Pub Date : 2025-05-13DOI: 10.1186/s41181-025-00341-y
Arnaud Deschavannes, Kazuma Terashi, Marie Piquemal, Catherine Rioufol, Anthony Clotagatide
Background
The increasing use of [⁶⁸Ga]Ga-based radiopharmaceuticals in PET imaging, requires efficient quality control procedures. The standard r-TLC method for verifying [⁶⁸Ga]Ga-EDOTREOTIDE (Somakit-TOC®) radiochemical purity (RCP) is time-consuming, creating workflow challenges in radiopharmacies. This study evaluates an optimized r-TLC method with a reduced migration distance (4 cm vs. 9 cm) to improve efficiency while maintaining analytical reliability. Tests for specificity, accuracy and robustness were performed using ITLC-SG – Acetate and ITLC-SG – Citrate systems. Additionally, migration time was analyzed to evaluate whether the alternative method could offer added benefits.
Results
The mean Rs for ITLC-SG – Acetate at 4 cm was 2.43 ± 0.28, while for ITLC-SG – Citrate with added [⁶⁸Ga]GaCl₃ was 5.58 ± 0.23, both exceeding the threshold of 1.5. The mean RCP at 4 cm was 98.90% ± 0.25%, and 99.21% ± 0.19% at 9 cm, with [⁶⁸Ga]Ga-uncomplexed remaining within acceptable limits. No [⁶⁸Ga]GaCl₃ was detected. The coefficient of variation (CV) for RCP between methods was < 2% (0.22%). Operator-based analysis yielded a mean Rs of 3.95 ± 0.06 (CV = 1.52%) and a mean [⁶⁸Ga]Ga-EDOTREOTIDE percentage of 99.60% ± 0.03% (CV = 0.03%). Migration times were significantly reduced with the alternative method (85% reduction).
Conclusion
Shortening the migration distance in r-TLC did not compromise specificity, accuracy or robustness while significantly reducing analysis time. The proposed method enhances PET radiopharmaceutical workflows, allowing faster patient dose preparation without quality loss. This approach could be investigated to other [68Ga]Ga-labeled compounds, supporting improved clinical and research applications in nuclear medicine.
{"title":"Optimization of radiochemical purity assessment for [68Ga]Ga-EDOTREOTIDE (Somakit-TOC®): a shortened r-TLC method for improved PET radiopharmaceutical workflow","authors":"Arnaud Deschavannes, Kazuma Terashi, Marie Piquemal, Catherine Rioufol, Anthony Clotagatide","doi":"10.1186/s41181-025-00341-y","DOIUrl":"10.1186/s41181-025-00341-y","url":null,"abstract":"<div><h3>Background</h3><p>The increasing use of [⁶⁸Ga]Ga-based radiopharmaceuticals in PET imaging, requires efficient quality control procedures. The standard r-TLC method for verifying [⁶⁸Ga]Ga-EDOTREOTIDE (Somakit-TOC<sup>®</sup>) radiochemical purity (RCP) is time-consuming, creating workflow challenges in radiopharmacies. This study evaluates an optimized r-TLC method with a reduced migration distance (4 cm vs. 9 cm) to improve efficiency while maintaining analytical reliability. Tests for specificity, accuracy and robustness were performed using ITLC-SG – Acetate and ITLC-SG – Citrate systems. Additionally, migration time was analyzed to evaluate whether the alternative method could offer added benefits.</p><h3>Results</h3><p>The mean Rs for ITLC-SG – Acetate at 4 cm was 2.43 ± 0.28, while for ITLC-SG – Citrate with added [⁶⁸Ga]GaCl₃ was 5.58 ± 0.23, both exceeding the threshold of 1.5. The mean RCP at 4 cm was 98.90% ± 0.25%, and 99.21% ± 0.19% at 9 cm, with [⁶⁸Ga]Ga-uncomplexed remaining within acceptable limits. No [⁶⁸Ga]GaCl₃ was detected. The coefficient of variation (CV) for RCP between methods was < 2% (0.22%). Operator-based analysis yielded a mean Rs of 3.95 ± 0.06 (CV = 1.52%) and a mean [⁶⁸Ga]Ga-EDOTREOTIDE percentage of 99.60% ± 0.03% (CV = 0.03%). Migration times were significantly reduced with the alternative method (85% reduction).</p><h3>Conclusion</h3><p>Shortening the migration distance in r-TLC did not compromise specificity, accuracy or robustness while significantly reducing analysis time. The proposed method enhances PET radiopharmaceutical workflows, allowing faster patient dose preparation without quality loss. This approach could be investigated to other [<sup>68</sup>Ga]Ga-labeled compounds, supporting improved clinical and research applications in nuclear medicine.</p></div>","PeriodicalId":534,"journal":{"name":"EJNMMI Radiopharmacy and Chemistry","volume":"10 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ejnmmipharmchem.springeropen.com/counter/pdf/10.1186/s41181-025-00341-y","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143944179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-13DOI: 10.1186/s41181-025-00345-8
Xiyan Rui, Yuzhou Ding, Nailian Zhang, Xinran Zhao, Chie Seki, Tomoteru Yamasaki, Masayuki Fujinaga, Ming-Rong Zhang, Jun Qian, Bin Ji, Rong Zhou
Background
Colony-stimulating factor 1 receptor (CSF1R) is a promising imaging biomarker for neuroinflammation and tumor-associated macrophages. However, existing positron emission tomography (PET) tracers for CSF1R imaging often suffer from limited specificity or sensitivity.
