scholarly journals Radiosynthesis of [18F]-Labelled Pro-Nucleotides (ProTides)

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 704
Author(s):  
Alessandra Cavaliere ◽  
Katrin C. Probst ◽  
Stephen J. Paisey ◽  
Christopher Marshall ◽  
Abdul K. H. Dheere ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Pet Imaging ◽  
Early Stage ◽  
Proof Of Concept ◽  
Synthesis Time ◽  
Positron Emission ◽  
Anti Cancer ◽  
Radiochemical Yields ◽  
Radiochemical Synthesis

Phosphoramidate pro-nucleotides (ProTides) have revolutionized the field of anti-viral and anti-cancer nucleoside therapy, overcoming the major limitations of nucleoside therapies and achieving clinical and commercial success. Despite the translation of ProTide technology into the clinic, there remain unresolved in vivo pharmacokinetic and pharmacodynamic questions. Positron Emission Tomography (PET) imaging using [18F]-labelled model ProTides could directly address key mechanistic questions and predict response to ProTide therapy. Here we report the first radiochemical synthesis of [18F]ProTides as novel probes for PET imaging. As a proof of concept, two chemically distinct radiolabelled ProTides have been synthesized as models of 3′- and 2′-fluorinated ProTides following different radiosynthetic approaches. The 3′-[18F]FLT ProTide was obtained via a late stage [18F]fluorination in radiochemical yields (RCY) of 15–30% (n = 5, decay-corrected from end of bombardment (EoB)), with high radiochemical purities (97%) and molar activities of 56 GBq/μmol (total synthesis time of 130 min.). The 2′-[18F]FIAU ProTide was obtained via an early stage [18F]fluorination approach with an RCY of 1–5% (n = 7, decay-corrected from EoB), with high radiochemical purities (98%) and molar activities of 53 GBq/μmol (total synthesis time of 240 min).

scholarly journals Current Perspectives on 89Zr-PET Imaging

2020 ◽  
Vol 21 (12) ◽  
pp. 4309
Author(s):  
Joon-Kee Yoon ◽  
Bok-Nam Park ◽  
Eun-Kyoung Ryu ◽  
Young-Sil An ◽  
Su-Jin Lee
Keyword(s):  
Pet Imaging ◽  
Cell Tracking ◽  
Current Status ◽  
Cancer Therapies ◽  
Ongoing Research ◽  
Positron Emission ◽  
Nanoparticle Imaging ◽  
Anti Cancer ◽  
Preclinical And Clinical Studies

89Zr is an emerging radionuclide that plays an essential role in immuno-positron emission tomography (PET) imaging. The long half-life of 89Zr (t1/2 = 3.3 days) is favorable for evaluating the in vivo distribution of monoclonal antibodies. Thus, the use of 89Zr is promising for monitoring antibody-based cancer therapies. Immuno-PET combines the sensitivity of PET with the specificity of antibodies. A number of studies have been conducted to investigate the feasibility of 89Zr immuno-PET imaging for predicting the efficacy of radioimmunotherapy and antibody therapies, imaging target expression, detecting target-expressing tumors, and the monitoring of anti-cancer chemotherapies. In this review, we summarize the current status of PET imaging using 89Zr in both preclinical and clinical studies by highlighting the use of immuno-PET for the targets of high clinical relevance. We also present 89Zr-PET applications other than immuno-PET, such as nanoparticle imaging and cell tracking. Finally, we discuss the limitations and the ongoing research being performed to overcome the remaining hurdles.

scholarly journals PET Imaging of Post-infarct Myocardial Inflammation

2021 ◽  
Vol 23 (8) ◽  
Author(s):  
Andrej Ćorović ◽  
Meritxell Nus ◽  
Ziad Mallat ◽  
James H. F. Rudd ◽  
Jason M. Tarkin
Keyword(s):  
Myocardial Infarction ◽  
Pet Imaging ◽  
Early Stage ◽  
Drug Efficacy ◽  
Myocardial Inflammation ◽  
Additional Advantage ◽  
Positron Emission ◽  
Detailed Assessment ◽  
Surrogate Measure

