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Renk DR, Skraban M, Bier D, Schulze A, Wabbals E, Wedekind F, Neumaier F, Neumaier B, Holschbach M. Design, synthesis and biological evaluation of Tozadenant analogues as adenosine A 2A receptor ligands. Eur J Med Chem 2021; 214:113214. [PMID: 33548636 DOI: 10.1016/j.ejmech.2021.113214] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 01/12/2021] [Accepted: 01/13/2021] [Indexed: 12/19/2022]
Abstract
With the aim to obtain potent adenosine A2A receptor (A2AR) ligands, a series of eighteen derivatives of 4-hydroxy-N-(4-methoxy-7-morpholin-4-yl-1,3-benzo[d]thiazol-2-yl)-4-methylpiperidine-1-carboxamide (SYN-115, Tozadenant) were designed and synthesized. The target compounds were obtained by a chemical building block principle that involved reaction of the appropriate aminobenzothiazole phenyl carbamates with either commercially available or readily synthesized functionalized piperidines. Their affinity and subtype selectivity with regard to human adenosine A1-and A2A receptors were determined using radioligand binding assays. Ki values for human A2AR ranged from 2.4 to 38 nM, with more than 120-fold selectivity over A1 receptors for all evaluated compounds except 13k which had a Ki of 361 nM and 18-fold selectivity. The most potent fluorine-containing derivatives 13e, 13g and 13l exhibited Ki values of 4.9 nM, 3.6 nM and 2.8 nM for the human A2AR. Interestingly, the corresponding values for rat A2AR were found to be four to five times higher. Their binding to A2AR was further confirmed by radiolabeling with 18F and in vitro autoradiography in rat brain slices, which showed almost exclusive striatal binding and complete displacement by the A2AR antagonist ZM 241385. We conclude that these compounds represent potential candidates for the visualization of the A2A receptor and open pathways to novel therapeutic treatments of neurodegenerative disorders or cancer.
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Affiliation(s)
- Dana R Renk
- Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Germany; University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, Kerpener Straße 62, 50937, Köln, Germany; Forschungszentrum Jülich GmbH, Germany
| | - Marcel Skraban
- Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Germany; Forschungszentrum Jülich GmbH, Germany
| | - Dirk Bier
- Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Germany; Forschungszentrum Jülich GmbH, Germany
| | - Annette Schulze
- Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Germany; Forschungszentrum Jülich GmbH, Germany
| | - Erika Wabbals
- Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Germany; Forschungszentrum Jülich GmbH, Germany
| | - Franziska Wedekind
- Molecular Organization of the Brain (INM-2), Wilhelm-Johnen-Straße, 52428, Jülich, Germany; Forschungszentrum Jülich GmbH, Germany
| | - Felix Neumaier
- Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Germany; University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, Kerpener Straße 62, 50937, Köln, Germany; Forschungszentrum Jülich GmbH, Germany
| | - Bernd Neumaier
- Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Germany; University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, Kerpener Straße 62, 50937, Köln, Germany; Forschungszentrum Jülich GmbH, Germany
| | - Marcus Holschbach
- Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Germany; Forschungszentrum Jülich GmbH, Germany.
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Holschbach MH, Bier D, Sihver W, Schulze A, Neumaier B. Synthesis and Pharmacological Evaluation of Identified and Putative Metabolites of the A 1 Adenosine Receptor Antagonist 8-Cyclopentyl-3-(3-fluoropropyl)-1-propylxanthine (CPFPX). ChemMedChem 2017; 12:770-784. [PMID: 28217962 DOI: 10.1002/cmdc.201600592] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 02/15/2017] [Indexed: 11/09/2022]
Abstract
The A1 adenosine receptor (A1 AR) antagonist [18 F]8-cyclopentyl-3-(3-fluoropropyl)-1-propylxanthine ([18 F]CPFPX), used in imaging human brain A1 ARs by positron emission tomography (PET), is stable in the brain, but rapidly undergoes transformation into one major (3-(3-fluoropropyl)-8-(3-oxocyclopenten-1-yl)-1-propylxanthine, M1) and several minor metabolites in blood. This report describes the synthesis of putative metabolites of CPFPX as standards for the identification of those metabolites. Analysis by (radio)HPLC revealed that extracts of human liver microsomes incubated with no-carrier-added (n.c.a.)[18 F]CPFPX contain the major metabolite, M1, as well as radioactive metabolites corresponding to derivatives functionalized at the cyclopentyl moiety, but no N1-despropyl species or metabolites resulting from functionalization of the N3-fluoropropyl chain. The putative metabolites were found to displace the binding of [3 H]CPFPX to the A1 AR in pig brain cortex at Ki values between 1.9 and 380 nm and the binding of [3 H]ZM241385 to the A2A AR in pig striatum at Ki values >180 nm. One metabolite, a derivative functionalized at the ω-position of the N1-propyl chain, showed high affinity (Ki 2 nm) to and very good selectivity (>9000) for the A1 AR.
