes various non-malignant cells that collectively shape an environment conducive to tumor growth. Non-cancer stromal cells, through the production of various growth factors, chemokines, and cytokines, promote extracellular matrix remodeling, induce angiogenesis, induce cell migration, develop drug resistance, and evade immune surveillance, thereby promoting tumor invasion and metastasis. Studies have confirmed that tumor-associated fibroblasts (CAFs) are a major component of non-cancer stromal cells in the tumor microenvironment, and fibroblast activation protein (FAP) is widely expressed on the surface of CAFs, making it a highly promising tumor biomarker.

[0004] FAP is a membrane-bound glycoprotein belonging to the dipeptidylpeptidase 4 (DPP4) family. It possesses both dipeptidyl peptidase and endopeptidase activities and shares 52% protein homology with DPP4. This protein consists of 760 amino acids, including a short intracellular region (6 amino acids), a transmembrane region (20 amino acids), and a large extracellular region (734 amino acids). In normal tissues, FAP is generally not expressed or expressed at very low levels, but it is overexpressed in fibroblasts (CAFs) and is also highly expressed in over 90% of epithelial tumors. It can directly promote the proliferation, migration, and invasion of mesenchymal fibroblasts and other cell types, leading to tumor angiogenesis, extracellular matrix degradation, and evasion of immune surveillance.

[0005] Recent studies have shown that FAP is a very promising target for radiotherapy-guided therapies for tumors. The University of Heidelberg in Germany has successfully developed a series of small molecule probes targeting FAP, such as FAPI-02 and FAPI-04, and has used them... 68 Ga and 177 Lu-labeled radiopharmaceuticals have become a form of integrated diagnostic and therapeutic radiopharmaceutical. Clemens Kratochwil et al. evaluated a total of 80 patients. 68 Ga-FAPI PET / CT scans were used by these patients. 18 F-FDG imaging or other traditional imaging methods cannot provide accurate diagnosis, but when drug administration is involved... 68 Following Ga-FAPI-04, 54 primary tumors and 229 metastatic lesions were detected among the 28 cancer types included in the analysis [Kratochwil C., et al.(68)Ga-FAPIPET / CT:Tracer Uptake in 28Different Kinds of Cancer.J Nucl Med,2019,60(6),801-805.]. 18 Compared to F-FDG, 68 Ga-FAPI-04 can detect more primary and metastatic tumor lesions. This probe can accurately diagnose and stage metastatic lesions of various tumors, showing great promise for application and potentially becoming a widely used screening and radionuclide therapy tool in clinical oncology. Furthermore, the imaging procedure of this probe is simplified, requiring no fasting or blood sugar control, making it more acceptable to patients.

[0006] FAP-2286, a cyclic peptide probe targeting FAP, consists of a 7-amino acid cyclic peptide and a metal ligand moiety, with an affinity ranging from 0.4 to 1.4 nM. It is compatible with small molecule FAP inhibitor probes. 177 Compared to the Lu-FAPI series 177 Lu-FAP-2286 still showed a high tumor uptake signal 72 hours after administration, while FAPI-46 showed only a weak signal in tumors. Therefore, radiotherapy drugs based on the cyclic peptide FAP-2286 have greater research and development potential in tumor treatment.

[0007] at present, 68 Ga-FAP-2286 and 177 The study of Lu-FAP-2286 is currently in Phase I / II clinical trials (NCT04939610). Although 68 Ga-FAP-2286 and 177Lu-FAP-2286 exhibits high uptake in tumors with high FAP expression, but its retention time in the kidneys is relatively long. At 3h, 24h, and 72h after administration, its uptake levels are 2.2% ID / g, 1.1% ID / g, and 0.6% ID / g, respectively, all higher than the small molecule probe FAPI-46, which can easily cause radiotoxic nephropathy or increase the renal burden [Zboralski D., et al. Preclinicale evaluation of FAP-2286 for fibroblast activation protein targeted radionuclide imaging and therapy. Eur J Nucl Med Mol Imaging, 2022, 49(11), 3651-3667.]. Although radiopharmaceuticals themselves do not cause damage to normal tissues under normal use due to small dosages, when they accumulate in large quantities and remain for a long time, the cumulative effect of long-term radioactivity can cause radiation damage to normal tissues. Furthermore, most patients receiving radiotherapy are in the late stages of cancer and have undergone radiotherapy and chemotherapy, and may have some liver and kidney dysfunction or underlying diseases.

