scholarly journals Evaluation of Organo [18F]Fluorosilicon Tetrazine as a Prosthetic Group for the Synthesis of PET Radiotracers

Molecules ◽  
2020 ◽  
Vol 25 (5) ◽  
pp. 1208 ◽  
Author(s):  
Sofia Otaru ◽  
Surachet Imlimthan ◽  
Mirkka Sarparanta ◽  
Kerttuli Helariutta ◽  
Kristiina Wähälä ◽  
...  
Keyword(s):  
Radiochemical Yield ◽  
Biological Evaluation ◽  
Prosthetic Group ◽  
Molar Activity ◽  
Positron Emission ◽  
Biological Studies ◽  
Model Protein ◽  
Improved Stability

Fluorine-18 is the most widely used positron emission tomography (PET) radionuclide currently in clinical application, due to its optimal nuclear properties. The synthesis of 18F-labeled radiotracers often requires harsh reaction conditions, limiting the use of sensitive bio- and macromolecules as precursors for direct radiolabeling with fluorine-18. We aimed to develop a milder and efficient in vitro and in vivo labeling method for trans-cyclooctene (TCO) functionalized proteins, through the bioorthogonal inverse-electron demand Diels-Alder (IEDDA) reaction with fluorine-18 radiolabeled tetrazine ([18F]SiFA-Tz). Here, we used TCO-modified bovine serum albumin (BSA) as the model protein, and isotopic exchange (IE) (19F/18F) chemistry as the labeling strategy. The radiolabeling of albumin-TCO with [18F]SiFA-Tz ([18F]6), providing [18F]fluoroalbumin ([18F]10) in high radiochemical yield (99.1 ± 0.2%, n = 3) and a molar activity (MA) of 1.1 GBq/µmol, confirmed the applicability of [18F]6 as a quick in vitro fluorination reagent for the TCO functionalized proteins. While the biological evaluation of [18F]6 demonstrated defluorination in vivo, limiting the utility for pretargeted applications, the in vivo stability of the radiotracer was dramatically improved when [18F]6 was used for the radiolabeling of albumin-TCO ([18F]10) in vitro, prior to administration. Due to the detected defluorination in vivo, structural optimization of the prosthetic group for improved stability is needed before further biological studies and application of pretargeted PET imaging.

scholarly journals Synthesis and Preclinical Evaluation of [18F]PF04217903, a Selective MET PET Tracer

2020 ◽  
Author(s):  
Vegard Torp Lien ◽  
Emily Hauge ◽  
Syed Nuruddin ◽  
Jo Klaveness ◽  
Dag Erlend Olberg
Keyword(s):  
Growth Factor Receptor ◽  
Radiochemical Yield ◽  
Molar Activity ◽  
Bioisosteric Replacement ◽  
Pet Tracer ◽  
Positron Emission ◽  
Wide Range ◽  
Hepatocyte Growth

<p>The tyrosine kinase MET (hepatocyte growth factor receptor) is abnormally activated in a wide range of cancers and is often correlated with a poor prognosis. Precision medicine with positron emission tomography (PET) can potentially aid in the assessment of tumor biochemistry and heterogeneity, which can prompt the selection of the most effective therapeutic regimes. The selective MET inhibitor PF04217903 (<b>1</b>) formed the basis for a bioisosteric replacement to the deoxyfluorinated analogue [<sup>18</sup>F]<b>2</b>, intended as a PET tracer for MET. [<sup>18</sup>F]<b>2 </b>could be synthesized with a “hydrous fluoroethylation” protocol in 6.3 ± 2.6% radiochemical yield and a molar activity of >50 GBq/µmol. <i>In vitro</i> autoradiography indicated that [<sup>18</sup>F]<b>2 </b>specifically binds to MET in PC3 tumor tissue, and <i>in vivo</i> biodistribution in mice showed predominantly a hepatobiliary excretion along with a low retention of radiotracer in other organs. </p>

scholarly journals Synthesis and Preclinical Evaluation of [18F]PF04217903, a Selective MET PET Tracer

2020 ◽  
Author(s):  
Vegard Torp Lien ◽  
Emily Hauge ◽  
Syed Nuruddin ◽  
Jo Klaveness ◽  
Dag Erlend Olberg
Keyword(s):  
Growth Factor Receptor ◽  
Radiochemical Yield ◽  
Molar Activity ◽  
Bioisosteric Replacement ◽  
Pet Tracer ◽  
Positron Emission ◽  
Wide Range ◽  
Hepatocyte Growth