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Affiliation(s)
- Marcus H Holschbach
- Institut für Neurowissenschaften und Medizin-Nuklearchemie, INM-5, Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
| | - Dirk Bier
- Institut für Neurowissenschaften und Medizin-Nuklearchemie, INM-5, Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
| | - Wiebke Sihver
- Institut für Radiopharmazeutische Krebsforschung, Helmholtz-Zentrum Dresden-Rossendorf, Bautzener Landstraße 400, 01328, Dresden, Germany
| | - Annette Schulze
- Institut für Neurowissenschaften und Medizin-Nuklearchemie, INM-5, Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
| | - Bernd Neumaier
- Institut für Neurowissenschaften und Medizin-Nuklearchemie, INM-5, Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
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3
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New potent A1 adenosine receptor radioligands for positron emission tomography. Nucl Med Biol 2017; 44:69-77. [DOI: 10.1016/j.nucmedbio.2016.09.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 08/31/2016] [Accepted: 09/08/2016] [Indexed: 01/05/2023]
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4
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Mishina M, Ishiwata K. Adenosine Receptor PET Imaging in Human Brain. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2014; 119:51-69. [DOI: 10.1016/b978-0-12-801022-8.00002-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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5
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Holschbach MH, Bier D, Wutz W, Willbold S, Olsson RA. Synthesis of the Main Metabolite in Human Blood of the A1 Adenosine Receptor Ligand [18F]CPFPX. Org Lett 2009; 11:4266-9. [DOI: 10.1021/ol900169f] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Marcus H. Holschbach
- Institute of Neuroscience and Medicine (INM-5) and Central Division of Analytical Chemistry, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
| | - Dirk Bier
- Institute of Neuroscience and Medicine (INM-5) and Central Division of Analytical Chemistry, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
| | - Walter Wutz
- Institute of Neuroscience and Medicine (INM-5) and Central Division of Analytical Chemistry, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
| | - Sabine Willbold
- Institute of Neuroscience and Medicine (INM-5) and Central Division of Analytical Chemistry, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
| | - Ray A. Olsson
- Institute of Neuroscience and Medicine (INM-5) and Central Division of Analytical Chemistry, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
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6
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Abstract
Advances in radiotracer chemistry have resulted in the development of novel molecular imaging probes for adenosine receptors (ARs). With the availability of these molecules, the function of ARs in human pathophysiology as well as the safety and efficacy of approaches to the different AR targets can now be determined. Molecular imaging is a rapidly growing field of research that allows the identification of molecular targets and functional processes in vivo. It is therefore gaining increasing interest as a tool in drug development because it permits the process of evaluating promising therapeutic targets to be stratified. Further, molecular imaging has the potential to evolve into a useful diagnostic tool, particularly for neurological and psychiatric disorders. This chapter focuses on currently available AR ligands that are suitable for molecular neuroimaging and describes first applications in healthy subjects and patients using positron emission tomography (PET).
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Affiliation(s)
- Andreas Bauer
- Institute of Neuroscience and Biophysics (INB-3), Research Center Jülich, 52425 Jülich, Germany.
