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Humpert S, Schneider D, Bier D, Schulze A, Neumaier F, Neumaier B, Holschbach M. 8-Bicycloalkyl-CPFPX derivatives as potent and selective tools for in vivo imaging of the A 1 adenosine receptor. Eur J Med Chem 2024; 271:116380. [PMID: 38615410 DOI: 10.1016/j.ejmech.2024.116380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 03/19/2024] [Accepted: 04/01/2024] [Indexed: 04/16/2024]
Abstract
Imaging of the A1 adenosine receptor (A1R) by positron emission tomography (PET) with 8-cyclopentyl-3-(3-[18F]fluoropropyl)-1-propyl-xanthine ([18F]CPFPX) has been widely used in preclinical and clinical studies. However, this radioligand suffers from rapid peripheral metabolism and subsequent accumulation of radiometabolites in the vascular compartment. In the present work, we prepared four derivatives of CPFPX by replacement of the cyclopentyl group with norbornane moieties. These derivatives were evaluated by competition binding studies, microsomal stability assays and LC-MS analysis of microsomal metabolites. In addition, the 18F-labeled isotopologue of 8-(1-norbornyl)-3-(3-fluoropropyl)-1-propylxanthine (1-NBX) as the most promising candidate was prepared by radiofluorination of the corresponding tosylate precursor and the resulting radioligand ([18F]1-NBX) was evaluated by permeability assays with Caco-2 cells and in vitro autoradiography in rat brain slices. Our results demonstrate that 1-NBX exhibits significantly improved A1R affinity and selectivity when compared to CPFPX and that it does not give rise to lipophilic metabolites expected to cross the blood-brain-barrier in microsomal assays. Furthermore, [18F]1-NBX showed a high passive permeability (Pc = 6.9 ± 2.9 × 10-5 cm/s) and in vitro autoradiography with this radioligand resulted in a distribution pattern matching A1R expression in the brain. Moreover, a low degree of non-specific binding (5%) was observed. Taken together, these findings identify [18F]1-NBX as a promising candidate for further preclinical evaluation as potential PET tracer for A1R imaging.
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Affiliation(s)
- Swen Humpert
- Forschungszentrum Jülich GmbH, Institute of Neurosciences and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428, Jülich, Germany
| | - Daniela Schneider
- Forschungszentrum Jülich GmbH, Institute of Neurosciences and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428, Jülich, Germany
| | - Dirk Bier
- Forschungszentrum Jülich GmbH, Institute of Neurosciences and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428, Jülich, Germany
| | - Annette Schulze
- Forschungszentrum Jülich GmbH, Institute of Neurosciences and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428, Jülich, Germany
| | - Felix Neumaier
- Forschungszentrum Jülich GmbH, Institute of Neurosciences and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428, Jülich, Germany; Institute of Radiochemistry and Experimental Molecular Imaging, Faculty of Medicine and University Hospital Cologne, University of Cologne, Kerpener Str. 62, 50937, Cologne, Germany
| | - Bernd Neumaier
- Forschungszentrum Jülich GmbH, Institute of Neurosciences and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428, Jülich, Germany; Institute of Radiochemistry and Experimental Molecular Imaging, Faculty of Medicine and University Hospital Cologne, University of Cologne, Kerpener Str. 62, 50937, Cologne, Germany; Max Planck Institute for Metabolism Research, Gleueler Straße 50, 50931, Cologne, Germany.
| | - Marcus Holschbach
- Forschungszentrum Jülich GmbH, Institute of Neurosciences and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428, Jülich, Germany
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Humpert S, Schneider D, Lang M, Schulze A, Neumaier F, Holschbach M, Bier D, Neumaier B. Radiosynthesis and In Vitro Evaluation of [ 11C]tozadenant as Adenosine A 2A Receptor Radioligand. Molecules 2024; 29:1089. [PMID: 38474602 DOI: 10.3390/molecules29051089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 02/23/2024] [Accepted: 02/27/2024] [Indexed: 03/14/2024] Open
Abstract
Tozadenant (4-hydroxy-N-(4-methoxy-7-morpholinobenzo[d]thiazol-2-yl)-4-methylpiperidine-1-carboxamide) is a highly selective adenosine A2A receptor (A2AR) antagonist and a promising lead structure for the development of A2AR-selective positron emission tomography (PET) probes. Although several 18F-labelled tozadenant derivatives showed favorable in vitro properties, recent in vivo PET studies observed poor brain penetration and lower specific binding than anticipated from the in vitro data. While these findings might be attributable to the structural modification associated with 18F-labelling, they could also reflect inherent properties of the parent compound. However, PET studies with radioisotopologues of tozadenant to evaluate its cerebral pharmacokinetics and brain distribution are still lacking. In the present work, we applied N-Boc-O-desmethyltozadenant as a suitable precursor for the preparation of [O-methyl-11C]tozadenant ([11C]tozadenant) by O-methylation with [11C]methyl iodide followed by acidic deprotection. This approach afforded [11C]tozadenant in radiochemical yields of 18 ± 2%, with molar activities of 50-60 GBq/µmol (1300-1600 mCi/µmol) and radiochemical purities of 95 ± 3%. In addition, in vitro autoradiography in pig and rat brain slices demonstrated the expected striatal accumulation pattern and confirmed the A2AR specificity of the radioligand, making it a promising tool for in vivo PET studies on the cerebral pharmacokinetics and brain distribution of tozadenant.
