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Gündel D, Toussaint M, Lai TH, Deuther-Conrad W, Cumming P, Schröder S, Teodoro R, Moldovan RP, Pan-Montojo F, Sattler B, Kopka K, Sabri O, Brust P. Quantitation of the A2A Adenosine Receptor Density in the Striatum of Mice and Pigs with [18F]FLUDA by Positron Emission Tomography. Pharmaceuticals (Basel) 2022; 15:ph15050516. [PMID: 35631343 PMCID: PMC9146919 DOI: 10.3390/ph15050516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 04/14/2022] [Accepted: 04/19/2022] [Indexed: 12/10/2022] Open
Abstract
The cerebral expression of the A2A adenosine receptor (A2AAR) is altered in neurodegenerative diseases such as Parkinson’s (PD) and Huntington’s (HD) diseases, making these receptors an attractive diagnostic and therapeutic target. We aimed to further investigate the pharmacokinetic properties in the brain of our recently developed A2AAR–specific antagonist radiotracer [18F]FLUDA. For this purpose, we retrospectively analysed dynamic PET studies of healthy mice and rotenone–treated mice, and conducted dynamic PET studies with healthy pigs. We performed analysis of mouse brain time–activity curves to calculate the mean residence time (MRT) by non–compartmental analysis, and the binding potential (BPND) of [18F]FLUDA using the simplified reference tissue model (SRTM). For the pig studies, we performed a Logan graphical analysis to calculate the radiotracer distribution volume (VT) at baseline and under blocking conditions with tozadenant. The MRT of [18F]FLUDA in the striatum of mice was decreased by 30% after treatment with the A2AAR antagonist istradefylline. Mouse results showed the highest BPND (3.9 to 5.9) in the striatum. SRTM analysis showed a 20% lower A2AAR availability in the rotenone–treated mice compared to the control–aged group. Tozadenant treatment significantly decreased the VT (14.6 vs. 8.5 mL · g−1) and BPND values (1.3 vs. 0.3) in pig striatum. This study confirms the target specificity and a high BPND of [18F]FLUDA in the striatum. We conclude that [18F]FLUDA is a suitable tool for the non–invasive quantitation of altered A2AAR expression in neurodegenerative diseases such as PD and HD, by PET.
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Affiliation(s)
- Daniel Gündel
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz–Zentrum Dresden–Rossendorf, 04308 Leipzig, Germany; (M.T.); (T.H.L.); (W.D.-C.); (R.T.); (R.-P.M.); (K.K.); (P.B.)
- Correspondence: ; Tel.: +49-341-234179-4615
| | - Magali Toussaint
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz–Zentrum Dresden–Rossendorf, 04308 Leipzig, Germany; (M.T.); (T.H.L.); (W.D.-C.); (R.T.); (R.-P.M.); (K.K.); (P.B.)
| | - Thu Hang Lai
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz–Zentrum Dresden–Rossendorf, 04308 Leipzig, Germany; (M.T.); (T.H.L.); (W.D.-C.); (R.T.); (R.-P.M.); (K.K.); (P.B.)
- Department of Research and Development, ROTOP Pharmaka Ltd., 01328 Dresden, Germany;
| | - Winnie Deuther-Conrad
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz–Zentrum Dresden–Rossendorf, 04308 Leipzig, Germany; (M.T.); (T.H.L.); (W.D.-C.); (R.T.); (R.-P.M.); (K.K.); (P.B.)
| | - Paul Cumming
- Department of Nuclear Medicine, Bern University Hospital, 3010 Bern, Switzerland;
- School of Psychology and Counselling, Queensland University of Technology, Brisbane 4000, Australia
| | - Susann Schröder
- Department of Research and Development, ROTOP Pharmaka Ltd., 01328 Dresden, Germany;
| | - Rodrigo Teodoro
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz–Zentrum Dresden–Rossendorf, 04308 Leipzig, Germany; (M.T.); (T.H.L.); (W.D.-C.); (R.T.); (R.-P.M.); (K.K.); (P.B.)