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7
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Priego EM, Pérez-Pérez MJ, von Frijtag Drabbe Kuenzel JK, de Vries H, Ijzerman AP, Camarasa MJ, Martín-Santamaría S. Selective human adenosine A3 antagonists based on pyrido[2,1-f]purine-2,4-diones: novel features of hA3 antagonist binding. ChemMedChem 2008; 3:111-9. [PMID: 18000937 DOI: 10.1002/cmdc.200700173] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Based on our previous results on the potent antagonist effect of 1H,3H-pyrido[2,1-f]purine-2,4-diones at the human A(3) adenosine receptor, new series of this family of compounds have been synthesized and evaluated in radioligand binding studies against the human A(1), A(2A), A(2B), and A(3) receptors. A remarkable improvement in potency, and most noticeable, in selectivity has been achieved, as exemplified by the 3-cyclopropylmethyl-8-methoxy-1-(4-methylbenzyl)-1H,3H-pyrido[2,1-f]purine-2,4-dione (10) that combines a very high affinity at hA(3) (K(i)=2.24 nM), with lack of affinity for the A(1), A(2A), and A(2B) receptors. On the basis of the published hA(3) receptor model (PDB 1OEA), molecular modeling studies, including molecular dynamics (MD) simulations, have been performed to depict the binding mode of the 1 H,3H-pyrido[2,1-f]purine-2,4-diones and to justify the selectivity against the other adenosine receptors. These studies have led to novel features of the cavity where our antagonists are bound so that the cavity is lined by the hydrogen-bonded Gln 167-Asn 250 pair and by the highly conserved Phe 168.
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Affiliation(s)
- Eva-María Priego
- Instituto de Química Médica, C.S.I.C. Juan de la Cierva 3, E-28006 Madrid, Spain
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8
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Biodistribution and radiation dosimetry of the A1 adenosine receptor ligand 18F-CPFPX determined from human whole-body PET. Eur J Nucl Med Mol Imaging 2008; 35:1499-506. [DOI: 10.1007/s00259-008-0753-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2007] [Accepted: 02/15/2008] [Indexed: 10/22/2022]
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9
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Wang X, Chen Y, Guo Y, Li A, Ma X, Liu J. Synthesis of 1‐(Alkyl)‐5‐dimethylamino‐6‐phenethyluracils as Potent Nonnucleoside HIV‐1 RT Inhibitors. SYNTHETIC COMMUN 2007. [DOI: 10.1080/00397910701412737] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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10
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Bier D, Holschbach MH, Wutz W, Olsson RA, Coenen HH. METABOLISM OF THE A1 ADENOSINE RECEPTOR POSITRON EMISSION TOMOGRAPHY LIGAND [18F]8-CYCLOPENTYL-3-(3-FLUOROPROPYL)-1-PROPYLXANTHINE ([18F]CPFPX) IN RODENTS AND HUMANS. Drug Metab Dispos 2006; 34:570-6. [PMID: 16415116 DOI: 10.1124/dmd.105.006411] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Studies of plasma from mice, rats, and human volunteers evaluated methods for the extraction and quantification of the positron emission tomography ligand [(18)F]8-cyclopentyl-3-(3-fluoropropyl)-1-propylxanthine ([(18)F]CPFPX) and identification of its metabolites in plasma by thin-layer chromatography and high-performance liquid chromatography (HPLC). Analysis of human, mouse, and rat plasma extracts by HPLC identified four identical radioactive metabolites in each species. The low mass of radioligand administered to humans (0.5 - 5 nmol) prevented direct identification of metabolites. However, incubating liver microsomes with CPFPX and analysis by means of liquid chromatography-mass spectrometry (LC-MS) identified seven compounds, four having the same retention times as the metabolites in human plasma. Analysis of microsomal metabolites by LC-MS identified five [M + H](+) ions of m/z equivalent to hydroxy derivatives, 339, one of m/z equivalent to an oxo derivative, m/z 337, and one of m/z equivalent to a difunctionalized oxo-desaturation species, m/z 335, which is prominent in rat and mouse plasma and is the main metabolite in human plasma. An [M + H](+) ion corresponding to a N-dealkylated derivative was not detected. Thus, like the natural methylxanthines, CPFPX seems to undergo oxidation by liver microsomes but, unlike those methylxanthines, dealkylation did not occur. LC-MS experiments with "in source" fragmentation identified the cyclopentyl moiety to be the most functionalized part of the molecule by liver microsomes and in vivo oxidations. Except for two metabolites, hydroxylated at the N1 propyl chain, all oxidative modifications found took place at the cyclopentyl ring.