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Affiliation(s)
- Swen Humpert
- Forschungszentrum Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428 Jülich, Germany
| | - Daniela Schneider
- Forschungszentrum Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428 Jülich, Germany
| | - Markus Lang
- Forschungszentrum Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428 Jülich, Germany
| | - Annette Schulze
- Forschungszentrum Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428 Jülich, Germany
| | - Felix Neumaier
- Forschungszentrum Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428 Jülich, Germany
- Institute of Radiochemistry and Experimental Molecular Imaging, Faculty of Medicine and University Hospital Cologne, University of Cologne, Kerpener Str. 62, 50937 Cologne, Germany
| | - Marcus Holschbach
- Forschungszentrum Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428 Jülich, Germany
| | - Dirk Bier
- Forschungszentrum Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428 Jülich, Germany
| | - Bernd Neumaier
- Forschungszentrum Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Wilhelm-Johnen-Str., 52428 Jülich, Germany
- Institute of Radiochemistry and Experimental Molecular Imaging, Faculty of Medicine and University Hospital Cologne, University of Cologne, Kerpener Str. 62, 50937 Cologne, Germany
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Kolks N, Neumaier F, Neumaier B, Zlatopolskiy BD. Preparation of NIn-Methyl-6-[ 18F]fluoro- and 5-Hydroxy-7-[ 18F]fluorotryptophans as Candidate PET-Tracers for Pathway-Specific Visualization of Tryptophan Metabolism. Int J Mol Sci 2023; 24:15251. [PMID: 37894930 PMCID: PMC10607147 DOI: 10.3390/ijms242015251] [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] [Received: 09/15/2023] [Revised: 10/09/2023] [Accepted: 10/14/2023] [Indexed: 10/29/2023] Open
Abstract
Tryptophan (Trp) is an essential proteinogenic amino acid and metabolic precursor for several signaling molecules that has been implicated in many physiological and pathological processes. Since the two main branches of Trp metabolism-serotonin biosynthesis and kynurenine pathway-are differently affected by a variety of neurological and neoplastic diseases, selective visualization of these pathways is of high clinical relevance. However, while positron emission tomography (PET) with existing probes can be used for non-invasive assessment of total Trp metabolism, optimal imaging agents for pathway-specific PET imaging are still lacking. In this work, we describe the preparation of two 18F-labeled Trp derivatives, NIn-methyl-6-[18F]fluorotryptophan (NIn-Me-6-[18F]FTrp) and 5-hydroxy-7-[18F]fluorotryptophan (5-HO-7-[18F]FTrp). We also report feasible synthetic routes for the preparation of the hitherto unknown boronate radiolabeling precursors and non-radioactive reference compounds. Under optimized conditions, alcohol-enhanced Cu-mediated radiofluorination of the respective precursors afforded NIn-Me-6-[18F]FTrp and 5-HO-7-[18F]FTrp as application-ready solutions in radiochemical yields of 45 ± 7% and 29 ± 4%, respectively. As such, our work provides access to two promising candidate probes for pathway-specific visualization of Trp metabolism in amounts sufficient for their preclinical evaluation.
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Affiliation(s)
- Niklas Kolks
- Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Str., 52428 Jülich, Germany; (N.K.); (F.N.); (B.D.Z.)
- Institute of Radiochemistry and Experimental Molecular Imaging, Faculty of Medicine and University Hospital Cologne, University of Cologne, Kerpener Str. 62, 50937 Cologne, Germany
| | - Felix Neumaier
- Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Str., 52428 Jülich, Germany; (N.K.); (F.N.); (B.D.Z.)
- Institute of Radiochemistry and Experimental Molecular Imaging, Faculty of Medicine and University Hospital Cologne, University of Cologne, Kerpener Str. 62, 50937 Cologne, Germany
| | - Bernd Neumaier
- Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Str., 52428 Jülich, Germany; (N.K.); (F.N.); (B.D.Z.)
- Institute of Radiochemistry and Experimental Molecular Imaging, Faculty of Medicine and University Hospital Cologne, University of Cologne, Kerpener Str. 62, 50937 Cologne, Germany
| | - Boris D. Zlatopolskiy
- Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5), Forschungszentrum Jülich GmbH, Wilhelm-Johnen-Str., 52428 Jülich, Germany; (N.K.); (F.N.); (B.D.Z.)
