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Wright JS, Sharninghausen LS, Lapsys A, Sanford MS, Scott PJH. C-H Labeling with [ 18F]Fluoride: An Emerging Methodology in Radiochemistry. ACS CENTRAL SCIENCE 2024; 10:1674-1688. [PMID: 39364044 PMCID: PMC11447958 DOI: 10.1021/acscentsci.4c00997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/20/2024] [Revised: 08/07/2024] [Accepted: 08/08/2024] [Indexed: 10/05/2024]
Abstract
Fluorine-18 is the most routinely employed radioisotope for positron emission tomography, a dynamic nuclear imaging modality. The radiolabeling of C-H bonds is an attractive method for installing fluorine-18 into organic molecules since it can preclude the cumbersome prefunctionalization of requisite precursors. Although electrophilic "F+" reagents (e.g., [18F]F2) are effective for C-H radiolabeling, state-of-the-art methodologies predominantly leverage high molar activity nucleophilic [18F]fluoride sources (e.g., [18F]KF) with substantial (pre)clinical advantages. Reflecting this, multiple nucleophilic C-H radiolabeling techniques of high utility have been disclosed over the past decade. However, the adoption of (pre)clinical C-H radiolabeling has been slow, and PET imaging agents are still routinely prepared via methods that, despite a high level of practicality, are limited in scope (e.g., SNAr, SN2 radiofluorinations). By addressing the drawbacks inherent to these strategies, C-H radiofluorination and radiofluoroalkylation carry the potential to complement and supersede state-of-the-art labeling methods, facilitating the expedited production of PET agents used in disease staging and drug development. In this Outlook, we showcase recent C-H labeling developments with fluorine-18 and discuss the merits, potential, and barriers to adoption in (pre)clinical settings. In addition, we highlight trends, challenges, and directions in this emerging field of study.
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Affiliation(s)
- Jay S Wright
- Department of Radiology, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Liam S Sharninghausen
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Alex Lapsys
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Melanie S Sanford
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Peter J H Scott
- Department of Radiology, University of Michigan, Ann Arbor, Michigan 48109, United States
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2
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Lin D, Lechermann LM, Huestis MP, Marik J, Sap JBI. Light-Driven Radiochemistry with Fluorine-18, Carbon-11 and Zirconium-89. Angew Chem Int Ed Engl 2024; 63:e202317136. [PMID: 38135665 DOI: 10.1002/anie.202317136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2023] [Revised: 12/18/2023] [Accepted: 12/20/2023] [Indexed: 12/24/2023]
Abstract
This review discusses recent advances in light-driven radiochemistry for three key isotopes: fluorine-18, carbon-11, and zirconium-89, and their applications in positron emission tomography (PET). In the case of fluorine-18, the predominant approach involves the use of cyclotron-produced [18F]fluoride or reagents derived thereof. Light serves to activate either the substrate or the fluorine-18 labeled reagent. Advancements in carbon-11 photo-mediated radiochemistry have been leveraged for the radiolabeling of small molecules, achieving various transformations, including 11C-methylation, 11C-carboxylation, 11C-carbonylation, and 11C-cyanation. Contrastingly, zirconium-89 photo-mediated radiochemistry differs from fluorine-18 and carbon-11 approaches. In these cases, light facilitates a postlabeling click reaction, which has proven valuable for the labeling of large biomolecules such as monoclonal antibodies (mAbs). New technological developments, such as the incorporation of photoreactors in commercial radiosynthesizers, illustrate the commitment the field is making in embracing photochemistry. Taken together, these advances in photo-mediated radiochemistry enable radiochemists to apply new retrosynthetic strategies in accessing novel PET radiotracers.
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Affiliation(s)
- Daniel Lin
- Department of Translational Imaging, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA
- Current address: University of Southern California Department of Chemistry, Loker Hydrocarbon Research Institute, 837 Bloom Walk, Los Angeles, CA 90089, USA
| | - Laura M Lechermann
- Department of Translational Imaging, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Malcolm P Huestis
- Discovery Chemistry, Genentech, Inc., DNA Way, South San Francisco, CA 94080, USA
| | - Jan Marik
- Department of Translational Imaging, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA
- Discovery Chemistry, Genentech, Inc., DNA Way, South San Francisco, CA 94080, USA
| | - Jeroen B I Sap
- Department of Translational Imaging, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA
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3
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Uzuegbunam BC, Rummel C, Librizzi D, Culmsee C, Hooshyar Yousefi B. Radiotracers for Imaging of Inflammatory Biomarkers TSPO and COX-2 in the Brain and in the Periphery. Int J Mol Sci 2023; 24:17419. [PMID: 38139248 PMCID: PMC10743508 DOI: 10.3390/ijms242417419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 12/01/2023] [Accepted: 12/04/2023] [Indexed: 12/24/2023] Open
Abstract
Inflammation involves the activation of innate immune cells and is believed to play an important role in the development and progression of both infectious and non-infectious diseases such as neurodegeneration, autoimmune diseases, pulmonary and cancer. Inflammation in the brain is marked by the upregulation of translocator protein (TSPO) in microglia. High TSPO levels are also found, for example, in macrophages in cases of rheumatoid arthritis and in malignant tumor cells compared to their relatively low physiological expression. The same applies for cyclooxgenase-2 (COX-2), which is constitutively expressed in the kidney, brain, thymus and gastrointestinal tract, but induced in microglia, macrophages and synoviocytes during inflammation. This puts TSPO and COX-2 in the spotlight as important targets for the diagnosis of inflammation. Imaging modalities, such as positron emission tomography and single-photon emission tomography, can be used to localize inflammatory processes and to track their progression over time. They could also enable the monitoring of the efficacy of therapy and predict its outcome. This review focuses on the current development of PET and SPECT tracers, not only for the detection of neuroinflammation, but also for emerging diagnostic measures in infectious and other non-infectious diseases such as rheumatic arthritis, cancer, cardiac inflammation and in lung diseases.