- Department of Research and Development, Life Molecular Imaging GmbH, 13353 Berlin, Germany
| | - Rareş-Petru Moldovan
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz–Zentrum Dresden–Rossendorf, 04308 Leipzig, Germany; (M.T.); (T.H.L.); (W.D.-C.); (R.T.); (R.-P.M.); (K.K.); (P.B.)
| | - Francisco Pan-Montojo
- Department of Psychiatry, University Hospital Munich, Ludwig–Maximilians–Universität (LMU) Munich, 80336 Munich, Germany;
- Department of Neurology, University Hospital Munich, Ludwig–Maximilians–Universität (LMU) Munich, 81377 Munich, Germany
| | - Bernhard Sattler
- Department for Nuclear Medicine, University Hospital Leipzig, 04103 Leipzig, Germany; (B.S.); (O.S.)
| | - Klaus Kopka
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz–Zentrum Dresden–Rossendorf, 04308 Leipzig, Germany; (M.T.); (T.H.L.); (W.D.-C.); (R.T.); (R.-P.M.); (K.K.); (P.B.)
- Faculty of Chemistry and Food Chemistry, School of Science, TU Dresden, 01069 Dresden, Germany
| | - Osama Sabri
- Department for Nuclear Medicine, University Hospital Leipzig, 04103 Leipzig, Germany; (B.S.); (O.S.)
| | - Peter Brust
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz–Zentrum Dresden–Rossendorf, 04308 Leipzig, Germany; (M.T.); (T.H.L.); (W.D.-C.); (R.T.); (R.-P.M.); (K.K.); (P.B.)
- The Lübeck Institute of Experimental Dermatology, University Medical Center Schleswig–Holstein, 23562 Lübeck, Germany
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Lai TH, Toussaint M, Teodoro R, Dukić-Stefanović S, Gündel D, Ludwig FA, Wenzel B, Schröder S, Sattler B, Moldovan RP, Falkenburger BH, Sabri O, Deuther-Conrad W, Brust P. Improved in vivo PET imaging of the adenosine A 2A receptor in the brain using [ 18F]FLUDA, a deuterated radiotracer with high metabolic stability. Eur J Nucl Med Mol Imaging 2021; 48:2727-2736. [PMID: 33532910 PMCID: PMC8263428 DOI: 10.1007/s00259-020-05164-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 12/13/2020] [Indexed: 02/07/2023]
Abstract
PURPOSE The adenosine A2A receptor has emerged as a therapeutic target for multiple diseases, and thus the non-invasive imaging of the expression or occupancy of the A2A receptor has potential to contribute to diagnosis and drug development. We aimed at the development of a metabolically stable A2A receptor radiotracer and report herein the preclinical evaluation of [18F]FLUDA, a deuterated isotopologue of [18F]FESCH. METHODS [18F]FLUDA was synthesized by a two-step one-pot approach and evaluated in vitro by autoradiographic studies as well as in vivo by metabolism and dynamic PET/MRI studies in mice and piglets under baseline and blocking conditions. A single-dose toxicity study was performed in rats. RESULTS [18F]FLUDA was obtained with a radiochemical yield of 19% and molar activities of 72-180 GBq/μmol. Autoradiography proved A2A receptor-specific accumulation of [18F]FLUDA in the striatum of a mouse and pig brain. In vivo evaluation in mice revealed improved stability of [18F]FLUDA compared to that of [18F]FESCH, resulting in the absence of brain-penetrant radiometabolites. Furthermore, the radiometabolites detected in piglets are expected to have a low tendency for brain penetration. PET/MRI studies confirmed high specific binding of [18F]FLUDA towards striatal A2A receptor with a maximum specific-to-non-specific binding ratio in mice of 8.3. The toxicity study revealed no adverse effects of FLUDA up to 30 μg/kg, ~ 4000-fold the dose applied in human PET studies using [18F]FLUDA. CONCLUSIONS The new radiotracer [18F]FLUDA is suitable to detect the availability of the A2A receptor in the brain with high target specificity. It is regarded ready for human application.
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Affiliation(s)
- Thu Hang Lai
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany.