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Affiliation(s)
- Dirk Bier
- Institut für Nuklearchemie, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany.
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11
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Massip S, Guillon J, Bertarelli D, Bosc JJ, Léger JM, Lacher S, Bontemps C, Dupont T, Müller CE, Jarry C. Synthesis and preliminary evaluation of new 1- and 3-[1-(2-hydroxy-3-phenoxypropyl)]xanthines from 2-amino-2-oxazolines as potential A1 and A2A adenosine receptor antagonists. Bioorg Med Chem 2005; 14:2697-719. [PMID: 16386423 DOI: 10.1016/j.bmc.2005.11.050] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2005] [Revised: 11/22/2005] [Accepted: 11/28/2005] [Indexed: 11/17/2022]
Abstract
The development of potent and selective adenosine receptor ligands as potential drugs is an active area of research. Xanthines are one of the most important classes of adenosine receptor antagonists and have been widely developed in terms of affinity and selectivity for adenosine receptors. We recently developed new original pathways for the synthesis of xanthine analogues starting from 5-substituted-2-amino-2-oxazoline 5 as a synthon. These procedures allowed us to selectively introduce a large, functionalized and beta-adrenergic 2-hydroxy-3-phenoxypropyl pharmacophore at the 1- and 3-position of the xanthine moiety which allowed further structural modifications. In this study, we present a new synthetic access to racemic xanthine derivatives 1-4 from 5, and their evaluation as adenosine A1, A2A and A3 receptor ligands in radioligand binding studies. The 2-hydroxy-3-phenoxypropyl moiety was well tolerated in the 3-position of the xanthine core, while its introduction in the 1-position of the xanthine moiety led to a large decrease in adenosine receptor affinity. 1,7-Dimethyl-3-[1-(2-chloro-3-phenoxypropyl)]-8-(3,4,5-trimethoxystyryl)xanthine (2n) was the most potent and selective A2A antagonist of the present series (Ki=44 nM, >>200-fold selective vs A1). 1-Propyl-3-[1-(2-hydroxy-3-phenoxypropyl)]-8-noradamantylxanthine (3f) was identified as a potent (KiA1=21 nM) and highly selective (>>350-fold vs A2A and A3 receptor) adenosine A1 receptor antagonist.
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Affiliation(s)
- Stéphane Massip
- EA 2962-Pharmacochimie, UFR des Sciences Pharmaceutiques, Université Victor Segalen Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France
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12
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Synthesis of novel C4-linked imidazole ribonucleoside phosphoramidites for probing general acid and base catalysis in ribozyme. Tetrahedron 2005. [DOI: 10.1016/j.tet.2005.09.063] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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13
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Baraldi PG, Preti D, Tabrizi MA, Fruttarolo F, Romagnoli R, Zaid NA, Moorman AR, Merighi S, Varani K, Borea PA. New pyrrolo[2,1-f]purine-2,4-dione and imidazo[2,1-f]purine-2,4-dione derivatives as potent and selective human A3 adenosine receptor antagonists. J Med Chem 2005; 48:4697-701. [PMID: 16000006 DOI: 10.1021/jm058008c] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Compounds presenting an additional fused ring on the xanthine nucleus have been reported to exhibit antagonistic activity with various levels of affinity and selectivity toward the four adenosine receptors subtypes A(1), A(2A), A(2B), and A(3). This paper reports synthesis and biological evaluation of new 1-benzyl-3-propyl-1H,6H-pyrrolo[2,1-f]purine-2,4-diones and 1-benzyl-3-propyl-1H,8H-imidazo[2,1-f]purine-2,4-diones, among which we identified potent and selective A(3) adenosine receptors antagonists. In particular, 1-benzyl-7-methyl-3-propyl-1H,8H-imidazo[2,1-f]purine-2,4-dione (11e) shows a K(i) (hA(3)) value from binding assay of 0.8 nM.
