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Belov V, Guehl NJ, Duvvuri S, Iredale P, Moon SH, Dhaynaut M, Chakilam S, MacDonagh AC, Rice PA, Yokell DL, Renger JJ, El Fakhri G, Normandin MD. PET imaging of M4 muscarinic acetylcholine receptors in rhesus macaques using [ 11C]MK-6884: Quantification with kinetic modeling and receptor occupancy by CVL-231 (emraclidine), a novel positive allosteric modulator. J Cereb Blood Flow Metab 2024; 44:1329-1342. [PMID: 38477292 DOI: 10.1177/0271678x241238820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 03/14/2024]
Abstract
Stimulation of the M4 muscarinic acetylcholine receptor reduces striatal hyperdopaminergia, suggesting its potential as a therapeutic target for schizophrenia. Emraclidine (CVL-231) is a novel, highly selective, positive allosteric modulator (PAM) of M4 muscarinic acetylcholine receptors i.e. acts as a modulator that increases the response of these receptors. First, we aimed to further characterize the positron emission tomography (PET) imaging and quantification performance of a recently developed M4 PAM radiotracer, [11C]MK-6884, in non-human primates (NHPs). Second, we applied these results to determine the receptor occupancy of CVL-231 as a function of dose. Using paired baseline-blocking PET scans, we quantified total volume of distribution, binding potential, and receptor occupancy. Both blood-based and reference region-based methods quantified M4 receptor levels across brain regions. The 2-tissue 4-parameter kinetic model best fitted regional [11C]MK-6884-time activity curves. Only the caudate nucleus and putamen displayed statistically significant [11C]MK-6884 uptake and dose-dependent blocking by CVL-231. For binding potential and receptor occupancy quantification, the simplified reference tissue model using the grey cerebellum as a reference region was employed. CVL-231 demonstrated dose-dependent M4 receptor occupancy in the striatum of the NHP brain and shows promise for further development in clinical trials.
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Affiliation(s)
- Vasily Belov
- Gordon Center for Medical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Nicolas J Guehl
- Gordon Center for Medical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | | | | | - Sung-Hyun Moon
- Gordon Center for Medical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Maeva Dhaynaut
- Gordon Center for Medical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | | | - Alexander C MacDonagh
- Gordon Center for Medical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Peter A Rice
- Gordon Center for Medical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Daniel L Yokell
- Gordon Center for Medical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | | | - Georges El Fakhri
- Gordon Center for Medical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Marc D Normandin
- Gordon Center for Medical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
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Jiang H, Zhou C, Qiu L, Gropler RJ, Brier MR, Wu GF, Cross AH, Perlmutter JS, Benzinger TLS, Tu Z. Quantitative Analysis of S1PR1 Expression in the Postmortem Multiple Sclerosis Central Nervous System. ACS Chem Neurosci 2023; 14:4039-4050. [PMID: 37882753 PMCID: PMC11037862 DOI: 10.1021/acschemneuro.3c00581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2023] Open
Abstract
Multiple sclerosis (MS) is an immune-mediated disease that is characterized by demyelination and inflammation in the central nervous system (CNS). Previous studies demonstrated that sphingosine-1-phosphate receptor (S1PR) modulators effectively inhibit S1PR1 in immune cell trafficking and reduce entry of pathogenic cells into the CNS. Studies have also implicated a nonimmune, inflammatory role of S1PR1 within the CNS in MS. In this study, we explored the expression of S1PR1 in the development and progression of demyelinating pathology of MS by quantitative assessment of S1PR1 expression using our S1PR1-specific radioligand, [3H]CS1P1, in the postmortem human CNS tissues including cortex, cerebellum, and spinal cord of MS cases and age- and sex-matched healthy cases. Immunohistochemistry with whole slide scanning for S1PR1 and various myelin proteins was also performed. Autoradiographic analysis using [3H]CS1P1 showed that the expression of S1PR1 was statistically significantly elevated in lesions compared to nonlesion regions in the MS cases, as well as normal healthy controls. The uptake of [3H]CS1P1 in the gray matter and nonlesion white matter did not significantly differ between healthy and MS CNS tissues. Saturation autoradiography analysis showed an increased binding affinity (Kd) of [3H]CS1P1 to S1PR1 in both gray matter and white matter of MS brains compared to healthy brains. Our blocking study using NIBR-0213, a S1PR1 antagonist, indicated [3H]CS1P1 is highly specific to S1PR1. Our findings demonstrated the activation of S1PR1 and an increased uptake of [3H]CS1P1 in the lesions of MS CNS. In summary, our quantitative autoradiography analysis using [3H]CS1P1 on human postmortem tissues shows the feasibility of novel imaging strategies for MS by targeting S1PR1.
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Affiliation(s)
- Hao Jiang
- Department of Radiology, Washington University School of Medicine, St Louis, Missouri 63110, United States
| | - Charles Zhou
- Department of Radiology, Washington University School of Medicine, St Louis, Missouri 63110, United States
| | - Lin Qiu
- Department of Radiology, Washington University School of Medicine, St Louis, Missouri 63110, United States
| | - Robert J Gropler
- Department of Radiology, Washington University School of Medicine, St Louis, Missouri 63110, United States
| | - Matthew R Brier
- Department of Radiology, Washington University School of Medicine, St Louis, Missouri 63110, United States
- Department of Neurology, Washington University School of Medicine, St Louis, Missouri 63110, United States
| | - Gregory F Wu
- Department of Neurology, Washington University School of Medicine, St Louis, Missouri 63110, United States
| | - Anne H Cross
- Department of Neurology, Washington University School of Medicine, St Louis, Missouri 63110, United States
| | - Joel S Perlmutter
- Department of Radiology, Washington University School of Medicine, St Louis, Missouri 63110, United States
- Department of Neurology, Washington University School of Medicine, St Louis, Missouri 63110, United States
| | - Tammie L S Benzinger
- Department of Radiology, Washington University School of Medicine, St Louis, Missouri 63110, United States
- Department of Neurological Surgery, Washington University School of Medicine, St Louis, Missouri 63110, United States
| | - Zhude Tu
- Department of Radiology, Washington University School of Medicine, St Louis, Missouri 63110, United States
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Tan Z, Haider A, Zhang S, Chen J, Wei J, Liao K, Li G, Wei H, Dong C, Ran W, Li Y, Li Y, Rong J, Li Y, Liang SH, Xu H, Wang L. Quantitative assessment of translocator protein (TSPO) in the non-human primate brain and clinical translation of [ 18F]LW223 as a TSPO-targeted PET radioligand. Pharmacol Res 2023; 189:106681. [PMID: 36746361 DOI: 10.1016/j.phrs.2023.106681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 01/12/2023] [Accepted: 01/30/2023] [Indexed: 02/05/2023]
Abstract
OBJECTIVES Translocator protein 18 kDa (TSPO) positron emission tomography (PET) can be harnessed for the non-invasive detection of macrophage-driven inflammation. [18F]LW223, a newly reported TSPO PET tracer which was insensitive to rs6971 polymorphism, showed favorable performance characteristics in a recent imaging study involving a rat myocardial infarction model. To enable quantitative neuroimaging with [18F]LW223, we conducted kinetic analysis in the non-human primate (NHP) brain. Further, we sought to assess the utility of [18F]LW223-based TSPO imaging in a first-in-human study. METHODS Radiosynthesis of [18F]LW223 was accomplished on an automated module, whereas molar activities, stability in formulation, lipophilicity and unbound free fraction (fu) of the probe were measured. Brain penetration and target specificity of [18F]LW223 in NHPs were corroborated by PET-MR imaging under baseline and pre-blocking conditions using the validated TSPO inhibitor, (R)-PK11195, at doses ranging from 5 to 10 mg/kg. Kinetic modeling was performed using one-tissue compartment model (1TCM), two-tissue compartment model (2TCM) and Logan graphical analyses, using dynamic PET data acquisition, arterial blood collection and metabolic stability testing. Clinical PET scans were performed in two healthy volunteers (HVs). Regional brain standard uptake value ratio (SUVr) was assessed for different time intervals. RESULTS [18F]LW223 was synthesized in non-decay corrected radiochemical yields (n.d.c. RCYs) of 33.3 ± 6.5% with molar activities ranging from 1.8 ± 0.7 Ci/µmol (n = 11). [18F]LW223 was stable in formulation for up to 4 h and LogD7.4 of 2.31 ± 0.13 (n = 6) and fu of 5.80 ± 1.42% (n = 6) were determined. [18F]LW223 exhibited good brain penetration in NHPs, with a peak SUV value of ca. 1.79 in the whole brain. Pre-treatment with (R)-PK11195 substantially accelerated the washout and attenuated the area under the time-activity curve, indicating in vivo specificity of [18F]LW223 towards TSPO. Kinetic modeling demonstrated that 2TCM was the most suitable model for [18F]LW223-based neuroimaging. Global transfer rate constants (K1) and total volumes of distribution (VT) were found to be 0.10 ± 0.01 mL/cm3/min and 2.30 ± 0.17 mL/cm3, respectively. Dynamic PET data analyses across distinct time windows revealed that the VT values were relatively stable after 60 min post-injection. In a preliminary clinical study with two healthy volunteers, [18F]LW223 exhibited good brain uptake and considerable tracer retention across all analyzed brain regions. Of note, an excellent correlation between SUVr with VT was obtained when assessing the time interval from 20 to 40 min post tracer injection (SUVr(20-40 min), R2 = 0.94, p < 0.0001), suggesting this time window may be suitable to estimate specific binding to TSPO in human brain. CONCLUSION Our findings indicate that [18F]LW223 is suitable for quantitative TSPO-targeted PET imaging in higher species. Employing state-of-the-art kinetic modeling, we found that [18F]LW223 was effective in mapping TSPO throughout the NHP brain, with best model fits obtained from 2TCM and Logan graphical analyses. Overall, our results indicate that [18F]LW223 exhibits favorable tracer performance characteristics in higher species, and this novel imaging tool may hold promise to provide effective neuroinflammation imaging in patients with neurological disease.
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Affiliation(s)
- Zhiqiang Tan
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Ahmed Haider
- Department of Radiology and Imaging Sciences, Emory University, 1364 Clifton Rd, Atlanta, GA 30322, USA
| | - Shaojuan Zhang
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Jiahui Chen
- Department of Radiology and Imaging Sciences, Emory University, 1364 Clifton Rd, Atlanta, GA 30322, USA
| | - Junjie Wei
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Kai Liao
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Guocong Li
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Huiyi Wei
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Chenchen Dong
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Wenqing Ran
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Ying Li
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China
| | - Yuefeng Li
- Guangdong Landau Biotechnology Co. Ltd., Guangzhou 510555, China
| | - Jian Rong
- Department of Radiology and Imaging Sciences, Emory University, 1364 Clifton Rd, Atlanta, GA 30322, USA
| | - Yinlong Li
- Department of Radiology and Imaging Sciences, Emory University, 1364 Clifton Rd, Atlanta, GA 30322, USA
| | - Steven H Liang
- Department of Radiology and Imaging Sciences, Emory University, 1364 Clifton Rd, Atlanta, GA 30322, USA.
| | - Hao Xu
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China.
| | - Lu Wang
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China.