- Department of Research and Development, ROTOP Pharmaka Ltd., Dresden, Germany.
| | - Magali Toussaint
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany.
| | - Rodrigo Teodoro
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | - Sladjana Dukić-Stefanović
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | - Daniel Gündel
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | - Friedrich-Alexander Ludwig
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | - Barbara Wenzel
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | - Susann Schröder
- Department of Research and Development, ROTOP Pharmaka Ltd., Dresden, Germany
| | - Bernhard Sattler
- Department of Nuclear Medicine, University Hospital Leipzig, Leipzig, Germany
| | - Rareş-Petru Moldovan
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | | | - Osama Sabri
- Department of Nuclear Medicine, University Hospital Leipzig, Leipzig, Germany
| | - Winnie Deuther-Conrad
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
| | - Peter Brust
- Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Leipzig, Germany
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Yang X, Heitman LH, IJzerman AP, van der Es D. Molecular probes for the human adenosine receptors. Purinergic Signal 2021; 17:85-108. [PMID: 33313997 PMCID: PMC7954947 DOI: 10.1007/s11302-020-09753-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 11/01/2020] [Indexed: 11/29/2022] Open
Abstract
Adenosine receptors, G protein-coupled receptors (GPCRs) that are activated by the endogenous ligand adenosine, have been considered potential therapeutic targets in several disorders. To date however, only very few adenosine receptor modulators have made it to the market. Increased understanding of these receptors is required to improve the success rate of adenosine receptor drug discovery. To improve our understanding of receptor structure and function, over the past decades, a diverse array of molecular probes has been developed and applied. These probes, including radioactive or fluorescent moieties, have proven invaluable in GPCR research in general. Specifically for adenosine receptors, the development and application of covalent or reversible probes, whether radiolabeled or fluorescent, have been instrumental in the discovery of new chemical entities, the characterization and interrogation of adenosine receptor subtypes, and the study of adenosine receptor behavior in physiological and pathophysiological conditions. This review summarizes these applications, and also serves as an invitation to walk another mile to further improve probe characteristics and develop additional tags that allow the investigation of adenosine receptors and other GPCRs in even finer detail.
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Affiliation(s)
- Xue Yang
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Laura H. Heitman
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Adriaan P. IJzerman
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Daan van der Es
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
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Lai TH, Schröder S, Toussaint M, Dukić-Stefanović S, Kranz M, Ludwig FA, Fischer S, Steinbach J, Deuther-Conrad W, Brust P, Moldovan RP. Development of 18F-Labeled Radiotracers for PET Imaging of the Adenosine A 2A Receptor: Synthesis, Radiolabeling and Preliminary Biological Evaluation. Int J Mol Sci 2021; 22:ijms22052285. [PMID: 33669003 PMCID: PMC7956753 DOI: 10.3390/ijms22052285] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 02/21/2021] [Accepted: 02/22/2021] [Indexed: 12/19/2022] Open
Abstract
The adenosine A2A receptor (A2AR) represents a potential therapeutic target for neurodegenerative diseases. Aiming at the development of a positron emission tomography (PET) radiotracer to monitor changes of receptor density and/or occupancy during the A2AR-tailored therapy, we designed a library of fluorinated analogs based on a recently published lead compound (PPY). Among those, the highly affine 4-fluorobenzyl derivate (PPY1; Ki(hA2AR) = 5.3 nM) and the 2-fluorobenzyl derivate (PPY2; Ki(hA2AR) = 2.1 nM) were chosen for 18F-labeling via an alcohol-enhanced copper-mediated procedure starting from the corresponding boronic acid pinacol ester precursors. Investigations of the metabolic stability of [18F]PPY1 and [18F]PPY2 in CD-1 mice by radio-HPLC analysis revealed parent fractions of more than 76% of total activity in the brain. Specific binding of [18F]PPY2 on mice brain slices was demonstrated by in vitro autoradiography. In vivo PET/magnetic resonance imaging (MRI) studies in CD-1 mice revealed a reasonable high initial brain uptake for both radiotracers, followed by a fast clearance.
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Affiliation(s)
- Thu Hang Lai
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, 04318 Leipzig, Germany; (M.T.); (S.D.-S.); (M.K.); (F.-A.L.); (S.F.); (J.S.); (W.D.-C.); (P.B.)
- Department of Research and Development, ROTOP Pharmaka Ltd., Dresden 01328, Germany;
- Correspondence: (T.H.L.); (R.-P.M.); Tel.: +49-341-234-179-4635 (T.H.L.); +49-341-234-179-4634 (R.-P.M.)
| | - Susann Schröder
- Department of Research and Development, ROTOP Pharmaka Ltd., Dresden 01328, Germany;
| | - Magali Toussaint
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, 04318 Leipzig, Germany; (M.T.); (S.D.-S.); (M.K.); (F.-A.L.); (S.F.); (J.S.); (W.D.-C.); (P.B.)
| | - Sladjana Dukić-Stefanović
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, 04318 Leipzig, Germany; (M.T.); (S.D.-S.); (M.K.); (F.-A.L.); (S.F.); (J.S.); (W.D.-C.); (P.B.)
| | - Mathias Kranz
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, 04318 Leipzig, Germany; (M.T.); (S.D.-S.); (M.K.); (F.-A.L.); (S.F.); (J.S.); (W.D.-C.); (P.B.)
