1
|
Takamura Y, Kakuta H. In Vivo Receptor Visualization and Evaluation of Receptor Occupancy with Positron Emission Tomography. J Med Chem 2021; 64:5226-5251. [PMID: 33905258 DOI: 10.1021/acs.jmedchem.0c01714] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Positron emission tomography (PET) is useful for noninvasive in vivo visualization of disease-related receptors, for evaluation of receptor occupancy to determine an appropriate drug dosage, and for proof-of-concept of drug candidates in translational research. For these purposes, the specificity of the PET tracer for the target receptor is critical. Here, we review work in this area, focusing on the chemical structures of reported PET tracers, their Ki/Kd values, and the physical properties relevant to target receptor selectivity. Among these physical properties, such as cLogP, cLogD, molecular weight, topological polar surface area, number of hydrogen bond donors, and pKa, we focus especially on LogD and LogP as important physical properties that can be easily compared across a range of studies. We discuss the success of PET tracers in evaluating receptor occupancy and consider likely future developments in the field.
Collapse
Affiliation(s)
- Yuta Takamura
- Division of Pharmaceutical Sciences, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 1-1-1, Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
| | - Hiroki Kakuta
- Division of Pharmaceutical Sciences, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 1-1-1, Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
| |
Collapse
|
2
|
Hou L, Rong J, Haider A, Ogasawara D, Varlow C, Schafroth MA, Mu L, Gan J, Xu H, Fowler CJ, Zhang MR, Vasdev N, Ametamey S, Cravatt BF, Wang L, Liang SH. Positron Emission Tomography Imaging of the Endocannabinoid System: Opportunities and Challenges in Radiotracer Development. J Med Chem 2020; 64:123-149. [PMID: 33379862 DOI: 10.1021/acs.jmedchem.0c01459] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The endocannabinoid system (ECS) is involved in a wide range of biological functions and comprises cannabinoid receptors and enzymes responsible for endocannabinoid synthesis and degradation. Over the past 2 decades, significant advances toward developing drugs and positron emission tomography (PET) tracers targeting different components of the ECS have been made. Herein, we summarized the recent development of PET tracers for imaging cannabinoid receptors 1 (CB1R) and 2 (CB2R) as well as the key enzymes monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), particularly focusing on PET neuroimaging applications. State-of-the-art PET tracers for the ECS will be reviewed including their chemical design, pharmacological properties, radiolabeling, as well as preclinical and human PET imaging. In addition, this review addresses the current challenges for ECS PET biomarker development and highlights the important role of PET ligands to study disease pathophysiology as well as to facilitate drug discovery.
Collapse
Affiliation(s)
- Lu Hou
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, 613 West Huangpu Road, Tianhe District, Guangzhou 510630, China
| | - Jian Rong
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, and Department of Radiology, Harvard Medical School, Boston, Massachusetts 02114, United States
| | - Ahmed Haider
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, and Department of Radiology, Harvard Medical School, Boston, Massachusetts 02114, United States
| | - Daisuke Ogasawara
- The Skaggs Institute for Chemical Biology and Department of Chemical Physiology, The Scripps Research Institute, SR107, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Cassis Varlow
- Azrieli Centre for Neuro-Radiochemistry, Brain Health Imaging Centre, Centre for Addiction and Mental Health, and Department of Psychiatry/Institute of Medical Science, University of Toronto, 250 College Street, Toronto, M5T 1R8 ON, Canada
| | - Michael A Schafroth
- The Skaggs Institute for Chemical Biology and Department of Chemical Physiology, The Scripps Research Institute, SR107, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Linjing Mu
- Center for Radiopharmaceutical Sciences of ETH, PSI, and USZ, and Institute of Pharmaceutical Sciences, ETH Zurich, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Jiefeng Gan
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, 613 West Huangpu Road, Tianhe District, Guangzhou 510630, China
| | - Hao Xu
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, 613 West Huangpu Road, Tianhe District, Guangzhou 510630, China
| | - Christopher J Fowler
- Department of Pharmacology and Clinical Neuroscience, Umeå University, SE-901 87 Umeå, Sweden
| | - 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
| | - Neil Vasdev
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, and Department of Radiology, Harvard Medical School, Boston, Massachusetts 02114, United States.,Azrieli Centre for Neuro-Radiochemistry, Brain Health Imaging Centre, Centre for Addiction and Mental Health, and Department of Psychiatry/Institute of Medical Science, University of Toronto, 250 College Street, Toronto, M5T 1R8 ON, Canada
| | - Simon Ametamey
- Center for Radiopharmaceutical Sciences of ETH, PSI, and USZ, and Institute of Pharmaceutical Sciences, ETH Zurich, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Benjamin F Cravatt
- The Skaggs Institute for Chemical Biology and Department of Chemical Physiology, The Scripps Research Institute, SR107, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Lu Wang
- Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, 613 West Huangpu Road, Tianhe District, Guangzhou 510630, China.,Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, and Department of Radiology, Harvard Medical School, Boston, Massachusetts 02114, United States
| | - Steven H Liang
- Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, and Department of Radiology, Harvard Medical School, Boston, Massachusetts 02114, United States
| |
Collapse
|
3
|
Miederer I, Wiegand V, Bausbacher N, Leukel P, Maus S, Hoffmann MA, Lutz B, Schreckenberger M. Quantification of the Cannabinoid Type 1 Receptor Availability in the Mouse Brain. Front Neuroanat 2020; 14:593793. [PMID: 33328905 PMCID: PMC7714830 DOI: 10.3389/fnana.2020.593793] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 11/03/2020] [Indexed: 11/13/2022] Open
Abstract
Introduction: The endocannabinoid system is involved in several diseases such as addictive disorders, schizophrenia, post-traumatic stress disorder, and eating disorders. As often mice are used as the preferred animal model in translational research, in particular when using genetically modified mice, this study aimed to provide a systematic analysis of in vivo cannabinoid type 1 (CB1) receptor ligand-binding capacity using positron emission tomography (PET) using the ligand [18F]MK-9470. We then compared the PET results with literature data from immunohistochemistry (IHC) to review the consistency between ex vivo protein expression and in vivo ligand binding. Methods: Six male C57BL/6J (6–9 weeks) mice were examined with the CB1 receptor ligand [18F]MK-9470 and small animal PET. Different brain regions were evaluated using the parameter %ID/ml. The PET results of the [18F]MK-9470 accumulation in the mouse brain were compared with immunohistochemical literature data. Results: The ligand [18F]MK-9470 was taken up into the mouse brain within 5 min after injection and exhibited slow kinetics. It accumulated highly in most parts of the brain. PET and IHC classifications were consistent for most parts of the telencephalon, while brain regions of the diencephalon, mesencephalon, and rhombencephalon were rated higher with PET than IHC. Conclusions: This preclinical [18F]MK-9470 study demonstrated the radioligand’s applicability for imaging the region-specific CB1 receptor availability in the healthy adult mouse brain and thus offers the potential to study CB1 receptor availability in pathological conditions.