Results
We have performed 11C-labeled radiosynthesis of compound FJRD (3-((2-amino-5-(1-methyl-1H-pyrazol-4-yl)pyridin-3-yl)ethynyl)-N-(4-methoxyphenyl)-4-methylbenzamide), which exhibits excellent affinity for CSF1R, and evaluated its in vivo and in vitro binding properties. PET images of [11C]FJRD show low brain uptake and specific binding in the living organs, except the kidneys in both normal mice and rats. In vitro autoradiographs demonstrate high levels of specific binding in all investigated organs, including the brain, spleen, liver, kidneys and lungs, when self-blocking was used. The addition of CPPC partially blocked in vitro [11C]FJRD binding in these organs, with blocking effects ranging from 9 to 67%. In contrast, the other two CSF1R inhibitors, GW2580 and BLZ945, showed minimal blocking effects, suggesting unignorable off-target binding in these organs. Furthermore, specific binding of [11C]CPPC and [11C]GW2580 was faint in the mouse organs, with [11C]CPPC demonstrating detectable binding only in the spleen.
Conclusions
These results suggest that [11C]FJRD is a potential CSF1R-PET tracer for more sensitive detection of CSF1R, compared to [11C]CPPC and [11C]GW2580. However, the high level off-target binding necessitates further improvements in specificity for CSF1R imaging.
{"title":"Evaluation of in vivo and in vitro binding property of a novel candidate PET tracer for CSF1R imaging and comparison with two currently-used CSF1R-PET tracers","authors":"Xiyan Rui, Yuzhou Ding, Nailian Zhang, Xinran Zhao, Chie Seki, Tomoteru Yamasaki, Masayuki Fujinaga, Ming-Rong Zhang, Jun Qian, Bin Ji, Rong Zhou","doi":"10.1186/s41181-025-00345-8","DOIUrl":"10.1186/s41181-025-00345-8","url":null,"abstract":"<div><h3>Background</h3><p>Colony-stimulating factor 1 receptor (CSF1R) is a promising imaging biomarker for neuroinflammation and tumor-associated macrophages. However, existing positron emission tomography (PET) tracers for CSF1R imaging often suffer from limited specificity or sensitivity.</p><h3>Results</h3><p>We have performed <sup>11</sup>C-labeled radiosynthesis of compound FJRD (3-((2-amino-5-(1-methyl-1<i>H</i>-pyrazol-4-yl)pyridin-3-yl)ethynyl)-<i>N</i>-(4-methoxyphenyl)-4-methylbenzamide), which exhibits excellent affinity for CSF1R, and evaluated its in vivo and in vitro binding properties. PET images of [<sup>11</sup>C]FJRD show low brain uptake and specific binding in the living organs, except the kidneys in both normal mice and rats. In vitro autoradiographs demonstrate high levels of specific binding in all investigated organs, including the brain, spleen, liver, kidneys and lungs, when self-blocking was used. The addition of CPPC partially blocked in vitro [<sup>11</sup>C]FJRD binding in these organs, with blocking effects ranging from 9 to 67%. In contrast, the other two CSF1R inhibitors, GW2580 and BLZ945, showed minimal blocking effects, suggesting unignorable off-target binding in these organs. Furthermore, specific binding of [<sup>11</sup>C]CPPC and [<sup>11</sup>C]GW2580 was faint in the mouse organs, with [<sup>11</sup>C]CPPC demonstrating detectable binding only in the spleen.</p><h3>Conclusions</h3><p>These results suggest that [<sup>11</sup>C]FJRD is a potential CSF1R-PET tracer for more sensitive detection of CSF1R, compared to [<sup>11</sup>C]CPPC and [<sup>11</sup>C]GW2580. However, the high level off-target binding necessitates further improvements in specificity for CSF1R imaging.</p></div>","PeriodicalId":534,"journal":{"name":"EJNMMI Radiopharmacy and Chemistry","volume":"10 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ejnmmipharmchem.springeropen.com/counter/pdf/10.1186/s41181-025-00345-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143944178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-04DOI: 10.1186/s41181-025-00343-w
Ammar Alfteimi, Yi Zhao, Ulf Lützen, Alexander Helm, Michael Jüptner, Maaz Zuhayra
Background
[18F]Fallypride PET has been used to study D2/3 receptor occupancy and density in neuropsychiatric disorders including Huntington’s disease (HD) and aging in humans. Nevertheless, the various synthetic methods including those provided by commercial synthesizers for [18F]fallypride exhibit a disadvantage concerning the necessity of using a HPLC purification step, which causes difficulties in the automation, leads to long synthesis times and moderate yields. Therefore utilizing the purification step by SPE cartridges is considered highly desirable for future commercialization of radiopharmaceutical cassettes. In our lab we have developed a simplified reliable automatic Radiosynthesis of [18F]fallypride by using SPE cartridges for the purification step without the need of HPLC.
Results
A simplified Radiosynthesis of [18F]fallypride has been developed without the use of HPLC for both a commercial cassette based synthesis system (AllinOne (AiO) system, Trasis, Belgium) and a research synthesis module with fixed tubing (RNplus, Synthra, Germany). The cleaning step involves a serial combination of several SPE cartridges. The synthesis time was shortened by 44% compared to synthesis using HPLC. At the same time the not decay corrected yield increases from 44 to 59% by using TBAHCO3 as phase transfer catalysts and from 17 to 31% for the synthesis with K2CO3/Kryptofix-[2.2.2] compared to synthesis using HPLC. The Radiochemical purity was always > 98% and all quality control parameters (e.g. sterility, endotoxin, stability and Radiochemical purity) conformed with requirements of the European Pharmacopoeia.
Conclusions
A GMP compliant automatic synthesis of [18F]fallypride including purification using simple solid phase extraction cartridges instead of HPLC was developed and evaluated. The implementation of the simplified synthesis in both used commercial modules allows efficient and reproducible Radiosynthesis of [18F]fallypride and leads to short synthesis times and high radiochemical yields with high radiochemical purity.