- PET Imaging Center, University Hospital of North Norway (UNN), 9009 Tromsø, Norway
- Nuclear Medicine and Radiation Biology Research Group, The Arctic University of Norway, 9009 Tromsø, Norway
| | - Friedrich-Alexander Ludwig
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, 04318 Leipzig, Germany; (M.T.); (S.D.-S.); (M.K.); (F.-A.L.); (S.F.); (J.S.); (W.D.-C.); (P.B.)
| | - Steffen Fischer
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, 04318 Leipzig, Germany; (M.T.); (S.D.-S.); (M.K.); (F.-A.L.); (S.F.); (J.S.); (W.D.-C.); (P.B.)
| | - Jörg Steinbach
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, 04318 Leipzig, Germany; (M.T.); (S.D.-S.); (M.K.); (F.-A.L.); (S.F.); (J.S.); (W.D.-C.); (P.B.)
- Department of Research and Development, ROTOP Pharmaka Ltd., Dresden 01328, Germany;
| | - Winnie Deuther-Conrad
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, 04318 Leipzig, Germany; (M.T.); (S.D.-S.); (M.K.); (F.-A.L.); (S.F.); (J.S.); (W.D.-C.); (P.B.)
| | - Peter Brust
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, 04318 Leipzig, Germany; (M.T.); (S.D.-S.); (M.K.); (F.-A.L.); (S.F.); (J.S.); (W.D.-C.); (P.B.)
| | - Rareş-Petru Moldovan
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, 04318 Leipzig, Germany; (M.T.); (S.D.-S.); (M.K.); (F.-A.L.); (S.F.); (J.S.); (W.D.-C.); (P.B.)
- Correspondence: (T.H.L.); (R.-P.M.); Tel.: +49-341-234-179-4635 (T.H.L.); +49-341-234-179-4634 (R.-P.M.)
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Schröder S, Lai TH, Toussaint M, Kranz M, Chovsepian A, Shang Q, Dukić-Stefanović S, Deuther-Conrad W, Teodoro R, Wenzel B, Moldovan RP, Pan-Montojo F, Brust P. PET Imaging of the Adenosine A 2A Receptor in the Rotenone-Based Mouse Model of Parkinson's Disease with [ 18F]FESCH Synthesized by a Simplified Two-Step One-Pot Radiolabeling Strategy. Molecules 2020; 25:molecules25071633. [PMID: 32252340 PMCID: PMC7180622 DOI: 10.3390/molecules25071633] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 03/27/2020] [Accepted: 03/27/2020] [Indexed: 12/16/2022] Open
Abstract
The adenosine A2A receptor (A2AR) is regarded as a particularly appropriate target for non-dopaminergic treatment of Parkinson’s disease (PD). An increased A2AR availability has been found in the human striatum at early stages of PD and in patients with PD and dyskinesias. The aim of this small animal positron emission tomography/magnetic resonance (PET/MR) imaging study was to investigate whether rotenone-treated mice reflect the aspect of striatal A2AR upregulation in PD. For that purpose, we selected the known A2AR-specific radiotracer [18F]FESCH and developed a simplified two-step one-pot radiosynthesis. PET images showed a high uptake of [18F]FESCH in the mouse striatum. Concomitantly, metabolism studies with [18F]FESCH revealed the presence of a brain-penetrant radiometabolite. In rotenone-treated mice, a slightly higher striatal A2AR binding of [18F]FESCH was found. Nonetheless, the correlation between the increased A2AR levels within the proposed PD animal model remains to be further investigated.
