Synthesis and preclinical evaluation of gastrin releasing peptide receptor antagonist [18F]MeTz-PEG2-RM26 for positron emission tomography
Abstract Background The gastrin-releasing peptide receptor (GRPR) is overexpressed in the majority of primary prostate cancer lesions, with persistent expression in lymph nodes and bone metastases, making it a legitimate molecular target for diagnostic imaging and staging. This study presents the sy...
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2025-03-01
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| Series: | EJNMMI Radiopharmacy and Chemistry |
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| Online Access: | https://doi.org/10.1186/s41181-025-00336-9 |
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| author | Panagiotis Kanellopoulos Fanny Lundmark Ayman Abouzayed Lorenzo Jacopo Ilic Balestri Esther Olaniran Håkansson Karim Obeid Luke R. Odell Vladimir Tolmachev Ulrika Rosenström Jonas Eriksson Anna Orlova |
| author_facet | Panagiotis Kanellopoulos Fanny Lundmark Ayman Abouzayed Lorenzo Jacopo Ilic Balestri Esther Olaniran Håkansson Karim Obeid Luke R. Odell Vladimir Tolmachev Ulrika Rosenström Jonas Eriksson Anna Orlova |
| author_sort | Panagiotis Kanellopoulos |
| collection | DOAJ |
| description | Abstract Background The gastrin-releasing peptide receptor (GRPR) is overexpressed in the majority of primary prostate cancer lesions, with persistent expression in lymph nodes and bone metastases, making it a legitimate molecular target for diagnostic imaging and staging. This study presents the synthesis and preclinical evaluation of [18F]MeTz-PEG2-RM26, a GRPR antagonist which utilises the Inverse Electron Demand Diels-Alder (IEDDA) reaction for 18F-labelling. This click-chemistry approach allows for site-specific incorporation of fluorine-18 under mild conditions, preserving the peptide’s structural integrity and biological activity. Receptor specificity and affinity of [18F]MeTz-PEG2-RM26 were evaluated in vitro using GRPR-expressing PC-3 cells. Furthermore, the biodistribution profile of [18F]MeTz-PEG2-RM26 was assessed in NMRI mice and its tumour-targeting capability was investigated in mice bearing PC-3 xenografts. Results The labelling of TCO-PEG2-RM26 precursor involved three steps: (1) synthesis of an 18F-labelled activated ester on a quaternary methyl ammonium (QMA) cartridge, (2) conjugation of the labelled ester to a tetrazine amine, and (3) attachment to TCO-PEG2-RM26 via an IEDDA click reaction. This production method of [18F]MeTz-PEG2-RM26 afforded a high apparent molar activity of 3.5–4.3 GBq/µmol and radiochemical purity exceeding 98%, with 43–70 MBq activity incorporation, while the entire synthesis was completed within 75 min. Both in vitro and in vivo studies confirmed the specific binding of [18F]MeTz-PEG2-RM26 to GRPR, with a significant reduction in activity uptake observed upon receptor saturation. The radioligand exhibited rapid blood clearance and minimal bone uptake, confirming the stability of the fluorine-carbon bond. However, high hepatic uptake (12–13% IA/g at 1 h post-injection) indicated predominant hepatobiliary excretion. Receptor-mediated uptake was observed in the tumours and pancreatic tissue, although the overall activity uptake in tumours was low, likely due to the rapid hepatobiliary clearance of [18F]MeTz-PEG2-RM26. Conclusions These findings demonstrate the effectiveness of the IEDDA click reaction for fluorine-18 labelling of GRPR-targeting PET tracers. Future studies should focus on increasing the hydrophilicity of the imaging probe to improve the targeting properties and biodistribution profile of the radioligand. |
| format | Article |
| id | doaj-art-f964daf8be164ac38ff723d227826d7c |
| institution | OA Journals |
| issn | 2365-421X |
| language | English |
| publishDate | 2025-03-01 |
| publisher | SpringerOpen |
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| series | EJNMMI Radiopharmacy and Chemistry |