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14
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Holschbach MH, Bier D, Wutz W, Sihver W, Schüller M, Olsson RA. Derivatives of 4,6-diamino-1,2-dihydro-2-phenyl-1,2,4-triazolo[4,3-a]quinoxalin-2H-1-one: potential antagonist ligands for imaging the A2A adenosine receptor by positron emission tomography (PET). Eur J Med Chem 2005; 40:421-37. [PMID: 15893016 DOI: 10.1016/j.ejmech.2004.12.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Revised: 12/20/2004] [Accepted: 12/21/2004] [Indexed: 10/25/2022]
Abstract
The importance of the brain A2A adenosine receptor (A(2A)AR) in movement disorders urges the development of radiolabeled ligands for imaging those receptors by positron emission tomography (PET). This study evaluated one class of A(2A)AR antagonists, derivatives of 4-amino-6-benzylamino-1,2-dihydro-2-phenyl-1,2,4-triazolo[4,3-a]quinoxalin-2H-1-one, 10a, as agents for imaging brain A(2A)ARs by PET.. Modifications of a literature synthesis of 10a efficiently generated analogs 10b-s for pharmacological evaluation. Radioligand binding experiments showed affinities for the rat brain A(2A)AR in the low nanomolar range but similar affinities for the A1AR and substantial unspecific binding. Autoradiography employing [3H]10a, showing that high unspecific binding obscured specific binding to both the A1AR and A(2A)AR. Thus, compounds 10b-s are unsuitable as ligands for imaging brain A(2A)ARs by PET.
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Affiliation(s)
- Marcus H Holschbach
- Institut für Nuklearchemie, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
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15
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Meyer PT, Elmenhorst D, Zilles K, Bauer A. Simplified quantification of cerebral A1 adenosine receptors using [18F]CPFPX and PET: Analyses based on venous blood sampling. Synapse 2005; 55:212-23. [PMID: 15668990 DOI: 10.1002/syn.20113] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
[(18)F]CPFPX was proposed as a novel ligand for in vivo quantification of cerebral A(1) adenosine receptors (A(1)AR) using positron emission tomography (PET). The present study investigates the applicability of non-invasive non-compartment analyses to quantify the [(18)F]CPFPX total distribution volume (DV(') (t)) without arterial blood sampling. Five healthy volunteers underwent dynamic PET (90 min) with arterial and venous blood sampling after [(18)F]CPFPX bolus injection. Area under curve (AUC) analysis and Logan's graphical analysis (GA) were performed employing venous blood samples as non-invasive analyses. AUC analysis without data extrapolation (AUC(r)) and venous GA were also applied on voxel-level to generate parametric images. A conventional two-tissue compartment model (2TCM) using arterial blood samples served as reference method. Regional DV(') (t) estimates provided by venous AUC and GA analyses and 2TCM demonstrated very high agreement (venous AUC vs. 2TCM: r(2) = 0.968, linear regression slope = 0.943; venous GA vs. 2TCM: r(2) = 0.972, slope = 0.906). Although on voxel-level the venous AUC(r) and GA analyses were affected by a slight negative bias, they were still very highly correlated with the 2TCM (voxel-wise venous AUC(r) vs. 2TCM: r(2) = 0.969, slope = 0.858; voxel-wise venous GA vs. 2TCM: r(2) = 0.959, slope = 0.867). The proposed non-invasive analysis methods (particularly venous GA) allow reliable quantification of human [(18)F]CPFPX PET studies. In populations with altered metabolic/kinetic properties, the applicability of venous sampling has to be separately verified. The applicability of [(18)F]CPFPX PET in basic and clinical neurosciences will be considerably enhanced by the avoidance of arterial blood sampling.
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Affiliation(s)
- Philipp T Meyer
- Institute of Medicine, Research Centre Juelich, 52425 Juelich, Germany.