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Affiliation(s)
| | - Christoph Rummel
- Institute of Veterinary Physiology and Biochemistry, Justus Liebig University Giessen, 35392 Gießen, Germany;
- Center for Mind Brain and Behavior, Universities Giessen and Marburg, 35043 Marburg, Germany;
| | - Damiano Librizzi
- Department of Nuclear Medicine, Philipps University of Marburg, 35043 Marburg, Germany;
| | - Carsten Culmsee
- Center for Mind Brain and Behavior, Universities Giessen and Marburg, 35043 Marburg, Germany;
- Institute of Pharmacology and Clinical Pharmacy, Philipps University of Marburg, 35037 Marburg, Germany
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4
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Neumann KD, Broshek DK, Newman BT, Druzgal TJ, Kundu BK, Resch JE. Concussion: Beyond the Cascade. Cells 2023; 12:2128. [PMID: 37681861 PMCID: PMC10487087 DOI: 10.3390/cells12172128] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Revised: 08/14/2023] [Accepted: 08/17/2023] [Indexed: 09/09/2023] Open
Abstract
Sport concussion affects millions of athletes each year at all levels of sport. Increasing evidence demonstrates clinical and physiological recovery are becoming more divergent definitions, as evidenced by several studies examining blood-based biomarkers of inflammation and imaging studies of the central nervous system (CNS). Recent studies have shown elevated microglial activation in the CNS in active and retired American football players, as well as in active collegiate athletes who were diagnosed with a concussion and returned to sport. These data are supportive of discordance in clinical symptomology and the inflammatory response in the CNS upon symptom resolution. In this review, we will summarize recent advances in the understanding of the inflammatory response associated with sport concussion and broader mild traumatic brain injury, as well as provide an outlook for important research questions to better align clinical and physiological recovery.
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Affiliation(s)
- Kiel D. Neumann
- Department of Diagnostic Imaging, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA;
| | - Donna K. Broshek
- Department of Psychiatry and Neurobehavioral Sciences, University of Virginia, Charlottesville, VA 22903, USA;
| | - Benjamin T. Newman
- Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA 22903, USA; (B.T.N.); (T.J.D.); (B.K.K.)
| | - T. Jason Druzgal
- Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA 22903, USA; (B.T.N.); (T.J.D.); (B.K.K.)
| | - Bijoy K. Kundu
- Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA 22903, USA; (B.T.N.); (T.J.D.); (B.K.K.)
| | - Jacob E. Resch
- Department of Kinesiology, University of Virginia, Charlottesville, VA 22903, USA
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5
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Berger M, Lenhard MS, Waldvogel SR. Para-Fluorination of Anilides Using Electrochemically Generated Hypervalent Iodoarenes. Chemistry 2022; 28:e202201029. [PMID: 35510825 PMCID: PMC9401020 DOI: 10.1002/chem.202201029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Indexed: 11/23/2022]
Abstract
The para-selective fluorination reaction of anilides using electrochemically generated hypervalent ArIF2 is reported, with Et3 N ⋅ 5HF serving as fluoride source and as supporting electrolyte. This electrochemical reaction is characterized by a simple set-up, easy scalability and affords a broad variety of fluorinated anilides from easily accessible anilides in good yields up to 86 %.
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Affiliation(s)
- Michael Berger
- Department of ChemistryJohannes Gutenberg University MainzDuesbergweg 10–1455128MainzGermany
| | - Marola S. Lenhard
- Department of ChemistryJohannes Gutenberg University MainzDuesbergweg 10–1455128MainzGermany
| | - Siegfried R. Waldvogel
- Department of ChemistryJohannes Gutenberg University MainzDuesbergweg 10–1455128MainzGermany
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6
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Kaur J, Bhardwaj A, Wuest F. Fluorine-18 Labelled Radioligands for PET Imaging of Cyclooxygenase-2. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27123722. [PMID: 35744851 PMCID: PMC9227202 DOI: 10.3390/molecules27123722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 06/03/2022] [Accepted: 06/07/2022] [Indexed: 11/18/2022]
Abstract
Molecular imaging probes enable the early and accurate detection of disease-specific biomarkers and facilitate personalized treatment of many chronic diseases, including cancer. Among current clinically used functional imaging modalities, positron emission tomography (PET) plays a significant role in cancer detection and in monitoring the response to therapeutic interventions. Several preclinical and clinical studies have demonstrated the crucial involvement of cyclooxygenase-2 (COX-2) isozyme in cancer development and progression, making COX-2 a promising cancer biomarker. A variety of COX-2-targeting PET radioligands has been developed based on anti-inflammatory drugs and selective COX-2 inhibitors. However, many of those suffer from non-specific binding and insufficient metabolic stability. This article highlights examples of COX-2-targeting PET radioligands labelled with the short-lived positron emitter 18F, including radiosynthesis and PET imaging studies published in the last decade (2012–2021).