<p>The tyrosine kinase MET (hepatocyte growth factor receptor) is abnormally activated in a wide range of cancers and is often correlated with a poor prognosis. Precision medicine with positron emission tomography (PET) can potentially aid in the assessment of tumor biochemistry and heterogeneity, which can prompt the selection of the most effective therapeutic regimes. The selective MET inhibitor PF04217903 (<b>1</b>) formed the basis for a bioisosteric replacement to the deoxyfluorinated analogue [<sup>18</sup>F]<b>2</b>, intended as a PET tracer for MET. [<sup>18</sup>F]<b>2 </b>could be synthesized with a “hydrous fluoroethylation” protocol in 6.3 ± 2.6% radiochemical yield and a molar activity of >50 GBq/µmol. <i>In vitro</i> autoradiography indicated that [<sup>18</sup>F]<b>2 </b>specifically binds to MET in PC3 tumor tissue, and <i>in vivo</i> biodistribution in mice showed predominantly a hepatobiliary excretion along with a low retention of radiotracer in other organs. </p>

scholarly journals Synthesis and Biological Evaluation of a Radiolabeled PET Probe for Visualization of In Vivo α-Fucosidase Expression

2021 ◽  
Vol 14 (8) ◽  
pp. 745
Author(s):  
Jonathan Cotton ◽  
Chris Marc Goehring ◽  
Anna Kuehn ◽  
Andreas Maurer ◽  
Kerstin Fuchs ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Sodium Hydride ◽  
Biological Evaluation ◽  
Tracer Uptake ◽  
Mouse Serum ◽  
Molar Activity ◽  
Pet Tracer ◽  
Positron Emission

The acidic hydrolase α-fucosidase (AF) is a biomarker for maladies such as cancer and inflammation. The most advanced probes for α-fucosidase are unfortunately constrained to ex vivo or in vitro applications. The in vivo detection and quantification of AF using positron emission tomography would allow for better discovery and diagnosis of disease as well as provide better understanding of disease progression. We synthesized, characterized, and evaluated a radiolabeled small molecule inhibitor of AF based on a known molecule. The radiosynthesis involved the 11C methylation of a phenoxide, which was generated in situ by ultrasonification of the precursor with sodium hydride. The tracer was produced with a decay corrected yield of 41.7 ± 16.5% and had a molar activity of 65.4 ± 30.3 GBq/μmol. The tracer was shown to be stable in mouse serum at 60 min. To test the new tracer, HCT116 colorectal carcinoma cells were engineered to overexpress human AF. In vitro evaluation revealed 3.5-fold higher uptake in HCT116AF cells compared to HCT116 controls (26.4 ± 7.8 vs. 7.5 ± 1.0 kBq/106 cells). Static PET scans 50 min post injection revealed 2.5-fold higher tracer uptake in the HCT116AF tumors (3.0 ± 0.8%ID/cc (n = 6)) compared with the controls (1.2 ± 0.8 (n = 5)). Dynamic scans showed higher uptake in the HCT116AF tumors at all time-points (n = 2). Ex vivo analysis of the tumors, utilizing fluorescent DDK2 antibodies, confirmed the expression of human AF in the HCT116AF xenografts. We have developed a novel PET tracer to image AF in vivo and will now apply this to relevant disease models.

scholarly journals Radiosynthesis and Biological Investigation of a Novel Fluorine-18 Labeled Benzoimidazotriazine- Based Radioligand for the Imaging of Phosphodiesterase 2A with Positron Emission Tomography

Molecules ◽  
2019 ◽  
Vol 24 (22) ◽  
pp. 4149
Author(s):  
Ritawidya ◽  
Wenzel ◽  
Teodoro ◽  
Toussaint ◽  
Kranz ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Specific Binding ◽  
Standardized Uptake Value ◽  
Radiochemical Yield ◽  
Biological Evaluation ◽  
Emission Tomography ◽  
Biological Investigation ◽  
Positron Emission