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16
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Meyer PT, Elmenhorst D, Bier D, Holschbach MH, Matusch A, Coenen HH, Zilles K, Bauer A. Quantification of cerebral A1 adenosine receptors in humans using [18F]CPFPX and PET: an equilibrium approach. Neuroimage 2004; 24:1192-204. [PMID: 15670697 DOI: 10.1016/j.neuroimage.2004.10.029] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Revised: 10/25/2004] [Accepted: 10/26/2004] [Indexed: 11/18/2022] Open
Abstract
The cerebral A(1) adenosine receptor (A(1)AR) has recently become accessible for in vivo imaging using the selective A(1)AR ligand [(18)F]CPFPX and PET. For broad application in neurosciences, imaging at distribution equilibrium is advantageous to quantify stimulus-dependent changes in receptor availability and to avoid arterial blood sampling. Here we propose a bolus/infusion (B/I) protocol to assess the total distribution volume (DV(t)) of [(18)F]CPFPX under equilibrium conditions. Employing a bolus-to-infusion ratio of 0.8 h, (near) equilibrium conditions were attained within 60 min. The regional DV(t)' given by arterial and venous equilibrium analyses agreed well with conventional two-tissue compartment model analyses (r(2) > 0.94 and r(2) > 0.84, respectively) and Logan's graphical analyses (r(2) = 1.0 and r(2) > 0.93, respectively) (n = 4 healthy volunteers). The mean regional DV(t)' values of these equilibrium analyses and of venous equilibrium analyses in additional seven volunteers demonstrated excellent agreement with the results of earlier bolus studies (r(2) > 0.98). Error simulations show that minor deviations from true equilibrium are associated with negligible to small DV(t) errors. In conclusion, [(18)F]CPFPX shows suitable characteristics for A(1)AR quantification by B/I PET scanning. Carefully standardized venous equilibrium analyses may substitute arterial analyses and thus considerably enhance applicability of A(1)AR PET in clinical routine.
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Affiliation(s)
- Philipp T Meyer
- Institute of Medicine, Molecular Neuroimaging, Research Center Juelich, Leo-Brandt-Str., 52425 Juelich, Germany.
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Meyer PT, Bier D, Holschbach MH, Boy C, Olsson RA, Coenen HH, Zilles K, Bauer A. Quantification of cerebral A1 adenosine receptors in humans using [18F]CPFPX and PET. J Cereb Blood Flow Metab 2004; 24:323-33. [PMID: 15091113 DOI: 10.1097/01.wcb.0000110531.48786.9d] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Adenosine is an important neuromodulator. Basic cerebral effects of adenosine are exerted by the A1 adenosine receptor (A1AR), which is accessible in vivo by the novel ligand [F]8-cyclopentyl-3-(3-fluoropropyl)-1-propylxanthine ([F]CPFPX) and positron emission tomography (PET). The present study investigates the applicability of kinetic models to describe the cerebral kinetics of [F]CPFPX in order to quantify A1AR density in vivo. Six healthy volunteers underwent dynamic PET scanning and arterial blood sampling after bolus injection of [F]CPFPX. For quantitative analysis, a standard two-tissue compartment model (2TCM) was compared with a one-tissue compartment model (1TCM) and Logan's graphical analysis (GA). The 2TCM described the cerebral kinetics of [F]CPFPX significantly better than the 1TCM (in all regions and subjects examined). The estimated values of the regional total distribution volumes (DVt) correlated strongly between the 2TCM and GA (linear regression r = 0.99, slope: 1.007). The DVt correlation between the 2TCM and the 1TCM was comparably high, but there was a significant bias towards lower DVt estimates given by the 1TCM (r: 0.99, slope: 0.929). It is concluded that a 2TCM satisfactorily accounts for the cerebral kinetics of [F]CPFPX. GA represents an attractive alternative method of analysis.
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Affiliation(s)
- Philipp T Meyer
- Institute of Medicine, Research Center Juelich, Juelich, Germany.
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Araki L, Harusawa S, Yamaguchi M, Yonezawa S, Taniguchi N, Lilley DM, Zhao ZY, Kurihara T. Synthesis of C4-linked imidazole ribonucleoside phosphoramidite with pivaloyloxymethyl (POM) group. Tetrahedron Lett 2004. [DOI: 10.1016/j.tetlet.2004.01.132] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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19
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Sihver W, Holschbach MH, Bier D, Wutz W, Schulze A, Olsson RA, Coenen HH. Evaluation of radioiodinated 8-Cyclopentyl-3-[(E)-3-iodoprop-2-en-1-yl]-1-propylxanthine ([*I]CPIPX) as a new potential A1 adenosine receptor antagonist for SPECT. Nucl Med Biol 2003; 30:661-8. [PMID: 12900292 DOI: 10.1016/s0969-8051(03)00053-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
8-Cyclopentyl-3-[(E)-3-[(131)I]iodoprop-2-en-1-yl]-1-propylxanthine (2*) was generated by iododestannylation of the tributyl-stannyl-precursor with [(131)I]NaI and chloramine T. The radiochemical yield of 2* was 82 +/- 4%, and the purity exceeded 98%. The specific activity was 33 +/- 19 GBq/micromol. Affinities for rat, pig and human A(1) adenosine receptors (A(1)ARs) were in the low nanomolar range, but poor selectivity for the human A(1)AR over the A(2A)AR was found. Additionally, in vitro and ex vivo autoradiographic studies revealed high unspecific binding which makes this ligand unsuitable for SPECT imaging.