Collapse
Affiliation(s)
- Isabelle Miederer
- Department of Nuclear Medicine, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Viktoria Wiegand
- Department of Nuclear Medicine, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Nicole Bausbacher
- Department of Nuclear Medicine, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Petra Leukel
- Institute of Neuropathology, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Stephan Maus
- Department of Nuclear Medicine, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Manuela A Hoffmann
- Department of Nuclear Medicine, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany.,Department of Occupational Health and Safety, Federal Ministry of Defense, Bonn, Germany
| | - Beat Lutz
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany.,Leibniz Institute for Resilience Research, Mainz, Germany
| | - Mathias Schreckenberger
- Department of Nuclear Medicine, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| |
Collapse
|
4
|
Colom M, Vidal B, Zimmer L. Is There a Role for GPCR Agonist Radiotracers in PET Neuroimaging? Front Mol Neurosci 2019; 12:255. [PMID: 31680859 PMCID: PMC6813225 DOI: 10.3389/fnmol.2019.00255] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 10/02/2019] [Indexed: 12/30/2022] Open
Abstract
Positron emission tomography (PET) is a molecular imaging modality that enables in vivo exploration of metabolic processes and especially the pharmacology of neuroreceptors. G protein-coupled receptors (GPCRs) play an important role in numerous pathophysiologic disorders of the central nervous system. Thus, they are targets of choice in PET imaging to bring proof concept of change in density in pathological conditions or in pharmacological challenge. At present, most radiotracers are antagonist ligands. In vitro data suggest that properties differ between GPCR agonists and antagonists: antagonists bind to receptors with a single affinity, whereas agonists are characterized by two different affinities: high affinity for receptors that undergo functional coupling to G-proteins, and low affinity for those that are not coupled. In this context, agonist radiotracers may be useful tools to give functional images of GPCRs in the brain, with high sensitivity to neurotransmitter release. Here, we review all existing PET radiotracers used from animals to humans and their role for understanding the ligand-receptor paradigm of GPCR in comparison with corresponding antagonist radiotracers.
Collapse
Affiliation(s)
- Matthieu Colom
- Lyon Neuroscience Research Center, INSERM, CNRS, Université de Lyon, Lyon, France.,CERMEP, Hospices Civils de Lyon, Bron, France
| | - Benjamin Vidal
- Lyon Neuroscience Research Center, INSERM, CNRS, Université de Lyon, Lyon, France
| | - Luc Zimmer
- Lyon Neuroscience Research Center, INSERM, CNRS, Université de Lyon, Lyon, France.,CERMEP, Hospices Civils de Lyon, Bron, France.,Institut National des Sciences et Techniques Nucléaires, CEA Saclay, Gif-sur-Yvette, France
| |
Collapse
|
5
|
Cooper A, Singh S, Hook S, Tyndall JDA, Vernall AJ. Chemical Tools for Studying Lipid-Binding Class A G Protein-Coupled Receptors. Pharmacol Rev 2017; 69:316-353. [PMID: 28655732 DOI: 10.1124/pr.116.013243] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 05/15/2017] [Indexed: 12/16/2022] Open
Abstract
Cannabinoid, free fatty acid, lysophosphatidic acid, sphingosine 1-phosphate, prostanoid, leukotriene, bile acid, and platelet-activating factor receptor families are class A G protein-coupled receptors with endogenous lipid ligands. Pharmacological tools are crucial for studying these receptors and addressing the many unanswered questions surrounding expression of these receptors in normal and diseased tissues. An inherent challenge for developing tools for these lipid receptors is balancing the often lipophilic requirements of the receptor-binding pharmacophore with favorable physicochemical properties to optimize highly specific binding. In this study, we review the radioligands, fluorescent ligands, covalent ligands, and antibodies that have been used to study these lipid-binding receptors. For each tool type, the characteristics and design rationale along with in vitro and in vivo applications are detailed.