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Affiliation(s)
- Jatinder Kaur
- Department of Oncology, University of Alberta, Edmonton, AB T6G 1Z2, Canada;
- Correspondence: (J.K.); (F.W.)
| | - Atul Bhardwaj
- Department of Oncology, University of Alberta, Edmonton, AB T6G 1Z2, Canada;
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, AB T6G 1Z2, Canada
| | - Frank Wuest
- Department of Oncology, University of Alberta, Edmonton, AB T6G 1Z2, Canada;
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, AB T6G 1Z2, Canada
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 1Z2, Canada
- Correspondence: (J.K.); (F.W.)
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7
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Kenou BV, Manly LS, Rubovits SB, Umeozulu SA, Van Buskirk MG, Zhang AS, Pike VW, Zanotti-Fregonara P, Henter ID, Innis RB. Cyclooxygenases as Potential PET Imaging Biomarkers to Explore Neuroinflammation in Dementia. J Nucl Med 2022; 63:53S-59S. [PMID: 35649646 DOI: 10.2967/jnumed.121.263199] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 01/12/2022] [Indexed: 12/18/2022] Open
Abstract
The most frequently studied target of neuroinflammation using PET is 18-kDa translocator protein, but its limitations have spurred the molecular imaging community to find more promising targets. This article reviews the development of PET radioligands for cyclooxygenase (COX) subtypes 1 and 2, enzymes that catalyze the production of inflammatory prostanoids in the periphery and brain. Although both isozymes produce the same precursor compound, prostaglandin H2, they have distinct functions based on their differential cellular localization in the periphery and brain. For example, COX-1 is located primarily in microglia, a resident inflammatory cell in the brain whose role in producing inflammatory cytokines is well documented. In contrast, COX-2 is located primarily in neurons and can be markedly upregulated by inflammatory and excitatory stimuli, but its functions are poorly understood. This article reviews these 2 isozymes as biomarkers of neuroinflammation, as well as the radioligands that have recently been developed to image them in animals and humans. To place this work into context, the properties of COX-1 and COX-2 are compared with 18-kDa translocator protein, with special consideration of their application in Alzheimer disease as a representative neurodegenerative disorder.
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Affiliation(s)
- Bruny V Kenou
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland
| | - Lester S Manly
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland
| | - Sara B Rubovits
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland
| | - Somachukwu A Umeozulu
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland
| | - Maia G Van Buskirk
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland
| | - Andrea S Zhang
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland
| | - Victor W Pike
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland
| | - Paolo Zanotti-Fregonara
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland
| | - Ioline D Henter
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland
| | - Robert B Innis
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland
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8
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Tay NES, Lehnherr D, Rovis T. Photons or Electrons? A Critical Comparison of Electrochemistry and Photoredox Catalysis for Organic Synthesis. Chem Rev 2022; 122:2487-2649. [PMID: 34751568 PMCID: PMC10021920 DOI: 10.1021/acs.chemrev.1c00384] [Citation(s) in RCA: 143] [Impact Index Per Article: 71.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Redox processes are at the heart of synthetic methods that rely on either electrochemistry or photoredox catalysis, but how do electrochemistry and photoredox catalysis compare? Both approaches provide access to high energy intermediates (e.g., radicals) that enable bond formations not constrained by the rules of ionic or 2 electron (e) mechanisms. Instead, they enable 1e mechanisms capable of bypassing electronic or steric limitations and protecting group requirements, thus enabling synthetic chemists to disconnect molecules in new and different ways. However, while providing access to similar intermediates, electrochemistry and photoredox catalysis differ in several physical chemistry principles. Understanding those differences can be key to designing new transformations and forging new bond disconnections. This review aims to highlight these differences and similarities between electrochemistry and photoredox catalysis by comparing their underlying physical chemistry principles and describing their impact on electrochemical and photochemical methods.
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Affiliation(s)
- Nicholas E. S. Tay
- Department of Chemistry, Columbia University, New York, New York, 10027, United States
| | - Dan Lehnherr
- Process Research and Development, Merck & Co., Inc., Rahway, New Jersey 07065, United States
| | - Tomislav Rovis
- Department of Chemistry, Columbia University, New York, New York, 10027, United States
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9
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Chen Z, Haider A, Chen J, Xiao Z, Gobbi L, Honer M, Grether U, Arnold SE, Josephson L, Liang SH. The Repertoire of Small-Molecule PET Probes for Neuroinflammation Imaging: Challenges and Opportunities beyond TSPO. J Med Chem 2021; 64:17656-17689. [PMID: 34905377 PMCID: PMC9094091 DOI: 10.1021/acs.jmedchem.1c01571] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Neuroinflammation is an adaptive response of the central nervous system to diverse potentially injurious stimuli, which is closely associated with neurodegeneration and typically characterized by activation of microglia and astrocytes. As a noninvasive and translational molecular imaging tool, positron emission tomography (PET) could provide a better understanding of neuroinflammation and its role in neurodegenerative diseases. Ligands to translator protein (TSPO), a putative marker of neuroinflammation, have been the most commonly studied in this context, but they suffer from serious limitations. Herein we present a repertoire of different structural chemotypes and novel PET ligand design for classical and emerging neuroinflammatory targets beyond TSPO. We believe that this Perspective will support multidisciplinary collaborations in academic and industrial institutions working on neuroinflammation and facilitate the progress of neuroinflammation PET probe development for clinical use.
