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Wang L, Chen CC, Zhang Z, Kuo HT, Zhang C, Colpo N, Merkens H, Bénard F, Lin KS. Synthesis and Evaluation of Novel 68Ga-Labeled [D-Phe 6,Leu 13ψThz 14]bombesin(6-14) Analogs for Cancer Imaging with Positron Emission Tomography. Pharmaceuticals (Basel) 2024; 17:621. [PMID: 38794191 PMCID: PMC11124507 DOI: 10.3390/ph17050621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2024] [Revised: 05/05/2024] [Accepted: 05/09/2024] [Indexed: 05/26/2024] Open
Abstract
Gastrin-releasing peptide receptor (GRPR) is overexpressed in various cancers and is a promising target for cancer diagnosis and therapy. However, the high pancreas uptake and/or metabolic instability observed for most reported GRPR-targeted radioligands might limit their clinical applications. Our group recently reported a GRPR-targeted antagonist tracer, [68Ga]Ga-TacsBOMB2 ([68Ga]Ga-DOTA-Pip-D-Phe6-Gln7-Trp8-Ala9-Val10-Gly11-His12-Leu13ψThz14-NH2), which showed a minimal pancreas uptake in a preclinical mouse model. In this study, we synthesized four derivatives with unnatural amino acid substitutions (Tle10-derived Ga-LW01158, NMe-His12-derived Ga-LW01160, α-Me-Trp8- and Tle10-derived Ga-LW01186, and Tle10- and N-Me-Gly11-derived Ga-LW02002) and evaluated their potential for detecting GRPR-expressing tumors with positron emission tomography (PET). The binding affinities (Ki(GRPR)) of Ga-LW01158, Ga-LW01160, Ga-LW01186, and Ga-LW02002 were 5.11 ± 0.47, 187 ± 17.8, 6.94 ± 0.95, and 11.0 ± 0.39 nM, respectively. [68Ga]Ga-LW01158, [68Ga]Ga-LW01186, and [68Ga]Ga-LW02002 enabled clear visualization of subcutaneously implanted human prostate cancer PC-3 tumor xenografts in mice in PET images. Ex vivo biodistribution studies showed that [68Ga]Ga-LW01158 had the highest tumor uptake (11.2 ± 0.65 %ID/g) and good tumor-to-background uptake ratios at 1 h post-injection. Comparable in vivo stabilities were observed for [68Ga]Ga-LW01158, [68Ga]Ga-LW01186, and [68Ga]Ga-LW02002 (76.5-80.7% remaining intact in mouse plasma at 15 min post-injection). In summary, the Tle10 substitution, either alone or combined with α-Me-Trp8 or NMe-Gly11 substitution, in Ga-TacsBOMB2 generates derivatives that retained good GRPR binding affinity and in vivo stability. With good tumor uptake and tumor-to-background imaging contrast, [68Ga]Ga-LW01158 is promising for detecting GRPR-expressing lesions with PET.
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Affiliation(s)
- Lei Wang
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC V5Z 1L3, Canada; (L.W.); (C.-C.C.); (Z.Z.); (H.-T.K.); (C.Z.); (N.C.); (H.M.); (F.B.)
| | - Chao-Cheng Chen
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC V5Z 1L3, Canada; (L.W.); (C.-C.C.); (Z.Z.); (H.-T.K.); (C.Z.); (N.C.); (H.M.); (F.B.)
| | - Zhengxing Zhang
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC V5Z 1L3, Canada; (L.W.); (C.-C.C.); (Z.Z.); (H.-T.K.); (C.Z.); (N.C.); (H.M.); (F.B.)
| | - Hsiou-Ting Kuo
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC V5Z 1L3, Canada; (L.W.); (C.-C.C.); (Z.Z.); (H.-T.K.); (C.Z.); (N.C.); (H.M.); (F.B.)
| | - Chengcheng Zhang
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC V5Z 1L3, Canada; (L.W.); (C.-C.C.); (Z.Z.); (H.-T.K.); (C.Z.); (N.C.); (H.M.); (F.B.)
| | - Nadine Colpo
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC V5Z 1L3, Canada; (L.W.); (C.-C.C.); (Z.Z.); (H.-T.K.); (C.Z.); (N.C.); (H.M.); (F.B.)
- Department of Molecular Imaging and Therapy, BC Cancer, Vancouver, BC V5Z 4E6, Canada
| | - Helen Merkens
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC V5Z 1L3, Canada; (L.W.); (C.-C.C.); (Z.Z.); (H.-T.K.); (C.Z.); (N.C.); (H.M.); (F.B.)
| | - François Bénard
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC V5Z 1L3, Canada; (L.W.); (C.-C.C.); (Z.Z.); (H.-T.K.); (C.Z.); (N.C.); (H.M.); (F.B.)
- Department of Molecular Imaging and Therapy, BC Cancer, Vancouver, BC V5Z 4E6, Canada
- Department of Radiology, University of British Columbia, Vancouver, BC V5Z 1M9, Canada
| | - Kuo-Shyan Lin
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC V5Z 1L3, Canada; (L.W.); (C.-C.C.); (Z.Z.); (H.-T.K.); (C.Z.); (N.C.); (H.M.); (F.B.)