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Evaluation of (R)-[ 11C]PK11195 PET/MRI for Spinal Cord-Related Neuropathic Pain in Patients with Cervical Spinal Disorders. J Clin Med 2022; 12:jcm12010116. [PMID: 36614916 PMCID: PMC9821277 DOI: 10.3390/jcm12010116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Revised: 12/19/2022] [Accepted: 12/21/2022] [Indexed: 12/28/2022] Open
Abstract
Activated microglia are involved in secondary injury after acute spinal cord injury (SCI) and in development of spinal cord-related neuropathic pain (NeP). The aim of the study was to assess expression of translocator protein 18 kDa (TSPO) as an indicator of microglial activation and to investigate visualization of the dynamics of activated microglia in the injured spinal cord using PET imaging with (R)-[11C]PK11195, a specific ligand for TSPO. In SCI chimeric animal models, TSPO was expressed mainly in activated microglia. Accumulation of (R)-[3H]PK11195 was confirmed in autoradiography and its dynamics in the injured spinal cord were visualized by (R)-[11C]PK11195 PET imaging in the acute phase after SCI. In clinical application of (R)-[11C]PK11195 PET/MRI of the cervical spinal cord in patients with NeP related to cervical disorders, uptake was found in cases up to 10 months after injury or surgery. No uptake could be visualized in the injured spinal cord in patients with chronic NeP at more than 1 year after injury or surgery, regardless of the degree of NeP. However, a positive correlation was found between standardized uptake value ratio and the severity of NeP, suggesting the potential of clinical application for objective evaluation of chronic NeP.
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18F-Radiolabeled Translocator Protein (TSPO) PET Tracers: Recent Development of TSPO Radioligands and Their Application to PET Study. Pharmaceutics 2022; 14:pharmaceutics14112545. [PMID: 36432736 PMCID: PMC9697781 DOI: 10.3390/pharmaceutics14112545] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 11/16/2022] [Accepted: 11/17/2022] [Indexed: 11/23/2022] Open
Abstract
Translocator protein 18 kDa (TSPO) is a transmembrane protein in the mitochondrial membrane, which has been identified as a peripheral benzodiazepine receptor. TSPO is generally present at high concentrations in steroid-producing cells and plays an important role in steroid synthesis, apoptosis, and cell proliferation. In the central nervous system, TSPO expression is relatively modest under normal physiological circumstances. However, some pathological disorders can lead to changes in TSPO expression. Overexpression of TSPO is associated with several diseases, such as neurodegenerative diseases, neuroinflammation, brain injury, and cancers. TSPO has therefore become an effective biomarker of related diseases. Positron emission tomography (PET), a non-invasive molecular imaging technique used for the clinical diagnosis of numerous diseases, can detect diseases related to TSPO expression. Several radiolabeled TSPO ligands have been developed for PET. In this review, we describe recent advances in the development of TSPO ligands, and 18F-radiolabeled TSPO in particular, as PET tracers. This review covers pharmacokinetic studies, preclinical and clinical trials of 18F-labeled TSPO PET ligands, and the synthesis of TSPO ligands.
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Viviano M, Barresi E, Siméon FG, Costa B, Taliani S, Da Settimo F, Pike VW, Castellano S. Essential Principles and Recent Progress in the Development of TSPO PET Ligands for Neuroinflammation Imaging. Curr Med Chem 2022; 29:4862-4890. [PMID: 35352645 PMCID: PMC10080361 DOI: 10.2174/0929867329666220329204054] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 12/21/2021] [Accepted: 01/25/2022] [Indexed: 11/22/2022]
Abstract
The translocator protein 18kDa (TSPO) is expressed in the outer mitochondrial membrane and is implicated in several functions, including cholesterol transport and steroidogenesis. Under normal physiological conditions, TSPO is present in very low concentrations in the human brain but is markedly upregulated in response to brain injury and inflammation. This upregulation is strongly associated with activated microglia. Therefore, TSPO is particularly suited for assessing active gliosis associated with brain lesions following injury or disease. For over three decades, TSPO has been studied as a biomarker. Numerous radioligands for positron emission tomography (PET) that target TSPO have been developed for imaging inflammatory progression in the brain. Although [11C]PK11195, the prototypical first-generation PET radioligand, is still widely used for in vivo studies, mainly now as its single more potent R-enantiomer, it has severe limitations, including low sensitivity and poor amenability to quantification. Second-generation radioligands are characterized by higher TSPO specific signals but suffer from other drawbacks, such as sensitivity to the TSPO single nucleotide polymorphism (SNP) rs6971. Therefore, their applications in human studies have the burden of needing to genotype subjects. Consequently, recent efforts are focused on developing improved radioligands that combine the optimal features of the second generation with the ability to overcome the differences in binding affinities across the population. This review presents essential principles in the design and development of TSPO PET ligands and discusses prominent examples among the main chemotypes.
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Affiliation(s)
- Monica Viviano
- Department of Pharmacy, University of Salerno, 84084 Fisciano (SA), Italy
| | | | - Fabrice G. Siméon
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - Barbara Costa
- Department of Pharmacy, University of Pisa, 56126, Pisa, Italy
| | - Sabrina Taliani
- Department of Pharmacy, University of Pisa, 56126, Pisa, Italy
| | | | - Victor W. Pike
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sabrina Castellano
- Department of Pharmacy, University of Salerno, 84084 Fisciano (SA), Italy
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Siméon FG, Lee JH, Morse CL, Stukes I, Zoghbi SS, Manly LS, Liow JS, Gladding RL, Dick RM, Yan X, Taliani S, Costa B, Martini C, Da Settimo F, Castellano S, Innis RB, Pike VW. Synthesis and Screening in Mice of Fluorine-Containing PET Radioligands for TSPO: Discovery of a Promising 18F-Labeled Ligand. J Med Chem 2021; 64:16731-16745. [PMID: 34756026 PMCID: PMC8817670 DOI: 10.1021/acs.jmedchem.1c01562] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Translocator protein 18 kDa (TSPO) is a biomarker of neuroinflammation. [11C]ER176 robustly quantifies TSPO in the human brain with positron emission tomography (PET), irrespective of subject genotype. We aimed to develop an ER176 analog with potential for labeling with longer-lived fluorine-18 (t1/2 = 109.8 min). New fluoro and trifluoromethyl analogs of ER176 were prepared through a concise synthetic strategy. These ligands showed high TSPO affinity and low human genotype sensitivity. Each ligand was initially labeled by a generic 11C-methylation procedure, thereby enabling speedy screening in mice. Each radioligand was rapidly taken up and well retained in the mouse brain at baseline after intravenous injection. Preblocking of TSPO showed that high proportions of brain uptake were specifically bound to TSPO at baseline. Overall, the 3-fluoro analog of [11C]ER176 ([11C]3b) displayed the most promising imaging properties. Therefore, a method was developed to label 3b with [18F]fluoride ion. [18F]3b gave similarly promising PET imaging results and deserves evaluation in higher species.
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Affiliation(s)
- Fabrice G Siméon
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Jae-Hoon Lee
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
- Department of Nuclear Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 03772, South Korea
| | - Cheryl L Morse
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Ian Stukes
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Sami S Zoghbi
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Lester S Manly
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Jeih-San Liow
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Robert L Gladding
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Rachel M Dick
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Xuefeng Yan
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Sabrina Taliani
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy
| | - Barbara Costa
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy
| | - Claudia Martini
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy
| | | | - Sabrina Castellano
- Department of Pharmacy, University of Salerno, 84084 Fisciano, SA, Italy
| | - Robert B Innis
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Victor W Pike
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, United States
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Direct Comparison of [ 18F]F-DPA with [ 18F]DPA-714 and [ 11C]PBR28 for Neuroinflammation Imaging in the same Alzheimer's Disease Model Mice and Healthy Controls. Mol Imaging Biol 2021; 24:157-166. [PMID: 34542805 PMCID: PMC8760190 DOI: 10.1007/s11307-021-01646-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Revised: 07/22/2021] [Accepted: 08/23/2021] [Indexed: 11/02/2022]
Abstract
PURPOSE In this study we compared the recently developed TSPO tracer [18F]F-DPA, with [18F]DPA-714 and [11C]PBR28 by performing in vivo PET imaging on the same Alzheimer's disease mouse model APP/PS1-21 (TG) and wild-type (WT) mice with all three radiotracers. PROCEDURES To compare the radiotracer uptake, percentage of injected dose/mL (%ID/mL), standardized uptake value ratios to cerebellum (SUVRCB), and voxel-wise analyses were performed. RESULTS The peak uptake of [18F]F-DPA was higher than 4.3% ID/mL, while [18F]DPA-714 reached just over 3% ID/mL, and [11C]PBR28 was over 4% ID/mL in only one brain region in the WT mice. The peak/60-min uptake ratios of [18F]F-DPA were significantly higher (p < 0.001) than those of [18F]DPA-714 and [11C]PBR28. The differences in [18F]F-DPA SUVRCB between WT and TG mice were highly significant (p < 0.001) in the three studied time periods after injection. [18F]DPA-714 uptake was significantly higher in TG mice starting in the 20-40-min timeframe and increased thereafter, whereas [11C]PBR28 uptake became significant at 10-20 min (p < 0.05). The voxel-wise analysis confirmed the differences between the radiotracers. CONCLUSIONS [18F]F-DPA displays higher brain uptake, higher TG-to-WT SUVRCB ratios, and faster clearance than [18F]DPA-714 and [11C]PBR28, and could prove useful for detecting low levels of inflammation and allow for shorter dynamic PET scans.
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Mokrov GV, Deeva OA, Gudasheva TA. The Ligands of Translocator Protein: Design and Biological Properties. Curr Pharm Des 2021; 27:217-237. [PMID: 32881658 DOI: 10.2174/1381612826666200903122025] [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: 03/30/2020] [Accepted: 07/15/2020] [Indexed: 11/22/2022]
Abstract
In 2020, it is already 43 years since Braestrup and Squires discovered 18 kDa translocator protein (TSPO), known until 2006 as "peripheral benzodiazepine receptor". During this time, the functions of this receptor, which is located on the outer membrane of mitochondria, were studied in detail. One of the key functions of TSPO is the transfer of cholesterol from the outer to the inner mitochondrial membrane, which is the limiting stage in the synthesis of neurosteroids. TSPO is also involved in the transport of porphyrins, mitochondrial respiration, the opening of mitochondrial pores, apoptosis and cell proliferation. This review presents current information on the structure of TSPO, the mechanism of its participation in neurosteroidogenesis, as well as endogenous and synthetic TSPO ligands. Particular emphasis is placed on the analysis of approaches to the design of synthetic ligands and their neuropsychotropic activity in vitro and in vivo. The presented review demonstrates the promise of constructing new neuropsychotropic drugs in the series of TSPO ligands.
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Affiliation(s)
- Grigory V Mokrov
- Zakusov Research Institute of Pharmacology, 125315, Moscow, Russian Federation
| | - Olga A Deeva
- Zakusov Research Institute of Pharmacology, 125315, Moscow, Russian Federation
| | - Tatiana A Gudasheva
- Zakusov Research Institute of Pharmacology, 125315, Moscow, Russian Federation
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An update into the medicinal chemistry of translocator protein (TSPO) ligands. Eur J Med Chem 2020; 209:112924. [PMID: 33081988 DOI: 10.1016/j.ejmech.2020.112924] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 10/06/2020] [Accepted: 10/06/2020] [Indexed: 01/16/2023]
Abstract
The Translocator Protein 18 kDa (TSPO) has been discovered in 1977 as an alternative binding site for the benzodiazepine diazepam. It is an evolutionary well-conserved and tryptophan-rich 169-amino acids protein with five alpha helical transmembrane domains stretching the outer mitochondrial membrane, with the carboxyl-terminus in the cytosol and a short amino-terminus in the intermembrane space of mitochondrion. At this level, together with the voltage-dependent anion channel (VDAC) and the adenine nucleotide translocase (ANT), it forms the mitochondrial permeability transition pore (MPTP). TSPO expression is ubiquitary, with higher levels in steroid producing tissues; in the central nervous system, it is mainly expressed in glial cells and in neurons. TSPO is implicated in a variety of fundamental cellular processes including steroidogenesis, heme biosynthesis, mitochondrial respiration, mitochondrial membrane potential, cell proliferation and differentiation, cell life/death balance, oxidative stress. Altered TSPO expression has been found in some pathological conditions. In particular, high TSPO expression levels have been documented in cancer, neuroinflammation, and brain injury. Conversely, low TSPO expression levels have been evidenced in anxiety disorders. Therefore, TSPO is not only an interesting drug target for therapeutic purpose (anticonvulsant, anxiolytic, etc.), but also a valid diagnostic marker of related-diseases detectable by fluorescent or radiolabeled ligands. The aim of this report is to present an update of previous reviews dealing with the medicinal chemistry of TSPO and to highlight the most outstanding advances in the development of TSPO ligands as potential therapeutic or diagnostic tools, especially referring to the last five years.