Collapse
Affiliation(s)
- Anna Cooper
- School of Pharmacy, University of Otago, Dunedin, New Zealand
| | - Sameek Singh
- School of Pharmacy, University of Otago, Dunedin, New Zealand
| | - Sarah Hook
- School of Pharmacy, University of Otago, Dunedin, New Zealand
| | | | | |
Collapse
|
6
|
Altomonte S, Baillie GL, Ross RA, Zanda M. 4-Cyano-5-(2-thiophenyl)-pyrazoles are high affinity CB1 receptor ligands. RSC Adv 2015. [DOI: 10.1039/c4ra17274d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Introduction of a 4-CN group on 5-thiophenyl-pyrazoles afforded high affinity cannabinoid ligands having low nM Ki values and moderate CB1 receptor selectivity. Log P and TPSA values suggest that some of the compounds might be peripherally restricted.
Collapse
Affiliation(s)
- Stefano Altomonte
- Kosterlitz Centre for Therapeutics
- Institute of Medical Sciences
- University of Aberdeen
- UK
| | | | - Ruth A. Ross
- Medical Sciences Building
- University of Toronto
- Toronto
- Canada
| | - Matteo Zanda
- Kosterlitz Centre for Therapeutics
- Institute of Medical Sciences
- University of Aberdeen
- UK
- C.N.R.-Istituto di Chimica del Riconoscimento Molecolare
| |
Collapse
|
7
|
Volk DW, Eggan SM, Horti AG, Wong DF, Lewis DA. Reciprocal alterations in cortical cannabinoid receptor 1 binding relative to protein immunoreactivity and transcript levels in schizophrenia. Schizophr Res 2014; 159:124-9. [PMID: 25107849 PMCID: PMC4177350 DOI: 10.1016/j.schres.2014.07.017] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 07/08/2014] [Accepted: 07/09/2014] [Indexed: 11/18/2022]
Abstract
The deleterious effects of cannabis use in schizophrenia have been linked, in part, to underlying disturbances in endogenous cannabinoid signaling in the prefrontal cortex. However, while receptor autoradiography studies of the primary cannabinoid receptor (CB1R) have consistently found higher CB1R binding in the prefrontal cortex in schizophrenia, deficits in CB1R mRNA levels and protein immunoreactivity have also been reported in the illness. To investigate this apparent discrepancy, we quantified CB1R binding using receptor autoradiography with the selective CB1R ligand [(3)H]-OMAR in the prefrontal cortex of 21 subjects with schizophrenia who were previously found to have lower levels of both CB1R mRNA using in situ hybridization and CB1R protein using radioimmunocytochemistry relative to matched healthy comparison subjects. We observed higher levels of [(3)H]-OMAR binding in the prefrontal cortex of schizophrenia subjects that did not appear to be attributable to psychotropic medications or substance abuse. The combination of lower levels of CB1R mRNA and immunoreactivity with higher CB1R receptor binding may reflect 1) altered trafficking of the receptor resulting in higher levels of membrane-bound CB1R or 2) higher CB1R affinity. In either case, greater CB1R receptor availability may contribute to the increased susceptibility of schizophrenia subjects to the deleterious effects of cannabis use.
Collapse
Affiliation(s)
- David W Volk
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15213, United States.
| | - Stephen M Eggan
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15213, United States
| | - Andrew G Horti
- Department of Radiology, Johns Hopkins University, Baltimore, MD 21287, United States
| | - Dean F Wong
- Department of Radiology, Johns Hopkins University, Baltimore, MD 21287, United States; Department of Psychiatry, Johns Hopkins University, Baltimore, MD 21287, United States; Department of Neuroscience, Johns Hopkins University, Baltimore, MD 21287, United States
| | - David A Lewis
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15213, United States; Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15213, United States
| |
Collapse
|
8
|
Altomonte S, Baillie GL, Ross RA, Riley J, Zanda M. The pentafluorosulfanyl group in cannabinoid receptor ligands: synthesis and comparison with trifluoromethyl and tert-butyl analogues. RSC Adv 2014. [DOI: 10.1039/c4ra01212g] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Competitive CB1 receptor antagonists carrying an aromatic SF5 group in position 3 of a pyrazole ring were synthesised and compared with their CF3 and tert-butyl analogues. Results confirmed that an aromatic SF5 group can be used as a bioisosteric analogue of a CF3 group and possibly of a bulky aliphatic group too.