{"title":"GMP compliant simplified fast and high yielding automated synthesis of [18F]fallypride without the need of HPLC purification","authors":"Ammar Alfteimi, Yi Zhao, Ulf Lützen, Alexander Helm, Michael Jüptner, Maaz Zuhayra","doi":"10.1186/s41181-025-00343-w","DOIUrl":"10.1186/s41181-025-00343-w","url":null,"abstract":"<div><h3>Background</h3><p>[<sup>18</sup>F]Fallypride PET has been used to study D2/3 receptor occupancy and density in neuropsychiatric disorders including Huntington’s disease (HD) and aging in humans. Nevertheless, the various synthetic methods including those provided by commercial synthesizers for [<sup>18</sup>F]fallypride exhibit a disadvantage concerning the necessity of using a HPLC purification step, which causes difficulties in the automation, leads to long synthesis times and moderate yields. Therefore utilizing the purification step by SPE cartridges is considered highly desirable for future commercialization of radiopharmaceutical cassettes. In our lab we have developed a simplified reliable automatic Radiosynthesis of [<sup>18</sup>F]fallypride by using SPE cartridges for the purification step without the need of HPLC.</p><h3>Results</h3><p>A simplified Radiosynthesis of [<sup>18</sup>F]fallypride has been developed without the use of HPLC for both a commercial cassette based synthesis system (AllinOne (AiO) system, Trasis, Belgium) and a research synthesis module with fixed tubing (RNplus, Synthra, Germany). The cleaning step involves a serial combination of several SPE cartridges. The synthesis time was shortened by 44% compared to synthesis using HPLC. At the same time the not decay corrected yield increases from 44 to 59% by using TBAHCO<sub>3</sub> as phase transfer catalysts and from 17 to 31% for the synthesis with K<sub>2</sub>CO<sub>3</sub>/Kryptofix-[2.2.2] compared to synthesis using HPLC. The Radiochemical purity was always > 98% and all quality control parameters (e.g. sterility, endotoxin, stability and Radiochemical purity) conformed with requirements of the European Pharmacopoeia.</p><h3>Conclusions</h3><p>A GMP compliant automatic synthesis of [<sup>18</sup>F]fallypride including purification using simple solid phase extraction cartridges instead of HPLC was developed and evaluated. The implementation of the simplified synthesis in both used commercial modules allows efficient and reproducible Radiosynthesis of [<sup>18</sup>F]fallypride and leads to short synthesis times and high radiochemical yields with high radiochemical purity.</p></div>","PeriodicalId":534,"journal":{"name":"EJNMMI Radiopharmacy and Chemistry","volume":"10 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ejnmmipharmchem.springeropen.com/counter/pdf/10.1186/s41181-025-00343-w","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143904751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-04DOI: 10.1186/s41181-025-00344-9
Michela Aurilio, Aureliana Esposito, Monica Buonanno, Anna Morisco, Costantina Maisto, Stefania Scala, Secondo Lastoria
Background
Targeted Alpha Therapy shows very promising clinical results in a cancer treatment and it should be comparable or better than chemotherapy and β-radionuclide therapy, in terms of efficacy and toxicity. The use of α-emission offers advantages over β-emission due to the high linear energy transfer and the limited range in tissue. Actinium-225 is an α-emitter with a half-life of 9.92 days, which is an appropriate half-life for convenient treatment. Actinium-225 is introduced to tumor-targeting vectors through its complexation by a chelating moiety. On this basis, the aim of this study is to develop an [225Ac]Ac-PSMA 617 production method, to assess the efficiency and reliability of the radiosynthesis as a support for establish a clinical routine production for metastatic castration resistant prostate cancer treatment.
Results
different radiolabeling conditions and different reaction times have been used and compared. The best radiochemical yields (> 95%) were obtained when the peptide was dissolved in water and it was used at quantity of 100 µg in gentisic buffer, without stabilizing agent. The reaction was conducted at 97 °C and no significant change in labeling yield was observed when the time reaction increased. This condition ensures an adequate stability at 24 h around 90%.
Conclusions
the radiolabeling method employed in our experiments has demonstrated consistent reproducibility, enabling us to produce a radiopharmaceutical that meets pharmaceutical-grade standards. Greater difficulties occurred in defining the optimal procedures for quality controls, due to the unique physical properties of actinium. Efforts were made to standardize the quality control methods in accordance with pharmacopoeia standards; however, the methods’ feasibility is still uncertain.
{"title":"[225Ac]Ac-PSMA-617 production method: development of an efficient and reproducible radiolabelling process for establish a clinical routine production","authors":"Michela Aurilio, Aureliana Esposito, Monica Buonanno, Anna Morisco, Costantina Maisto, Stefania Scala, Secondo Lastoria","doi":"10.1186/s41181-025-00344-9","DOIUrl":"10.1186/s41181-025-00344-9","url":null,"abstract":"<div><h3>Background</h3><p>Targeted Alpha Therapy shows very promising clinical results in a cancer treatment and it should be comparable or better than chemotherapy and β-radionuclide therapy, in terms of efficacy and toxicity. The use of α-emission offers advantages over β-emission due to the high linear energy transfer and the limited range in tissue. Actinium-225 is an α-emitter with a half-life of 9.92 days, which is an appropriate half-life for convenient treatment. Actinium-225 is introduced to tumor-targeting vectors through its complexation by a chelating moiety. On this basis, the aim of this study is to develop an [<sup>225</sup>Ac]Ac-PSMA 617 production method, to assess the efficiency and reliability of the radiosynthesis as a support for establish a clinical routine production for metastatic castration resistant prostate cancer treatment.</p><h3>Results</h3><p>different radiolabeling conditions and different reaction times have been used and compared. The best radiochemical yields (> 95%) were obtained when the peptide was dissolved in water and it was used at quantity of 100 µg in gentisic buffer, without stabilizing agent. The reaction was conducted at 97 °C and no significant change in labeling yield was observed when the time reaction increased. This condition ensures an adequate stability at 24 h around 90%.</p><h3>Conclusions</h3><p>the radiolabeling method employed in our experiments has demonstrated consistent reproducibility, enabling us to produce a radiopharmaceutical that meets pharmaceutical-grade standards. Greater difficulties occurred in defining the optimal procedures for quality controls, due to the unique physical properties of actinium. Efforts were made to standardize the quality control methods in accordance with pharmacopoeia standards; however, the methods’ feasibility is still uncertain.</p></div>","PeriodicalId":534,"journal":{"name":"EJNMMI Radiopharmacy and Chemistry","volume":"10 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ejnmmipharmchem.springeropen.com/counter/pdf/10.1186/s41181-025-00344-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143904753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mesothelin is a 40 kDa glycoprotein overexpressed in several cancers, including triple-negative breast cancer (TNBC). The anti-mesothelin single-domain antibody (sdAb, or nanobody) A1 can serve as a radio-theranostic agent, but random DOTA conjugation on lysines yields heterogeneous products.