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Buck JR, Saleh S, Claus T, Lovly C, Hight MR, Nickels ML, Noor Tantawy M, Charles Manning H. N-[ 18F]-Fluoroacetylcrizotinib: A potentially potent and selective PET tracer for molecular imaging of non-small cell lung cancer. Bioorg Med Chem Lett 2020; 30:127257. [PMID: 32631505 PMCID: PMC7357882 DOI: 10.1016/j.bmcl.2020.127257] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 05/08/2020] [Accepted: 05/09/2020] [Indexed: 12/24/2022]
Abstract
N-[18F]fluoroacetylcrizotinib, a fluorine-18 labeled derivative of the first FDA approved tyrosine kinase inhibitor (TKI) for the treatment of Anaplastic lymphoma kinase (ALK)-rearranged non-small cell lung cancer (NSCLC), crizotinib, was successfully synthesized for use in positron emission tomography (PET). Sequential in vitro biological evaluation of fluoracetylcrizotinib and in vivo biodistribution studies of [18F]fluoroacetylcrizotinib demonstrated that the biological activity of the parent compound remained unchanged, with potent ALK kinase inhibition and effective tumor growth inhibition. These results show that [18F]fluoroacetylcrizotinib has the potential to be a promising PET ligand for use in NSCLC imaging. The utility of PET in this context provides a non-invasive, quantifiable method to inform on the pharmacokinetics of an ALK-inhibitor such as crizotinib prior to a clinical trial, as well as during a trial in the event of acquired drug resistance.
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Affiliation(s)
- Jason R Buck
- Vanderbilt Center for Molecular Probes, United States; Vanderbilt University, Institute of Imaging Science, United States; Vanderbilt University Medical Center, United States
| | - Samir Saleh
- Vanderbilt Center for Molecular Probes, United States; Vanderbilt University, Institute of Imaging Science, United States; Vanderbilt University Medical Center, United States
| | - Trey Claus
- Vanderbilt Center for Molecular Probes, United States; Vanderbilt University, Institute of Imaging Science, United States; Vanderbilt University Medical Center, United States
| | - Christine Lovly
- Vanderbilt University Medical Center, United States; Vanderbilt Ingram Cancer Center, United States; Department of Hematology and Oncology, Vanderbilt University Medical Center, United States
| | - Matthew R Hight
- Vanderbilt Center for Molecular Probes, United States; Vanderbilt University, Institute of Imaging Science, United States; Vanderbilt University Medical Center, United States
| | - Michael L Nickels
- Vanderbilt Center for Molecular Probes, United States; Vanderbilt University, Institute of Imaging Science, United States; Vanderbilt University Medical Center, United States; Mallinckrodt Institute of Radiology, Washington University School of Medicine, United States
| | - M Noor Tantawy
- Vanderbilt University, Institute of Imaging Science, United States; Vanderbilt University Medical Center, United States
| | - H Charles Manning
- Vanderbilt Center for Molecular Probes, United States; Vanderbilt University, Institute of Imaging Science, United States; Vanderbilt University Medical Center, United States; Department of Radiology, Vanderbilt University Medical Center, United States.
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Evans BJ, King AT, Katsifis A, Matesic L, Jamie JF. Methods to Enhance the Metabolic Stability of Peptide-Based PET Radiopharmaceuticals. Molecules 2020; 25:molecules25102314. [PMID: 32423178 PMCID: PMC7287708 DOI: 10.3390/molecules25102314] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 05/11/2020] [Accepted: 05/13/2020] [Indexed: 12/28/2022] Open
Abstract
The high affinity and specificity of peptides towards biological targets, in addition to their favorable pharmacological properties, has encouraged the development of many peptide-based pharmaceuticals, including peptide-based positron emission tomography (PET) radiopharmaceuticals. However, the poor in vivo stability of unmodified peptides against proteolysis is a major challenge that must be overcome, as it can result in an impractically short in vivo biological half-life and a subsequently poor bioavailability when used in imaging and therapeutic applications. Consequently, many biologically and pharmacologically interesting peptide-based drugs may never see application. A potential way to overcome this is using peptide analogues designed to mimic the pharmacophore of a native peptide while also containing unnatural modifications that act to maintain or improve the pharmacological properties. This review explores strategies that have been developed to increase the metabolic stability of peptide-based pharmaceuticals. It includes modifications of the C- and/or N-termini, introduction of d- or other unnatural amino acids, backbone modification, PEGylation and alkyl chain incorporation, cyclization and peptide bond substitution, and where those strategies have been, or could be, applied to PET peptide-based radiopharmaceuticals.
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Affiliation(s)
- Brendan J. Evans
- Department of Molecular Sciences, Macquarie University, Sydney, NSW 2109, Australia; (B.J.E.); (A.T.K.)
| | - Andrew T. King
- Department of Molecular Sciences, Macquarie University, Sydney, NSW 2109, Australia; (B.J.E.); (A.T.K.)
| | - Andrew Katsifis
- Department of Molecular Imaging, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia;
| | - Lidia Matesic
- Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW 2234, Australia;
| | - Joanne F. Jamie
- Department of Molecular Sciences, Macquarie University, Sydney, NSW 2109, Australia; (B.J.E.); (A.T.K.)
- Correspondence: ; Tel.: +61-2-9850-8283
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Cybulska K, Perk L, Booij J, Laverman P, Rijpkema M. Huntington's Disease: A Review of the Known PET Imaging Biomarkers and Targeting Radiotracers. Molecules 2020; 25:molecules25030482. [PMID: 31979301 PMCID: PMC7038198 DOI: 10.3390/molecules25030482] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 01/14/2020] [Accepted: 01/15/2020] [Indexed: 12/19/2022] Open
Abstract
Huntington’s disease (HD) is a fatal neurodegenerative disease caused by a CAG expansion mutation in the huntingtin gene. As a result, intranuclear inclusions of mutant huntingtin protein are formed, which damage striatal medium spiny neurons (MSNs). A review of Positron Emission Tomography (PET) studies relating to HD was performed, including clinical and preclinical data. PET is a powerful tool for visualisation of the HD pathology by non-invasive imaging of specific radiopharmaceuticals, which provide a detailed molecular snapshot of complex mechanistic pathways within the brain. Nowadays, radiochemists are equipped with an impressive arsenal of radioligands to accurately recognise particular receptors of interest. These include key biomarkers of HD: adenosine, cannabinoid, dopaminergic and glutamateric receptors, microglial activation, phosphodiesterase 10 A and synaptic vesicle proteins. This review aims to provide a radiochemical picture of the recent developments in the field of HD PET, with significant attention devoted to radiosynthetic routes towards the tracers relevant to this disease.
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Affiliation(s)
- Klaudia Cybulska
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Geert Grooteplein-Zuid 10, 6525 EZ Nijmegen, The Netherlands; (J.B.); (P.L.); (M.R.)
- Radboud Translational Medicine B.V., Radboud University Medical Center, Geert Grooteplein 21 (route 142), 6525 EZ Nijmegen, The Netherlands;
- Correspondence:
| | - Lars Perk
- Radboud Translational Medicine B.V., Radboud University Medical Center, Geert Grooteplein 21 (route 142), 6525 EZ Nijmegen, The Netherlands;
| | - Jan Booij
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Geert Grooteplein-Zuid 10, 6525 EZ Nijmegen, The Netherlands; (J.B.); (P.L.); (M.R.)
- Department of Radiology and Nuclear Medicine, Amsterdam University Medical Centers, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
| | - Peter Laverman
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Geert Grooteplein-Zuid 10, 6525 EZ Nijmegen, The Netherlands; (J.B.); (P.L.); (M.R.)
| | - Mark Rijpkema
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Geert Grooteplein-Zuid 10, 6525 EZ Nijmegen, The Netherlands; (J.B.); (P.L.); (M.R.)
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Knapp KA, Nickels ML, Manning HC. The Current Role of Microfluidics in Radiofluorination Chemistry. Mol Imaging Biol 2019; 22:463-475. [DOI: 10.1007/s11307-019-01414-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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15
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Fujinaga M, Kumata K, Zhang Y, Hatori A, Yamasaki T, Mori W, Ohkubo T, Xie L, Nengaki N, Zhang MR. Synthesis of two novel [ 18F]fluorobenzene-containing radiotracers via spirocyclic iodonium ylides and positron emission tomography imaging of translocator protein (18 kDa) in ischemic brain. Org Biomol Chem 2019; 16:8325-8335. [PMID: 30206613 DOI: 10.1039/c8ob01700j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Two novel radiotracers, namely, N-(4-[18F]fluorobenzyl)-N-methyl-2-(7-methyl-8-oxo-2-phenyl-7,8-dihydro-9H-purin-9-yl)acetamide ([18F]5) and 2-(5-(4-[18F]fluorophenyl)-2-oxobenzo[d]oxazol-3(2H)-yl)-N-methyl-N-phenylacetamide ([18F]6), were developed for positron emission tomography (PET) imaging of translocator protein (18 kDa) (TSPO) in ischemic brain in this study. The two radiotracers with a [18F]fluorobenzene ring were derived from the corresponding [18F]fluoroethyl tracers [18F]7 and [18F]8 which underwent [18F]defluoroethylation in vivo easily. [18F]5 or [18F]6 was synthesized by the radiofluorination of the spirocyclic iodonium ylide precursor 10 or 17 with [18F]F- in 23 ± 10% (n = 7) or 56 ± 9% (n = 7) radiochemical yields (decay-corrected, based on [18F]F-). [18F]5 and [18F]6 showed high in vitro binding affinities (Ki = 0.70 nM and 5.9 nM) for TSPO and moderate lipophilicities (log D = 2.9 and 3.4). Low uptake of radioactivity for both radiotracers was observed in mouse bones. Metabolite analysis showed that the in vivo stability of [18F]5 and [18F]6 was improved in comparison to the parent radiotracers [18F]7 and [18F]8. In particular, no radiolabelled metabolite of [18F]5 was found in the mouse brains at 60 min after the radiotracer injection. PET studies with [18F]5 on ischemic rat brains revealed a higher binding potential (BPND = 3.42) and maximum uptake ratio (4.49) between the ipsilateral and contralateral sides. Thus, [18F]5 was shown to be a useful PET radiotracer for visualizing TSPO in neuroinflammation models.