- Department of Molecular Imaging and Therapy, BC Cancer, Vancouver, BC V5Z 4E6, Canada
- Department of Radiology, University of British Columbia, Vancouver, BC V5Z 1M9, Canada
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Wang L, Kuo HT, Zhang Z, Zhang C, Chen CC, Chapple D, Wilson R, Colpo N, François Bénard, Lin KS. Unnatural amino acid substitutions to improve in vivo stability and tumor uptake of 68Ga-labeled GRPR-targeted TacBOMB2 derivatives for cancer imaging with positron emission tomography. EJNMMI Radiopharm Chem 2024; 9:8. [PMID: 38305955 PMCID: PMC10837402 DOI: 10.1186/s41181-024-00241-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Accepted: 01/25/2024] [Indexed: 02/03/2024] Open
Abstract
BACKGROUND Overexpressed in various solid tumors, gastrin-releasing peptide receptor (GRPR) is a promising cancer imaging marker and therapeutic target. Although antagonists are preferable for the development of GRPR-targeted radiopharmaceuticals due to potentially fewer side effects, internalization of agonists may lead to longer tumor retention and better treatment efficacy. In this study, we systematically investigated unnatural amino acid substitutions to improve in vivo stability and tumor uptake of a previously reported GRPR-targeted agonist tracer, [68Ga]Ga-TacBOMB2 (68Ga-DOTA-Pip-D-Phe6-Gln7-Trp8-Ala9-Val10-Gly11-His12-Leu13-Thz14-NH2). RESULTS Unnatural amino acid substitutions were conducted for Gln7, Trp8, Ala9, Val10, Gly11 and His12, either alone or in combination. Out of 25 unnatural amino acid substitutions, tert-Leu10 (Tle10) and NMe-His12 substitutions were identified to be preferable modifications especially in combination. Compared with the previously reported [68Ga]Ga-TacBOMB2, the Tle10 and NMe-His12 derived [68Ga]Ga-LW01110 showed retained agonist characteristics and improved GRPR binding affinity (Ki = 7.62 vs 1.39 nM), in vivo stability (12.7 vs 89.0% intact tracer in mouse plasma at 15 min post-injection) and tumor uptake (5.95 vs 16.6 %ID/g at 1 h post-injection). CONCLUSIONS Unnatural amino acid substitution is an effective strategy to improve in vivo stability and tumor uptake of peptide-based radiopharmaceuticals. With excellent tumor uptake and tumor-to-background contrast, [68Ga]Ga-LW01110 is promising for detecting GRPR-expressing cancer lesions with PET. Since agonists can lead to internalization upon binding to receptors and foreseeable long tumor retention, our optimized GRPR-targeted sequence, [Tle10,NMe-His12,Thz14]Bombesin(7-14), is a promising template for use for the design of GRPR-targeted radiotherapeutic agents.
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Affiliation(s)
- Lei Wang
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC, V5Z1L3, Canada
| | - Hsiou-Ting Kuo
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC, V5Z1L3, Canada
| | - Zhengxing Zhang
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC, V5Z1L3, Canada
| | - Chengcheng Zhang
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC, V5Z1L3, Canada
| | - Chao-Cheng Chen
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC, V5Z1L3, Canada
| | - Devon Chapple
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC, V5Z1L3, Canada
| | - Ryan Wilson
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC, V5Z1L3, Canada
| | - Nadine Colpo
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC, V5Z1L3, Canada
- Department of Molecular Imaging and Therapy, BC Cancer, Vancouver, BC, V5Z4E6, Canada
| | - François Bénard
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC, V5Z1L3, Canada
- Department of Molecular Imaging and Therapy, BC Cancer, Vancouver, BC, V5Z4E6, Canada
- Department of Radiology, University of British Columbia, Vancouver, BC, V5Z1M9, Canada
| | - Kuo-Shyan Lin
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, BC, V5Z1L3, Canada.
- Department of Molecular Imaging and Therapy, BC Cancer, Vancouver, BC, V5Z4E6, Canada.
- Department of Radiology, University of British Columbia, Vancouver, BC, V5Z1M9, Canada.
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Ma Y, Gao F. Advances of radiolabeled GRPR ligands for PET/CT imaging of cancers. Cancer Imaging 2024; 24:19. [PMID: 38279185 PMCID: PMC10811881 DOI: 10.1186/s40644-024-00658-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 01/09/2024] [Indexed: 01/28/2024] Open
Abstract
GRPR is a type of seven-transmembrane G-protein coupled receptor that belongs to the bombesin protein receptor family. It is highly expressed in various cancers, including prostate cancer, breast cancer, lung cancer, gastrointestinal cancer, and so on. As a result, molecular imaging studies have been conducted using radiolabeled GRPR ligands for tumor diagnosis, as well as monitoring of recurrence and metastasis. In this paper, we provided a comprehensive overview of relevant literature from the past two decades, with a specific focus on the advancements made in radiolabeled GRPR ligands for imaging prostate cancer and breast cancer.