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Affiliation(s)
- Susann Schröder
- ROTOP Pharmaka Ltd., Department of Research and Development, Dresden 01328, Germany
- Correspondence: ; Tel.: +49-341-234-179-4631
| | - Thu Hang Lai
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Leipzig 04318, Germany; (T.H.L.); (M.T.); (S.D.-S.); (W.D.-C.); (R.T.); (B.W.); (R.-P.M.); (P.B.)
| | - Magali Toussaint
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Leipzig 04318, Germany; (T.H.L.); (M.T.); (S.D.-S.); (W.D.-C.); (R.T.); (B.W.); (R.-P.M.); (P.B.)
| | - Mathias Kranz
- PET Imaging Center, University Hospital of North Norway (UNN), Tromsø 9009, Norway;
- Nuclear Medicine and Radiation Biology Research Group, The Arctic University of Norway, Tromsø 9009, Norway
| | - Alexandra Chovsepian
- University Hospital Munich, Department of Psychiatry, Ludwig-Maximilians-Universität (LMU) Munich, Munich 80336, Germany; (A.C.); (F.P.-M.)
| | - Qi Shang
- University Hospital Munich, Department of Neurology, Ludwig-Maximilians-Universität (LMU) Munich, Munich 81377, Germany;
- University Hospital Carl Gustav Carus, Clinic of Neurology, Technische Universität Dresden (TUD), Dresden 01307, Germany
| | - Sladjana Dukić-Stefanović
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Leipzig 04318, Germany; (T.H.L.); (M.T.); (S.D.-S.); (W.D.-C.); (R.T.); (B.W.); (R.-P.M.); (P.B.)
| | - Winnie Deuther-Conrad
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Leipzig 04318, Germany; (T.H.L.); (M.T.); (S.D.-S.); (W.D.-C.); (R.T.); (B.W.); (R.-P.M.); (P.B.)
| | - Rodrigo Teodoro
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Leipzig 04318, Germany; (T.H.L.); (M.T.); (S.D.-S.); (W.D.-C.); (R.T.); (B.W.); (R.-P.M.); (P.B.)
| | - Barbara Wenzel
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Leipzig 04318, Germany; (T.H.L.); (M.T.); (S.D.-S.); (W.D.-C.); (R.T.); (B.W.); (R.-P.M.); (P.B.)
| | - Rareş-Petru Moldovan
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Leipzig 04318, Germany; (T.H.L.); (M.T.); (S.D.-S.); (W.D.-C.); (R.T.); (B.W.); (R.-P.M.); (P.B.)
| | - Francisco Pan-Montojo
- University Hospital Munich, Department of Psychiatry, Ludwig-Maximilians-Universität (LMU) Munich, Munich 80336, Germany; (A.C.); (F.P.-M.)
- University Hospital Munich, Department of Neurology, Ludwig-Maximilians-Universität (LMU) Munich, Munich 81377, Germany;
| | - Peter Brust
- Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Research Site Leipzig, Leipzig 04318, Germany; (T.H.L.); (M.T.); (S.D.-S.); (W.D.-C.); (R.T.); (B.W.); (R.-P.M.); (P.B.)
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McCluskey SP, Plisson C, Rabiner EA, Howes O. Advances in CNS PET: the state-of-the-art for new imaging targets for pathophysiology and drug development. Eur J Nucl Med Mol Imaging 2020; 47:451-489. [PMID: 31541283 PMCID: PMC6974496 DOI: 10.1007/s00259-019-04488-0] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 08/15/2019] [Indexed: 02/07/2023]
Abstract
PURPOSE A limit on developing new treatments for a number of central nervous system (CNS) disorders has been the inadequate understanding of the in vivo pathophysiology underlying neurological and psychiatric disorders and the lack of in vivo tools to determine brain penetrance, target engagement, and relevant molecular activity of novel drugs. Molecular neuroimaging provides the tools to address this. This article aims to provide a state-of-the-art review of new PET tracers for CNS targets, focusing on developments in the last 5 years for targets recently available for in-human imaging. METHODS We provide an overview of the criteria used to evaluate PET tracers. We then used the National Institute of Mental Health Research Priorities list to identify the key CNS targets. We conducted a PubMed search (search period 1st of January 2013 to 31st of December 2018), which yielded 40 new PET tracers across 16 CNS targets which met our selectivity criteria. For each tracer, we summarised the evidence of its properties and potential for use in studies of CNS pathophysiology and drug evaluation, including its target selectivity and affinity, inter and intra-subject variability, and pharmacokinetic parameters. We also consider its potential limitations and missing characterisation data, but not specific applications in drug development. Where multiple tracers were present for a target, we provide a comparison of their properties. RESULTS AND CONCLUSIONS Our review shows that multiple new tracers have been developed for proteinopathy targets, particularly tau, as well as the purinoceptor P2X7, phosphodiesterase enzyme PDE10A, and synaptic vesicle glycoprotein 2A (SV2A), amongst others. Some of the most promising of these include 18F-MK-6240 for tau imaging, 11C-UCB-J for imaging SV2A, 11C-CURB and 11C-MK-3168 for characterisation of fatty acid amide hydrolase, 18F-FIMX for metabotropic glutamate receptor 1, and 18F-MNI-444 for imaging adenosine 2A. Our review also identifies recurrent issues within the field. Many of the tracers discussed lack in vivo blocking data, reducing confidence in selectivity. Additionally, late-stage identification of substantial off-target sites for multiple tracers highlights incomplete pre-clinical characterisation prior to translation, as well as human disease state studies carried out without confirmation of test-retest reproducibility.