A specific radioligand for the imaging of cyclic nucleotide phosphodiesterase 2A (PDE2A) via positron emission tomography (PET) would be helpful for research on the physiology and disease-related changes in the expression of this enzyme in the brain. In this report, the radiosynthesis of a novel PDE2A radioligand and the subsequent biological evaluation were described. Our prospective compound 1-(2-chloro-5-methoxy phenyl)-8-(2-fluoropyridin-4-yl)-3- methylbenzo[e]imidazo[5,1-c][1,2,4]triazine, benzoimidazotriazine (BIT1) (IC50 PDE2A = 3.33 nM; 16-fold selectivity over PDE10A) was fluorine-18 labeled via aromatic nucleophilic substitution of the corresponding nitro precursor using the K[18F]F‐K2.2.2‐carbonate complex system. The new radioligand [18F]BIT1 was obtained with a high radiochemical yield (54 ± 2%, n = 3), a high radiochemical purity (≥99%), and high molar activities (155–175 GBq/μmol, n = 3). In vitro autoradiography on pig brain cryosections exhibited a heterogeneous spatial distribution of [18F]BIT1 corresponding to the known pattern of expression of PDE2A. The investigation of in vivo metabolism of [18F]BIT1 in a mouse revealed sufficient metabolic stability. PET studies in mouse exhibited a moderate brain uptake of [18F]BIT1 with a maximum standardized uptake value of ~0.7 at 5 minutes p.i. However, in vivo blocking studies revealed a non-target specific binding of [18F]BIT1. Therefore, further structural modifications are needed to improve target selectivity.

scholarly journals Biological Evaluation of [18F]AlF-NOTA-NSC-GLU as a Positron Emission Tomography Tracer for Hepatocellular Carcinoma

2021 ◽  
Vol 9 ◽  
Author(s):  
Liping Lin ◽  
Xianhong Xiang ◽  
Shu Su ◽  
Shaoyu Liu ◽  
Ying Xiong ◽  
...  
Keyword(s):  
Competitive Inhibition ◽  
Radiochemical Yield ◽  
Biological Evaluation ◽  
Uptake Ratio ◽  
Liver Uptake ◽  
Positron Emission ◽  
Pet Ct ◽  
Protein Incorporation

Purpose: N-(2-[18F]fluoropropionyl)-L-glutamate ([18F]FPGLU) for hepatocellular carcinoma (HCC) imaging has been performed in our previous studies, but its radiosynthesis method and stability in vivo need to be improved. Hence, we evaluated the synthesis and biological properties of a simple [18F]-labeled glutamate analog, [18F]AlF-1,4,7-triazacyclononane-1,4,7-triacetic-acid-2-S-(4-isothiocyanatobenzyl)-l-glutamate ([18F]AlF-NOTA-NSC-GLU), for HCC imaging.Procedures: [18F]AlF-NOTA-NSC-GLU was synthesized via a one-step reaction sequence from NOTA-NSC-GLU. In order to investigate the imaging value of [18F]AlF-NOTA-NSC-GLU in HCC, we conducted positron emission tomography/computed tomography (PET/CT) imaging and competitive binding of [18F]AlF-NOTA-NSC-GLU in human Hep3B tumor-bearing mice. The transport mechanism of [18F]AlF-NOTA-NSC-GLU was determined by competitive inhibition and protein incorporation experiments in vitro.Results: [18F]AlF-NOTA-NSC-GLU was prepared with an overall radiochemical yield of 29.3 ± 5.6% (n = 10) without decay correction within 20 min. In vitro competitive inhibition experiments demonstrated that the Na+-dependent systems XAG-, B0+, ASC, and minor XC- were involved in the uptake of [18F]AlF-NOTA-NSC-GLU, with the Na+-dependent system XAG- possibly playing a more dominant role. Protein incorporation studies of the Hep3B human hepatoma cell line showed almost no protein incorporation. Micro-PET/CT imaging with [18F]AlF-NOTA-NSC-GLU showed good tumor-to-background contrast in Hep3B human hepatoma-bearing mouse models. After [18F]AlF-NOTA-NSC-GLU injection, the tumor-to-liver uptake ratio of [18F]AlF-NOTA-NSC-GLU was 2.06 ± 0.17 at 30 min post-injection. In vivo competitive binding experiments showed that the tumor-to-liver uptake ratio decreased with the addition of inhibitors to block the XAG system.Conclusions: We have successfully synthesized [18F]AlF-NOTA-NSC-GLU as a novel PET tracer with good radiochemical yield and high radiochemical purity. Our findings indicate that [18F]AlF-NOTA-NSC-GLU may be a potential candidate for HCC imaging. Also, a further biological evaluation is underway.