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Affiliation(s)
- W Sihver
- Institute of Nuclear Chemistry, Research Center Jülich GmbH, D-52428 Jülich, Germany.
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20
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Holschbach MH, Wutz W, Schüller M, Bier D, Coenen H. Tritium-labelled 8-cyclopentyl-3-(3-fluoropropyl)-1-propylxanthine ([3H]CPFPX), a potent and selective antagonist for the A1adenosine receptor. J Labelled Comp Radiopharm 2003. [DOI: 10.1002/jlcr.679] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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21
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Holschbach MH, Olsson RA, Bier D, Wutz W, Sihver W, Schüller M, Palm B, Coenen HH. Synthesis and evaluation of no-carrier-added 8-cyclopentyl-3-(3-[(18)F]fluoropropyl)-1-propylxanthine ([(18)F]CPFPX): a potent and selective A(1)-adenosine receptor antagonist for in vivo imaging. J Med Chem 2002; 45:5150-6. [PMID: 12408725 DOI: 10.1021/jm020905i] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This report describes the precursor synthesis and the no-carrier-added (nca) radiosynthesis of the new A(1) adenosine receptor (A(1)AR) antagonist [(18)F]8-cyclopentyl-3-(3-fluoropropyl)-1-propylxanthine (CPFPX), 3, with fluorine-18 (half-life = 109.6 min). Nucleophilic radiofluorination of the precursor tosylate 8-cyclopentyl-3-(3-tosyloxypropyl)-7-pivaloyloxymethyl-1-propylxanthine, 2, with nca [(18)F]KF under aminopolyether-mediated conditions (Kryptofix 2.2.2/K(2)CO(3)) followed by deprotection was straightforward and, after formulation, gave the radioligand ready for injection with a radiochemical yield of 45 +/- 7%, a radiochemical purity of >98% and a specific radioactivity of >270 GBq/micromol (>7.2 Ci/micromol). Preparation time averaged 55 min. The synthesis proved reliable for high batch yields ( approximately 7.5 GBq) in routine production (n = 120 runs). The radiotracer was pharmacologically evaluated in vitro and in vivo and its pharmacokinetics in rodents determined in detail. After iv injection a high accumulation of radioactivity occurred in several regions of mouse brain including thalamus, striatum, cortex, and cerebellum. Antagonism by the specific A(1)AR antagonists 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and N(6)-cyclopentyl-9-methyladenine (N-0840), but not with the A(2)AR antagonist 3,7-dimethyl-1-propargylxanthine (DMPX), indicated specific and reversible binding of the radioligand to A(1)AR in cortical and subcortical regions of interest. In mouse blood at least two polar metabolites formed rapidly (50% at 5 min after tracer application). However, chromatographic analyses of brain homogenate extracts taken 60 min pi showed that >98% of radioactivity was unchanged radioligand. Chromatographic isolation and reinjection of peripherally formed radioactive metabolites revealed no accumulation of radioactivity in mouse brain, probably due to the polarity of the metabolites. These preliminary results suggest that nca [(18)F]CPFPX is a useful radioligand for the noninvasive imaging of the brain A(1)AR.
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22
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Beauglehole AR, Baker SP, Scammells PJ. New irreversible adenosine A(1) antagonists based on FSCPX. Bioorg Med Chem Lett 2002; 12:3179-82. [PMID: 12372528 DOI: 10.1016/s0960-894x(02)00639-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
FSCPX (1) and its amide analogue (2) have been reported to exhibit potent and selective irreversible antagonism of the A(1) adenosine receptor (A(1)AR) when used in in vitro biological preparations. In order to obtain an irreversible A(1)AR antagonist with improved stability, analogues of FSCPX incorporating the chemoreactive 4-(fluorosulfonyl)phenyl moiety separated from the xanthine pharmacophore by a ketone linkage were explored. Compounds 4a-c exhibited improved affinity for the A(1)AR and concentration-dependent irreversible binding to the A(1)AR.