Abstract Purpose of Review To examine the use of positron emission tomography (PET) for imaging post-infarct myocardial inflammation and repair. Recent Findings Dysregulated immune responses after myocardial infarction are associated with adverse cardiac remodelling and an increased likelihood of ischaemic heart failure. PET imaging utilising novel tracers can be applied to visualise different components of the post-infarction inflammatory and repair processes. This approach could offer unique pathophysiological insights that could prove useful for the identification and risk-stratification of individuals who would ultimately benefit most from emerging immune-modulating therapies. PET imaging could also bridge the clinical translational gap as a surrogate measure of drug efficacy in early-stage clinical trials in patients with myocardial infarction. The use of hybrid PET/MR imaging, in particular, offers the additional advantage of simultaneous in vivo molecular imaging and detailed assessment of myocardial function, viability and tissue characterisation. Summary Further research is needed to realise the true clinical translational value of PET imaging after myocardial infarction.

scholarly journals Adamantane/Cucurbituril: A Potential Pretargeted Imaging Strategy in Immuno-PET

2018 ◽  
Vol 17 ◽  
pp. 153601211879983 ◽  
Author(s):  
Martin G. Strebl ◽  
Jane Yang ◽  
Lyle Isaacs ◽  
Jacob M. Hooker
Keyword(s):  
Pet Imaging ◽  
Biological Macromolecules ◽  
Proof Of Concept ◽  
Positron Emission ◽  
Slow Kinetics ◽  
Early Proof ◽  
Antibody Conjugation ◽  
Imaging Strategy ◽  
The Stability

Positron emission tomography (PET) imaging with biological macromolecules greatly expands the possibilities of molecular imaging. There are, however, practical aspects limiting the potential of the approach, including the dosimetric consequences of the slow kinetics of radiolabeled biomacromolecules. Pretargeting strategies have led to impactful improvements in the field but are themselves limited by shortcomings of available bioconjugation methodology. We report our initial findings concerning the suitability of the adamantane/cucurbit[7]uril system for pretargeted immuno-PET imaging and provide proof-of-concept PET/computed tomography imaging experiments to establish the stability and rapid formation of host–guest complexes in vivo. The adamantane/cucurbit[7]uril system itself without antibody conjugation has shown remarkably fast association kinetics and clearance in vivo. We further demonstrate the modulation of biodistribution achievable by cucurbituril complexation with relevance for pharmaceutical formulation as well as the radiosynthetic access to relevant reporter molecules labeled with 11C or 18F. This work, an early proof-of-concept, supports the notion that the adamantane/cucurbit[7]uril system warrants further exploration in pretargeted PET imaging applications.

scholarly journals Development of a blood sample detector for multi-tracer positron emission tomography using gamma spectroscopy

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Carlos Velasco ◽  
Adriana Mota-Cobián ◽  
Jesús Mateo ◽  
Samuel España
Keyword(s):  
Positron Emission Tomography ◽  
Blood Sample ◽  
Pet Imaging ◽  
Spectroscopic Analysis ◽  
Gamma Spectroscopy ◽  
Emission Tomography ◽  
Blood Samples ◽  
Positron Emission

Abstract Background Multi-tracer positron emission tomography (PET) imaging can be accomplished by applying multi-tracer compartment modeling. Recently, a method has been proposed in which the arterial input functions (AIFs) of the multi-tracer PET scan are explicitly derived. For that purpose, a gamma spectroscopic analysis is performed on blood samples manually withdrawn from the patient when at least one of the co-injected tracers is based on a non-pure positron emitter. Alternatively, these blood samples required for the spectroscopic analysis may be obtained and analyzed on site by an automated detection device, thus minimizing analysis time and radiation exposure of the operating personnel. In this work, a new automated blood sample detector based on silicon photomultipliers (SiPMs) for single- and multi-tracer PET imaging is presented, characterized, and tested in vitro and in vivo. Results The detector presented in this work stores and analyzes on-the-fly single and coincidence detected events. A sensitivity of 22.6 cps/(kBq/mL) and 1.7 cps/(kBq/mL) was obtained for single and coincidence events respectively. An energy resolution of 35% full-width-half-maximum (FWHM) at 511 keV and a minimum detectable activity of 0.30 ± 0.08 kBq/mL in single mode were obtained. The in vivo AIFs obtained with the detector show an excellent Pearson’s correlation (r = 0.996, p < 0.0001) with the ones obtained from well counter analysis of discrete blood samples. Moreover, in vitro experiments demonstrate the capability of the detector to apply the gamma spectroscopic analysis on a mixture of 68Ga and 18F and separate the individual signal emitted from each one. Conclusions Characterization and in vivo evaluation under realistic experimental conditions showed that the detector proposed in this work offers excellent sensibility and stability. The device also showed to successfully separate individual signals emitted from a mixture of radioisotopes. Therefore, the blood sample detector presented in this study allows fully automatic AIFs measurements during single- and multi-tracer PET studies.