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Affiliation(s)
- Zhen Chen
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital & Department of Radiology, Harvard Medical School, Boston, MA, 02114, United States
| | - Ahmed Haider
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital & Department of Radiology, Harvard Medical School, Boston, MA, 02114, United States
| | - Jiahui Chen
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital & Department of Radiology, Harvard Medical School, Boston, MA, 02114, United States
| | - Zhiwei Xiao
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital & Department of Radiology, Harvard Medical School, Boston, MA, 02114, United States
| | - Luca Gobbi
- Pharma Research and Early Development, F. Hoffmann-La Roche Ltd, CH-4070 Basel, Switzerland
| | - Michael Honer
- Pharma Research and Early Development, F. Hoffmann-La Roche Ltd, CH-4070 Basel, Switzerland
| | - Uwe Grether
- Pharma Research and Early Development, F. Hoffmann-La Roche Ltd, CH-4070 Basel, Switzerland
| | - Steven E. Arnold
- Department of Neurology and the Massachusetts Alzheimer’s Disease Research Center, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Charlestown, Massachusetts 02129, USA
| | - Lee Josephson
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital & Department of Radiology, Harvard Medical School, Boston, MA, 02114, United States
| | - Steven H. Liang
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital & Department of Radiology, Harvard Medical School, Boston, MA, 02114, United States
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10
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Ajenjo J, Destro G, Cornelissen B, Gouverneur V. Closing the gap between 19F and 18F chemistry. EJNMMI Radiopharm Chem 2021; 6:33. [PMID: 34564781 PMCID: PMC8464544 DOI: 10.1186/s41181-021-00143-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 08/03/2021] [Indexed: 11/10/2022] Open
Abstract
Positron emission tomography (PET) has become an invaluable tool for drug discovery and diagnosis. The positron-emitting radionuclide fluorine-18 is frequently used in PET radiopharmaceuticals due to its advantageous characteristics; hence, methods streamlining access to 18F-labelled radiotracers can make a direct impact in medicine. For many years, access to 18F-labelled radiotracers was limited by the paucity of methodologies available, and the poor diversity of precursors amenable to 18F-incorporation. During the last two decades, 18F-radiochemistry has progressed at a fast pace with the appearance of numerous methodologies for late-stage 18F-incorporation onto complex molecules from a range of readily available precursors including those that do not require pre-functionalisation. Key to these advances is the inclusion of new activation modes to facilitate 18F-incorporation. Specifically, new advances in late-stage 19F-fluorination under transition metal catalysis, photoredox catalysis, and organocatalysis combined with the availability of novel 18F-labelled fluorination reagents have enabled the invention of novel processes for 18F-incorporation onto complex (bio)molecules. This review describes these major breakthroughs with a focus on methodologies for C-18F bond formation. This reinvigorated interest in 18F-radiochemistry that we have witnessed in recent years has made a direct impact on 19F-chemistry with many laboratories refocusing their efforts on the development of methods using nucleophilic fluoride instead of fluorination reagents derived from molecular fluorine gas.
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Affiliation(s)
- Javier Ajenjo
- Medical Research Council Oxford Institute for Radiation Oncology, University of Oxford, Oxford, OX3 7DQ, UK
| | - Gianluca Destro
- Medical Research Council Oxford Institute for Radiation Oncology, University of Oxford, Oxford, OX3 7DQ, UK
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, OX1 3TA, UK
| | - Bart Cornelissen
- Medical Research Council Oxford Institute for Radiation Oncology, University of Oxford, Oxford, OX3 7DQ, UK
| | - Véronique Gouverneur
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, OX1 3TA, UK.
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11
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Beaino W, Janssen B, Vugts DJ, de Vries HE, Windhorst AD. Towards PET imaging of the dynamic phenotypes of microglia. Clin Exp Immunol 2021; 206:282-300. [PMID: 34331705 PMCID: PMC8561701 DOI: 10.1111/cei.13649] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 07/21/2021] [Accepted: 07/21/2021] [Indexed: 02/06/2023] Open
Abstract
There is increasing evidence showing the heterogeneity of microglia activation in neuroinflammatory and neurodegenerative diseases. It has been hypothesized that pro‐inflammatory microglia are detrimental and contribute to disease progression, while anti‐inflammatory microglia play a role in damage repair and remission. The development of therapeutics targeting the deleterious glial activity and modulating it into a regenerative phenotype relies heavily upon a clearer understanding of the microglia dynamics during disease progression and the ability to monitor therapeutic outcome in vivo. To that end, molecular imaging techniques are required to assess microglia dynamics and study their role in disease progression as well as to evaluate the outcome of therapeutic interventions. Positron emission tomography (PET) is such a molecular imaging technique, and provides unique capabilities for non‐invasive quantification of neuroinflammation and has the potential to discriminate between microglia phenotypes and define their role in the disease process. However, several obstacles limit the possibility for selective in vivo imaging of microglia phenotypes mainly related to the poor characterization of specific targets that distinguish the two ends of the microglia activation spectrum and lack of suitable tracers. PET tracers targeting translocator protein 18 kDa (TSPO) have been extensively explored, but despite the success in evaluating neuroinflammation they failed to discriminate between microglia activation statuses. In this review, we highlight the current knowledge on the microglia phenotypes in the major neuroinflammatory and neurodegenerative diseases. We also discuss the current and emerging PET imaging targets, the tracers and their potential in discriminating between the pro‐ and anti‐inflammatory microglia activation states.