Results
We reengineered A1-His by directed mutagenesis to produce four single-lysine variants (A1K1-His, A1K2-His, A1K3-His, and A1K4-His). Each was site-specifically conjugated with p-SCN-Bn-DOTA, radiolabeled with 68Ga, and evaluated by PET imaging in mice bearing HCC70 TNBC xenografts, followed by ex vivo biodistribution at 1 h post-injection. All mutants were successfully produced and site-specifically conjugated. A1K1-His showed lower conjugation efficiency and increased liver/spleen retention, whereas A1K3-His exhibited reduced stability. A1K2-His and A1K4-His performed best overall. Removing the His-tag and administering gelofusin further lowered renal uptake. Notably, A1K2 displayed tumor-to-kidney and tumor-to-liver ratios 2.4 and 1.9 times higher, respectively, than A1K4 (p < 0.01).
Conclusions
For the first time, site-specific DOTA conjugation using sdAb derivatives containing a single lysine was achieved, avoiding the production of mixed final compounds. These findings identify 68Ga-DOTA-A1K2 as the leading candidate for mesothelin-expressing tumor imaging with minimal off-target uptake. Ongoing studies will assess its therapeutic utility with 177Lu-DOTA-A1K2. Since these four lysines are conserved in many sdAbs, this strategy may be broadly applicable for site-specific sdAb labeling.
{"title":"Enhancing theranostic potential of anti-mesothelin sdAb through site-specific labeling at a unique conserved lysine by molecular engineering","authors":"Émilien N’Guessan, Florian Raes, Mitra Ahmadi, Sandrine Bacot, Laurent Dumas, Julien Leenhardt, Marlène Debiossat, Clémence André, Jean-Luc Lenormand, Catherine Ghezzi, Daniel Fagret, Charlotte Lombardi, Alexis Broisat","doi":"10.1186/s41181-025-00340-z","DOIUrl":"10.1186/s41181-025-00340-z","url":null,"abstract":"<div><h3>Background</h3><p>Mesothelin is a 40 kDa glycoprotein overexpressed in several cancers, including triple-negative breast cancer (TNBC). The anti-mesothelin single-domain antibody (sdAb, or nanobody) A1 can serve as a radio-theranostic agent, but random DOTA conjugation on lysines yields heterogeneous products.</p><h3>Results</h3><p>We reengineered A1-His by directed mutagenesis to produce four single-lysine variants (A1K1-His, A1K2-His, A1K3-His, and A1K4-His). Each was site-specifically conjugated with p-SCN-Bn-DOTA, radiolabeled with <sup>68</sup>Ga, and evaluated by PET imaging in mice bearing HCC70 TNBC xenografts, followed by ex vivo biodistribution at 1 h post-injection. All mutants were successfully produced and site-specifically conjugated. A1K1-His showed lower conjugation efficiency and increased liver/spleen retention, whereas A1K3-His exhibited reduced stability. A1K2-His and A1K4-His performed best overall. Removing the His-tag and administering gelofusin further lowered renal uptake. Notably, A1K2 displayed tumor-to-kidney and tumor-to-liver ratios 2.4 and 1.9 times higher, respectively, than A1K4 (<i>p</i> < 0.01).</p><h3>Conclusions</h3><p>For the first time, site-specific DOTA conjugation using sdAb derivatives containing a single lysine was achieved, avoiding the production of mixed final compounds. These findings identify <sup>68</sup>Ga-DOTA-A1K2 as the leading candidate for mesothelin-expressing tumor imaging with minimal off-target uptake. Ongoing studies will assess its therapeutic utility with <sup>177</sup>Lu-DOTA-A1K2. Since these four lysines are conserved in many sdAbs, this strategy may be broadly applicable for site-specific sdAb labeling.</p></div>","PeriodicalId":534,"journal":{"name":"EJNMMI Radiopharmacy and Chemistry","volume":"10 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ejnmmipharmchem.springeropen.com/counter/pdf/10.1186/s41181-025-00340-z","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143883669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-11DOI: 10.1186/s41181-025-00339-6
Joana F. Santos, Camille Van Laere, Catarina D. Silva, Irwin Cassells, Célia Fernandes, Paula Raposinho, Ana Belchior, Catarina I. G. Pinto, Filipa Mendes, Christopher Cawthorne, Maarten Ooms, Michiel Van de Voorde, Frederik Cleeren, António Paulo
Background
Strategies that focus on delivering Auger electron emitters to highly radiosensitive intracellular targets—such as the nucleus, cell membrane, or mitochondria—are gaining attention. Targeting these organelles could enhance therapeutic efficacy while minimizing off-target toxicity by allowing lower administered doses. In this context, this study explores the therapeutic potential of 161Tb-labeled radiocomplexes that integrate the mitochondria-targeting triphenylphosphonium (TPP) moiety with a prostate-specific membrane antigen (PSMA) targeting vector. The goal is to assess these dual-targeted radiocomplexes for their ability to deliver conversion electrons (CE) and Auger electrons (AEs) to prostate cancer (PCa) cells, specifically targeting the mitochondria to enhance therapeutic efficacy.