scholarly journals Optimised GMP-compliant production of [18F]DPA-714 on the Trasis AllinOne module

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Klaudia A. Cybulska ◽  
Vera Bloemers ◽  
Lars R. Perk ◽  
Peter Laverman
Keyword(s):  
Significant Degree ◽  
Translocator Protein ◽  
Positron Emission ◽  
Leaving Group ◽  
Inflammatory Processes ◽  
Single Production ◽  
Translocator Protein 18 Kda ◽  
Radiochemical Yields ◽  
Specific Ligand

Abstract Background The translocator protein 18 kDa is recognised as an important biomarker for neuroinflammation due to its soaring expression in microglia. This process is common for various neurological disorders. DPA-714 is a potent TSPO-specific ligand which found its use in Positron Emission Tomography following substitution of fluorine-19 with fluorine-18, a positron-emitting radionuclide. [18F]DPA-714 enables visualisation of inflammatory processes in vivo non-invasively. Radiolabelling of this tracer is well described in literature, including validation for clinical use. Here, we report significant enhancements to the process which resulted in the design of a fully GMP-compliant robust synthesis of [18F]DPA-714 on a popular cassette-based system, Trasis AllinOne, boosting reliability, throughput, and introducing a significant degree of simplicity. Results [18F]DPA-714 was synthesised using the classic nucleophilic aliphatic substitution on a good leaving group, tosylate, with [18F]fluoride using tetraethylammonium bicarbonate in acetonitrile at 100∘C. The process was fully automated on a Trasis AllinOne synthesiser using an in-house designed cassette and sequence. With a relatively small precursor load of 4 mg, [18F]DPA-714 was obtained with consistently high radiochemical yields of 55-71% (n=6) and molar activities of 117-350 GBq/µmol at end of synthesis. With a single production batch, starting with 31-42 GBq of [18F]fluoride, between 13-20 GBq of the tracer can be produced, enabling multi-centre studies. Conclusion To the best of our knowledge, the process presented herein is the most efficient [18F]DPA-714 synthesis, with advantageous GMP compliance. The use of a Trasis AllinOne synthesiser increases reliability and allows rapid training of production staff.

scholarly journals Simplified 89Zr-Labeling Protocol of Oxine (8-Hydroxyquinoline) Enabling Prolonged Tracking of Liposome-Based Nanomedicines and Cells

Pharmaceutics ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1097
Author(s):  
Andras Polyak ◽  
Jens P. Bankstahl ◽  
Karen F. W. Besecke ◽  
Constantin Hozsa ◽  
Wiebke Triebert ◽  
...  
Keyword(s):  
Reaction Times ◽  
Extraction Methods ◽  
Cell Labeling ◽  
Size Exclusion ◽  
Cell Therapies ◽  
Biodistribution Studies ◽  
Positron Emission ◽  
Human Ipscs ◽  
Radiochemical Yields

In this work, a method for the preparation of the highly lipophilic labeling synthon [89Zr]Zr(oxinate)4 was optimized for the radiolabeling of liposomes and human induced pluripotent stem cells (hiPSCs). The aim was to establish a robust and reliable labeling protocol for enabling up to one week positron emission tomography (PET) tracing of lipid-based nanomedicines and transplanted or injected cells, respectively. [89Zr]Zr(oxinate)4 was prepared from oxine (8-hydroxyquinoline) and [89Zr]Zr(OH)2(C2O4). Earlier introduced liquid–liquid extraction methods were simplified by the optimization of buffering, pH, temperature and reaction times. For quality control, thin-layer chromatography (TLC), size-exclusion chromatography (SEC) and centrifugation were employed. Subsequently, the 89Zr-complex was incorporated into liposome formulations. PET/CT imaging of 89Zr-labeled liposomes was performed in healthy mice. Cell labeling was accomplished in PBS using suspensions of 3 × 106 hiPSCs, each. [89Zr]Zr(oxinate)4 was synthesized in very high radiochemical yields of 98.7% (96.8% ± 2.8%). Similarly, high internalization rates (≥90%) of [89Zr]Zr(oxinate)4 into liposomes were obtained over an 18 h incubation period. MicroPET and biodistribution studies confirmed the labeled nanocarriers’ in vivo stability. Human iPSCs incorporated the labeling agent within 30 min with ~50% efficiency. Prolonged PET imaging is an ideal tool in the development of lipid-based nanocarriers for drug delivery and cell therapies. To this end, a reliable and reproducible 89Zr radiolabeling method was developed and tested successfully in a model liposome system and in hiPSCs alike.