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Affiliation(s)
- Wissam Beaino
- Department of Radiology and Nuclear Medicine, Tracer Center Amsterdam, Amsterdam UMC, Vrije Universiteit, Amsterdam, the Netherlands
| | - Bieneke Janssen
- Department of Radiology and Nuclear Medicine, Tracer Center Amsterdam, Amsterdam UMC, Vrije Universiteit, Amsterdam, the Netherlands
| | - Danielle J Vugts
- Department of Radiology and Nuclear Medicine, Tracer Center Amsterdam, Amsterdam UMC, Vrije Universiteit, Amsterdam, the Netherlands
| | - Helga E de Vries
- Department of Molecular Cell Biology and Immunology, MS Center Amsterdam, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit, Amsterdam, the Netherlands
| | - Albert D Windhorst
- Department of Radiology and Nuclear Medicine, Tracer Center Amsterdam, Amsterdam UMC, Vrije Universiteit, Amsterdam, the Netherlands
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12
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Prabhakaran J, Molotkov A, Mintz A, Mann JJ. Progress in PET Imaging of Neuroinflammation Targeting COX-2 Enzyme. Molecules 2021; 26:molecules26113208. [PMID: 34071951 PMCID: PMC8198977 DOI: 10.3390/molecules26113208] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 05/12/2021] [Accepted: 05/24/2021] [Indexed: 01/01/2023] Open
Abstract
Neuroinflammation and cyclooxygenase-2 (COX-2) upregulation are associated with the pathogenesis of degenerative brain diseases such as Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), epilepsy, and a response to traumatic brain injury (TBI) or stroke. COX-2 is also induced in acute pain, depression, schizophrenia, various cancers, arthritis and in acute allograft rejection. Positron emission tomography (PET) imaging allows for the direct measurement of in vivo COX-2 upregulation and thereby enables disease staging, therapy evaluation and aid quantifying target occupancy of novel nonsteroidal anti-inflammatory drugs or NSAIDs. Thus far, no clinically useful radioligand is established for monitoring COX-2 induction in brain diseases due to the delay in identifying qualified COX-2-selective inhibitors entering the brain. This review examines radiolabeled COX-2 inhibitors reported in the past decade and identifies the most promising radioligands for development as clinically useful PET radioligands. Among the radioligands reported so far, the three tracers that show potential for clinical translation are, [11CTMI], [11C]MC1 and [18F]MTP. These radioligands demonstrated BBB permeablity and in vivo binding to constitutive COX-2 in the brain or induced COX-2 during neuroinflammation.
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Affiliation(s)
- Jaya Prabhakaran
- Department of Psychiatry, Columbia University Medical Center, New York, NY 10032, USA;
- Correspondence:
| | - Andrei Molotkov
- Department of Radiology, Columbia University Medical Center, New York, NY 10032, USA; (A.M.); (A.M.)
| | - Akiva Mintz
- Department of Radiology, Columbia University Medical Center, New York, NY 10032, USA; (A.M.); (A.M.)
- Area Molecular Imaging and Neuropathology, New York State Psychiatric Institute, New York, NY 10032, USA
| | - J. John Mann
- Department of Psychiatry, Columbia University Medical Center, New York, NY 10032, USA;
- Area Molecular Imaging and Neuropathology, New York State Psychiatric Institute, New York, NY 10032, USA
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13
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Hernández-Valdés D, Sadeghi S. Electrochemical Radiofluorination of Small Molecules: New Advances. CHEM REC 2021; 21:2397-2410. [PMID: 34010479 DOI: 10.1002/tcr.202100086] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 04/20/2021] [Indexed: 12/14/2022]
Abstract
The development of new 18 F-based radiopharmaceuticals constantly demands innovations in the search for new radiofluorination methods. [18 F]fluoride is the simplest and most convenient chemical form of the isotope for the synthesis of 18 F-based radiopharmaceuticals. The ease of production and handling, as well as the possibility of obtaining high molar activities, makes it the preferred choice for radiofluorination. However, the use of [18 F]fluoride in late-stage radiofluorination comes with challenges, especially for the radiolabeling of electron-rich molecules where SN 2 and SN Ar reactions are not suitable. New developments in fluorination chemistry have been extensively studied to overcome these difficulties. Selective electrochemical oxidation of precursors, using a controlled potential, is one method to create reactive intermediates and overcome the activation energy required for nucleophilic fluorination of electron-rich moieties. This method has been used for years in cold fluorination of organic molecules and more recently has been adapted as an alternative to traditional radiofluorination methods. Although relatively young, this field stands out as a promising route for the synthesis of new PET probes as well as fluorinated pharmaceuticals. This review focuses on recent advances in electrochemical radiofluorination as an alternative for the late-stage radiolabeling of organic molecules.