Click Chemistry Expedited Radiosynthesis: Sulfur [18F]fluoride Exchange of Aryl Fluorosulfates

2019 ◽  
Author(s):  
Qinheng Zheng ◽  
Hongtao Xu ◽  
Hua Wang ◽  
Wen-Ge Han Du ◽  
Nan Wang ◽  
...  
Keyword(s):  
Click Chemistry ◽  
High Performance ◽  
Isotopic Exchange ◽  
Tumor Imaging ◽  
Radiochemical Yield ◽  
Exchange Method ◽  
Molar Activity ◽  
Positron Emission ◽  
Sulfur Fluoride

The lack of simple, efficient [<sup>18</sup>F]fluorination processes and new target-specific organofluorine probes remains the major challenge of fluorine-18-based positron emission tomography (PET). We report here a fast isotopic exchange method for the radiosynthesis of aryl [<sup>18</sup>F]fluorosulfate based PET agents enabled by the emerging sulfur fluoride exchange (SuFEx) click chemistry. The method has been applied to the fully-automated <sup>18</sup>F-radiolabeling of twenty-five structurally diverse aryl fluorosulfates with excellent radiochemical yield (83–100%) and high molar activity (up to 281 GBq µmol<sup>–1</sup>) at room temperature in 30 seconds. The purification of radiotracers requires no time-consuming high-performance liquid chromatography (HPLC), but rather a simple cartridge filtration. The utility of aryl [<sup>18</sup>F]fluorosulfate is demonstrated by the <i>in vivo</i> tumor imaging by targeting poly(ADP-ribose) polymerase 1 (PARP1).

scholarly journals Development of 18F-Labeled Radiotracers for PET Imaging of the Adenosine A2A Receptor: Synthesis, Radiolabeling and Preliminary Biological Evaluation

2021 ◽  
Vol 22 (5) ◽  
pp. 2285
Author(s):  
Thu Hang Lai ◽  
Susann Schröder ◽  
Magali Toussaint ◽  
Sladjana Dukić-Stefanović ◽  
Mathias Kranz ◽  
...  
Keyword(s):  
Specific Binding ◽  
Brain Slices ◽  
Total Activity ◽  
Biological Evaluation ◽  
Adenosine A2a Receptor ◽  
Positron Emission ◽  
A2a Receptor ◽  
Adenosine A2a

The adenosine A2A receptor (A2AR) represents a potential therapeutic target for neurodegenerative diseases. Aiming at the development of a positron emission tomography (PET) radiotracer to monitor changes of receptor density and/or occupancy during the A2AR-tailored therapy, we designed a library of fluorinated analogs based on a recently published lead compound (PPY). Among those, the highly affine 4-fluorobenzyl derivate (PPY1; Ki(hA2AR) = 5.3 nM) and the 2-fluorobenzyl derivate (PPY2; Ki(hA2AR) = 2.1 nM) were chosen for 18F-labeling via an alcohol-enhanced copper-mediated procedure starting from the corresponding boronic acid pinacol ester precursors. Investigations of the metabolic stability of [18F]PPY1 and [18F]PPY2 in CD-1 mice by radio-HPLC analysis revealed parent fractions of more than 76% of total activity in the brain. Specific binding of [18F]PPY2 on mice brain slices was demonstrated by in vitro autoradiography. In vivo PET/magnetic resonance imaging (MRI) studies in CD-1 mice revealed a reasonable high initial brain uptake for both radiotracers, followed by a fast clearance.

scholarly journals Synthesis and Evaluation of [18F]FEtLos and [18F]AMBF3Los as Novel 18F-Labelled Losartan Derivatives for Molecular Imaging of Angiotensin II Type 1 Receptors

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1872
Author(s):  
Martha Sahylí Ortega Pijeira ◽  
Paulo Sérgio Gonçalves Nunes ◽  
Sofia Nascimento dos Santos ◽  
Zhengxing Zhang ◽  
Arian Pérez Nario ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Binding Affinity ◽  
Renin Angiotensin System ◽  
Prosthetic Group ◽  
Positron Emission ◽  
One Step ◽  
Group 2