Results
Two novel radiocomplexes, [161Tb]Tb-TPP-PSMA and [161Tb]Tb-TPP-G3-PSMA, were synthesized with high radiochemical yield and purity. The proposed structures were validated using HPLC and ESI-MS analysis, with their natTb counterparts serving as reference compounds. In vitro experiments included cellular uptake, internalization, mitochondrial uptake, and DNA damage assays in PSMA-positive PCa cell lines. Clonogenic assays were performed to evaluate cell survival post-treatment. In vivo studies were conducted using SCID/Beige mice bearing PCa xenografts and involved µSPECT/CT imaging and radiometabolite analysis to evaluate biodistribution, pharmacokinetics, tumor uptake and in vivo stability of the radiocomplexes. Both [161Tb]Tb-TPP-PSMA and [161Tb]Tb-TPP-G3-PSMA showed high radiochemical stability and were efficiently internalized by PSMA-positive cells, while showing minimal uptake in PSMA-negative cells. These dual-targeted radiocomplexes demonstrated significantly higher mitochondrial uptake compared to the non-TPP-containing [161Tb]Tb-PSMA-617, leading to increased DNA damage and enhanced radiocytotoxicity. In vivo, the dual-targeted complexes demonstrated PSMA-specific tumor uptake and pharmacokinetics comparable to [161Tb]Tb-PSMA-617, with effective clearance from non-target tissues.
Conclusions
The TPP-modified 161Tb-radiocomplexes effectively targeted the mitochondria of PSMA-positive PCa cells, leading to increased DNA damage and reduced cell viability compared to single-targeted radiocomplexes. These findings suggest that dual-targeting strategies, which combine PSMA and mitochondrial targeting, can enhance the therapeutic potential of radiopharmaceuticals for prostate cancer treatment.
{"title":"Mitochondria-tropic radioconjugates to enhance the therapeutic potential of terbium-161","authors":"Joana F. Santos, Camille Van Laere, Catarina D. Silva, Irwin Cassells, Célia Fernandes, Paula Raposinho, Ana Belchior, Catarina I. G. Pinto, Filipa Mendes, Christopher Cawthorne, Maarten Ooms, Michiel Van de Voorde, Frederik Cleeren, António Paulo","doi":"10.1186/s41181-025-00339-6","DOIUrl":"10.1186/s41181-025-00339-6","url":null,"abstract":"<div><h3>Background</h3><p>Strategies that focus on delivering Auger electron emitters to highly radiosensitive intracellular targets—such as the nucleus, cell membrane, or mitochondria—are gaining attention. Targeting these organelles could enhance therapeutic efficacy while minimizing off-target toxicity by allowing lower administered doses. In this context, this study explores the therapeutic potential of <sup>161</sup>Tb-labeled radiocomplexes that integrate the mitochondria-targeting triphenylphosphonium (TPP) moiety with a prostate-specific membrane antigen (PSMA) targeting vector. The goal is to assess these dual-targeted radiocomplexes for their ability to deliver conversion electrons (CE) and Auger electrons (AEs) to prostate cancer (PCa) cells, specifically targeting the mitochondria to enhance therapeutic efficacy.</p><h3>Results</h3><p>Two novel radiocomplexes, [<sup>161</sup>Tb]Tb-TPP-PSMA and [<sup>161</sup>Tb]Tb-TPP-G<sub>3</sub>-PSMA, were synthesized with high radiochemical yield and purity. The proposed structures were validated using HPLC and ESI-MS analysis, with their <sup>nat</sup>Tb counterparts serving as reference compounds. In vitro experiments included cellular uptake, internalization, mitochondrial uptake, and DNA damage assays in PSMA-positive PCa cell lines. Clonogenic assays were performed to evaluate cell survival post-treatment. In vivo studies were conducted using SCID/Beige mice bearing PCa xenografts and involved µSPECT/CT imaging and radiometabolite analysis to evaluate biodistribution, pharmacokinetics, tumor uptake and in vivo stability of the radiocomplexes. Both [<sup>161</sup>Tb]Tb-TPP-PSMA and [<sup>161</sup>Tb]Tb-TPP-G<sub>3</sub>-PSMA showed high radiochemical stability and were efficiently internalized by PSMA-positive cells, while showing minimal uptake in PSMA-negative cells. These dual-targeted radiocomplexes demonstrated significantly higher mitochondrial uptake compared to the non-TPP-containing [<sup>161</sup>Tb]Tb-PSMA-617, leading to increased DNA damage and enhanced radiocytotoxicity. In vivo, the dual-targeted complexes demonstrated PSMA-specific tumor uptake and pharmacokinetics comparable to [<sup>161</sup>Tb]Tb-PSMA-617, with effective clearance from non-target tissues.</p><h3>Conclusions</h3><p>The TPP-modified <sup>161</sup>Tb-radiocomplexes effectively targeted the mitochondria of PSMA-positive PCa cells, leading to increased DNA damage and reduced cell viability compared to single-targeted radiocomplexes. These findings suggest that dual-targeting strategies, which combine PSMA and mitochondrial targeting, can enhance the therapeutic potential of radiopharmaceuticals for prostate cancer treatment.</p></div>","PeriodicalId":534,"journal":{"name":"EJNMMI Radiopharmacy and Chemistry","volume":"10 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ejnmmipharmchem.springeropen.com/counter/pdf/10.1186/s41181-025-00339-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143821937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
[11C]TGN-020 has been developed as a positron emission tomography (PET) tracer for imaging aquaporin-4 (AQP4) in the brain and used in clinical studies. Previously, [11C]TGN-020 was synthesized through the acylation of [11C]nicotinic acid, produced by the reaction of 3-bromopyridine and n-butyllithium with [11C]CO2, with 2-amino-1,3,4-thiadiazole. In this study, to enhance the automated radiosynthesis efficiency of [11C]TGN-020, we optimized its radiosynthesis procedure using our in-house developed 11C-labeling synthesizer.