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Affiliation(s)
- Daniel Hernández-Valdés
- Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4 L8, Canada
| | - Saman Sadeghi
- Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4 L8, Canada.,Department of Molecular and Medical Pharmacology and Crump Institute for Molecular Imaging, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
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14
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Scheide MR, Nicoleti CR, Martins GM, Braga AL. Electrohalogenation of organic compounds. Org Biomol Chem 2021; 19:2578-2602. [DOI: 10.1039/d0ob02459g] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this review we target sp, sp2 and sp3 carbon fluorination, chlorination, bromination and iodination reactions using electrolysis as a redox medium. Mechanistic insights and substrate reactivity are also discussed.
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Affiliation(s)
- Marcos R. Scheide
- Departamento de Química
- Universidade Federal de Santa Catarina – UFSC
- Florianópolis
- Brazil
| | - Celso R. Nicoleti
- Departamento de Química
- Universidade Federal de Santa Catarina – UFSC
- Florianópolis
- Brazil
| | - Guilherme M. Martins
- Departamento de Química
- Universidade Federal de Santa Catarina – UFSC
- Florianópolis
- Brazil
| | - Antonio L. Braga
- Departamento de Química
- Universidade Federal de Santa Catarina – UFSC
- Florianópolis
- Brazil
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15
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Affiliation(s)
- Pavel K. Mykhailiuk
- Enamine Ltd., Chervonotkatska 78, 02094 Kyiv, Ukraine
- Chemistry Department, Taras Shevchenko National University of Kyiv, Volodymyrska 64, 01601 Kyiv, Ukraine
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16
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Laube M, Gassner C, Neuber C, Wodtke R, Ullrich M, Haase-Kohn C, Löser R, Köckerling M, Kopka K, Kniess T, Hey-Hawkins E, Pietzsch J. Deuteration versus ethylation - strategies to improve the metabolic fate of an 18F-labeled celecoxib derivative. RSC Adv 2020; 10:38601-38611. [PMID: 35517533 PMCID: PMC9057277 DOI: 10.1039/d0ra04494f] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 10/11/2020] [Indexed: 12/14/2022] Open
Abstract
The inducible isoenzyme cyclooxygenase-2 (COX-2) is closely associated with chemo-/radioresistance and poor prognosis of solid tumors. Therefore, COX-2 represents an attractive target for functional characterization of tumors by positron emission tomography (PET). In this study, the celecoxib derivative 3-([18F]fluoromethyl)-1-[4-(methylsulfonyl)phenyl]-5-(p-tolyl)-1H-pyrazole ([18F]5a) was chosen as a lead compound having a reported high COX-2 inhibitory potency and a potentially low carbonic anhydrase binding tendency. The respective deuterated analog [D2,18F]5a and the fluoroethyl-substituted derivative [18F]5b were selected to study the influence of these modifications with respect to COX inhibition potency in vitro and metabolic stability of the radiolabeled tracers in vivo. COX-2 inhibitory potency was found to be influenced by elongation of the side chain but, as expected, not by deuteration. An automated radiosynthesis comprising 18F-fluorination and purification under comparable conditions provided the radiotracers [18F]5a,b and [D2,18F]5a in good radiochemical yields (RCY) and high radiochemical purity (RCP). Biodistribution and PET studies comparing all three compounds revealed bone accumulation of 18F-activity to be lowest for the ethyl derivative [18F]5b. However, the deuterated analog [D2,18F]5a turned out to be the most stable compound of the three derivatives studied here. Time-dependent degradation of [18F]5a,b and [D2,18F]5a after incubation in murine liver microsomes was in accordance with the data on metabolism in vivo. Furthermore, metabolites were identified based on UPLC-MS/MS. The aim of this study is to investigate the influence of deuteration and elongation on an 18F-labeled COX-2 inhibitor with focus on metabolic stability to develop suitable COX-2 targeting radiotracers.![]()
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Affiliation(s)
- Markus Laube
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Cemena Gassner
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany .,Faculty of Chemistry and Food Chemistry, School of Science, Technische Universität Dresden Mommsenstrasse 4 D-01062 Dresden Germany
| | - Christin Neuber
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Robert Wodtke
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Martin Ullrich
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Cathleen Haase-Kohn
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Reik Löser
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Martin Köckerling
- University of Rostock, Institute of Chemistry, Department of Inorganic Solid State Chemistry Albert-Einstein-Str. 3a D-18059 Rostock Germany
| | - Klaus Kopka
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Torsten Kniess
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Evamarie Hey-Hawkins
- Leipzig University, Faculty of Chemistry and Mineralogy, Institute of Inorganic Chemistry Johannisallee 29 D-04103 Leipzig Germany
| | - Jens Pietzsch
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany .,Faculty of Chemistry and Food Chemistry, School of Science, Technische Universität Dresden Mommsenstrasse 4 D-01062 Dresden Germany