[0008] Therefore, renal retention time is a crucial factor to consider in radiopharmaceutical research and should be a primary focus from the outset of drug design. Modifying the structure of this molecule to reduce its accumulation in liver and kidneys while maintaining high tumor uptake, and developing a "best-in-class" FAP-targeting cyclic peptide radiopharmaceutical with independent intellectual property rights, possesses significant clinical translational value and feasibility. Summary of the Invention

[0009] This invention modifies the linker portion forming the cyclic peptide based on the structure of peptide FAP-2286, and further introduces monosaccharide or disaccharide molecules to obtain a series of novel glycopeptides. After radiolabeling, these glycopeptides exhibit superior tumor uptake and lower liver uptake compared to FAP-2286, resulting in better imaging outcomes. This facilitates the development of candidate radionuclide therapeutics with further research value, and ultimately yields a "best-in-class" FAP-targeting cyclic peptide radiopharmaceutical with independent intellectual property rights.

[0010] In one aspect, the present invention provides a compound represented by Formula I, or a salt thereof, or a radiolabeled form thereof:

[0011]

[0012] G represents a monosaccharide, disaccharide, or trisaccharide group, or a phenyl group substituted with a monosaccharide, disaccharide, or trisaccharide group; L represents a dipeptide or tripeptide linker.

[0013] M represents a metal chelating group that can bind to radioactive nuclides;

[0014] n is an integer from 1 to 3, especially 1 or 2.

[0015] In some implementations, G is independently selected from the following groups:

[0016]

[0017]

[0018] In some implementations, G is independently selected from the following groups:

[0019]

[0020] In some embodiments, L is selected from the following groups:

[0021]

[0022] In some embodiments, M and L are linked by an amide bond (i.e., M is attached to the NH terminal of L), and M is selected from groups with the following structures:

[0023]

[0024]

[0025] More preferably, M is Here, "---" indicates that the substituent is attached at this point.

[0026] In some embodiments, the compound of formula I is selected from:

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033] In some embodiments, the radionuclide is selected from radiodiagnostic radionuclides and the radiotherapy radionuclides, but is not limited thereto. Radiodiagnostic radionuclide markers can be used for tumor imaging, which is beneficial for tumor diagnosis, while radiotherapy radionuclide markers can be used for the diagnosis and treatment of tumors.

[0034] The radioactive diagnostic nuclide can be selected from... 86 Y、 18 F, 51 Mn, 52m Mn, 52g Mn, Al[ 18 F]、 64 Cu、 67 Ga、 68 Ga、 89 Zr、 99m Tc, 111 In、 123 I, 124 I, 125 I, 44 Sc、 47 Any one or more of Sc, preferably 86 Y, Al[ 18 F]、 64 Cu、 68 Ga、 89 Zr、 99 mTc, 124 Any one or more of I; more preferably 68 Ga or 64 Cu.

[0035] The radiotherapy nuclide can be selected from... 67 Cu、 90 Y、 125 I, 131 I, 153 Sm、 166 Ho、 177 Lu、 227 Th, 186 Re、 188 Re、 211 At、 212 Pb, 203 Pb, 212 Bi、 213 Bi、 223 Ra、 225 Ac、 227 Any one or more of Th; preferred 67 Cu、 90 Y、 125I, 131 I, 177 Lu、 227 Th、 223 Ra、 225 Ac、 211 Any one or more of At; more preferably 227 Th、 177 Lu、 225 Ac or 212 Pb;

[0036] In some embodiments, the radionuclide label is:

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043] Another aspect of the present invention provides the use of the above-mentioned compounds or their salts or their radionuclide labels in the preparation of tumor imaging agents or antitumor drugs.

[0044] In some embodiments, the tumor is a solid tumor. In particular, the solid tumor is an epithelial tumor, and specifically, the tumor includes, but is not limited to, sarcoma, mesothelioma, esophageal tumor, glioblastoma, colorectal tumor, pancreatic cancer, lung cancer, breast cancer, gastric cancer, melanoma, etc.

[0045] Another aspect of the present invention relates to a compound of formula II or a salt thereof.

[0046]

[0047] The definitions of M, L, and n are as described above.