scholarly journals 11C- and 18F-Radiotracers for In Vivo Imaging of the Dopamine System: Past, Present and Future

Biomedicines ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 108
Author(s):  
Michael R. Kilbourn
Keyword(s):  
Pet Imaging ◽  
In Vivo Imaging ◽  
Dopamine Synthesis ◽  
Dopamine System ◽  
Synaptic Release ◽  
Positron Emission ◽  
The Central Nervous System ◽  
Pet Radiotracers ◽  
Selection Of

The applications of positron emission tomography (PET) imaging to study brain biochemistry, and in particular the aspects of dopamine neurotransmission, have grown significantly over the 40 years since the first successful in vivo imaging studies in humans. In vivo PET imaging of dopaminergic functions of the central nervous system (CNS) including dopamine synthesis, vesicular storage, synaptic release and receptor binding, and reuptake processes, are now routinely used for studies in neurology, psychiatry, drug abuse and addiction, and drug development. Underlying these advances in PET imaging has been the development of the unique radiotracers labeled with positron-emitting radionuclides such as carbon-11 and fluorine-18. This review focuses on a selection of the more accepted and utilized PET radiotracers currently available, with a look at their past, present and future.

STING-driven interferon signaling triggers metabolic alterations in pancreas cancer cells visualized by [18F]FLT PET imaging

2021 ◽  
Vol 118 (36) ◽  
pp. e2105390118 ◽  
Author(s):  
Keke Liang ◽  
Evan R. Abt ◽  
Thuc M. Le ◽  
Arthur Cho ◽  
Amanda M. Dann ◽  
...  
Keyword(s):  
Pet Imaging ◽  
Cell Metabolism ◽  
Nucleotide Metabolism ◽  
Type I Interferons ◽  
Ductal Adenocarcinoma ◽  
Type I ◽  
Flt Pet ◽  
Positron Emission ◽  
Pharmacodynamic Biomarkers

Type I interferons (IFNs) are critical effectors of emerging cancer immunotherapies designed to activate pattern recognition receptors (PRRs). A challenge in the clinical translation of these agents is the lack of noninvasive pharmacodynamic biomarkers that indicate increased intratumoral IFN signaling following PRR activation. Positron emission tomography (PET) imaging enables the visualization of tissue metabolic activity, but whether IFN signaling–induced alterations in tumor cell metabolism can be detected using PET has not been investigated. We found that IFN signaling augments pancreatic ductal adenocarcinoma (PDAC) cell nucleotide metabolism via transcriptional induction of metabolism-associated genes including thymidine phosphorylase (TYMP). TYMP catalyzes the first step in the catabolism of thymidine, which competitively inhibits intratumoral accumulation of the nucleoside analog PET probe 3′-deoxy-3′-[18F]fluorothymidine ([18F]FLT). Accordingly, IFN treatment up-regulates cancer cell [18F]FLT uptake in the presence of thymidine, and this effect is dependent upon TYMP expression. In vivo, genetic activation of stimulator of interferon genes (STING), a PRR highly expressed in PDAC, enhances the [18F]FLT avidity of xenograft tumors. Additionally, small molecule STING agonists trigger IFN signaling–dependent TYMP expression in PDAC cells and increase tumor [18F]FLT uptake in vivo following systemic treatment. These findings indicate that [18F]FLT accumulation in tumors is sensitive to IFN signaling and that [18F]FLT PET may serve as a pharmacodynamic biomarker for STING agonist–based therapies in PDAC and possibly other malignancies characterized by elevated STING expression.

scholarly journals [18F]AZD2461, an Insight on Difference in PARP Binding Profiles for DNA Damage Response PET Imaging