- Institute of Radiochemistry and Experimental Molecular Imaging, Faculty of Medicine and University Hospital Cologne, University of Cologne, Kerpener Str. 62, 50937 Cologne, Germany
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Gröner B, Willmann M, Donnerstag L, Urusova EA, Neumaier F, Humpert S, Endepols H, Neumaier B, Zlatopolskiy BD. 7-[ 18F]Fluoro-8-azaisatoic Anhydrides: Versatile Prosthetic Groups for the Preparation of PET Tracers. J Med Chem 2023; 66:12629-12644. [PMID: 37625106 PMCID: PMC10510393 DOI: 10.1021/acs.jmedchem.3c01310] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Indexed: 08/27/2023]
Abstract
18F-Fluorination of sensitive molecules is often challenging, but can be accomplished under suitably mild conditions using radiofluorinated prosthetic groups (PGs). Herein, 1-alkylamino-7-[18F]fluoro-8-azaisatoic anhydrides ([18F]AFAs) are introduced as versatile 18F-labeled building blocks that can be used as amine-reactive or "click chemistry" PGs. [18F]AFAs were efficiently prepared within 15 min by "on cartridge" radiolabeling of readily accessible trimethylammonium precursors. Conjugation with a range of amines afforded the corresponding 2-alkylamino-6-[18F]fluoronicotinamides in radiochemical conversions (RCCs) of 15-98%. In addition, radiolabeling of alkyne- or azide-functionalized precursors with azidopropyl- or propargyl-substituted [18F]AFAs using Cu-catalyzed click cycloaddition afforded the corresponding conjugates in RCCs of 44-88%. The practical utility of the PGs was confirmed by the preparation of three 18F-labeled PSMA ligands in radiochemical yields of 28-42%. Biological evaluation in rats demonstrated excellent in vivo stability of all three conjugates. In addition, one conjugate ([18F]JK-PSMA-15) showed favorable imaging properties for high-contrast visualization of small PSMA-positive lesions.
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Affiliation(s)
- Benedikt Gröner
- Forschungszentrum
Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear
Chemistry (INM-5), Wilhelm-Johnen-Straße, 52428 Jülich, Germany
- Faculty
of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University
of Cologne, Kerpener
Straße 62, 50937 Cologne, Germany
| | - Michael Willmann
- Forschungszentrum
Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear
Chemistry (INM-5), Wilhelm-Johnen-Straße, 52428 Jülich, Germany
| | - Lisa Donnerstag
- Forschungszentrum
Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear
Chemistry (INM-5), Wilhelm-Johnen-Straße, 52428 Jülich, Germany
- Faculty
of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University
of Cologne, Kerpener
Straße 62, 50937 Cologne, Germany
| | - Elizaveta A. Urusova
- Forschungszentrum
Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear
Chemistry (INM-5), Wilhelm-Johnen-Straße, 52428 Jülich, Germany
- Faculty
of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University
of Cologne, Kerpener
Straße 62, 50937 Cologne, Germany
| | - Felix Neumaier
- Forschungszentrum
Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear
Chemistry (INM-5), Wilhelm-Johnen-Straße, 52428 Jülich, Germany
- Faculty
of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University
of Cologne, Kerpener
Straße 62, 50937 Cologne, Germany
| | - Swen Humpert
- Forschungszentrum
Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear
Chemistry (INM-5), Wilhelm-Johnen-Straße, 52428 Jülich, Germany
| | - Heike Endepols
- Forschungszentrum
Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear
Chemistry (INM-5), Wilhelm-Johnen-Straße, 52428 Jülich, Germany
- Faculty
of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University
of Cologne, Kerpener
Straße 62, 50937 Cologne, Germany
- Faculty
of Medicine and University Hospital Cologne, Department of Nuclear
Medicine, University of Cologne, Kerpener Straße 62, 50937 Cologne, Germany
| | - Bernd Neumaier
- Forschungszentrum
Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear
Chemistry (INM-5), Wilhelm-Johnen-Straße, 52428 Jülich, Germany
- Faculty
of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University
of Cologne, Kerpener
Straße 62, 50937 Cologne, Germany
- Max
Planck Institute for Metabolism Research, Gleueler Straße 50, 50931 Cologne, Germany
| | - Boris D. Zlatopolskiy
- Forschungszentrum
Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear
Chemistry (INM-5), Wilhelm-Johnen-Straße, 52428 Jülich, Germany
- Faculty
of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging, University
of Cologne, Kerpener
Straße 62, 50937 Cologne, Germany
- Max
Planck Institute for Metabolism Research, Gleueler Straße 50, 50931 Cologne, Germany
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