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Affiliation(s)
- Stuart P McCluskey
- Invicro LLC, A Konica Minolta Company, Burlington Danes Building, Imperial College London, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK.
- Psychiatric Imaging Group, MRC London Institute of Medical Sciences, Imperial College London, Hammersmith Hospital, London, UK.
| | - Christophe Plisson
- Invicro LLC, A Konica Minolta Company, Burlington Danes Building, Imperial College London, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - Eugenii A Rabiner
- Invicro LLC, A Konica Minolta Company, Burlington Danes Building, Imperial College London, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK
| | - Oliver Howes
- Psychiatric Imaging Group, MRC London Institute of Medical Sciences, Imperial College London, Hammersmith Hospital, London, UK
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Effects of intra-accumbal or intra-prefrontal cortex microinjections of adenosine 2A receptor ligands on responses to cocaine reward and seeking in rats. Psychopharmacology (Berl) 2018; 235:3509-3523. [PMID: 30426181 PMCID: PMC6267142 DOI: 10.1007/s00213-018-5072-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 10/10/2018] [Indexed: 12/11/2022]
Abstract
RATIONALE AND OBJECTIVES Many studies indicated that adenosine via its A2A receptors influences the behavioral effects of cocaine by modulating dopamine neurotransmission. The hypothesis was tested that A2A receptors in the nucleus accumbens (NAc) or the prefrontral cortex (PFc) may modulate cocaine reward and/or cocaine seeking behavior in rats. METHODS The effects of local bilateral microinjections of the selective A2A receptor agonist CGS 21680 or the A2A receptor antagonists KW 6002 and SCH 58261 were investigated on cocaine self-administration on reinstatement of cocaine seeking. RESULTS The intra-NAc shell, but not intra-infralimbic PFc, administration of CGS 21680 significantly reduced the number of active lever presses and the number of cocaine (0.25 mg/kg) infusions. However, tonic activation of A2A receptors located in the NAc or PFc did not play a role in modulating the rewarding actions of cocaine since neither KW 6002 nor SCH 58261 microinjections altered the cocaine (0.5 mg/kg) infusions. The intra-NAc but not intra-PFc microinjections of CGS 21680 dose- dependently attenuated the reinstatement of active lever presses induced by cocaine (10 mg/kg, i.p.) and the drug-associated combined conditioned stimuli using the subthreshold dose of cocaine (2.5 mg/kg, i.p.). On the other hand, the intra-NAc pretreatment with SCH 58261, but not with KW 6002, given alone evoked reinstatement of cocaine seeking behavior. CONCLUSION The results strongly support the involvement of accumbal shell A2A receptors as a target, the activation of which exerts an inhibitory control over cocaine reward and cocaine seeking.
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van Waarde A, Dierckx RAJO, Zhou X, Khanapur S, Tsukada H, Ishiwata K, Luurtsema G, de Vries EFJ, Elsinga PH. Potential Therapeutic Applications of Adenosine A 2A Receptor Ligands and Opportunities for A 2A Receptor Imaging. Med Res Rev 2017; 38:5-56. [PMID: 28128443 DOI: 10.1002/med.21432] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 10/31/2016] [Accepted: 11/14/2016] [Indexed: 12/13/2022]
Abstract
Adenosine A2A receptors (A2A Rs) are highly expressed in the human striatum, and at lower densities in the cerebral cortex, the hippocampus, and cells of the immune system. Antagonists of these receptors are potentially useful for the treatment of motor fluctuations, epilepsy, postischemic brain damage, or cognitive impairment, and for the control of an immune checkpoint during immunotherapy of cancer. A2A R agonists may suppress transplant rejection and graft-versus-host disease; be used to treat inflammatory disorders such as asthma, inflammatory bowel disease, and rheumatoid arthritis; be locally applied to promote wound healing and be employed in a strategy for transient opening of the blood-brain barrier (BBB) so that therapeutic drugs and monoclonal antibodies can enter the brain. Increasing A2A R signaling in adipose tissue is also a potential strategy to combat obesity. Several radioligands for positron emission tomography (PET) imaging of A2A Rs have been developed in recent years. This review article presents a critical overview of the potential therapeutic applications of A2A R ligands, the use of A2A R imaging in drug development, and opportunities and limitations of PET imaging in future research.