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Affiliation(s)
- Masayuki Fujinaga
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
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16
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López-Picón FR, Kirjavainen AK, Forsback S, Takkinen JS, Peters D, Haaparanta-Solin M, Solin O. In vivo characterization of a novel norepinephrine transporter PET tracer [ 18F]NS12137 in adult and immature Sprague-Dawley rats. Am J Cancer Res 2019; 9:11-19. [PMID: 30662550 PMCID: PMC6332804 DOI: 10.7150/thno.29740] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 11/16/2018] [Indexed: 12/31/2022] Open
Abstract
Norepinephrine modulates cognitive processes such as working and episodic memory. Pathological changes in norepinephrine and norepinephrine transporter (NET) function and degeneration of the locus coeruleus produce irreversible impairments within the whole norepinephrine system, disrupting cognitive processes. Monitoring these changes could enhance diagnostic accuracy and support development of novel therapeutic components for several neurodegenerative diseases. Thus, we aimed to develop a straightforward nucleophilic fluorination method with high molar activity for the novel NET radiotracer [18F]NS12137 and to demonstrate the ability of [18F]NS12137 to quantify changes in NET expression. Methods: We applied an 18F-radiolabeling method in which a brominated precursor was debrominated by nucleophilic 18F-fluorination in dimethyl sulfoxide. Radiolabeling was followed by a deprotection step, purification, and formulation of the radiotracer. The [18F]NS12137 brain uptake and distribution were studied with in vivo PET/CT and ex vivo autoradiography using both adult and immature Sprague-Dawley rats because postnatal NET expression peaks at 10-20 days post birth. The NET specificity for the tracer was demonstrated by pretreatment of the animals with nisoxetine, which is well-known to have a high affinity for NET. Results: [18F]NS12137 was successfully synthesized with radiochemical yields of 18.6±5.6%, radiochemical purity of >99%, and molar activity of >500 GBq/μmol at the end of synthesis. The in vivo [18F]NS12137 uptake showed peak standard uptake values (SUV) of over 1.5 (adult) and 2.2 (immature) in the different brain regions. Peak SUV/30 min and peak SUV/60 min ratios were calculated for the different brain regions of the adult and immature rats, with a peak SUV/60 min ratio of more than 4.5 in the striatum of adult rats. As expected, in vivo studies demonstrated uptake of the tracer in brain areas rich in NET, particularly thalamus, neocortex, and striatum, and remarkably also in the locus coeruleus, a quite small volume for imaging with PET. The uptake was significantly higher in immature rats compared to the adult animals. Ex vivo studies using autoradiography showed very strong specific binding in NET-rich areas such as the locus coeruleus and the bed nucleus of the stria terminalis, and high binding in larger grey matter areas such as the neocortex and striatum. The uptake of [18F]NS12137 was dramatically reduced both in vivo and ex vivo by pretreatment with nisoxetine, demonstrating the specificity of binding. Conclusions: [18F]NS12137 was synthesized in good yield and high molar activity and demonstrated the characteristics of a good radiotracer, such as good brain penetration, fast washout, and high specific binding to NET.
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Huang S, Li C, Guo J, Zhang L, Wu S, Wang H, Liang S. Monitoring the Progression of Chronic Liver Damage in Rats Using [18F]PBR06. Mol Imaging Biol 2018; 21:669-675. [DOI: 10.1007/s11307-018-1282-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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18
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Simmons DA, James ML, Belichenko NP, Semaan S, Condon C, Kuan J, Shuhendler AJ, Miao Z, Chin FT, Longo FM. TSPO-PET imaging using [18F]PBR06 is a potential translatable biomarker for treatment response in Huntington's disease: preclinical evidence with the p75NTR ligand LM11A-31. Hum Mol Genet 2018; 27:2893-2912. [PMID: 29860333 PMCID: PMC6077813 DOI: 10.1093/hmg/ddy202] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 05/04/2018] [Accepted: 05/21/2018] [Indexed: 12/11/2022] Open
Abstract
Huntington's disease (HD) is an inherited neurodegenerative disorder that has no cure. HD therapeutic development would benefit from a non-invasive translatable biomarker to track disease progression and treatment response. A potential biomarker is using positron emission tomography (PET) imaging with a translocator protein 18 kDa (TSPO) radiotracer to detect microglial activation, a key contributor to HD pathogenesis. The ability of TSPO-PET to identify microglial activation in HD mouse models, essential for a translatable biomarker, or therapeutic efficacy in HD patients or mice is unknown. Thus, this study assessed the feasibility of utilizing PET imaging with the TSPO tracer, [18F]PBR06, to detect activated microglia in two HD mouse models and to monitor response to treatment with LM11A-31, a p75NTR ligand known to reduce neuroinflammation in HD mice. [18F]PBR06-PET detected microglial activation in striatum, cortex and hippocampus of vehicle-treated R6/2 mice at a late disease stage and, notably, also in early and mid-stage symptomatic BACHD mice. After oral administration of LM11A-31 to R6/2 and BACHD mice, [18F]PBR06-PET discerned the reductive effects of LM11A-31 on neuroinflammation in both HD mouse models. [18F]PBR06-PET signal had a spatial distribution similar to ex vivo brain autoradiography and correlated with microglial activation markers: increased IBA-1 and TSPO immunostaining/blotting and striatal levels of cytokines IL-6 and TNFα. These results suggest that [18F]PBR06-PET is a useful surrogate marker of therapeutic efficacy in HD mice with high potential as a translatable biomarker for preclinical and clinical HD trials.
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Affiliation(s)
- Danielle A Simmons
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Michelle L James
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
- Department of Radiology, Molecular Imaging Program at Stanford, Stanford University, Stanford, CA, USA
| | - Nadia P Belichenko
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Sarah Semaan
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Christina Condon
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Jason Kuan
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Adam J Shuhendler
- Department of Radiology, Molecular Imaging Program at Stanford, Stanford University, Stanford, CA, USA
| | - Zheng Miao
- Department of Radiology, Molecular Imaging Program at Stanford, Stanford University, Stanford, CA, USA
| | - Frederick T Chin
- Department of Radiology, Molecular Imaging Program at Stanford, Stanford University, Stanford, CA, USA
| | - Frank M Longo
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
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Matesic L, Kallinen A, Greguric I, Pascali G. Dose-on-demand production of diverse 18 F-radiotracers for preclinical applications using a continuous flow microfluidic system. Nucl Med Biol 2017; 52:24-31. [DOI: 10.1016/j.nucmedbio.2017.05.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 05/08/2017] [Accepted: 05/10/2017] [Indexed: 12/30/2022]
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20
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Fujinaga M, Luo R, Kumata K, Zhang Y, Hatori A, Yamasaki T, Xie L, Mori W, Kurihara Y, Ogawa M, Nengaki N, Wang F, Zhang MR. Development of a 18F-Labeled Radiotracer with Improved Brain Kinetics for Positron Emission Tomography Imaging of Translocator Protein (18 kDa) in Ischemic Brain and Glioma. J Med Chem 2017; 60:4047-4061. [PMID: 28422499 DOI: 10.1021/acs.jmedchem.7b00374] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We designed four novel acetamidobenzoxazolone compounds 7a-d as candidates for positron emission tomography (PET) radiotracers for imaging the translocator protein (18 kDa, TSPO) in ischemic brain and glioma. Among these compounds, 2-(5-(6-fluoropyridin-3-yl)-2-oxobenzo[d]oxazol-3(2H)-yl)-N-methyl-N-phenylacetamide (7d) exhibited high binding affinity (Ki = 13.4 nM) with the TSPO and moderate lipophilicity (log D = 1.92). [18F]7d was radiosynthesized by [18F]fluorination of the bromopyridine precursor 7h with [18F]F- in 12 ± 5% radiochemical yield (n = 6, decay-corrected). In vitro autoradiography and PET studies of ischemic rat brain revealed higher binding of [18F]7d with TSPO on the ipsilateral side, as compared to the contralateral side, and improved brain kinetics compared with our previously developed radiotracers. Metabolite study of [18F]7d showed 93% of unchanged form in the ischemic brain at 30 min after injection. Moreover, PET study with [18F]7d provided a clear tumor image in a glioma-bearing rat model. We demonstrated that [18F]7d is a useful PET radiotracer for visualizing not only neuroinflammation but also glioma and will translate this radiotracer to a "first-in-human" study in our facility.
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Affiliation(s)
- Masayuki Fujinaga
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Rui Luo
- Department of Nuclear Medicine, Nanjing First Hospital, Nanjing Medical University , 68 Chanle Road, Nanjing 210006, China
| | - Katsushi Kumata
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Yiding Zhang
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Akiko Hatori
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Tomoteru Yamasaki
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Lin Xie
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Wakana Mori
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Yusuke Kurihara
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.,SHI Accelerator Service Co. , 1-17-6 Osaki, Shinagawa-ku, Tokyo 141-0032, Japan
| | - Masanao Ogawa
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.,SHI Accelerator Service Co. , 1-17-6 Osaki, Shinagawa-ku, Tokyo 141-0032, Japan
| | - Nobuki Nengaki
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.,SHI Accelerator Service Co. , 1-17-6 Osaki, Shinagawa-ku, Tokyo 141-0032, Japan
| | - Feng Wang
- Department of Nuclear Medicine, Nanjing First Hospital, Nanjing Medical University , 68 Chanle Road, Nanjing 210006, China
| | - Ming-Rong Zhang
- Department of Radiopharmaceuticals Development, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology , 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
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Eberl S, Katsifis A, Peyronneau MA, Wen L, Henderson D, Loc'h C, Greguric I, Verschuer J, Pham T, Lam P, Mattner F, Mohamed A, Fulham MJ. Preclinical in vivo and in vitro comparison of the translocator protein PET ligands [ 18F]PBR102 and [ 18F]PBR111. Eur J Nucl Med Mol Imaging 2016; 44:296-307. [PMID: 27699720 DOI: 10.1007/s00259-016-3517-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 09/05/2016] [Indexed: 11/27/2022]
Abstract
PURPOSE To determine the metabolic profiles of the translocator protein ligands PBR102 and PBR111 in rat and human microsomes and compare their in vivo binding and metabolite uptake in the brain of non-human primates (Papio hamadryas) using PET-CT. METHODS In vitro metabolic profiles of PBR102 and PBR111 in rat and human liver microsomes were assessed by liquid chromatography-tandem mass spectrometry. [18F]PBR102 and [18F]PBR111 were prepared by nucleophilic substitution of their corresponding p-toluenesulfonyl precursors with [18F]fluoride. List mode PET-CT brain imaging with arterial blood sampling was performed in non-human primates. Blood plasma measurements and metabolite analysis, using solid-phase extraction, provided the metabolite profile and metabolite-corrected input functions for kinetic model fitting. Blocking and displacement PET-CT scans, using PK11195, were performed. RESULTS Microsomal analyses identified the O-de-alkylated, hydroxylated and N-de-ethyl derivatives of PBR102 and PBR111 as the main metabolites. The O-de-alkylated compounds were the major metabolites in both species; human liver microsomes were less active than those from rat. Metabolic profiles in vivo in non-human primates and previously published rat experiments were consistent with the microsomal results. PET-CT studies showed that K1 was similar for baseline and blocking studies for both radiotracers; VT was reduced during the blocking study, suggesting low non-specific binding and lack of appreciable metabolite uptake in the brain. CONCLUSIONS [18F]PBR102 and [18F]PBR111 have distinct metabolic profiles in rat and non-human primates. Radiometabolites contributed to non-specific binding and confounded in vivo brain analysis of [18F]PBR102 in rodents; the impact in primates was less pronounced. Both [18F]PBR102 and [18F]PBR111 are suitable for PET imaging of TSPO in vivo. In vitro metabolite studies can be used to predict in vivo radioligand metabolism and can assist in the design and development of better radioligands.