Results
[11C]TGN-020 was synthesized via direct [11C]CO2 fixation using n-butyllithium and 3-bromopyridine in tetrahydrofuran, followed by treatment of lithium [11C]nicotinic acetate with isobutyl chloroformate and subsequent acylation with 2-amino-1,3,4-thiadiazole in the presence of N,N-diisopropylethylamine. The optimized process significantly improved the radiosynthesis efficiency of [11C]TGN-020, achieving a high radiochemical yield based on [11C]CO2 (610‒1700 MBq, 2.8 ± 0.7%) at the end of synthesis (n = 12) and molar activity (Am) of 160–360 GBq/μmol at the end of synthesis (n = 5). The radiosynthesis time and radiochemical purity were approximately 60 min and > 95% (n = 12), respectively. PET studies based on [11C]TGN-020 with different Am values were performed using healthy rats. The radioactive uptake of [11C]TGN-020 with high Am in the cerebral cortex was slightly higher than that with low Am.
Conclusions
[11C]TGN-020 with high Am was obtained in reproducible radiochemical yield. Overall, the proposed optimization process for the radiosynthesis of [11C]TGN-020 can facilitate its application as a PET radiopharmaceutical for clinical use.
{"title":"Efficient one-pot radiosynthesis of the 11C-labeled aquaporin-4 inhibitor TGN-020","authors":"Kazunori Kawamura, Katsushi Kumata, Tomoteru Yamasaki, Masanao Ogawa, Yusuke Kurihara, Nobuki Nengaki, Yukimi Nakamura, Maiko Ono, Yuhei Takado, Hironaka Igarashi, Ming-Rong Zhang","doi":"10.1186/s41181-025-00338-7","DOIUrl":"10.1186/s41181-025-00338-7","url":null,"abstract":"<div><h3>Background</h3><p>[<sup>11</sup>C]TGN-020 has been developed as a positron emission tomography (PET) tracer for imaging aquaporin-4 (AQP4) in the brain and used in clinical studies. Previously, [<sup>11</sup>C]TGN-020 was synthesized through the acylation of [<sup>11</sup>C]nicotinic acid, produced by the reaction of 3-bromopyridine and <i>n</i>-butyllithium with [<sup>11</sup>C]CO<sub>2</sub>, with 2-amino-1,3,4-thiadiazole. In this study, to enhance the automated radiosynthesis efficiency of [<sup>11</sup>C]TGN-020, we optimized its radiosynthesis procedure using our in-house developed <sup>11</sup>C-labeling synthesizer.</p><h3>Results</h3><p>[<sup>11</sup>C]TGN-020 was synthesized via direct [<sup>11</sup>C]CO<sub>2</sub> fixation using <i>n</i>-butyllithium and 3-bromopyridine in tetrahydrofuran, followed by treatment of lithium [<sup>11</sup>C]nicotinic acetate with isobutyl chloroformate and subsequent acylation with 2-amino-1,3,4-thiadiazole in the presence of <i>N</i>,<i>N</i>-diisopropylethylamine. The optimized process significantly improved the radiosynthesis efficiency of [<sup>11</sup>C]TGN-020, achieving a high radiochemical yield based on [<sup>11</sup>C]CO<sub>2</sub> (610‒1700 MBq, 2.8 ± 0.7%) at the end of synthesis (<i>n</i> = 12) and molar activity (<i>A</i><sub>m</sub>) of 160–360 GBq/μmol at the end of synthesis (<i>n</i> = 5). The radiosynthesis time and radiochemical purity were approximately 60 min and > 95% (<i>n</i> = 12), respectively. PET studies based on [<sup>11</sup>C]TGN-020 with different <i>A</i><sub>m</sub> values were performed using healthy rats. The radioactive uptake of [<sup>11</sup>C]TGN-020 with high <i>A</i><sub>m</sub> in the cerebral cortex was slightly higher than that with low <i>A</i><sub>m</sub>.</p><h3>Conclusions</h3><p>[<sup>11</sup>C]TGN-020 with high <i>A</i><sub>m</sub> was obtained in reproducible radiochemical yield. Overall, the proposed optimization process for the radiosynthesis of [<sup>11</sup>C]TGN-020 can facilitate its application as a PET radiopharmaceutical for clinical use.</p></div>","PeriodicalId":534,"journal":{"name":"EJNMMI Radiopharmacy and Chemistry","volume":"10 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ejnmmipharmchem.springeropen.com/counter/pdf/10.1186/s41181-025-00338-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143784212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-04-04DOI: 10.1186/s41181-025-00337-8
Kateřina Ondrák Fialová, Lukáš Ondrák, Martin Vlk, Ján Kozempel, Kateřina Nováková, Zbyněk Nový, Katarína Hajduová, Marián Hajdúch, Miloš Petřík, Marek Pruszynski, Frank Bruchertseifer, Alfred Morgenstern
Background
Overexpression of human epidermal growth factor receptor type 2 (HER2) occurs in multiple carcinomas. For example, up to 20% of breast cancer cases are classified as HER2 positive (HER2+). Treatment of this condition typically involves immunotherapy using monoclonal antibodies, such as trastuzumab or pertuzumab. The precise targeting of monoclonal antibodies to HER2+ tumour lesions can be used as well in radioimmunotherapy to deliver medical radionuclides exactly to the afflicted area and therefore minimize radiation exposure of healthy tissues. In this study, DOTA conjugates of monoclonal antibodies trastuzumab and pertuzumab were prepared and tested in vitro. One of these, 225Ac-DOTA-pertuzumab, was also the subject of an ex vivo biodistribution study with normal as well as HER2+ and HER2- tumour-xenografted mice. This radioconjugate has not been previously described.