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Affiliation(s)
- Yuze Ma
- Research Center for Experimental Nuclear Medicine, School of Basic Medical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Feng Gao
- Research Center for Experimental Nuclear Medicine, School of Basic Medical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China.
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68Ga-Labeled [Thz 14]Bombesin(7-14) Analogs: Promising GRPR-Targeting Agonist PET Tracers with Low Pancreas Uptake. Molecules 2023; 28:molecules28041977. [PMID: 36838968 PMCID: PMC9962964 DOI: 10.3390/molecules28041977] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Revised: 02/15/2023] [Accepted: 02/17/2023] [Indexed: 02/22/2023] Open
Abstract
With overexpression in various cancers, the gastrin-releasing peptide receptor (GRPR) is a promising target for cancer imaging and therapy. However, the high pancreas uptake of reported GRPR-targeting radioligands limits their clinical application. Our goal was to develop 68Ga-labeled agonist tracers for detecting GRPR-expressing tumors with positron emission tomography (PET), and compare them with the clinically validated agonist PET tracer, [68Ga]Ga-AMBA. Ga-TacBOMB2, TacBOMB3, and TacBOMB4, derived from [Thz14]Bombesin(7-14), were confirmed to be GRPR agonists by a calcium mobilization study, and their binding affinities (Ki(GRPR)) were determined to be 7.62 ± 0.19, 6.02 ± 0.59, and 590 ± 36.5 nM, respectively, via in vitro competition binding assays. [68Ga]Ga-TacBOMB2, [68Ga]Ga-TacBOMB3, and [68Ga]Ga-AMBA clearly visualized PC-3 tumor xenografts in a PET imaging study. [68Ga]Ga-TacBOMB2 showed comparable tumor uptake but superior tumor-to-background contrast ratios when compared to [68Ga]Ga-AMBA. Moreover, [68Ga]Ga-TacBOMB2 and [68Ga]Ga-TacBOMB3 showed a much lower rate of uptake in the pancreas (1.30 ± 0.14 and 2.41 ± 0.72%ID/g, respectively) than [68Ga]Ga-AMBA (62.4 ± 4.26%ID/g). In conclusion, replacing Met14 in the GRPR-targeting sequence with Thz14 retains high GRPR-binding affinity and agonist properties. With good tumor uptake and tumor-to-background uptake ratios, [68Ga]Ga-TacBOMB2 is promising for detecting GRPR-expressing tumors. The much lower pancreas uptake of [68Ga]Ga-TacBOMB2 and [68Ga]Ga-TacBOMB3 suggests that [Thz14]Bombesin(7-14) is a promising targeting vector for the design of GRPR-targeting radiopharmaceuticals, especially for radioligand therapy application.
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Günther T, Konrad M, Stopper L, Kunert JP, Fischer S, Beck R, Casini A, Wester HJ. Optimization of the Pharmacokinetic Profile of [ 99mTc]Tc-N 4-Bombesin Derivatives by Modification of the Pharmacophoric Gln-Trp Sequence. Pharmaceuticals (Basel) 2022; 15:ph15091133. [PMID: 36145354 PMCID: PMC9500665 DOI: 10.3390/ph15091133] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 09/06/2022] [Accepted: 09/06/2022] [Indexed: 11/16/2022] Open
Abstract
Current radiolabeled gastrin-releasing peptide receptor (GRPR) ligands usually suffer from high accumulation in GRPR-positive organs (pancreas, stomach), limiting tumor-to-background contrast in the abdomen. In novel N4-bombesin derivatives this was addressed by substitutions at the Gln7-Trp8 site within the MJ9 peptide (H-Pip5-phe6-Gln7-Trp8-Ala9-Val10-Gly11-His12-Sta13-Leu14-NH2) either by homoserine (Hse7), β-(3-benzothienyl) alanine (Bta8) or α-methyl tryptophan (α-Me-Trp8), with the aim of optimizing pharmacokinetics. We prepared and characterized the peptide conjugates 6-carboxy-1,4,8,11-tetraazaundecane (N4)-asp-MJ9, N4-asp-[Bta8]MJ9, N4-[Hse7]MJ9 and N4-[α-Me-Trp8]MJ9, and evaluated these compounds in vitro (GRPR affinity via IC50,inverse; internalization; lipophilicity via logD7.4) and in vivo (biodistribution and μSPECT/CT studies at 1 h post injection (p.i.) in PC-3 tumor-bearing CB17-SCID mice). 99mTc-labeling resulted in radiochemical yields (RCYs) > 95%. All 99mTc-labeled MJ9 analogues showed comparable or higher GRPR affinity than the external reference [99mTc]Tc-Demobesin 4. Receptor-bound fractions were noticeably higher than that of the reference. Despite a slightly enhanced lipophilicity, all novel MJ9 derivatives revealed improved in vivo pharmacokinetics compared to the reference. The Bta8-modified ligand revealed the most favorable tumor-to-abdomen contrast at 1 h p.i. Substitutions at the Gln7-Trp8 site within GRPR ligands hold great potential to modify pharmacokinetics for improved imaging.
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