[0048] In some embodiments, the compound of formula II is selected from:

[0049]

[0050]

[0051] Another aspect of the present invention relates to compounds of the following formula or salts thereof:

[0052]

[0053] The compounds according to the present invention can be prepared by those skilled in the art using the synthesis methods described in the examples in combination with existing techniques. Attached Figure Description

[0054] Figure 1 is 68 PET / CT images of Ga-labeled FAP2286 at 30 min, 1 h, and 2 h in the U87 tumor mouse model.

[0055] Figure 2 is 68 PET / CT images of Ga-labeled compound g4 at 30 min, 1 h, and 2 h in the U87 tumor mouse model. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0057] Unless otherwise specified, the raw materials, reagents, and methods used in the embodiments are all conventional raw materials, reagents, and methods in the art.

[0058] Experimental materials and analytical instruments:

[0059] H-Cys(Trt)-2-Chlorotrityl Resin was purchased from Jier Biochemical (Shanghai) Co., Ltd.

[0060] C18 reversed-phase chromatography preparative system: preparative liquid chromatograph (LC-20AR), C18 column is XBridge BEH C18 column (4.6 mm x 150 mm);

[0061] The MALDI-TOF mass spectrometer is a matrix-assisted laser desorption / ionization time-of-flight mass spectrometer.

[0062] The Sep-Pak C18 column is WAT023501SEP-PAK LIGHT C18;

[0063] The biomolecular interaction instrument is model Biacore T200;

[0064] The protein is a Sino Biological Recombinant Human FAP Protein;

[0065] All reagents used for chip coupling and regeneration were purchased from Cytivo.

[0066] The instrument used to determine the radioactivity of tissue biodistribution counters is the WIZARD2 2-Detector gamma counter, model number 2470-0020;

[0067] All other reagents were purchased from domestic pharmaceutical companies.

[0068] Explanation of English abbreviations:

[0069] DCM: Dichloromethane;

[0070] DMF: N,N-dimethylformamide;

[0071] HBTU: Benzotriazole-N,N,N,N-Tetramethylurea hexafluorophosphate;

[0072] DIEA: N,N-Diisopropylethylamine

[0073] TFA: Trifluoroacetic acid

[0074] EDT: 1,2-Ethylenedithiol

[0075] TIS: Triisopropylsilane

[0076] tBu-DOTA: Tri-tert-butyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid

[0077] Example 1: Synthesis of Compound a

[0078]

[0079] S1: Place 0.6g of H-Cys(Trt)-2-Chlorotrityl Resin with a degree of substitution of 0.336mmol / g into a peptide synthesizer (CS Bio, CS336X) and set the program;

[0080] S2: Resin swelling: Add about 10 mL of DMF to the reaction flask and shake for 30 min;

[0081] S3: Deprotection twice, each time adding 10 mL of DMF solution containing 20% ​​volumetric piperidine and reacting for 15 min, then washing the resin with DMF three times and DCM three times;

[0082] S4: Add the first amino acid Fmoc-L-Phe-OH: Add Fmoc-L-Phe-OH, based on 4 times the molar amount of HBTU and 8 times the molar amount of DIEA, condense the reaction for 3 hours, rinse the resin with DMF 3 times, and rinse the resin with DCM 3 times.

[0083] S5: Repeat S3 to S4, and connect Fmoc-L-Gln(Trt)-OH, Fmoc-L-Thr(tBu)-OH, Fmoc-L-Pro-OH, Fmoc-L-Pro-OH, and Fmoc-L-Cys(Trt)-OH in sequence;

[0084] S6: Deprotect twice, each time adding 10 mL of DMF solution containing 20% ​​piperidine and reacting for 15 min, then washing the resin with DMF three times and DCM three times;

[0085] S7: Remove solvent. In the last XX1 step of the program, add a 5 mL LDM solution of hexanoic acid (4 times the molar amount) to the solution for condensation.

[0086] S8: Resin removal: Remove the solvent, add 20 mL of lysis buffer with a volume ratio of TFA:TIS:EDT:ddH2O = 95%:2.5%:1.25%:1.25%, and react for 2.5 h;

[0087] S9: Cutting completed, solvent is removed by rotary evaporator to obtain crude peptide dissolved in TFA;

[0088] S10: Precipitation of peptides: Transfer the crude peptide dissolved in TFA to a centrifuge tube, add 10 times the volume of ice-cold ether, and then centrifuge at 4°C and 8000g to remove the solvent, and obtain the precipitated crude peptide.