| spelling | doaj-art-f964daf8be164ac38ff723d227826d7c2025-08-20T02:10:14ZengSpringerOpenEJNMMI Radiopharmacy and Chemistry2365-421X2025-03-0110111710.1186/s41181-025-00336-9Synthesis and preclinical evaluation of gastrin releasing peptide receptor antagonist [18F]MeTz-PEG2-RM26 for positron emission tomographyPanagiotis Kanellopoulos0Fanny Lundmark1Ayman Abouzayed2Lorenzo Jacopo Ilic Balestri3Esther Olaniran Håkansson4Karim Obeid5Luke R. Odell6Vladimir Tolmachev7Ulrika Rosenström8Jonas Eriksson9Anna Orlova10Department of Medicinal Chemistry, Uppsala UniversityDepartment of Medicinal Chemistry, Uppsala UniversityDepartment of Medicinal Chemistry, Uppsala UniversityDepartment of Medicinal Chemistry, Uppsala UniversityDepartment of Medicinal Chemistry, Uppsala UniversityDepartment of Medicinal Chemistry, Uppsala UniversityDepartment of Medicinal Chemistry, Uppsala UniversityDepartment of Immunology, Genetics and Pathology, Uppsala UniversityDepartment of Medicinal Chemistry, Uppsala UniversityDepartment of Medicinal Chemistry, Uppsala UniversityDepartment of Medicinal Chemistry, Uppsala UniversityAbstract Background The gastrin-releasing peptide receptor (GRPR) is overexpressed in the majority of primary prostate cancer lesions, with persistent expression in lymph nodes and bone metastases, making it a legitimate molecular target for diagnostic imaging and staging. This study presents the synthesis and preclinical evaluation of [18F]MeTz-PEG2-RM26, a GRPR antagonist which utilises the Inverse Electron Demand Diels-Alder (IEDDA) reaction for 18F-labelling. This click-chemistry approach allows for site-specific incorporation of fluorine-18 under mild conditions, preserving the peptide’s structural integrity and biological activity. Receptor specificity and affinity of [18F]MeTz-PEG2-RM26 were evaluated in vitro using GRPR-expressing PC-3 cells. Furthermore, the biodistribution profile of [18F]MeTz-PEG2-RM26 was assessed in NMRI mice and its tumour-targeting capability was investigated in mice bearing PC-3 xenografts. Results The labelling of TCO-PEG2-RM26 precursor involved three steps: (1) synthesis of an 18F-labelled activated ester on a quaternary methyl ammonium (QMA) cartridge, (2) conjugation of the labelled ester to a tetrazine amine, and (3) attachment to TCO-PEG2-RM26 via an IEDDA click reaction. This production method of [18F]MeTz-PEG2-RM26 afforded a high apparent molar activity of 3.5–4.3 GBq/µmol and radiochemical purity exceeding 98%, with 43–70 MBq activity incorporation, while the entire synthesis was completed within 75 min. Both in vitro and in vivo studies confirmed the specific binding of [18F]MeTz-PEG2-RM26 to GRPR, with a significant reduction in activity uptake observed upon receptor saturation. The radioligand exhibited rapid blood clearance and minimal bone uptake, confirming the stability of the fluorine-carbon bond. However, high hepatic uptake (12–13% IA/g at 1 h post-injection) indicated predominant hepatobiliary excretion. Receptor-mediated uptake was observed in the tumours and pancreatic tissue, although the overall activity uptake in tumours was low, likely due to the rapid hepatobiliary clearance of [18F]MeTz-PEG2-RM26. Conclusions These findings demonstrate the effectiveness of the IEDDA click reaction for fluorine-18 labelling of GRPR-targeting PET tracers. Future studies should focus on increasing the hydrophilicity of the imaging probe to improve the targeting properties and biodistribution profile of the radioligand.https://doi.org/10.1186/s41181-025-00336-9Fluorine-18TCOTetrazineIEDDA click chemistryGRPRBombesin |
| spellingShingle | Panagiotis Kanellopoulos Fanny Lundmark Ayman Abouzayed Lorenzo Jacopo Ilic Balestri Esther Olaniran Håkansson Karim Obeid Luke R. Odell Vladimir Tolmachev Ulrika Rosenström Jonas Eriksson Anna Orlova Synthesis and preclinical evaluation of gastrin releasing peptide receptor antagonist [18F]MeTz-PEG2-RM26 for positron emission tomography EJNMMI Radiopharmacy and Chemistry Fluorine-18 TCO Tetrazine IEDDA click chemistry GRPR Bombesin |
| title | Synthesis and preclinical evaluation of gastrin releasing peptide receptor antagonist [18F]MeTz-PEG2-RM26 for positron emission tomography |
| title_full | Synthesis and preclinical evaluation of gastrin releasing peptide receptor antagonist [18F]MeTz-PEG2-RM26 for positron emission tomography |
| title_fullStr | Synthesis and preclinical evaluation of gastrin releasing peptide receptor antagonist [18F]MeTz-PEG2-RM26 for positron emission tomography |
| title_full_unstemmed | Synthesis and preclinical evaluation of gastrin releasing peptide receptor antagonist [18F]MeTz-PEG2-RM26 for positron emission tomography |
| title_short | Synthesis and preclinical evaluation of gastrin releasing peptide receptor antagonist [18F]MeTz-PEG2-RM26 for positron emission tomography |
| title_sort | synthesis and preclinical evaluation of gastrin releasing peptide receptor antagonist 18f metz peg2 rm26 for positron emission tomography |
| topic | Fluorine-18 TCO Tetrazine IEDDA click chemistry GRPR Bombesin |
| url | https://doi.org/10.1186/s41181-025-00336-9 |
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