Losartan is widely used in clinics to treat cardiovascular related diseases by selectively blocking the angiotensin II type 1 receptors (AT1Rs), which regulate the renin-angiotensin system (RAS). Therefore, monitoring the physiological and pathological biodistribution of AT1R using positron emission tomography (PET) might be a valuable tool to assess the functionality of RAS. Herein, we describe the synthesis and characterization of two novel losartan derivatives PET tracers, [18F]fluoroethyl-losartan ([18F]FEtLos) and [18F]ammoniomethyltrifluoroborate-losartan ([18F]AMBF3Los). [18F]FEtLos was radiolabeled by 18F-fluoroalkylation of losartan potassium using the prosthetic group 2-[18F]fluoroethyl tosylate; whereas [18F]AMBF3Los was prepared following an one-step 18F-19F isotopic exchange reaction, in an overall yield of 2.7 ± 0.9% and 11 ± 4%, respectively, with high radiochemical purity (>95%). Binding competition assays in AT1R-expressing membranes showed that AMBF3Los presented an almost equivalent binding affinity (Ki 7.9 nM) as the cold reference Losartan (Ki 1.5 nM), unlike FEtLos (Ki 2000 nM). In vitro and in vivo assays showed that [18F]AMBF3Los displayed a good binding affinity for AT1R-overexpressing CHO cells and was able to specifically bind to renal AT1R. Hence, our data demonstrate [18F]AMBF3Los as a new tool for PET imaging of AT1R with possible applications for the diagnosis of cardiovascular, inflammatory and cancer diseases.

scholarly journals [18F]SuFEx Click Chemistry Enabled Ultrafast Late-stage Radiosynthesis

2020 ◽  
Author(s):  
Qinheng Zheng ◽  
Hongtao Xu ◽  
Hua Wang ◽  
Wen-Ge Han Du ◽  
Nan Wang ◽  
...  
Keyword(s):  
Click Chemistry ◽  
High Performance ◽  
Isotopic Exchange ◽  
Tumor Imaging ◽  
Radiochemical Yield ◽  
Exchange Method ◽  
Molar Activity ◽  
Positron Emission ◽  
Sulfur Fluoride

The lack of simple, efficient [<sup>18</sup>F]fluorination processes and new target-specific organofluorine probes remains the major challenge of fluorine-18-based positron emission tomography (PET). We report here a fast isotopic exchange method for the radiosynthesis of aryl [<sup>18</sup>F]fluorosulfate based PET agents enabled by the emerging sulfur fluoride exchange (SuFEx) click chemistry. The method has been applied to the fully-automated <sup>18</sup>F-radiolabeling of twenty-five structurally diverse aryl fluorosulfates with excellent radiochemical yield (83–100%) and high molar activity (up to 281 GBq µmol<sup>–1</sup>) at room temperature in 30 seconds. The purification of radiotracers requires no time-consuming high-performance liquid chromatography (HPLC), but rather a simple cartridge filtration. The utility of aryl [<sup>18</sup>F]fluorosulfate is demonstrated by the <i>in vivo</i> tumor imaging by targeting poly(ADP-ribose) polymerase 1 (PARP1).

[18F]SuFEx Click Chemistry Enabled Ultrafast Late-stage Radiosynthesis

2020 ◽  
Author(s):  
Qinheng Zheng ◽  
Hongtao Xu ◽  
Hua Wang ◽  
Wen-Ge Han Du ◽  
Nan Wang ◽  
...  
Keyword(s):  
Click Chemistry ◽  
High Performance ◽  
Isotopic Exchange ◽  
Tumor Imaging ◽  
Radiochemical Yield ◽  
Exchange Method ◽  
Molar Activity ◽  
Positron Emission ◽  
Sulfur Fluoride

The lack of simple, efficient [<sup>18</sup>F]fluorination processes and new target-specific organofluorine probes remains the major challenge of fluorine-18-based positron emission tomography (PET). We report here a fast isotopic exchange method for the radiosynthesis of aryl [<sup>18</sup>F]fluorosulfate based PET agents enabled by the emerging sulfur fluoride exchange (SuFEx) click chemistry. The method has been applied to the fully-automated <sup>18</sup>F-radiolabeling of twenty-five structurally diverse aryl fluorosulfates with excellent radiochemical yield (83–100%) and high molar activity (up to 281 GBq µmol<sup>–1</sup>) at room temperature in 30 seconds. The purification of radiotracers requires no time-consuming high-performance liquid chromatography (HPLC), but rather a simple cartridge filtration. The utility of aryl [<sup>18</sup>F]fluorosulfate is demonstrated by the <i>in vivo</i> tumor imaging by targeting poly(ADP-ribose) polymerase 1 (PARP1).

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