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Affiliation(s)
- Anthony R Beauglehole
- Department of Medicinal Chemistry, Victorian College of Pharmacy, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia
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23
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Abstract
Potent adenosine receptor (AR) agonists and antagonists with high selectivity for the A1AR subtype have been developed during the past decades. However, some of the compounds considered to be selective may not be as selective in humans as in rats, and may not be very selective versus the new AR subtypes A3 or A2B. Partial agonists have been developed that may exhibit fewer side effects than full agonists. Low water solubility of many A1 antagonists remains a problem. A1 AR antagonists can be classified as neutral antagonists or inverse agonists; the pharmacological consequences of inverse agonism versus neutral antagonism will have to be the subject of future investigations. Some medicinal plants (e.g. Hypericum perforatum and Valeriana officinalis) contain compounds that are antagonists or partial agonists at A1 ARs; effects on ARs may contribute to their pharmacological activity. 18F- and 11C-labeled A1 AR antagonists have been developed for positron emission tomography studies.
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Affiliation(s)
- C E Müller
- University of Bonn, Pharmaceutical Institute, Department of Pharmaceutical Chemistry, Germany.
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24
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Wakabayashi S, Nariai T, Ishiwata K, Nagaoka T, Hirakawa K, Oda K, Sakiyama Y, Shumiya S, Toyama H, Suzuki F, Senda M. A PET study of adenosine A1 receptor in anesthetized monkey brain. Nucl Med Biol 2000; 27:401-6. [PMID: 10938476 DOI: 10.1016/s0969-8051(00)00089-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We demonstrated the distribution of adenosine A1 receptors in the anesthetized monkey brain with positron emission tomography (PET) using [(11)C]KF15372 ([1-propyl-(11)C]8-dicyclopropylmethyl-1, 3-dipropylxanthine). [(11)C]KF15372 was injected intravenously. The regional standardized uptake values and the distribution volume were calculated. We also investigated the effect of carrier on the uptake and regional brain distribution of [(11)C]KF15372. The use of [(11)C]KF15372 with dynamic PET scanning could be an appropriate method to analyze the regional binding potential of adenosine A1 receptors in living brain.
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Affiliation(s)
- S Wakabayashi
- Department of Neurosurgery, Tokyo Medical and Dental University, Tokyo, Japan
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25
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Márián T, Boros I, Lengyel Z, Balkay L, Horváth G, Emri M, Sarkadi E, Szentmiklósi AJ, Fekete I, Trón L. Preparation and primary evaluation of [11C]CSC as a possible tracer for mapping adenosine A2A receptors by PET. Appl Radiat Isot 1999; 50:887-93. [PMID: 10214707 DOI: 10.1016/s0969-8043(98)00162-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A 11C labeled selective adenosine A2A antagonist, (E)-8-(3-chlorostyryl)-1,3-dimethyl-7-[11C]methylxanthine [11C]CSC) was prepared by the reaction of (E)-8-(3-chlorostyryl)-1,3-dimethylxanthine and [11C]methyl iodide. The decay-corrected radiochemical yield was 32.3% with a radiochemical purity of 99%, a specific activity of 1.85-5.55 GBq/mumol and a preparation time of 1 h. A primary evaluation of [11C]CSC as a potential tracer for mapping adenosine A2A receptors by positron emission tomography (PET) is also presented. Biodistribution and autoradiographic studies were carried out on Swiss mice and domestic rabbits. In mice the lung showed the highest uptake at 10 min after i.v. injection, followed by the liver, kidney, heart and brain. Inside the brain a high level of radioactivity accumulated in the striatum, in accordance with previous findings on the specific spatial distribution of A2A adenosine receptors and also in the medulla oblongata. Dynamic PET studies on rabbits showed a fast brain uptake of CSC, reaching a maximum in less then 2 min. On the basis of competition experiments with the unlabeled ligand [11C]CSC proves to bind specifically to the appropriate receptor.
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Affiliation(s)
- T Márián
- PET Centre, University Medical School of Debrecen, Hungary
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