Results
Three DOTA-conjugates of HER2 targeting monoclonal antibodies, one of trastuzumab and two of pertuzumab, were prepared and radiolabelled with 225Ac in different molar ratios. This procedure led to an optimisation of the preparation and radiolabelling process. The radioconjugates were shown to be highly stable in vitro in both fetal bovine serum and phosphate buffered saline under room temperature and decreased temperature for 10 days. In vitro cell studies with HER2-overexpressing cell-line (SKOV-3) and low HER2-expressing cell line (MDA-MB-231) proved that radioconjugates of both antibodies have high binding specificity and affinity towards HER2 receptors. These findings were confirmed for a novel radioconjugate 225Ac-DOTA-pertuzumab in an ex vivo biodistribution study, where uptake in HER2+ tumour was 50 ± 14% ID/g and HER2- tumour showed uptake comparable with healthy tissues (max. 5.0 ± 1.7% ID/g). The high uptake observed in the spleen can be attributed to the elimination of the antibody, as well as the use of an immunedeficient mouse strain (SCID).
Conclusions
During this study, the optimization of preparation and radiolabelling of HER2 targeting antibodies with 225Ac was accomplished. Furthermore, the radioconjugate 225Ac-DOTA-pertuzumab was prepared and evaluated for the first time. The radioconjugates of both tested antibodies demonstrated excellent qualities in terms of stability and HER2 receptor affinity. Initial ex vivo studies indicated that especially the radioconjugate 225Ac-DOTA-pertuzumab is a very promising candidate for further more detailed in vivo studies.
{"title":"In vitro and in vivo evaluation of anti-HER2 antibody conjugates labelled with 225Ac","authors":"Kateřina Ondrák Fialová, Lukáš Ondrák, Martin Vlk, Ján Kozempel, Kateřina Nováková, Zbyněk Nový, Katarína Hajduová, Marián Hajdúch, Miloš Petřík, Marek Pruszynski, Frank Bruchertseifer, Alfred Morgenstern","doi":"10.1186/s41181-025-00337-8","DOIUrl":"10.1186/s41181-025-00337-8","url":null,"abstract":"<div><h3>Background</h3><p>Overexpression of human epidermal growth factor receptor type 2 (HER2) occurs in multiple carcinomas. For example, up to 20% of breast cancer cases are classified as HER2 positive (HER2+). Treatment of this condition typically involves immunotherapy using monoclonal antibodies, such as trastuzumab or pertuzumab. The precise targeting of monoclonal antibodies to HER2+ tumour lesions can be used as well in radioimmunotherapy to deliver medical radionuclides exactly to the afflicted area and therefore minimize radiation exposure of healthy tissues. In this study, DOTA conjugates of monoclonal antibodies trastuzumab and pertuzumab were prepared and tested in vitro. One of these, <sup>225</sup>Ac-DOTA-pertuzumab, was also the subject of an ex vivo biodistribution study with normal as well as HER2+ and HER2- tumour-xenografted mice. This radioconjugate has not been previously described.</p><h3>Results</h3><p>Three DOTA-conjugates of HER2 targeting monoclonal antibodies, one of trastuzumab and two of pertuzumab, were prepared and radiolabelled with <sup>225</sup>Ac in different molar ratios. This procedure led to an optimisation of the preparation and radiolabelling process. The radioconjugates were shown to be highly stable in vitro in both fetal bovine serum and phosphate buffered saline under room temperature and decreased temperature for 10 days. In vitro cell studies with HER2-overexpressing cell-line (SKOV-3) and low HER2-expressing cell line (MDA-MB-231) proved that radioconjugates of both antibodies have high binding specificity and affinity towards HER2 receptors. These findings were confirmed for a novel radioconjugate <sup>225</sup>Ac-DOTA-pertuzumab in an ex vivo biodistribution study, where uptake in HER2+ tumour was 50 ± 14% ID/g and HER2- tumour showed uptake comparable with healthy tissues (max. 5.0 ± 1.7% ID/g). The high uptake observed in the spleen can be attributed to the elimination of the antibody, as well as the use of an immunedeficient mouse strain (SCID).</p><h3>Conclusions</h3><p>During this study, the optimization of preparation and radiolabelling of HER2 targeting antibodies with <sup>225</sup>Ac was accomplished. Furthermore, the radioconjugate <sup>225</sup>Ac-DOTA-pertuzumab was prepared and evaluated for the first time. The radioconjugates of both tested antibodies demonstrated excellent qualities in terms of stability and HER2 receptor affinity. Initial ex vivo studies indicated that especially the radioconjugate <sup>225</sup>Ac-DOTA-pertuzumab is a very promising candidate for further more detailed in vivo studies.</p></div>","PeriodicalId":534,"journal":{"name":"EJNMMI Radiopharmacy and Chemistry","volume":"10 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ejnmmipharmchem.springeropen.com/counter/pdf/10.1186/s41181-025-00337-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143769935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-31DOI: 10.1186/s41181-024-00325-4
Seham Mustafa, Abdelhamid Elgazzar
Background
Non-steroidal anti-inflammatory drugs (NSAIDs), such as diclofenac, are globally recognized as the primary choice for alleviating kidney pain and ureteric colic. This study examines the effects of long-term diclofenac administration on renography using two radiopharmaceuticals: 99mTc-mercaptoacetyltriglycine (99mTc-MAG3), which is excreted almost exclusively by the renal tubules, and 99mTc-diethylenetriamine pentaacetic acid (99mTc-DTPA), which is predominantly excreted by glomerular filtration.