[0089] S11: Dissolve 10 mg of crude polypeptide in a 1:3 (v / v) mixture of acetonitrile and dd water. Collect 0.5 mg of the sample in a C18 reversed-phase chromatography system to obtain the target peak solution. Set the HPLC parameters as follows: Wavelength: 210 nm and 254 nm; Flow Rate: 3 mL / min; Inj. Vol: 1 mL; Column Temp: 25 °C; Phase A: 0.1% TFA aqueous solution; Phase B: acetonitrile. Freeze-dry the target peak solution to obtain compound a, which is a precursor of FAP-2286, and store at -20 °C.

[0090] Example 2: Synthesis of compounds b and b1-b4

[0091]

[0092] S1: Place 0.5g of H-Cys(Trt)-2-Chlorotrityl Resin with a degree of substitution of 0.336mmol / g into a peptide synthesizer (CS Bio, CS336X) and set the program;

[0093] S2: Resin swelling: Add about 10 mL of DMF to the reaction flask and shake for 30 min;

[0094] S3: Deprotection twice, each time adding 20% ​​piperidine DMF solution (10 mL) and reacting for 15 min, then washing the resin with DMF three times and DCM three times;

[0095] S4: Add the first amino acid Fmoc-L-Lys(Boc)-OH: Add Fmoc-L-Lys(Boc)-OH, based on 4 times the molar amount of HBTU and 8 times the molar amount of DIEA, condense for 3 hours, rinse the resin with DMF 3 times, and rinse the resin with DCM 3 times.

[0096] S5: Repeat S3 to S4, connecting Fmoc-L-Val-OH and Fmoc-L-Met-OH in sequence;

[0097] S6: Deprotect twice, each time adding 10 mL of DMF solution containing 20% ​​piperidine and reacting for 15 min. Rinse the resin three times with DMF and three times with DCM.

[0098] S7: Remove solvent. In the last XX1 step of the program, add a pre-prepared DMF solution of 4 times the molar amount of tBu-DOTA for condensation.

[0099] S7: Resin removal: Remove the solvent, add pyrolysis buffer with a volume ratio of TFA:TIS:EDT:ddH2O = 95%:2.5%:1.25%:1.25%, and react for 3 hours;

[0100] S8: Cutting completed, solvent is removed by rotary evaporator to obtain crude peptide dissolved in TFA;

[0101] S7: Precipitation of peptides: Transfer the crude peptide dissolved in TFA to a centrifuge tube, add 10 times the amount of ice-cold ether, and then centrifuge at 4°C and 8000g to remove the solvent, and obtain the precipitated crude peptide.

[0102] S8: Dissolve 10 mg of crude polypeptide in a 1:3 (v / v) mixture of acetonitrile and dd water. Collect 0.5 mg of the sample in a C18 reversed-phase chromatography system to obtain the target peak solution. Set the HPLC parameters as follows: Wavelength: 210 nm and 254 nm; Flow Rate: 3 mL / min; Inj. Vol: 1 mL; Column Temp: 25 °C; Phase A: 0.1% TFA aqueous solution; Phase B: acetonitrile. Freeze-dry the target peak solution to obtain compound b, and store at -20 °C.

[0103] Except for replacing the amino acids to be linked in step S5 with the amino acids in Table 1 below, compounds b1 to b4 are obtained in the same manner.

[0104] Table 1

[0105] Compounds Amino Acid b1Fmoc-L-Val-OH, Fmoc-L-Nle-OHb2Fmoc-L-Phe-OH, Fmoc-L-Gly-OHb3Fmoc-L-Ala-OH, Fmoc -L-Pro-OH,Fmoc-L-Gly-OHb4Fmoc-L-Lys(Boc)-OH,Fmoc-L-Ala-OH,Fmoc-L-Pro-OH,Fmoc-L-Gly-OH surface

[0106] Example 3 Synthesis of compound d

[0107]

[0108] Compound a (3 mg, 3.363 μmol) and compound c (1 mg, 4.036 μmol) were dissolved in a mixed solution of acetonitrile and dd water. Saturated sodium bicarbonate was added to adjust the pH to approximately 8. The reaction was carried out at room temperature for 3 hours, quenched with formic acid, and concentrated with nitrogen to remove excess solvent. The target peak solution was collected using a C18 reversed-phase chromatography preparative system. The HPLC parameters were set as follows: Wavelength: 210 nm and 254 nm; Flow Rate: 3 mL / min; Inj. Vol: 1 mL; Column Temp: 25 °C; Mobile phase A: 0.1% TFA aqueous solution; Mobile phase B: acetonitrile, to obtain compound d.