2020 ◽  
Vol 22 (5) ◽  
pp. 1226-1234
Author(s):  
Florian Guibbal ◽  
Samantha L. Hopkins ◽  
Anna Pacelli ◽  
Patrick G. Isenegger ◽  
Michael Mosley ◽  
...  
Keyword(s):  
Pet Imaging ◽  
Parp Inhibitor ◽  
Parp Inhibitors ◽  
Cell Uptake ◽  
Pancreatic Cell ◽  
Anti Cancer ◽  
Damage Response ◽  
Automated Procedures

Abstract Background Poly (ADP-ribose) polymerase (PARP) inhibitors are extensively studied and used as anti-cancer drugs, as single agents or in combination with other therapies. Most radiotracers developed to date have been chosen on the basis of strong PARP1–3 affinity. Herein, we propose to study AZD2461, a PARP inhibitor with lower affinity towards PARP3, and to investigate its potential for PARP targeting in vivo. Methods Using the Cu-mediated 18F-fluorodeboronation of a carefully designed radiolabelling precursor, we accessed the 18F-labelled isotopologue of the PARP inhibitor AZD2461. Cell uptake of [18F]AZD2461 in vitro was assessed in a range of pancreatic cell lines (PSN-1, PANC-1, CFPAC-1 and AsPC-1) to assess PARP expression and in vivo in xenograft-bearing mice. Blocking experiments were performed with both olaparib and AZD2461. Results [18F]AZD2461 was efficiently radiolabelled via both manual and automated procedures (9 % ± 3 % and 3 % ± 1 % activity yields non-decay corrected). [18F]AZD2461 was taken up in vivo in PARP1-expressing tumours, and the highest uptake was observed for PSN-1 cells (7.34 ± 1.16 %ID/g). In vitro blocking experiments showed a lesser ability of olaparib to reduce [18F]AZD2461 binding, indicating a difference in selectivity between olaparib and AZD2461. Conclusion Taken together, we show the importance of screening the PARP selectivity profile of radiolabelled PARP inhibitors for use as PET imaging agents.

scholarly journals Imaging Cardiovascular and Lung Macrophages With the Positron Emission Tomography Sensor 64 Cu-Macrin in Mice, Rabbits, and Pigs

2020 ◽  
Vol 13 (10) ◽  
Author(s):  
Matthias Nahrendorf ◽  
Friedrich Felix Hoyer ◽  
Anu E. Meerwaldt ◽  
Mandy M.T. van Leent ◽  
Max L. Senders ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Flow Cytometry ◽  
Confocal Microscopy ◽  
Pet Imaging ◽  
Near Infrared ◽  
Emission Tomography ◽  
Imaging Biomarker ◽  
Positron Emission ◽  
Pulmonary Macrophages

Background: Macrophages, innate immune cells that reside in all organs, defend the host against infection and injury. In the heart and vasculature, inflammatory macrophages also enhance tissue damage and propel cardiovascular diseases. Methods: We here use in vivo positron emission tomography (PET) imaging, flow cytometry, and confocal microscopy to evaluate quantitative noninvasive assessment of cardiac, arterial, and pulmonary macrophages using the nanotracer 64 Cu-Macrin—a 20-nm spherical dextran nanoparticle assembled from nontoxic polyglucose. Results: PET imaging using 64 Cu-Macrin faithfully reported accumulation of macrophages in the heart and lung of mice with myocardial infarction, sepsis, or pneumonia. Flow cytometry and confocal microscopy detected the near-infrared fluorescent version of the nanoparticle ( VT680 Macrin) primarily in tissue macrophages. In 5-day-old mice, 64 Cu-Macrin PET imaging quantified physiologically more numerous cardiac macrophages. Upon intravenous administration of 64 Cu-Macrin in rabbits and pigs, we detected heightened macrophage numbers in the infarcted myocardium, inflamed lung regions, and atherosclerotic plaques using a clinical PET/magnetic resonance imaging scanner. Toxicity studies in rats and human dosimetry estimates suggest that 64 Cu-Macrin is safe for use in humans. Conclusions: Taken together, these results indicate 64 Cu-Macrin could serve as a facile PET nanotracer to survey spatiotemporal macrophage dynamics during various physiological and pathological conditions. 64 Cu-Macrin PET imaging could stage inflammatory cardiovascular disease activity, assist disease management, and serve as an imaging biomarker for emerging macrophage-targeted therapeutics.

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