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Affiliation(s)
- S Eberl
- Department of Molecular Imaging (PET and Nuclear Medicine), Royal Prince Alfred Hospital, Building 63, Level A7, Missenden Road, Camperdown, NSW, 2050, Australia. .,Faculty of Engineering and Information Technologies, University of Sydney, Sydney, NSW, 2006, Australia.
| | - A Katsifis
- Department of Molecular Imaging (PET and Nuclear Medicine), Royal Prince Alfred Hospital, Building 63, Level A7, Missenden Road, Camperdown, NSW, 2050, Australia.,Faculty of Pharmacy, University of Sydney, Sydney, NSW, 2006, Australia
| | - M A Peyronneau
- IMIV, CEA, Inserm, Univ. Paris-Sud, CNRS, Université Paris-Saclay, CEA-SHFJ, Orsay, France
| | - L Wen
- Department of Molecular Imaging (PET and Nuclear Medicine), Royal Prince Alfred Hospital, Building 63, Level A7, Missenden Road, Camperdown, NSW, 2050, Australia.,Faculty of Engineering and Information Technologies, University of Sydney, Sydney, NSW, 2006, Australia
| | - D Henderson
- Department of Molecular Imaging (PET and Nuclear Medicine), Royal Prince Alfred Hospital, Building 63, Level A7, Missenden Road, Camperdown, NSW, 2050, Australia
| | - C Loc'h
- Department of Molecular Imaging (PET and Nuclear Medicine), Royal Prince Alfred Hospital, Building 63, Level A7, Missenden Road, Camperdown, NSW, 2050, Australia
| | - I Greguric
- Radiochemistry and Radiotracers Platform, ANSTO, New Illawarra Road, Lucas Heights, NSW, 2234, Australia
| | - J Verschuer
- Department of Molecular Imaging (PET and Nuclear Medicine), Royal Prince Alfred Hospital, Building 63, Level A7, Missenden Road, Camperdown, NSW, 2050, Australia
| | - T Pham
- Radiochemistry and Radiotracers Platform, ANSTO, New Illawarra Road, Lucas Heights, NSW, 2234, Australia
| | - P Lam
- Department of Molecular Imaging (PET and Nuclear Medicine), Royal Prince Alfred Hospital, Building 63, Level A7, Missenden Road, Camperdown, NSW, 2050, Australia
| | - F Mattner
- Department of Molecular Imaging (PET and Nuclear Medicine), Royal Prince Alfred Hospital, Building 63, Level A7, Missenden Road, Camperdown, NSW, 2050, Australia
| | - A Mohamed
- Department of Molecular Imaging (PET and Nuclear Medicine), Royal Prince Alfred Hospital, Building 63, Level A7, Missenden Road, Camperdown, NSW, 2050, Australia.,Sydney Medical School, University of Sydney, Sydney, NSW, 2006, Australia
| | - M J Fulham
- Department of Molecular Imaging (PET and Nuclear Medicine), Royal Prince Alfred Hospital, Building 63, Level A7, Missenden Road, Camperdown, NSW, 2050, Australia.,Faculty of Engineering and Information Technologies, University of Sydney, Sydney, NSW, 2006, Australia.,Sydney Medical School, University of Sydney, Sydney, NSW, 2006, Australia
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22
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Di Grigoli G, Monterisi C, Belloli S, Masiello V, Politi LS, Valenti S, Paolino M, Anzini M, Matarrese M, Cappelli A, Moresco RM. Radiosynthesis and Preliminary Biological Evaluation of [18F]VC701, a Radioligand for Translocator Protein. Mol Imaging 2016; 14. [PMID: 26044669 DOI: 10.2310/7290.2015.00007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Positron emission tomography (PET) can be used to monitor in vivo translocator protein (TSPO) expression by using specific radioligands. Recently, several [11C]PK11195 analogues have been synthesized to improve binding stability and brain availability. [18F]VC701 was synthesized and validated in CD healthy rats by biodistribution and inhibition analysis. Imaging studies were also conducted on animals injected unilaterally in the striatum with quinolinic acid (QA) to evaluate the TSPO ligand uptake in a neuroinflammation/neurodegenerative model. [18F]VC701 was synthesized with a good chemical and radiochemical purity and specific activity higher than 37 GBq/μmol. Kinetic studies performed on healthy animals showed the highest tracer biodistribution in TSPO-rich organs, and preadministration of cold PK11195 caused an overall radioactivity reduction. Metabolism studies showed the absence of radiometabolites in the rat brain of QA lesioned rats, and biodistribution analysis revealed a progressive increase in radioactivity ratios (lesioned to nonlesioned striatum) during time, reaching an approximate value of 5 4 hours after tracer injection. These results encourage further evaluation of this TSPO radioligand in other models of central and peripheral diseases.
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23
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Pike VW. Considerations in the Development of Reversibly Binding PET Radioligands for Brain Imaging. Curr Med Chem 2016; 23:1818-69. [PMID: 27087244 PMCID: PMC5579844 DOI: 10.2174/0929867323666160418114826] [Citation(s) in RCA: 130] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 04/04/2016] [Accepted: 04/15/2016] [Indexed: 12/17/2022]
Abstract
The development of reversibly binding radioligands for imaging brain proteins in vivo, such as enzymes, neurotransmitter transporters, receptors and ion channels, with positron emission tomography (PET) is keenly sought for biomedical studies of neuropsychiatric disorders and for drug discovery and development, but is recognized as being highly challenging at the medicinal chemistry level. This article aims to compile and discuss the main considerations to be taken into account by chemists embarking on programs of radioligand development for PET imaging of brain protein targets.
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Affiliation(s)
- Victor W Pike
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Rm. B3C346A, 10 Center Drive, Bethesda, MD 20892, USA.
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24
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Kumar P, Bacchu V, Wiebe LI. The chemistry and radiochemistry of hypoxia-specific, radiohalogenated nitroaromatic imaging probes. Semin Nucl Med 2015; 45:122-35. [PMID: 25704385 DOI: 10.1053/j.semnuclmed.2014.10.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Hypoxia is prevalent in many solid tumors. Hypoxic tumors tend to exhibit rapid growth and aberrant vasculature, which lead to oxygen (O2) depletion and impaired drug delivery. The reductive environment in hypoxic tumors alters cellular metabolism, which can trigger transcriptional responses; induce genetic alterations; promote invasion, metastasis, resistance to radiotherapy and chemotherapy, tumor progression, and recurrence; and leads to poor local control and reduced survival rates. Therefore, exploiting the reductive microenvironment in hypoxic tumors by delivering electron-affinic, O2-mimetic radioactive drugs that bioreductively activate selectively in the hypoxic microenvironment offers a logical approach to molecular imaging of focal hypoxia. Because these agents also radiosensitize hypoxic cells, they provide an innovative approach to the therapy management of such tumors. To date, nuclear imaging of hypoxic tumor has proven to be clinically effective, whereas chemical radiosensitization by these compounds has not been helpful. The current review provides an insight into the chemistry, radiochemistry, and purification strategies for selected nitroaromatics that directly exploit the bioreductive environment in hypoxic cells. Both experimental and calculated single-electron reduction potentials of electron-affinic compounds, nitroimidazoles in particular, correlate with in vitro radiosensitizing properties, making them preferred choices for use as radiopharmaceuticals for diagnostic imaging and as sensitizers to enhance the killing effects of low-energy-transfer x-rays (O2-mimetic radiosensitization). Extensive research and careful drug design have led to the development of several potentially useful hypoxia-targeting drugs, for example, [(18)F]FAZA, [(18)F]FMISO, [(18)F]EF5, and [(123)I]IAZA, that accrue selectively in hypoxic cells. These molecular probes are now globally used in clinical hypoxia imaging, including cancer. Future innovative developments must, however, consider hypoxia-selective molecular processes and the physicochemical properties of the drugs that dictate their biodistribution, hypoxia-selective accumulation, pharmacokinetics, clearance, biochemical behavior, and metabolism. This will facilitate their ultimate transformation to effective molecular theranostics, leading to improved multimodal management of cancer.
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Affiliation(s)
- Piyush Kumar
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada.
| | - Veena Bacchu
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada
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25
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Methods to Increase the Metabolic Stability of (18)F-Radiotracers. Molecules 2015; 20:16186-220. [PMID: 26404227 PMCID: PMC6332123 DOI: 10.3390/molecules200916186] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 08/20/2015] [Accepted: 08/26/2015] [Indexed: 11/17/2022] Open
Abstract
The majority of pharmaceuticals and other organic compounds incorporating radiotracers that are considered foreign to the body undergo metabolic changes in vivo. Metabolic degradation of these drugs is commonly caused by a system of enzymes of low substrate specificity requirement, which is present mainly in the liver, but drug metabolism may also take place in the kidneys or other organs. Thus, radiotracers and all other pharmaceuticals are faced with enormous challenges to maintain their stability in vivo highlighting the importance of their structure. Often in practice, such biologically active molecules exhibit these properties in vitro, but fail during in vivo studies due to obtaining an increased metabolism within minutes. Many pharmacologically and biologically interesting compounds never see application due to their lack of stability. One of the most important issues of radiotracers development based on fluorine-18 is the stability in vitro and in vivo. Sometimes, the metabolism of 18F-radiotracers goes along with the cleavage of the C-F bond and with the rejection of [18F]fluoride mostly combined with high background and accumulation in the skeleton. This review deals with the impact of radiodefluorination and with approaches to stabilize the C-F bond to avoid the cleavage between fluorine and carbon.
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26
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The relationship between serial [(18) F]PBR06 PET imaging of microglial activation and motor function following stroke in mice. Mol Imaging Biol 2015; 16:821-9. [PMID: 24865401 DOI: 10.1007/s11307-014-0745-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
PURPOSE Using [(18) F]PBR06 positron emission tomography (PET) to characterize the time course of stroke-associated neuroinflammation (SAN) in mice, to evaluate whether brain microglia influences motor function after stroke, and to demonstrate the use of [(18) F]PBR06 PET as a therapeutic assessment tool. PROCEDURES Stroke was induced by transient middle cerebral artery occlusion (MCAO) in Balb/c mice (control, stroke, and stroke with poststroke minocycline treatment). [18 F]PBR06 PET/CT imaging, rotarod tests, and immunohistochemistry (IHC) were performed 3, 11, and 22 days poststroke induction (PSI). RESULTS The stroke group exhibited significantly increased microglial activation, and impaired motor function. Peak microglial activation was 11 days PSI. There was a strong association between microglial activation, motor function, and microglial protein expression on IHC. Minocycline significantly reduced microglial activation and improved motor function by day 22 PSI. CONCLUSION [18 F]PBR06 PET imaging noninvasively characterizes the time course of SAN, and shows increased microglial activation is associated with decreased motor function.