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17
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Motornov VA, Tabolin AA, Nelyubina YV, Nenajdenko VG, Ioffe SL. Acid‐Mediated Three Component Assembly of 4‐Fluoropyrazoles from α‐Fluoronitroalkenes, Hydrazines, and Aldehydes. European J Org Chem 2020. [DOI: 10.1002/ejoc.202000841] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Vladimir A. Motornov
- N. D. Zelinsky Institute of Organic Chemistry Russian Academy of Sciences Leninsky prosp. 47 119991 Moscow Russia
- Higher Chemical College D. I. Mendeleev University of Chemical Technology of Russia Miusskaya sq. 9 125047 Moscow Russia
| | - Andrey A. Tabolin
- N. D. Zelinsky Institute of Organic Chemistry Russian Academy of Sciences Leninsky prosp. 47 119991 Moscow Russia
| | - Yulia V. Nelyubina
- A. N. Nesmeyanov Institute of Organoelement Compounds Russian Academy of Sciencesm Vavilov str. 28 119991 Moscow Russia
| | - Valentine G. Nenajdenko
- Department of Chemistry M. V. Lomonosov Moscow State University Leninskie Gory 1 119991 Moscow Russia
| | - Sema L. Ioffe
- N. D. Zelinsky Institute of Organic Chemistry Russian Academy of Sciences Leninsky prosp. 47 119991 Moscow Russia
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18
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Pyrazoles as Key Scaffolds for the Development of Fluorine-18-Labeled Radiotracers for Positron Emission Tomography (PET). Molecules 2020; 25:molecules25071722. [PMID: 32283680 PMCID: PMC7181023 DOI: 10.3390/molecules25071722] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Revised: 04/02/2020] [Accepted: 04/08/2020] [Indexed: 02/07/2023] Open
Abstract
The need for increasingly personalized medicine solutions (precision medicine) and quality medical treatments, has led to a growing demand and research for image-guided therapeutic solutions. Positron emission tomography (PET) is a powerful imaging technique that can be established using complementary imaging systems and selective imaging agents—chemical probes or radiotracers—which are drugs labeled with a radionuclide, also called radiopharmaceuticals. PET has two complementary purposes: selective imaging for diagnosis and monitoring of disease progression and response to treatment. The development of selective imaging agents is a growing research area, with a high number of diverse drugs, labeled with different radionuclides, being reported nowadays. This review article is focused on the use of pyrazoles as suitable scaffolds for the development of 18F-labeled radiotracers for PET imaging. A brief introduction to PET and pyrazoles, as key scaffolds in medicinal chemistry, is presented, followed by a description of the most important [18F]pyrazole-derived radiotracers (PET tracers) that have been developed in the last 20 years for selective PET imaging, grouped according to their specific targets.
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19
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Litchfield M, Wuest M, Glubrecht D, Wuest F. Radiosynthesis and Biological Evaluation of [ 18F]Triacoxib: A New Radiotracer for PET Imaging of COX-2. Mol Pharm 2019; 17:251-261. [PMID: 31816246 DOI: 10.1021/acs.molpharmaceut.9b00986] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Inducible isozyme cyclooxygenase-2 (COX-2) is upregulated under acute and chronic inflammatory conditions, including cancer, wherein it promotes angiogenesis, tissue invasion, and resistance to apoptosis. Due to its high expression in various cancers, COX-2 has become an important biomarker for molecular imaging and therapy of cancer. Recently, our group applied in situ click chemistry for the identification of the highly potent and selective COX-2 inhibitor triacoxib. In this study, we present the radiosynthesis in vitro and in vivo radiopharmacological validation of [18F]triacoxib, a novel radiotracer for PET imaging of COX-2. Radiosynthesis of [18F]triacoxib was accomplished using copper-mediated late-stage radiofluorination chemistry. The radiosynthesis, including radio-HPLC purification, of [18F]triacoxib was accomplished within 90 min in decay-corrected radiochemical yields of 72% (n = 7) at molar activities exceeding 90 GBq/μmol. Cellular uptake and inhibition studies with [18F]triacoxib were carried out in COX-2 expressing HCA-7 cells. Cellular uptake of [18F]triacoxib in HCA-7 cells reached 25% radioactivity/mg protein after 60 min. Cellular uptake was reduced by 63% upon pretreatment with 0.1 mM celecoxib, and 90% of the radiotracer remained intact in vivo after 60 min p.i. in mice. [18F]Triacoxib was further evaluated in HCA-7 tumor-bearing mice using dynamic PET imaging, radiometabolite analysis, autoradiography, and immunohistochemistry. PET imaging revealed a favorable baseline radiotracer uptake in HCA-7 tumors (SUV60min = 0.76 ± 0.02 (n = 4)), which could be blocked by 20% through i.p. pretreatment with 2 mg of celecoxib. Autoradiography and immunohistochemistry experiments further the confirmed blocking of COX-2 in vivo. [18F]Triacoxib, whose nonradioactive analogue was identified through in situ click chemistry, is a novel radiotracer for PET imaging of COX-2 in cancer. Despite a substantial amount of nonspecific uptake in vivo, [18F]triacoxib displayed specific binding to COX-2 in vivo and reinforced the feasibility of optimal structure selection by in situ click chemistry. It remains to be elucidated how this novel radiotracer would perform in first-in-human studies to detect COX-2 with PET.