Collapse
Affiliation(s)
- Stefano Altomonte
- Kosterlitz Centre for Therapeutics
- Institute of Medical Sciences and “John Mallard” Scottish PET Centre
- University of Aberdeen
- Aberdeen AB25 2ZD, UK
| | - Gemma L. Baillie
- Medical Sciences Building
- University of Toronto
- 1 King's College Circle
- Toronto, Canada
| | - Ruth A. Ross
- Medical Sciences Building
- University of Toronto
- 1 King's College Circle
- Toronto, Canada
| | | | - Matteo Zanda
- Kosterlitz Centre for Therapeutics
- Institute of Medical Sciences and “John Mallard” Scottish PET Centre
- University of Aberdeen
- Aberdeen AB25 2ZD, UK
- C.N.R.-Istituto di Chimica del Riconoscimento Molecolare
| |
Collapse
|
9
|
Ahamed M, Verbruggen A, Bormans G. Synthetic strategies for radioligands forin vivoimaging of brain cannabinoid type-1 receptors. J Labelled Comp Radiopharm 2013; 56:207-14. [DOI: 10.1002/jlcr.3017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 11/28/2012] [Accepted: 11/30/2012] [Indexed: 02/03/2023]
Affiliation(s)
- Muneer Ahamed
- Laboratory for Radiopharmacy, IMIR KU Leuven, O&N2; Herestraat 49, Box 821; BE-3000; Leuven; Belgium
| | - Alfons Verbruggen
- Laboratory for Radiopharmacy, IMIR KU Leuven, O&N2; Herestraat 49, Box 821; BE-3000; Leuven; Belgium
| | - Guy Bormans
- Laboratory for Radiopharmacy, IMIR KU Leuven, O&N2; Herestraat 49, Box 821; BE-3000; Leuven; Belgium
| |
Collapse
|
10
|
Farkas S, Nagy K, Palkovits M, Kovács GG, Jia Z, Donohue S, Pike V, Halldin C, Máthé D, Harkany T, Gulyás B, Csiba L. [¹²⁵I]SD-7015 reveals fine modalities of CB₁ cannabinoid receptor density in the prefrontal cortex during progression of Alzheimer's disease. Neurochem Int 2011; 60:286-91. [PMID: 22222721 DOI: 10.1016/j.neuint.2011.11.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 10/25/2011] [Accepted: 11/08/2011] [Indexed: 02/01/2023]
Abstract
The cannabinoid type-1 receptor (CB₁R) is one of the most abundant members of the G protein-coupled receptor family in the central nervous system. Once activated by their cognate ligands, endocannabinoids, CB₁Rs generally limit the timing of neurotransmitter release at many cortical synapses. Prior studies have indicated the involvement of CB₁R in neurodegeneration and in various neuronal insults, with an emphasis on their neuroprotective role. In the present study we used a novel selective CB₁R radioligand to investigate regional variations in CB₁R ligand binding as a factor of progressive Braak tau pathology in the frontal cortex of Alzheimer's disease (AD) patients. The frontal cortex was chosen for this study due to the high density of CB₁Rs and their well-characterized involvement in the progression of AD. Post-mortem prefrontal cortex samples from AD patients from Braak stages I to VI and controls were subjected to CB₁R autoradiography with [¹²⁵I]SD-7015 as radioligand. Regional concentration of [¹²⁵I]SD-7015, corresponding to, and thereby representing, regional CB₁R densities, were expressed in fM/g_tissue. The results show that CB₁R density inversely correlates with Braak tau pathology with the following tendency: controls <AD Braak stage V-VI <AD Braak stage III-IV <AD Braak stage I-II. Differences were significant between control and AD Braak stage I-II groups, as well as between controls and the AD group comprising all Braak stages. These findings indicate an up-regulation of the tissue binding of the selective CB₁R radioligand [¹²⁵I]SD7015 in human brains, allowing the detection of fine modalities of receptor expression and radioligand binding during the progression of AD.
Collapse
Affiliation(s)
- Szabolcs Farkas
- Department of Neurology, University of Debrecen, H-4012 Debrecen, Hungary
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Herance R, Rojas S, Abad S, Jiménez X, Gispert JD, Millán O, Martín-García E, Burokas A, Serra MÀ, Maldonado R, Pareto D. Positron Emission Tomographic Imaging of the Cannabinoid Type 1 Receptor System with [11C]OMAR ([11C]JHU75528): Improvements in Image Quantification Using Wild-Type and Knockout Mice. Mol Imaging 2011. [DOI: 10.2310/7290.2011.00019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In this study, we assessed the feasibility of using positron emission tomography (PET) and the tracer [11C]OMAR ([11C]JHU75528), an analogue of rimonabant, to study the brain cannabinoid type 1 (CB1) receptor system. Wild-type (WT) andCB1 knockout (KO) animals were imaged at baseline and after pretreatment with blocking doses of rimonabant. Brain uptake in WT animals was higher (50%) than in KO animals in baseline conditions. After pretreatment with rimonabant, WT uptake lowered to the level of KO animals. The results of this study support the feasibility of using PET with the radiotracer [11C]JHU75528 to image the brain CB1 receptor system in mice. In addition, this methodology can be used to assess the effect of new drugs in preclinical studies using genetically manipulated animals.