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27
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Biesmans S, Acton PD, Cotto C, Langlois X, Ver Donck L, Bouwknecht JA, Aelvoet SA, Hellings N, Meert TF, Nuydens R. Effect of stress and peripheral immune activation on astrocyte activation in transgenic bioluminescent Gfap-luc mice. Glia 2015; 63:1126-37. [PMID: 25690758 DOI: 10.1002/glia.22804] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Accepted: 01/22/2015] [Indexed: 12/13/2022]
Abstract
Neuroinflammation and the accompanying activation of glial cells is an important feature of many neurodegenerative conditions. It is known that factors such as peripheral infections and stress can influence immune processes in the brain. However, the effect of these stressors on astrocyte activation in vivo remains elusive. In this study, transgenic Gfap-luc mice expressing the luciferase gene under the transcriptional control of the glial fibrillary acidic protein promoter were used to quantify the kinetics of in vivo astrocyte activation following immune challenges relevant to clinical inflammation. It was found that astrocytes respond rapidly to peripheral immune activation elicited by either bacterial lipopolysaccharide (LPS) or the viral mimetic polyinosinic:polycytidylic acid (poly(I:C)). By measuring bioluminescence and 18-kDa translocator protein radioligand binding in the same animal it was observed that LPS induces both astrocyte as well as microglial activation at 6 h post-administration. Furthermore, the astrocyte response decreased upon repeated systemic LPS injections, indicating development of tolerance to the LPS challenge. Finally, restraining Gfap-luc mice for 1 h daily on 5 consecutive days did not affect brain bioluminescence, thereby indicating that sub-chronic stress does not influence astrocyte activation under unchallenged conditions. However, stressed animals showed a reduced response to a subsequent systemic LPS injection, suggesting that the immune system is compromised in these animals. Here, we demonstrate that Gfap-luc mice can be used to study astrocyte activation in response to stimuli relevant for clinical inflammation and that this approach may provide a more complete characterization of existing and novel models of neuroinflammation
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Affiliation(s)
- Steven Biesmans
- Biomedical Research Institute, Hasselt University, Agoralaan C Building, Diepenbeek, Belgium; Neurosciences, Janssen Research & Development, A Division of Janssen Pharmaceutica NV, Beerse, Belgium
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28
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Zanotti-Fregonara P, Zhang Y, Jenko KJ, Gladding RL, Zoghbi SS, Fujita M, Sbardella G, Castellano S, Taliani S, Martini C, Innis RB, Da Settimo F, Pike VW. Synthesis and evaluation of translocator 18 kDa protein (TSPO) positron emission tomography (PET) radioligands with low binding sensitivity to human single nucleotide polymorphism rs6971. ACS Chem Neurosci 2014; 5:963-71. [PMID: 25123416 PMCID: PMC4210126 DOI: 10.1021/cn500138n] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
![]()
The imaging of translocator 18 kDa
protein (TSPO) in living human
brain with radioligands by positron emission tomography (PET) has
become an important means for the study of neuroinflammatory conditions
occurring in several neuropsychiatric disorders. The widely used prototypical
PET radioligand [11C](R)-PK 11195 ([11C](R)-1; [N-methyl-11C](R)-N-sec-butyl-1-(2-chlorophenyl)-N-methylisoquinoline-3-carboxamide) gives a low PET signal and is
difficult to quantify, whereas later generation radioligands have
binding sensitivity to a human single nucleotide polymorphism (SNP)
rs6971, which imposes limitations on their utility for comparative
quantitative PET studies of normal and diseased subjects. Recently,
azaisosteres of 1 have been developed with improved drug-like
properties, including enhanced TSPO affinity accompanied by moderated
lipophilicity. Here we selected three of these new ligands (7–9) for labeling with carbon-11 and for
evaluation in monkey as candidate PET radioligands for imaging brain
TSPO. Each radioligand was readily prepared by 11C-methylation
of an N-desmethyl precursor and was found to give
a high proportion of TSPO-specific binding in monkey brain. One of
these radioligands, [11C]7, the direct 4-azaisostere
of 1, presents many radioligand properties that are superior
to those reported for [11C]1, including higher
affinity, lower lipophilicity, and stable quantifiable PET signal.
Importantly, 7 was also found to show very low sensitivity
to the human SNP rs6971 in vitro. Therefore, [11C]7 now warrants evaluation in human subjects with PET to assess
its utility for imaging TSPO in human brain, irrespective of subject
genotype.
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Affiliation(s)
- Paolo Zanotti-Fregonara
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Yi Zhang
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Kimberly J. Jenko
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Robert L. Gladding
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Sami S. Zoghbi
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Masahiro Fujita
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Gianluca Sbardella
- Department
of Pharmacy, University of Salerno, 84084 Fisciano (SA), Italy
| | - Sabrina Castellano
- Department
of Pharmacy, University of Salerno, 84084 Fisciano (SA), Italy
| | - Sabrina Taliani
- Department
of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Claudia Martini
- Department
of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Robert B. Innis
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
| | - Federico Da Settimo
- Department
of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Victor W. Pike
- Molecular
Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-0001, United States
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29
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Rensch C, Lindner S, Salvamoser R, Leidner S, Böld C, Samper V, Taylor D, Baller M, Riese S, Bartenstein P, Wängler C, Wängler B. A solvent resistant lab-on-chip platform for radiochemistry applications. LAB ON A CHIP 2014; 14:2556-2564. [PMID: 24879121 DOI: 10.1039/c4lc00076e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The application of microfluidics to the synthesis of Positron Emission Tomography (PET) tracers has been explored for more than a decade. Microfluidic benefits such as superior temperature control have been successfully applied to PET tracer synthesis. However, the design of a compact microfluidic platform capable of executing a complete PET tracer synthesis workflow while maintaining prospects for commercialization remains a significant challenge. This study uses an integral system design approach to tackle commercialization challenges such as the material to process compatibility with a path towards cost effective lab-on-chip mass manufacturing from the start. It integrates all functional elements required for a simple PET tracer synthesis into one compact radiochemistry platform. For the lab-on-chip this includes the integration of on-chip valves, on-chip solid phase extraction (SPE), on-chip reactors and a reversible fluid interface while maintaining compatibility with all process chemicals, temperatures and chip mass manufacturing techniques. For the radiochemistry device it includes an automated chip-machine interface enabling one-move connection of all valve actuators and fluid connectors. A vial-based reagent supply as well as methods to transfer reagents efficiently from the vials to the chip has been integrated. After validation of all those functional elements, the microfluidic platform was exemplarily employed for the automated synthesis of a Gastrin-releasing peptide receptor (GRP-R) binding the PEGylated Bombesin BN(7-14)-derivative ([(18)F]PESIN) based PET tracer.
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Affiliation(s)
- Christian Rensch
- GE Global Research, Freisinger Landstrasse 50, 85748 Garching bei Munich, Germany.
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30
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Médran-Navarrete V, Damont A, Peyronneau MA, Kuhnast B, Bernards N, Pottier G, Marguet F, Puech F, Boisgard R, Dollé F. Preparation and evaluation of novel pyrazolo[1,5-a]pyrimidine acetamides, closely related to DPA-714, as potent ligands for imaging the TSPO 18kDa with PET. Bioorg Med Chem Lett 2014; 24:1550-6. [DOI: 10.1016/j.bmcl.2014.01.080] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 01/24/2014] [Accepted: 01/27/2014] [Indexed: 12/13/2022]
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Amii H, Nagaki A, Yoshida JI. Flow microreactor synthesis in organo-fluorine chemistry. Beilstein J Org Chem 2013; 9:2793-802. [PMID: 24367443 PMCID: PMC3869211 DOI: 10.3762/bjoc.9.314] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 11/05/2013] [Indexed: 11/23/2022] Open
Abstract
Organo-fluorine compounds are the substances of considerable interest in various industrial fields due to their unique physical and chemical properties. Despite increased demand in wide fields of science, synthesis of fluoro-organic compounds is still often faced with problems such as the difficulties in handling of fluorinating reagents and in controlling of chemical reactions. Recently, flow microreactor synthesis has emerged as a new methodology for producing chemical substances with high efficiency. This review outlines the successful examples of synthesis and reactions of fluorine-containing molecules by the use of flow microreactor systems to overcome long-standing problems in fluorine chemistry.
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Affiliation(s)
- Hideki Amii
- Division of Molecular Science, Graduate School of Science and Technology, Gunma University, Tenjin-cho, Kiryu, Gunma 376-8515, Japan
| | - Aiichiro Nagaki
- Department of Synthetic and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Jun-Ichi Yoshida
- Department of Synthetic and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
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32
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Pascali G, Watts P, Salvadori PA. Microfluidics in radiopharmaceutical chemistry. Nucl Med Biol 2013; 40:776-87. [DOI: 10.1016/j.nucmedbio.2013.04.004] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 03/20/2013] [Accepted: 04/03/2013] [Indexed: 11/28/2022]
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PET imaging of stroke-induced neuroinflammation in mice using [18F]PBR06. Mol Imaging Biol 2013; 16:109-17. [PMID: 23836504 DOI: 10.1007/s11307-013-0664-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 06/03/2013] [Accepted: 06/18/2013] [Indexed: 01/17/2023]
Abstract
PURPOSE The purpose of this study is to evaluate the 18 kDa translocator protein (TSPO) radioligand [(18)F]N-fluoroacetyl-N-(2,5-dimethoxybenzyl)-2-phenoxyaniline ([(18)F]PBR06) as a positron emission tomography (PET) imaging biomarker of stroke-induced neuroinflammation in a rodent model. PROCEDURES Stroke was induced by transient middle cerebral artery occlusion in Balb/c mice. Dynamic PET/CT imaging with displacement and preblocking using PK111195 was performed 3 days later. PET data were correlated with immunohistochemistry (IHC) for the activated microglial markers TSPO and CD68 and with autoradiography. RESULTS [(18)F]PBR06 accumulation peaked within the first 5 min postinjection, then decreased gradually, remaining significantly higher in infarct compared to noninfarct regions. Displacement or preblocking with PK11195 eliminated the difference in [(18)F]PBR06 uptake between infarct and noninfarct regions. Autoradiography and IHC correlated well spatially with uptake on PET. CONCLUSIONS [(18)F]PBR06 PET specifically images TSPO in microglial neuroinflammation in a mouse model of stroke and shows promise for imaging and monitoring microglial activation/neuroinflammation in other disease models.
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34
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Rensch C, Jackson A, Lindner S, Salvamoser R, Samper V, Riese S, Bartenstein P, Wängler C, Wängler B. Microfluidics: a groundbreaking technology for PET tracer production? Molecules 2013; 18:7930-56. [PMID: 23884128 PMCID: PMC6270045 DOI: 10.3390/molecules18077930] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 06/21/2013] [Accepted: 07/03/2013] [Indexed: 11/16/2022] Open
Abstract
Application of microfluidics to Positron Emission Tomography (PET) tracer synthesis has attracted increasing interest within the last decade. The technical advantages of microfluidics, in particular the high surface to volume ratio and resulting fast thermal heating and cooling rates of reagents can lead to reduced reaction times, increased synthesis yields and reduced by-products. In addition automated reaction optimization, reduced consumption of expensive reagents and a path towards a reduced system footprint have been successfully demonstrated. The processing of radioactivity levels required for routine production, use of microfluidic-produced PET tracer doses in preclinical and clinical imaging as well as feasibility studies on autoradiolytic decomposition have all given promising results. However, the number of microfluidic synthesizers utilized for commercial routine production of PET tracers is very limited. This study reviews the state of the art in microfluidic PET tracer synthesis, highlighting critical design aspects, strengths, weaknesses and presenting several characteristics of the diverse PET market space which are thought to have a significant impact on research, development and engineering of microfluidic devices in this field. Furthermore, the topics of batch- and single-dose production, cyclotron to quality control integration as well as centralized versus de-centralized market distribution models are addressed.
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Affiliation(s)
- Christian Rensch
- GE Global Research, Freisinger Landstrasse 50, Garching bei Munich 85748, Germany; E-Mails: (R.S.); (V.S.)
| | - Alexander Jackson
- GE Healthcare, Life Sciences, The Grove Centre, White Lion Rd., Amersham HP7 9LL, UK; E-Mails: (A.J.); (S.R.)
| | - Simon Lindner
- University Hospital Munich, Department of Nuclear Medicine, Ludwig Maximilians-University, Munich 81377, Germany; E-Mails: (S.L.); (P.B.); (C.W.)
| | - Ruben Salvamoser
- GE Global Research, Freisinger Landstrasse 50, Garching bei Munich 85748, Germany; E-Mails: (R.S.); (V.S.)
| | - Victor Samper
- GE Global Research, Freisinger Landstrasse 50, Garching bei Munich 85748, Germany; E-Mails: (R.S.); (V.S.)
| | - Stefan Riese
- GE Healthcare, Life Sciences, The Grove Centre, White Lion Rd., Amersham HP7 9LL, UK; E-Mails: (A.J.); (S.R.)
| | - Peter Bartenstein
- University Hospital Munich, Department of Nuclear Medicine, Ludwig Maximilians-University, Munich 81377, Germany; E-Mails: (S.L.); (P.B.); (C.W.)
| | - Carmen Wängler
- University Hospital Munich, Department of Nuclear Medicine, Ludwig Maximilians-University, Munich 81377, Germany; E-Mails: (S.L.); (P.B.); (C.W.)