[0109] Example 4: Synthesis of compounds e and e1 to e4

[0110]

[0111] Compound d (1 mg, 0.876 μmol) and compound b (0.8 mg, 0.876 μmol) were dissolved in 500 μL acetonitrile and 500 μL dd water. Saturated sodium bicarbonate was added to adjust the pH to approximately 8. The reaction was carried out overnight at room temperature, quenched with formic acid, and the solvent was removed by concentration. The target peak solution was collected in a C18 reversed-phase chromatography preparative system. The HPLC parameters were set as follows: Wavelength: 210 nm and 254 nm; Flow Rate: 3 mL / min; Inj. Vol: 1 mL; Column Temp: 25 °C; Mobile phase A: 0.1% TFA aqueous solution; Mobile phase B: acetonitrile, to obtain compound e.

[0112] Compounds e1 to e4 were synthesized in the same manner, except that compounds b1 to b4 were used to replace compound b, respectively.

[0113]

[0114]

[0115] Example 5: Synthesis of compounds g and g1-10

[0116]

[0117] Compound e (0.5 mg, 0.249 μmol) and compound f (0.234 mg, 0.747 μmol) were dissolved in DMF, and DIEA (0.161 mg, 1.245 mmol) was added. The mixture was reacted overnight at room temperature, diluted with dd water, and the target peak solution was collected in a C18 reversed-phase chromatography preparative system. The HPLC parameters were set as follows: Wavelength: 210 nm and 254 nm; Flow Rate: 3 mL / min; Inj. Vol: 1 mL; Column Temp: 25 °C; Mobile phase A: 0.1% TFA aqueous solution, Mobile phase B: acetonitrile, to obtain compound g.

[0118] According to Table 2 below, replace compound e with compounds e1-e4, and replace compound f with f1, f2 or f3 as follows, to obtain the corresponding compounds g1-g10 in the same way.

[0119]

[0120] Table 2

[0121] Compound raw materials g1e1+f2g2e1+f1g3e2+f2g4e2+f1g5e2+f3g6e3+f2g7e3+f1g8e3+f3g9e4+2 f1g10e4+2 f3 surface

[0122] Table 3 shows the MALDI-TOF data of the synthesized compounds.

[0123] Table 3

[0124] Theoretical calculated MALDI-TOF values ​​of compounds: a 892.4893.7 b 865.4866.4 b 1847.5848.8 b 2839.4840.8 b 3860.4861.9 b 4988.8990.4 d 1141.51143.7 e 2007.02009.6 e 11990.01991.5 e 21982.01983.1 e 32003.02003.9 e 42131 .02132.2g2321.02322.0g12379.02380.1g22303.02304.3g32371.02372.5g42295.02297.0g522 95.02296.5g62392.02393.9g72316.02317.2g82316.02317.0g92757.12758.3g102757.12758.3 surface

[0125] Comparative Example 1FAP-2286

[0126] FAP-2286 (purchased from MedChemExpress) was used as a comparative example.

[0127]

[0128] Example 6 68 Preparation of Ga-labeled compounds

[0129] Radiolabeled compounds were prepared using compounds g, g4, and FAP-2286 as precursors, respectively, via the following method. 68 Ga-g, 68 Ga-g4 and 68 Ga-FAP-2286.

[0130] S1: Take 1 μL of the precursor compound dissolved in dd water (concentration of 10 μg / μL) into an EP tube, and add 180 μL of 3M sodium acetate to adjust the pH.

[0131] S2: Add 400 μL of 0.6 M radioactive material.68 Ga was reacted in an EP tube at 95°C for 10 min;

[0132] S3: After the reaction, paper chromatography was performed to determine the purity. The developing solvent was methanol:1M ammonium formate = 1:1. If the purity was not above 90%, purification was performed using a Sep-Pak C18 column. The specific procedure was as follows: first, activate with 20 mL of anhydrous ethanol, then rinse once with 20 mL of dd water. Load the radioactive sample, then elute with 75% ethanol, discarding the first 500 μL of product. Each 100 μL tube was used as one tube, and the radioactive dose was measured. The tube with the highest radioactive dose was taken as the final product. 68 Ga-labeled products.