Collapse
Affiliation(s)
- Raúl Herance
- From the Institut d'Alta Tecnologia, Parc de Recerca Biomèdica de Barcelona, CRC Corporació Sanitaària, Barcelona, Spain; Centro Imagen Molecular, CRC Corporacioó Sanitaària, Barcelona, Spain; Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain; and Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra–PRBB, Barcelona, Spain
| | - Santiago Rojas
- From the Institut d'Alta Tecnologia, Parc de Recerca Biomèdica de Barcelona, CRC Corporació Sanitaària, Barcelona, Spain; Centro Imagen Molecular, CRC Corporacioó Sanitaària, Barcelona, Spain; Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain; and Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra–PRBB, Barcelona, Spain
| | - Sergio Abad
- From the Institut d'Alta Tecnologia, Parc de Recerca Biomèdica de Barcelona, CRC Corporació Sanitaària, Barcelona, Spain; Centro Imagen Molecular, CRC Corporacioó Sanitaària, Barcelona, Spain; Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain; and Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra–PRBB, Barcelona, Spain
| | - Xavier Jiménez
- From the Institut d'Alta Tecnologia, Parc de Recerca Biomèdica de Barcelona, CRC Corporació Sanitaària, Barcelona, Spain; Centro Imagen Molecular, CRC Corporacioó Sanitaària, Barcelona, Spain; Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain; and Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra–PRBB, Barcelona, Spain
| | - Juan Domingo Gispert
- From the Institut d'Alta Tecnologia, Parc de Recerca Biomèdica de Barcelona, CRC Corporació Sanitaària, Barcelona, Spain; Centro Imagen Molecular, CRC Corporacioó Sanitaària, Barcelona, Spain; Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain; and Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra–PRBB, Barcelona, Spain
| | - Olga Millán
- From the Institut d'Alta Tecnologia, Parc de Recerca Biomèdica de Barcelona, CRC Corporació Sanitaària, Barcelona, Spain; Centro Imagen Molecular, CRC Corporacioó Sanitaària, Barcelona, Spain; Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain; and Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra–PRBB, Barcelona, Spain
| | - Elena Martín-García
- From the Institut d'Alta Tecnologia, Parc de Recerca Biomèdica de Barcelona, CRC Corporació Sanitaària, Barcelona, Spain; Centro Imagen Molecular, CRC Corporacioó Sanitaària, Barcelona, Spain; Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain; and Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra–PRBB, Barcelona, Spain
| | - Aurelijus Burokas
- From the Institut d'Alta Tecnologia, Parc de Recerca Biomèdica de Barcelona, CRC Corporació Sanitaària, Barcelona, Spain; Centro Imagen Molecular, CRC Corporacioó Sanitaària, Barcelona, Spain; Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain; and Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra–PRBB, Barcelona, Spain
| | - Miquel Àngel Serra
- From the Institut d'Alta Tecnologia, Parc de Recerca Biomèdica de Barcelona, CRC Corporació Sanitaària, Barcelona, Spain; Centro Imagen Molecular, CRC Corporacioó Sanitaària, Barcelona, Spain; Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain; and Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra–PRBB, Barcelona, Spain
| | - Rafael Maldonado
- From the Institut d'Alta Tecnologia, Parc de Recerca Biomèdica de Barcelona, CRC Corporació Sanitaària, Barcelona, Spain; Centro Imagen Molecular, CRC Corporacioó Sanitaària, Barcelona, Spain; Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain; and Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra–PRBB, Barcelona, Spain
| | - Deborah Pareto
- From the Institut d'Alta Tecnologia, Parc de Recerca Biomèdica de Barcelona, CRC Corporació Sanitaària, Barcelona, Spain; Centro Imagen Molecular, CRC Corporacioó Sanitaària, Barcelona, Spain; Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain; and Laboratory of Neuropharmacology, Department of Experimental and Health Sciences, Universitat Pompeu Fabra–PRBB, Barcelona, Spain
| |
Collapse
|
12
|
Packeu A, Wennerberg M, Balendran A, Vauquelin G. Estimation of the dissociation rate of unlabelled ligand-receptor complexes by a 'two-step' competition binding approach. Br J Pharmacol 2011; 161:1311-28. [PMID: 20946109 DOI: 10.1111/j.1476-5381.2010.00931.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Because the in vivo effectiveness of ligands may also be determined by the rate by which they dissociate from their target receptors, drug candidates are being increasingly screened for this kinetic property. The dissociation rate of unlabelled ligand-receptor complexes can be estimated indirectly from their ability to slow the association of subsequently added radioligand molecules. EXPERIMENTAL APPROACH We used the 'two-step competition' binding approach consisting of pre-incubating the receptor preparation with a wide range of ligand concentrations, washing off free ligand molecules, adding radioligand and monitoring its receptor binding after a fixed time. Based on the rationale that binding of both ligands is mutually exclusive and that they bind according to the law of mass action to a single class of sites, the unlabelled ligand's dissociation rate can be estimated from the upward shift that the competition curve experiences after washing. KEY RESULTS The relevance of the 'two-step competition' approach was explored by computer simulations and by comparing the dissociation behaviour of unlabelled D(2) dopamine and CB(1) cannabinoid receptor antagonists in this and alternative approaches. Besides providing satisfactory estimations of dissociation rates, the method also detects the ability of the unlabelled ligand molecules to be released from 'sinks' such as the cell membrane. CONCLUSIONS AND IMPLICATIONS As the 'two-step competition' requires rapid intermediate washing steps and needs radioligand binding to be measured at only one time point, this approach is particularly suited for binding studies on intact plated cells. LINKED ARTICLES This article is part of a themed section on Analytical Receptor Pharmacology in Drug Discovery. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2010.161.issue-6.