- Biomedical Chemistry, Department of Clinical Radiology and Nuclear Medicine, Medical Faculty Mannheim of Heidelberg University, Mannheim 68167, Germany
| | - Björn Wängler
- Molecular Imaging and Radiochemistry, Department of Clinical Radiology and Nuclear Medicine, Medical Faculty Mannheim of Heidelberg University, Mannheim 68167, Germany
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35
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Liu Z, Li Y, Lozada J, Wong MQ, Greene J, Lin KS, Yapp D, Perrin DM. Kit-like 18F-labeling of RGD-19F-arytrifluroborate in high yield and at extraordinarily high specific activity with preliminary in vivo tumor imaging. Nucl Med Biol 2013; 40:841-9. [PMID: 23810487 DOI: 10.1016/j.nucmedbio.2013.05.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Revised: 05/01/2013] [Accepted: 05/07/2013] [Indexed: 02/01/2023]
Abstract
INTRODUCTION Positron Emission Tomography (PET) is a rapidly expanding, cutting edge technology for preclinical evaluation, cancer diagnosis and staging, and patient management. A one-step aqueous (18)F-labeling method, which can be applied to peptides to provide functional in vivo images, has been a long-standing challenge in PET imaging. Over the past few years, we have sought a rapid and mild radiolabeling method based on the aqueous radiosynthesis of in vivo stable aryltrifluoroborate (ArBF(3)(-)) conjugates. Recent access to production levels of (18)F-Fluoride led to a fluorescent-(18)F-ArBF(3)(-) at unprecedentedly high specific activities of 15Ci/μmol. However, extending this method to labeling peptides as imaging agents has not been explored. METHODS In order to extend these results to a peptide of clinical interest in the context of production-level radiosynthesis, we applied this new technology for labeling RGD, measured its specific activity by standard curve analysis, and carried out a preliminary evaluation of its imaging properties. RESULTS RGD was labeled in excellent radiochemical yields at exceptionally high specific activity (~14Ci/μmol) (n = 3). Preliminary tumor-specific images corroborated by ex vivo biodistribution data with blocking controls show statistically significant albeit relatively low tumor uptake along with reasonably high tumor:blood ratios (n = 3). CONCLUSIONS Isotope exchange on a clinically useful (18)F-ArBF(3)(-) radiotracer leads to excellent radiochemical yields and exceptionally high specific activities while the anionic nature of the aryltrifluoroborate prosthetic results in very rapid clearance. Since rapid clearance of the radioactive tracer is generally desirable for tracer development, these results suggest new directions for varying linker arm composition to slightly retard clearance rather than enhancing it. ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE This work is the first to use production levels of (18)F-activity to directly label RGD at specific activities that are an order of magnitude higher than most reports and thereby increases the distribution window for radiotracer production and delivery.
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Affiliation(s)
- Zhibo Liu
- Chemistry Department, 2036 Main Mall, University of British Columbia, Vancouver, B.C., Canada
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False-Positive Finding of Brain Metastasis on 18F-FDG PET Imaging Due to Early Subacute Ischemic Stroke. Clin Nucl Med 2013; 38:465-6. [DOI: 10.1097/rlu.0b013e31828e970e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Löser R, Fischer S, Hiller A, Köckerling M, Funke U, Maisonial A, Brust P, Steinbach J. Use of 3-[(18)F]fluoropropanesulfonyl chloride as a prosthetic agent for the radiolabelling of amines: Investigation of precursor molecules, labelling conditions and enzymatic stability of the corresponding sulfonamides. Beilstein J Org Chem 2013; 9:1002-11. [PMID: 23766817 PMCID: PMC3678395 DOI: 10.3762/bjoc.9.115] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 04/26/2013] [Indexed: 11/23/2022] Open
Abstract
3-[(18)F]Fluoropropanesulfonyl chloride, a recently proposed prosthetic agent for fluorine-18 labelling, was prepared in a two-step radiosynthesis via 3-[(18)F]fluoropropyl thiocyanate as an intermediate. Two benzenesulfonate-based radiolabelling precursors were prepared by various routes. Comparing the reactivities of 3-thiocyanatopropyl nosylate and the corresponding tosylate towards [(18)F]fluoride the former proved to be superior accounting for labelling yields of up to 85%. Conditions for a reliable transformation of 3-[(18)F]fluoropropyl thiocyanate to the corresponding sulfonyl chloride with the potential for automation have been identified. The reaction of 3-[(18)F]fluoropropanesulfonyl chloride with eight different aliphatic and aromatic amines was investigated and the identity of the resulting (18)F-labelled sulfonamides was confirmed chromatographically by comparison with their nonradioactive counterparts. Even for weakly nucleophilic amines such as 4-nitroaniline the desired radiolabelled sulfonamides were accessible in satisfactory yields owing to systematic variation of the reaction conditions. With respect to the application of the (18)F-fluoropropansulfonyl group to the labelling of compounds relevant as imaging agents for positron emission tomography (PET), the stability of N-(4-fluorophenyl)-3-fluoropropanesulfonamide against degradation catalysed by carboxylesterase was investigated and compared to that of the analogous fluoroacetamide.
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Affiliation(s)
- Reik Löser
- Institute of Radiopharmaceutical Cancer Research (formerly Institute of Radiopharmacy), Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany ; Department of Chemistry and Food Chemistry, Technical University of Dresden, Bergstraße 66c, 01062 Dresden, Germany
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Damont A, Roeda D, Dollé F. The potential of carbon-11 and fluorine-18 chemistry: illustration through the development of positron emission tomography radioligands targeting the translocator protein 18 kDa. J Labelled Comp Radiopharm 2013; 56:96-104. [DOI: 10.1002/jlcr.2992] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 07/18/2012] [Accepted: 11/06/2012] [Indexed: 11/05/2022]
Affiliation(s)
- Annelaure Damont
- CEA, I2BM, Service Hospitalier Frédéric Joliot; 4 place du Général Leclerc; F-91406; Orsay; France
| | - Dirk Roeda
- CEA, I2BM, Service Hospitalier Frédéric Joliot; 4 place du Général Leclerc; F-91406; Orsay; France
| | - Frédéric Dollé
- CEA, I2BM, Service Hospitalier Frédéric Joliot; 4 place du Général Leclerc; F-91406; Orsay; France
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Jia L, Cheng Z, Shi L, Li J, Wang C, Jiang D, Zhou W, Meng H, Qi Y, Cheng D, Zhang L. Fluorine-18 labeling by click chemistry: multiple probes in one pot. Appl Radiat Isot 2013; 75:64-70. [PMID: 23455406 DOI: 10.1016/j.apradiso.2013.01.033] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Revised: 12/31/2012] [Accepted: 01/29/2013] [Indexed: 12/18/2022]
Abstract
Click chemistry has been widely applied in drug development including radiopharmaceuticals and has shown great advantages. Here we reported a novel strategy for rapid preparation of multiple (18)F labeled PET probes in one pot using the 'Click Reaction' of Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition of terminal alkynes and organic azides (CuAAC). Preliminary results showed its high efficiency and potential for speeding up the preclinical screening of PET probes.
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Affiliation(s)
- Lina Jia
- Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Sciences, PR China
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Liu Z, Li Y, Lozada J, Schaffer P, Adam MJ, Ruth TJ, Perrin DM. Stoichiometric Leverage: Rapid18F-Aryltrifluoroborate Radiosynthesis at High Specific Activity for Click Conjugation. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201208551] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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41
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Liu Z, Li Y, Lozada J, Schaffer P, Adam MJ, Ruth TJ, Perrin DM. Stoichiometric Leverage: Rapid18F-Aryltrifluoroborate Radiosynthesis at High Specific Activity for Click Conjugation. Angew Chem Int Ed Engl 2013; 52:2303-7. [DOI: 10.1002/anie.201208551] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Indexed: 02/06/2023]
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Liu Z, Li Y, Lozada J, Pan J, Lin KS, Schaffer P, Perrin DM. Rapid, one-step, high yielding18F-labeling of an aryltrifluoroborate bioconjugate by isotope exchange at very high specific activity. J Labelled Comp Radiopharm 2012. [DOI: 10.1002/jlcr.2990] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Zhibo Liu
- Chemistry Department, 2036 Main Mall; University of British Columbia; Vancouver; B.C.; V6T-1Z1; Canada
| | - Ying Li
- Chemistry Department, 2036 Main Mall; University of British Columbia; Vancouver; B.C.; V6T-1Z1; Canada
| | - Jerome Lozada
- Chemistry Department, 2036 Main Mall; University of British Columbia; Vancouver; B.C.; V6T-1Z1; Canada
| | - Jinhe Pan
- BC Cancer Agency - Vancouver Centre; Centre for Functional Imaging; 600 West 10th Avenue; Vancouver; B.C.; V5Z-4E6; Canada
| | - Kuo-Shyan Lin
- BC Cancer Agency - Vancouver Centre; Centre for Functional Imaging; 600 West 10th Avenue; Vancouver; B.C.; V5Z-4E6; Canada
| | - Paul Schaffer
- Triumf; 4004 Wesbrook Mall; Vancouver; B.C.; V6T-2A3; Canada
| | - David M. Perrin
- Chemistry Department, 2036 Main Mall; University of British Columbia; Vancouver; B.C.; V6T-1Z1; Canada
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Philippe C, Ungersboeck J, Schirmer E, Zdravkovic M, Nics L, Zeilinger M, Shanab K, Lanzenberger R, Karanikas G, Spreitzer H, Viernstein H, Mitterhauser M, Wadsak W. [¹⁸F]FE@SNAP-A new PET tracer for the melanin concentrating hormone receptor 1 (MCHR1): microfluidic and vessel-based approaches. Bioorg Med Chem 2012; 20:5936-40. [PMID: 22921745 PMCID: PMC3460236 DOI: 10.1016/j.bmc.2012.07.051] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 07/23/2012] [Accepted: 07/23/2012] [Indexed: 11/30/2022]
Abstract
Changes in the expression of the melanin concentrating hormone receptor 1 (MCHR1) are involved in a variety of pathologies, especially obesity and anxiety disorders. To monitor these pathologies in-vivo positron emission tomography (PET) is a suitable method. After the successful radiosynthesis of [(11)C]SNAP-7941-the first PET-Tracer for the MCHR1, we aimed to synthesize its [(18)F]fluoroethylated analogue: [(18)F]FE@SNAP. Therefore, microfluidic and vessel-based approaches were tested. [(18)F]fluoroethylation was conducted via various [(18)F]fluoroalkylated synthons and direct [(18)F]fluorination. Only the direct [(18)F]fluorination of a tosylated precursor using a flow-through microreactor was successful, affording [(18)F]FE@SNAP in 44.3 ± 2.6%.