Results
Diclofenac administration caused a rightward shift in renograms, indicating delayed renal uptake and clearance for both tracers. For 99mTc-MAG3, the average time to peak activity (Tmax) increased from 2.88 ± 0.3 min (control) to 4.2 ± 0.3 min (treated), while time from peak to 50% activity (T½) rose from 4.16 ± 0.1 min to 5.48 ± 0.5 min. For 99mTc-DTPA, Tmax increased from 4.3 ± 0.4 min to 12.9 ± 2.0 min, and T½ extended from 13.35 ± 1.5 min to 29.75 ± 2.0 min (n = 12; *p < 0.05 for all comparisons). Delayed tracer arrival in the bladder was particularly pronounced with 99mTc-DTPA.
Conclusions
Chronic diclofenac exposure significantly delays Tmax and T½ for both tracers, with a greater impact observed using 99mTc-DTPA. These findings highlight 99mTc-MAG3 as the preferred radiopharmaceutical for renography in settings involving long-term NSAID administration, ensuring accurate and reliable interpretation and minimizing variability associated with radiopharmaceutical selection.
{"title":"Impact of prolonged use of NSAID (Diclofenac) on 99mTc-MAG3 and 99mTc-DTPA renography","authors":"Seham Mustafa, Abdelhamid Elgazzar","doi":"10.1186/s41181-024-00325-4","DOIUrl":"10.1186/s41181-024-00325-4","url":null,"abstract":"<div><h3>Background</h3><p>Non-steroidal anti-inflammatory drugs (NSAIDs), such as diclofenac, are globally recognized as the primary choice for alleviating kidney pain and ureteric colic. This study examines the effects of long-term diclofenac administration on renography using two radiopharmaceuticals: 99mTc-mercaptoacetyltriglycine (99mTc-MAG3), which is excreted almost exclusively by the renal tubules, and 99mTc-diethylenetriamine pentaacetic acid (99mTc-DTPA), which is predominantly excreted by glomerular filtration.</p><h3>Results</h3><p>Diclofenac administration caused a rightward shift in renograms, indicating delayed renal uptake and clearance for both tracers. For 99mTc-MAG3, the average time to peak activity (Tmax) increased from 2.88 ± 0.3 min (control) to 4.2 ± 0.3 min (treated), while time from peak to 50% activity (T½) rose from 4.16 ± 0.1 min to 5.48 ± 0.5 min. For 99mTc-DTPA, Tmax increased from 4.3 ± 0.4 min to 12.9 ± 2.0 min, and T½ extended from 13.35 ± 1.5 min to 29.75 ± 2.0 min (<i>n</i> = 12; *<i>p</i> < 0.05 for all comparisons). Delayed tracer arrival in the bladder was particularly pronounced with 99mTc-DTPA.</p><h3>Conclusions</h3><p>Chronic diclofenac exposure significantly delays Tmax and T½ for both tracers, with a greater impact observed using 99mTc-DTPA. These findings highlight 99mTc-MAG3 as the preferred radiopharmaceutical for renography in settings involving long-term NSAID administration, ensuring accurate and reliable interpretation and minimizing variability associated with radiopharmaceutical selection.</p></div>","PeriodicalId":534,"journal":{"name":"EJNMMI Radiopharmacy and Chemistry","volume":"10 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ejnmmipharmchem.springeropen.com/counter/pdf/10.1186/s41181-024-00325-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143740784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-26DOI: 10.1186/s41181-025-00336-9
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
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.
{"title":"Synthesis and preclinical evaluation of gastrin releasing peptide receptor antagonist [18F]MeTz-PEG2-RM26 for positron emission tomography","authors":"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","doi":"10.1186/s41181-025-00336-9","DOIUrl":"10.1186/s41181-025-00336-9","url":null,"abstract":"<div><h3>Background</h3><p>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 [<sup>18</sup>F]MeTz-PEG<sub>2</sub>-RM26, a GRPR antagonist which utilises the Inverse Electron Demand Diels-Alder (IEDDA) reaction for <sup>18</sup>F-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 [<sup>18</sup>F]MeTz-PEG<sub>2</sub>-RM26 were evaluated in vitro using GRPR-expressing PC-3 cells. Furthermore, the biodistribution profile of [<sup>18</sup>F]MeTz-PEG<sub>2</sub>-RM26 was assessed in NMRI mice and its tumour-targeting capability was investigated in mice bearing PC-3 xenografts.</p><h3>Results</h3><p>The labelling of TCO-PEG<sub>2</sub>-RM26 precursor involved three steps: (1) synthesis of an <sup>18</sup>F-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-PEG<sub>2</sub>-RM26 via an IEDDA click reaction. This production method of [<sup>18</sup>F]MeTz-PEG<sub>2</sub>-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 [<sup>18</sup>F]MeTz-PEG<sub>2</sub>-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 [<sup>18</sup>F]MeTz-PEG<sub>2</sub>-RM26.</p><h3>Conclusions</h3><p>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.</p></div>","PeriodicalId":534,"journal":{"name":"EJNMMI Radiopharmacy and Chemistry","volume":"10 1","pages":""},"PeriodicalIF":4.4,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ejnmmipharmchem.springeropen.com/counter/pdf/10.1186/s41181-025-00336-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143698450","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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