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Affiliation(s)
- Aren van Waarde
- University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine and Molecular Imaging, 1, 9713 GZ, Groningen, The Netherlands
| | - Rudi A J O Dierckx
- University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine and Molecular Imaging, 1, 9713 GZ, Groningen, The Netherlands.,Department of Nuclear Medicine, University Hospital, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium
| | - Xiaoyun Zhou
- University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine and Molecular Imaging, 1, 9713 GZ, Groningen, The Netherlands
| | - Shivashankar Khanapur
- University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine and Molecular Imaging, 1, 9713 GZ, Groningen, The Netherlands
| | - Hideo Tsukada
- Central Research Laboratory, Hamamatsu Photonics K.K., Hamakita, Hamamatsu, Shizuoka 434-8601, Japan
| | - Kiichi Ishiwata
- Research Institute of Cyclotron and Drug Discovery Research, Southern TOHOKU Research Institute for Neuroscience, 7-115 Yatsuyamada, Koriyama, 963-8052, Japan.,Department of Biofunctional Imaging, Fukushima Medical University, 1 Hikarigaoka, Fukushima, 960-1295, Japan.,Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan
| | - Gert Luurtsema
- University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine and Molecular Imaging, 1, 9713 GZ, Groningen, The Netherlands
| | - Erik F J de Vries
- University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine and Molecular Imaging, 1, 9713 GZ, Groningen, The Netherlands
| | - Philip H Elsinga
- University of Groningen, University Medical Center Groningen, Department of Nuclear Medicine and Molecular Imaging, 1, 9713 GZ, Groningen, The Netherlands
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Pedata F, Dettori I, Coppi E, Melani A, Fusco I, Corradetti R, Pugliese AM. Purinergic signalling in brain ischemia. Neuropharmacology 2015; 104:105-30. [PMID: 26581499 DOI: 10.1016/j.neuropharm.2015.11.007] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 11/04/2015] [Accepted: 11/06/2015] [Indexed: 12/18/2022]
Abstract
Ischemia is a multifactorial pathology characterized by different events evolving in the time. After ischemia a primary damage due to the early massive increase of extracellular glutamate is followed by activation of resident immune cells, i.e microglia, and production or activation of inflammation mediators. Protracted neuroinflammation is now recognized as the predominant mechanism of secondary brain injury progression. Extracellular concentrations of ATP and adenosine in the brain increase dramatically during ischemia in concentrations able to stimulate their respective specific P2 and P1 receptors. Both ATP P2 and adenosine P1 receptor subtypes exert important roles in ischemia. Although adenosine exerts a clear neuroprotective effect through A1 receptors during ischemia, the use of selective A1 agonists is hampered by undesirable peripheral effects. Evidence up to now in literature indicate that A2A receptor antagonists provide protection centrally by reducing excitotoxicity, while agonists at A2A (and possibly also A2B) and A3 receptors provide protection by controlling massive infiltration and neuroinflammation in the hours and days after brain ischemia. Among P2X receptors most evidence indicate that P2X7 receptor contribute to the damage induced by the ischemic insult due to intracellular Ca(2+) loading in central cells and facilitation of glutamate release. Antagonism of P2X7 receptors might represent a new treatment to attenuate brain damage and to promote proliferation and maturation of brain immature resident cells that can promote tissue repair following cerebral ischemia. Among P2Y receptors, antagonists of P2Y12 receptors are of value because of their antiplatelet activity and possibly because of additional anti-inflammatory effects. Moreover strategies that modify adenosine or ATP concentrations at injury sites might be of value to limit damage after ischemia. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.