Collapse
Affiliation(s)
- A Packeu
- Department of Molecular and Biochemical Pharmacology, Free University of Brussels (VUB), Brussels, Belgium
| | | | | | | |
Collapse
|
13
|
Donohue SR, Dannals RF, Halldin C, Pike VW. N-(4-cyanotetrahydro-2H-pyran-4-yl) and N-(1-cyanocyclohexyl) derivatives of 1,5-diarylpyrazole-3-carboxamides showing high affinity for 18 kDa translocator protein and/or cannabinoid receptors. J Med Chem 2011; 54:2961-70. [PMID: 21428406 PMCID: PMC3085958 DOI: 10.1021/jm2000536] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In order to develop improved radioligands for imaging brain CB(1) receptors with positron emission tomography (PET) based on rimonabant (5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-N-(piperidin-1-yl)-1H-pyrazole-3-carboxamide, 1), we synthesized compounds 9a-s in which the N-piperidinyl ring was replaced with a 4-(4-cyanotetrahydro-2H-pyranyl) or 1-cyanocyclohexyl ring. Such changes were expected to be almost isosteric with 1, confer greater metabolic resistance, and in the case of the 4-(4-cyanotetrahydro-2H-pyranyl) compounds, substantially reduce lipophilicity. One derivative, 1-(2-bromophenyl)-N-(1-cyanocyclohexyl)-5-(4-methoxyphenyl)-4-methylpyrazole-3-carboxamide (9n), showed high affinity (K(i) = 15.7 nM) and selectivity for binding to CB(1) receptors. The corresponding 4-(4-cyanotetrahydro-2H-pyranyl) derivative (9m) also showed quite high affinity for CB(1) receptors (K(i) = 62 nM) but was found to have even higher affinity (K(i) = 29 nM) for the structurally unrelated 18 kDa translocator protein (TSPO). Some other minor structural changes among 9a-s were also found to switch binding selectivity from CB(1) receptors to TSPO or vice versa. These unexpected findings and their implications for the development of selective ligands or PET radioligands for CB(1) receptors or TSPO are discussed in relation to current pharmacophore models of CB(1) receptor and TSPO binding sites.
Collapse
Affiliation(s)
- Sean R. Donohue
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-1003, United States
- Karolinska Institutet, Department of Clinical Neuroscience, Psychiatry Section, Karolinska Hospital, S-17176, Stockholm, Sweden
- Division of Nuclear Medicine, The Johns Hopkins PET Center, Baltimore, Maryland 21287, United States
| | - Robert F. Dannals
- Division of Nuclear Medicine, The Johns Hopkins PET Center, Baltimore, Maryland 21287, United States
| | - Christer Halldin
- Karolinska Institutet, Department of Clinical Neuroscience, Psychiatry Section, Karolinska Hospital, S-17176, Stockholm, Sweden
| | - Victor W. Pike
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-1003, United States
| |
Collapse
|
14
|
Kiferle L, Politis M, Muraro PA, Piccini P. Positron emission tomography imaging in multiple sclerosis-current status and future applications. Eur J Neurol 2011; 18:226-231. [PMID: 20636368 DOI: 10.1111/j.1468-1331.2010.03154.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND Multiple Sclerosis (MS) is traditionally considered as a central nervous system (CNS) white matter inflammatory disease. However, recent studies have focused on the neurodegenerative aspects of the disease, which occur early in the pathological process, providing an opportunity for therapeutic intervention and application of neuroprotective strategies. The relationship between neural inflammation and cell death remains controversial. The recent development of new radiolabelled ligands provides positron emission tomography (PET) imaging with a role for studying early aspects of the MS pathology. METHODS We provide an overview of current PET research in MS, particularly focussing on possible applications of new radioligands for studying inflammation and neurodegenerative processes. RESULTS Pathological aspects of neuroinflammation, axonal degeneration and neuronal repair may be explored in vivo with selective PET tracers. Specific radioligands for the cannabinoid system may be applied in MS research to understand the role of this neurotransmitter system in the pathogenesis of the disease. CONCLUSIONS PET imaging represents a promising tool for elucidating controversial aspects of MS pathology and for the assessment of selective and potentially neuroprotective therapies.
Collapse
Affiliation(s)
- L Kiferle
- Centre for Neuroscience and MRC Clinical Sciences Centre, Division of Experimental Medicine, Hammersmith Hospital, Imperial College London, London, UK
- Department of Neuroscience, University of Pisa, Pisa, Italy
| | - M Politis
- Centre for Neuroscience and MRC Clinical Sciences Centre, Division of Experimental Medicine, Hammersmith Hospital, Imperial College London, London, UK
| | - P A Muraro
- Centre for Neuroscience and MRC Clinical Sciences Centre, Division of Experimental Medicine, Hammersmith Hospital, Imperial College London, London, UK
| | - P Piccini
- Centre for Neuroscience and MRC Clinical Sciences Centre, Division of Experimental Medicine, Hammersmith Hospital, Imperial College London, London, UK
| |
Collapse
|
15
|
Quantification of cerebral cannabinoid receptors subtype 1 (CB1) in healthy subjects and schizophrenia by the novel PET radioligand [11C]OMAR. Neuroimage 2010; 52:1505-13. [PMID: 20406692 DOI: 10.1016/j.neuroimage.2010.04.034] [Citation(s) in RCA: 143] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Revised: 04/07/2010] [Accepted: 04/12/2010] [Indexed: 01/05/2023] Open
Abstract
Several studies have examined the link between the cannabinoid CB1 receptor and several neuropsychiatric illnesses, including schizophrenia. As such, there is a need for in vivo imaging tracers so that the relationship between CB1 and schizophrenia (SZ) can be further studied. In this paper, we present our first human studies in both healthy control patients and patients with schizophrenia using the novel PET tracer, [(11)C]OMAR (JHU75528), we have shown its utility as a tracer for imaging human CB1 receptors and to investigate normal aging and the differences in the cannabinoid system of healthy controls versus patients with schizophrenia. A total of ten healthy controls and nine patients with schizophrenia were included and studied with high specific activity [(11)C]OMAR. The CB1 binding (expressed as the distribution volume; V(T)) was highest in the globus pallidus and the cortex in both controls and patients with schizophrenia. Controls showed a correlation with the known distribution of CB1 and decline of [(11)C]OMAR binding with age, most significantly in the globus pallidus. Overall, we observed elevated mean binding in patients with schizophrenia across all regions studied, and this increase was statistically significant in the pons (p<0.05), by the Students t-test. When we ran a regression of the control subjects V(T) values with age and then compared the patient data to 95% prediction limits of the linear regression, three patients fell completely outside for the globus pallidus, and in all other regions there were at least 1-3 patients outside of the prediction intervals. There was no statistically significant correlations between PET measures and the individual Brief Psychiatry Rating Score (BPRS) subscores (r=0.49), but there was a significant correlation between V(T) and the ratio of the BPRS psychosis to withdrawal score in the frontal lobe (r=0.60), and middle and posterior cingulate regions (r=0.71 and r=0.79 respectively). In conclusion, we found that [(11)C] OMAR can image human CB1 receptors in normal aging and schizophrenia. In addition, our initial data in subjects with schizophrenia seem to suggest an association of elevated binding specific brain regions and symptoms of the disease.