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Affiliation(s)
- Marcus Litchfield
- Department of Oncology , University of Alberta , 11560 University Avenue , Edmonton , Alberta T6G 1Z2 , Canada
| | - Melinda Wuest
- Department of Oncology , University of Alberta , 11560 University Avenue , Edmonton , Alberta T6G 1Z2 , Canada.,Cancer Research Institute of Northern Alberta , University of Alberta , Edmonton , Alberta T6G 2S2 , Canada
| | - Darryl Glubrecht
- Department of Oncology , University of Alberta , 11560 University Avenue , Edmonton , Alberta T6G 1Z2 , Canada
| | - Frank Wuest
- Department of Oncology , University of Alberta , 11560 University Avenue , Edmonton , Alberta T6G 1Z2 , Canada.,Cancer Research Institute of Northern Alberta , University of Alberta , Edmonton , Alberta T6G 2S2 , Canada
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20
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Chen W, Huang Z, Tay NES, Giglio B, Wang M, Wang H, Wu Z, Nicewicz DA, Li Z. Direct arene C-H fluorination with 18F - via organic photoredox catalysis. Science 2019; 364:1170-1174. [PMID: 31221856 PMCID: PMC6680023 DOI: 10.1126/science.aav7019] [Citation(s) in RCA: 97] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 02/06/2019] [Accepted: 05/29/2019] [Indexed: 12/31/2022]
Abstract
Positron emission tomography (PET) plays key roles in drug discovery and development, as well as medical imaging. However, there is a dearth of efficient and simple radiolabeling methods for aromatic C-H bonds, which limits advancements in PET radiotracer development. Here, we disclose a mild method for the fluorine-18 (18F)-fluorination of aromatic C-H bonds by an [18F]F- salt via organic photoredox catalysis under blue light illumination. This strategy was applied to the synthesis of a wide range of 18F-labeled arenes and heteroaromatics, including pharmaceutical compounds. These products can serve as diagnostic agents or provide key information about the in vivo fate of the labeled substrates, as showcased in preliminary tracer studies in mice.
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Affiliation(s)
- Wei Chen
- Biomedical Research Imaging Center, Department of Radiology, and UNC Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27514, USA
| | - Zeng Huang
- Biomedical Research Imaging Center, Department of Radiology, and UNC Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27514, USA
| | - Nicholas E S Tay
- Department of Chemistry, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
| | - Benjamin Giglio
- Biomedical Research Imaging Center, Department of Radiology, and UNC Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27514, USA
| | - Mengzhe Wang
- Biomedical Research Imaging Center, Department of Radiology, and UNC Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27514, USA
| | - Hui Wang
- Biomedical Research Imaging Center, Department of Radiology, and UNC Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27514, USA
| | - Zhanhong Wu
- Biomedical Research Imaging Center, Department of Radiology, and UNC Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27514, USA
| | - David A Nicewicz
- Department of Chemistry, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA.
| | - Zibo Li
- Biomedical Research Imaging Center, Department of Radiology, and UNC Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27514, USA.
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21
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Development of brain PET imaging agents: Strategies for imaging neuroinflammation in Alzheimer's disease. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2019; 165:371-399. [DOI: 10.1016/bs.pmbts.2019.04.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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22
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Balandeh M, Rios A, Allison N, Shirazi D, Gomez A, Rambaran L, Holloway T, Sadeghi S. Electrochemical Flash Fluorination and Radiofluorination. ChemElectroChem 2018; 5:3353-3356. [PMID: 31475090 DOI: 10.1002/celc.201800973] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A new method for rapid late-stage fluorination using the cation pool technique is presented. Fluorination and no-carrier-added radiofluorination of methyl (phenylthio) acetate, methyl 2-(methylthio) acetate, and methyl 2-(ethylthio) acetate were performed. The carbocations formed through electrochemical oxidation were stabilized by using a divided electrochemical cell and 2,2,2-trifluoroethanol (TFE) as the solvent at -20 °C. At the end of electrolysis, either stable-isotope [19F]fluoride or no-carrier-added radioactive [18F]fluoride was added to the reaction mixture to form the fluorinated or radiofluorinated product.
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Affiliation(s)
- Mehrdad Balandeh
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California 90095, USA
| | - Alejandra Rios
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California 90095, USA.,Physics and Biology in Medicine Interdepartmental Graduate Program, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
| | - Nathanael Allison
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California 90095, USA
| | - Daniela Shirazi
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California 90095, USA
| | - Adrian Gomez
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California 90095, USA.,Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA
| | - Laura Rambaran
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California 90095, USA
| | - Travis Holloway
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California 90095, USA
| | - Saman Sadeghi
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California 90095, USA
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24
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Abstract
Neuroinflammation, which involves microglial activation, is thought to play a key role in the development and progression of neurodegenerative diseases and other brain pathologies. Positron emission tomography is an ideal imaging technique for studying biochemical processes in vivo, and particularly for studying the living brain. Neuroinflammation has been traditionally studied using radiotracers targeting the translocator protein 18 kDa, but this comes with certain limitations. The current review describes alternative biological targets that have gained interest for the imaging of microglial activation over recent years, such as the cannabinoid receptor type 2, cyclooxygenase-2, the P2X₇ receptor and reactive oxygen species, and some promising radiotracers for these targets. Although many advances have been made in the field of neuroinflammation imaging, current radiotracers all target the pro-inflammatory (M1) phenotype of activated microglia, since the number of known biological targets specific for the anti-inflammatory (M2) phenotype that are also suited as a target for radiotracer development is still limited. Next to proceeding the currently available tracers for M1 microglia into the clinic, the development of a suitable radiotracer for M2 microglia would mean a great advance in the field, as this would allow for imaging of the dynamics of microglial activation in different diseases.
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Affiliation(s)
- Bieneke Janssen
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Danielle J Vugts
- Department of Radiology & Nuclear Medicine, VU University Medical Center, 1081 HV Amsterdam, The Netherlands.
| | - Albert D Windhorst
- Department of Radiology & Nuclear Medicine, VU University Medical Center, 1081 HV Amsterdam, The Netherlands.
| | - Robert H Mach
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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