[0133] Example 7 68 PET imaging methods for Ga-labeled compounds in the glioblastoma model U87

[0134] Prepared using Example 6 68 Ga-g4 and 68 Ga-FAP-2286 was used as a radiolabeled compound in imaging experiments.

[0135] Approximately 150 μCi of radiolabeled compound was injected into mice with a glioblastoma model (U87 cells) via the tail vein. After 10 minutes, the mice were anesthetized with isoflurane and placed in a Siemens mouse PET / CT scanner for a 10-minute CT scan and a 15-minute PET scan.

[0136] The results are shown in Figures 1 and 2, respectively. Figure 1 shows the injection. 68 Imaging images at 30 min, 1 h, and 2 h after Ga-FAP-2286 injection. Figure 2 shows the injection... 68 Imaging images of Ga-g4 at 30 min, 1 h, and 2 h. Comparing the results in Figures 1-2, it can be seen that... 68 Compared to Ga-FAP-2286, 68 PET / CT imaging at 30 min showed higher uptake by the tumor and lower uptake by the liver in Ga-g4; secondly, due to 68 Ga-g4 metabolic ratio 68 Ga-FAP-2286 is faster and can better reduce radiation damage in the body.

[0137] The uptake rate of the radiolabeled compound was obtained by directly quantifying the imaging results using software, and the results are shown in Table 4.

[0138] Table 4. Uptake rates of tumors, liver, and kidneys

[0139]

[0140]

[0141] As shown in Table 4, the present invention 68 Ga-g4 uptake in tumors after injection is superior to 68 Ga-FAP-2286 has lower uptake by the liver and kidneys, resulting in better imaging results and reduced radiation damage in the body.

[0142] Example 8: SPR surface plasmon resonance determination of affinity Kd

[0143] The affinity Kd between FAP protein and FAP-2286, compounds g, and g1 was determined by surface plasmon resonance (SPR).

[0144] The experiment was conducted in a Biacore T200 device (GE) according to the operating manual. CM5 series chips with carboxyl groups were used. The coupling conditions were selected as pH 5.5, and the regeneration conditions as Glycine-HCl pH 2.0. The obtained affinity data are shown in Table 5.

[0145] Table 5

[0146] Compound Kd(M)FAP-22864.87E-08g1.61E-08g12.27E-08 surface

[0147] The results in Table 5 show that compounds g, g1 and FAP-2286 have the same order of magnitude affinity, and g1 is even better than FAP-2286, proving that the g series of compounds has a good affinity for human FAP protein.

Claims

1. The compound shown in formula g4, or its salts or their radiolabeled forms: 。 2. The use of the compound of claim 1, or a salt thereof, or a radiolabeled form thereof, in the preparation of a tumor imaging agent or an antitumor drug, wherein, The tumor is melanoma, sarcoma, mesothelioma, glioblastoma, or breast cancer.

3. The use as described in claim 2, wherein, The tumor is melanoma.

4. The use as described in claim 2, wherein, The tumor is a sarcoma.

5. The use as described in claim 2, wherein, The tumor is a mesothelioma.

6. The use as described in claim 2, wherein, The tumor is a glioblastoma.

7. The use as described in claim 2, wherein, The tumor is breast cancer.

8. Use of the compound of claim 1, or a salt thereof, or a radiolabeled form thereof, in the preparation of a tumor imaging agent or an antitumor drug, wherein, The tumor is an esophageal tumor, colorectal tumor, pancreatic cancer, lung cancer, or gastric cancer that expresses FAP.

9. The use as described in claim 8, wherein, The tumor is an esophageal tumor expressing FAP.

10. The use as described in claim 8, wherein, The tumor is a colorectal tumor expressing FAP.

11. The use as described in claim 8, wherein, The tumor is a pancreatic cancer expressing FAP.

12. The use as described in claim 8, wherein, The tumor is a lung cancer expressing FAP.

13. The use as described in claim 8, wherein, The tumor is a gastric cancer expressing FAP.

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