Collapse
|
16
|
|
17
|
Synthesis and in vitro autoradiographic evaluation of a novel high-affinity radioiodinated ligand for imaging brain cannabinoid subtype-1 receptors. Bioorg Med Chem Lett 2009; 19:6209-12. [PMID: 19767206 DOI: 10.1016/j.bmcl.2009.08.092] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2009] [Revised: 08/26/2009] [Accepted: 08/31/2009] [Indexed: 01/19/2023]
Abstract
There is strong interest to study the involvement of brain cannabinoid subtype-1 (CB1) receptors in neuropsychiatric disorders with single photon emission computed tomography (SPECT) and a suitable radioligand. Here we report the synthesis of a novel high-affinity radioiodinated CB1 receptor ligand ([125I]8, [125I]1-(2-iodophenyl)-4-cyano-5-(4-methoxyphenyl)-N-(piperidin-1-yl)-1H-pyrazole-3-carboxylate, [125I]SD7015). By autoradiography in vitro, [125I]8 showed selective binding to CB1 receptors on human brain postmortem cryosections and now merits labeling with iodine-123 for further evaluation as a SPECT radioligand in non-human primate.
Collapse
|
18
|
Finnema SJ, Donohue SR, Zoghbi SS, Brown AK, Gulyás B, Innis RB, Halldin C, Pike VW. Evaluation of [11C]PipISB and [18F]PipISB in monkey as candidate radioligands for imaging brain cannabinoid type-1 receptors in vivo. Synapse 2009; 63:22-30. [PMID: 18925657 DOI: 10.1002/syn.20578] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
N-(4-Fluorobenzyl)-4-[3-(piperidin-1-yl)indole-1-sulfonyl]benzamide] (PipISB, 3) is a selective and high-potency cannabinoid subtype-1 (CB1) receptor inverse agonist. We have previously reported radiosyntheses of [11C]3 and [18F]3. Here, we aimed to evaluate the uptake and CB(1) receptor-specific binding of each radioligand in monkey brain in vivo with positron emission tomography (PET). [11C]3 or [18F]3 was injected intravenously into rhesus or cynomolgus monkey, respectively, and examined with PET at baseline or after pretreatment with a receptor-saturating dose of CB1 receptor-selective ligand (3 for [11C]3 or 8 for [18F]3). In one PET experiment, the dose of 3 was administered at 100 min after [11C]3. Relative plasma concentrations of radioligand and radiometabolites were concurrently measured in baseline experiments with high-performance liquid chromatography. Brain radioactivity uptake was highest in striatum and cerebellum, and it reached 170-270% standardized uptake value (SUV) at 120 min after injection of [11C]3 and 180% SUV at 240 min after injection of [18F]3. Radioactivity was well retained in all CB1 receptor-rich regions. No reference region could be identified for nonspecifically bound radioligand. Under CB1 receptor pretreatment and displacement conditions, initial brain uptakes of radioactivity were similar to those at baseline. Regional brain radioactivity concentrations then became homogeneous and diminished to between 70 and 80% SUV at 120 min after injection of [11C]3 and to 25% SUV at 240 min after injection of [18F]3. [18F]3 was not defluorinated but was metabolized to less lipophilic radiometabolites, as was [11C]3. Hence, [11C]3 and [18F]3 showed high CB1 receptor-specific binding in monkey brain in vivo and merit further investigation as prospective PET radioligands in humans.