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Affiliation(s)
- Cécile Philippe
- Radiochemistry and Biomarker Development Unit, Department of Nuclear Medicine, Medical University of Vienna, Waehringer Guertel 18-20, Vienna 1090, Austria
- Department of Pharmaceutical Technology and Biopharmaceutics, University of Vienna, Vienna 1090, Austria
| | - Johanna Ungersboeck
- Radiochemistry and Biomarker Development Unit, Department of Nuclear Medicine, Medical University of Vienna, Waehringer Guertel 18-20, Vienna 1090, Austria
- Department of Inorganic Chemistry, University of Vienna, 1090 Vienna, Austria
| | - Eva Schirmer
- Department of Drug and Natural Product Synthesis, University of Vienna, Vienna 1090, Austria
| | - Milica Zdravkovic
- Department of Pharmaceutical Technology and Biopharmaceutics, University of Vienna, Vienna 1090, Austria
| | - Lukas Nics
- Radiochemistry and Biomarker Development Unit, Department of Nuclear Medicine, Medical University of Vienna, Waehringer Guertel 18-20, Vienna 1090, Austria
- Department of Nutritional Sciences, University of Vienna, Vienna 1090, Austria
| | - Markus Zeilinger
- Radiochemistry and Biomarker Development Unit, Department of Nuclear Medicine, Medical University of Vienna, Waehringer Guertel 18-20, Vienna 1090, Austria
| | - Karem Shanab
- Department of Drug and Natural Product Synthesis, University of Vienna, Vienna 1090, Austria
| | - Rupert Lanzenberger
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, 1090 Vienna, Austria
| | - Georgios Karanikas
- Radiochemistry and Biomarker Development Unit, Department of Nuclear Medicine, Medical University of Vienna, Waehringer Guertel 18-20, Vienna 1090, Austria
| | - Helmut Spreitzer
- Department of Drug and Natural Product Synthesis, University of Vienna, Vienna 1090, Austria
| | - Helmut Viernstein
- Department of Pharmaceutical Technology and Biopharmaceutics, University of Vienna, Vienna 1090, Austria
| | - Markus Mitterhauser
- Radiochemistry and Biomarker Development Unit, Department of Nuclear Medicine, Medical University of Vienna, Waehringer Guertel 18-20, Vienna 1090, Austria
- Department of Pharmaceutical Technology and Biopharmaceutics, University of Vienna, Vienna 1090, Austria
- Hospital Pharmacy of the General Hospital of Vienna, 1090 Vienna, Austria
| | - Wolfgang Wadsak
- Radiochemistry and Biomarker Development Unit, Department of Nuclear Medicine, Medical University of Vienna, Waehringer Guertel 18-20, Vienna 1090, Austria
- Department of Inorganic Chemistry, University of Vienna, 1090 Vienna, Austria
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Gallino A, Stuber M, Crea F, Falk E, Corti R, Lekakis J, Schwitter J, Camici P, Gaemperli O, Di Valentino M, Prior J, Garcia-Garcia HM, Vlachopoulos C, Cosentino F, Windecker S, Pedrazzini G, Conti R, Mach F, De Caterina R, Libby P. “In vivo” imaging of atherosclerosis. Atherosclerosis 2012; 224:25-36. [DOI: 10.1016/j.atherosclerosis.2012.04.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 04/18/2012] [Accepted: 04/18/2012] [Indexed: 12/20/2022]
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Radiation dosimetry of the translocator protein ligands [18F]PBR111 and [18F]PBR102. Nucl Med Biol 2012; 39:742-53. [DOI: 10.1016/j.nucmedbio.2011.11.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 11/05/2011] [Accepted: 11/19/2011] [Indexed: 11/21/2022]
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Fully automated synthesis of PET TSPO radioligands [11C]DAA1106 and [18F]FEDAA1106. Appl Radiat Isot 2012; 70:965-73. [DOI: 10.1016/j.apradiso.2012.03.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 02/09/2012] [Accepted: 03/05/2012] [Indexed: 11/17/2022]
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Ungersboeck J, Richter S, Collier L, Mitterhauser M, Karanikas G, Lanzenberger R, Dudczak R, Wadsak W. Radiolabeling of [18F]altanserin - a microfluidic approach. Nucl Med Biol 2012; 39:1087-92. [PMID: 22633218 DOI: 10.1016/j.nucmedbio.2012.04.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 03/23/2012] [Accepted: 04/08/2012] [Indexed: 12/12/2022]
Abstract
INTRODUCTION Our aim was the optimization of radiochemical parameters for the microfluidic preparation of [(18)F]altanserin. The four main parameters evaluated were (1) precursor concentration, (2) reaction temperature, (3) bolus flow rate through the microreactor and (4) bolus volume. METHODS For the determination of optimal reaction conditions within a flow-through microreactor synthesizer, 5-400 μL of precursor and dried [(18)F]fluoride solution were simultaneously pushed through the temperature-controlled reactor (180-220°C) with defined bolus flow rates of 10-60 μL/min. Radiochemical incorporation yields (RCIYs) were examined using a thin layer chromatography (TLC) set-up and radio- high-performance liquid chromatography (HPLC). RESULTS Optimum reaction parameters for the microfluidic set-up were determined as following: 220°C, 5-10 μL/min pump rate per reactant (10-20 μL/min reaction overall flow rate) and 2mg/mL precursor concentration in the reaction mixture. Applying these optimized conditions, RCIYs of 53.7 ± 7.9 were observed for scaled-up preparations. A positive "bolus effect" was observed: applying higher reaction volume resulted in increased RCIYs. CONCLUSION This study proved that the reaction bolus volume is an essential parameter influencing the RCIY of [(18)F]altanserin. A possible explanation is the inhomogeneous distribution within the reaction volume probably caused by diffusion at the bolus interface. This important finding should be considered an important variable for the evaluation of all novel radiotracers labeled using a flow-through reactor device.
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Affiliation(s)
- Johanna Ungersboeck
- Department of Nuclear Medicine, Radiochemistry and Biomarker Development Unit, Medical University of Vienna, A-1090 Vienna, Austria
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Camici PG, Rimoldi OE, Gaemperli O, Libby P. Non-invasive anatomic and functional imaging of vascular inflammation and unstable plaque. Eur Heart J 2012; 33:1309-17. [PMID: 22507974 DOI: 10.1093/eurheartj/ehs067] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Over the last several decades, basic cardiovascular research has significantly enhanced our understanding of pathobiological processes leading to formation, progression, and complications of atherosclerotic plaques. By harnessing these advances in cardiovascular biology, imaging has advanced beyond its traditional anatomical domains to a tool that permits probing of particular molecular structures to image cellular behaviour and metabolic pathways involved in atherosclerosis. From the nascent atherosclerotic plaque to the death of inflammatory cells, several potential molecular and micro-anatomical targets for imaging with particular selective imaging probes and with a variety of imaging modalities have emerged from preclinical and animal investigations. Yet, substantive barriers stand between experimental use and wide clinical application of these novel imaging strategies. Each of the imaging modalities described herein faces hurdles-for example, sensitivity, resolution, radiation exposure, reproducibility, availability, standardization, or costs. This review summarizes the published literature reporting on functional imaging of vascular inflammation in atherosclerotic plaques emphasizing those techniques that have the greatest and/or most immediate potential for broad application in clinical practice. The prospective evaluation of these techniques and standardization of protocols by multinational networks could serve to determine their added value in clinical practice and guide their development and deployment.
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Affiliation(s)
- Paolo G Camici
- Vita-Salute University and Scientific Institute San Raffaele, Via Olgettina 60, Milan, Italy.
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Zoghbi SS, Anderson KB, Jenko KJ, Luckenbaugh DA, Innis RB, Pike VW. On quantitative relationships between drug-like compound lipophilicity and plasma free fraction in monkey and human. J Pharm Sci 2011; 101:1028-39. [PMID: 22170327 DOI: 10.1002/jps.22822] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Revised: 10/26/2011] [Accepted: 10/28/2011] [Indexed: 12/25/2022]
Abstract
Drug interactions with plasma proteins influence their pharmacokinetics and pharmacodynamics. We aimed to test whether a strong quantitative relationship exists between plasma free fraction (f(P) ) and lipophilicity for low molecular weight nonacidic drug-like compounds. We measured the n-octanol-buffer distribution coefficients at pH 7.4 ((m) logD) of 18 diverse radiotracers (<470 Da) used for brain imaging with positron emission tomography in vivo. Lipophilicities were also computed as (c) logD with two software packages. The f(P) values for monkeys and humans were determined by ultrafiltration and transformed into m logD(pr/pl) values representing the log(10) of the within phase partition of the radiotracers between plasma proteins and remaining plasma. (m) logD(pr/pl) correlated strongly with (m) logD for human ((m) logD(pr/pl) = 0.733(m) logD-0.780, r(2) = 0.74) and monkey ((m) logD(pr/pl) = 0.780(m) logD-1.15, r(2) = 0.83), but less strongly with (c) logD. These relationships were significantly different between species (P = 0.006). Removal of eight fluorinated compounds from the datasets raised r(2) to 0.81 and 0.91 for humans and monkeys, respectively. For the tested compounds, we conclude that n-octanol-buffer (pH 7.4) distribution strongly models that between plasma proteins and remaining plasma and moreover that (m) logD accounts for over 74% of compound (m) logD(pr/pl) and is a strong determinant of f(P).
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Affiliation(s)
- Sami S Zoghbi
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Wang M, Gao M, Miller KD, Zheng QH. Synthesis of [¹¹C]PBR06 and [¹⁸F]PBR06 as agents for positron emission tomographic (PET) imaging of the translocator protein (TSPO). Steroids 2011; 76:1331-40. [PMID: 21756927 DOI: 10.1016/j.steroids.2011.06.012] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Revised: 06/27/2011] [Accepted: 06/29/2011] [Indexed: 11/18/2022]
Abstract
The translocator protein 18 kDa (TSPO) is an attractive target for molecular imaging of neuroinflammation and tumor progression. [(18)F]PBR06, a fluorine-18 labeled form of PBR06, is a promising PET TSPO radioligand originally developed at NIMH. [(11)C]PBR06, a carbon-11 labeled form of PBR06, was designed and synthesized for the first time. The standard PBR06 was synthesized from 2,5-dimethoxybenzaldehyde in three steps with 71% overall chemical yield. The radiolabeling precursor desmethyl-PBR06 was synthesized from 2-hydroxy-5-methoxybenzaldehyde in five steps with 12% overall chemical yield. The target tracer [(11)C]PBR06 was prepared by O-[(11)C]methylation of desmethyl-PBR06 with [(11)C]CH(3)OTf in CH(3)CN at 80°C under basic condition and isolated by HPLC combined with SPE purification with 40-60% decay corrected radiochemical yield and 222-740 GBq/μmol specific activity at EOB. On the similar grounds, [(18)F]PBR06 was also designed and synthesized. The previously described Br-PBR06 precursor was synthesized from 2,5-dimethoxybenzaldehyde in two steps with 78% overall chemical yield. A new radiolabeling precursor tosyloxy-PBR06, previously undescribed tosylate congener of PBR06, was designed and synthesized from ethyl 2-hydroxyacetate, 4-methylbenzene-1-sulfonyl chloride, and N-(2,5-dimethoxybenzyl)-2-phenoxyaniline in four steps with 50% overall chemical yield. [(18)F]PBR06 was prepared by the nucleophilic substitution of either new tosyloxy-PBR06 precursor or known Br-PBR06 precursor in DMSO at 140°C with K[(18)F]F/Kryptofix 2.2.2 for 15 min and HPLC combined with SPE purification in 20-60% decay corrected radiochemical yield, >99% radiochemical purity, 87-95% chemical purity, and 37-222 GBq/μmol specific activity at EOB. Radiosynthesis of [(18)F]PBR06 using new tosylated precursor gave similar radiochemical purity, and higher specific activity, radiochemical yield and chemical purity in comparison with radiosynthesis using bromine precursor.
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Affiliation(s)
- Min Wang
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, 1345 West 16th Street, L3-202, Indianapolis, IN 46202-2111, USA
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