Collapse
Affiliation(s)
- Sjoerd J Finnema
- Karolinska Institutet, Department of Clinical Neuroscience, Psychiatry Section, Karolinska Hospital, S-17176 Stockholm, Sweden
| | | | | | | | | | | | | | | |
Collapse
|
19
|
PET Imaging Studies in Rhesus Monkey with the Cannabinoid-1 (CB1) Receptor Ligand [11C]CB-119. Mol Imaging Biol 2009; 11:246-52. [DOI: 10.1007/s11307-008-0194-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 08/13/2008] [Accepted: 09/08/2008] [Indexed: 11/26/2022]
|
20
|
Donohue SR, Krushinski JH, Pike VW, Chernet E, Phebus L, Chesterfield AK, Felder CC, Halldin C, Schaus JM. Synthesis, ex vivo evaluation, and radiolabeling of potent 1,5-diphenylpyrrolidin-2-one cannabinoid subtype-1 receptor ligands as candidates for in vivo imaging. J Med Chem 2008; 51:5833-42. [PMID: 18800770 DOI: 10.1021/jm800416m] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have reported that [methyl- (11)C] (3 R,5 R)-5-(3-methoxyphenyl)-3-[(R)-1-phenylethylamino]-1-(4-trifluoromethylphenyl)pyrrolidin-2-one ([(11)C] 8, [(11)C]MePPEP) binds with high selectivity to cannabinoid type-1 (CB 1) receptors in monkey brain in vivo. We now describe the synthesis of 8 and four analogues, namely, the 4-fluorophenyl (16, FMePPEP), 3-fluoromethoxy (20, FMPEP), 3-fluoromethoxy- d 2 (21, FMPEP- d 2), and 3-fluoroethoxy analogues (22, FEPEP), and report their activity in an ex vivo model designed to identify compounds suitable for use as positron emission tomography (PET) ligands. These ligands exhibited high, selective potency at CB 1 receptors in vitro (K b < 1 nM). Each ligand (30 microg/kg, iv) was injected into rats under baseline and pretreatment conditions (3, rimonabant, 10 mg/kg, iv) and quantified at later times in frontal cortex ex vivo with liquid chromatography-mass spectrometry (LC-MS) detection. Maximal ligand uptakes were high (22.6-48.0 ng/g). Under pretreatment, maximal brain uptakes were greatly reduced (6.5-17.3 ng/g). Since each ligand readily entered brain and bound with high selectivity to CB 1 receptors, we then established and here describe methods for producing [(11)C] 8, [(11)C] 16, and [(18)F] 20- 22 in adequate activities for evaluation as candidate PET radioligands in vivo.
Collapse
Affiliation(s)
- Sean R Donohue
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Donohue SR, Pike VW, Finnema SJ, Truong P, Andersson J, Gulyás B, Halldin C. Discovery and labeling of high-affinity 3,4-diarylpyrazolines as candidate radioligands for in vivo imaging of cannabinoid subtype-1 (CB1) receptors. J Med Chem 2008; 51:5608-16. [PMID: 18754613 DOI: 10.1021/jm800329z] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Imaging of cannabinoid subtype-1 (CB1) receptors in vivo with positron emission tomography (PET) is likely to be important for understanding their role in neuropsychiatric disorders and for drug development. Radioligands for imaging with PET are required for this purpose. We synthesized new ligands from a 3,4- diarylpyrazoline platform of which (-)-12a ((-)-3-(4-chlorophenyl)-N'-[(4-cyanophenyl)sulfonyl]-4-phenyl- 4,5-dihydro-1H-pyrazole-1-carboxamidine) was found to have high-affinity and selectivity for binding to CB1 receptors. (-)-12a and its lower affinity enantiomer ((+)-12a) were labeled with carbon-11 (t1/2 ) 20.4 min) using [11C]cyanide ion as labeling agent and evaluated as PET radioligands in cynomolgus monkeys. After injection of [11C](-)-12a, there was high uptake and retention of radioactivity across brain according to the rank order of CB1 receptor densities. The distomer, [11C](+)-12a, failed to give a sustained CB1 receptor-specific distribution. Polar radiometabolites of [11C](-)-12a appeared moderately slowly in plasma. Radioligand [11C](-)-12a is promising for the study of brain CB1 receptors and merits further investigation in human subjects.
Collapse
Affiliation(s)
- Sean R Donohue
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, USA.
| | | | | | | | | | | | | |
Collapse
|
22
|
Fan H, Kotsikorou E, Hoffman AF, Ravert HT, Holt D, Hurst DP, Lupica CR, Reggio PH, Dannals RF, Horti AG. Analogs of JHU75528, a PET ligand for imaging of cerebral cannabinoid receptors (CB1): development of ligands with optimized lipophilicity and binding affinity. Eur J Med Chem 2008; 44:593-608. [PMID: 18511157 DOI: 10.1016/j.ejmech.2008.03.040] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 03/21/2008] [Accepted: 03/27/2008] [Indexed: 11/16/2022]
Abstract
Cyano analogs of Rimonabant with high binding affinity for the cerebral cannabinoid receptor (CB1) and with optimized lipophilicity have been synthesized as potential positron emission tomography (PET) ligands. The best ligands of the series are optimal targets for the future radiolabeling with PET isotopes and in vivo evaluation as radioligands with enhanced properties for PET imaging of CB1 receptors in human subjects. Extracellular electrophysiological recordings in rodent brain slices demonstrated that JHU75528, 4, the lead compound of the new series, has functional CB antagonist properties that are consistent with its structural relationship to Rimonabant. Molecular modeling analysis revealed an important role of the binding of the cyano group with the CB1 binding pocket.
Collapse
Affiliation(s)
- Hong Fan
- PET Center, Division of Nuclear Medicine, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Donohue SR, Halldin C, Schou M, Hong J, Phebus L, Chernet E, Hitchcock SA, Gardinier KM, Ruley KM, Krushinski JH, Schaus J, Pike VW. Radiolabeling of a high potency cannabinoid subtype-1 receptor ligand,N-(4-fluoro-benzyl)-4-(3-(piperidin-1-yl)-indole-1-sulfonyl)benzamide (PipISB), with carbon-11 or fluorine-18. J Labelled Comp Radiopharm 2008. [DOI: 10.1002/jlcr.1491] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|