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Affiliation(s)
- Felicita Pedata
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Viale Pieraccini, 6, 50139 Florence, Italy.
| | - Ilaria Dettori
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Viale Pieraccini, 6, 50139 Florence, Italy
| | - Elisabetta Coppi
- Department of Health Sciences, University of Florence, Viale Pieraccini, 6, 50139 Florence, Italy
| | - Alessia Melani
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Viale Pieraccini, 6, 50139 Florence, Italy
| | - Irene Fusco
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Viale Pieraccini, 6, 50139 Florence, Italy
| | - Renato Corradetti
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Viale Pieraccini, 6, 50139 Florence, Italy
| | - Anna Maria Pugliese
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Viale Pieraccini, 6, 50139 Florence, Italy
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Alnouri MW, Jepards S, Casari A, Schiedel AC, Hinz S, Müller CE. Selectivity is species-dependent: Characterization of standard agonists and antagonists at human, rat, and mouse adenosine receptors. Purinergic Signal 2015; 11:389-407. [PMID: 26126429 PMCID: PMC4529847 DOI: 10.1007/s11302-015-9460-9] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 06/17/2015] [Indexed: 12/14/2022] Open
Abstract
Adenosine receptors (ARs) have emerged as new drug targets. The majority of data on affinity/potency and selectivity of AR ligands described in the literature has been obtained for the human species. However, preclinical studies are mostly performed in mouse or rat, and standard AR agonists and antagonists are frequently used for studies in rodents without knowing their selectivity in the investigated species. In the present study, we selected a set of frequently used standard AR ligands, 8 agonists and 16 antagonists, and investigated them in radioligand binding studies at all four AR subtypes, A1, A2A, A2B, and A3, of three species, human, rat, and mouse. Recommended, selective agonists include CCPA (for A1AR of rat and mouse), CGS-21680 (for A2A AR of rat), and Cl-IB-MECA (for A3AR of all three species). The functionally selective partial A2B agonist BAY60-6583 was found to additionally bind to A1 and A3AR and act as an antagonist at both receptor subtypes. The antagonists PSB-36 (A1), preladenant (A2A), and PSB-603 (A2B) displayed high selectivity in all three investigated species. MRS-1523 acts as a selective A3AR antagonist in human and rat, but is only moderately selective in mouse. The comprehensive data presented herein provide a solid basis for selecting suitable AR ligands for biological studies.
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MESH Headings
- Adenosine A1 Receptor Agonists/metabolism
- Adenosine A1 Receptor Agonists/pharmacology
- Adenosine A1 Receptor Antagonists/metabolism
- Adenosine A1 Receptor Antagonists/pharmacology
- Adenosine A2 Receptor Agonists/metabolism
- Adenosine A2 Receptor Agonists/pharmacology
- Adenosine A2 Receptor Antagonists/metabolism
- Adenosine A2 Receptor Antagonists/pharmacology
- Adenosine A3 Receptor Agonists/metabolism
- Adenosine A3 Receptor Agonists/pharmacology
- Adenosine A3 Receptor Antagonists/metabolism
- Adenosine A3 Receptor Antagonists/pharmacology
- Animals
- Arrestin/metabolism
- Binding, Competitive/drug effects
- CHO Cells
- Cell Membrane/drug effects
- Cell Membrane/metabolism
- Cricetinae
- Cricetulus
- Cyclic AMP/metabolism
- DNA, Complementary/drug effects
- DNA, Complementary/genetics
- Humans
- Mice
- Rats
- Receptor, Adenosine A2A/drug effects
- Receptor, Adenosine A2A/genetics
- Receptor, Adenosine A2A/metabolism
- Receptor, Adenosine A2B/drug effects
- Receptor, Adenosine A2B/genetics
- Receptor, Adenosine A2B/metabolism
- Receptors, Purinergic P1/drug effects
- Receptors, Purinergic P1/genetics
- Receptors, Purinergic P1/metabolism
- Species Specificity
- Structure-Activity Relationship
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Affiliation(s)
- Mohamad Wessam Alnouri
- Pharma Center Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany
| | - Stephan Jepards
- Pharma Center Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany
| | - Alessandro Casari
- Pharma Center Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany
| | - Anke C. Schiedel
- Pharma Center Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany
| | - Sonja Hinz
- Pharma Center Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany
| | - Christa E. Müller
- Pharma Center Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany
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Barret O, Hannestad J, Vala C, Alagille D, Tavares A, Laruelle M, Jennings D, Marek K, Russell D, Seibyl J, Tamagnan G. Characterization in humans of 18F-MNI-444, a PET radiotracer for brain adenosine 2A receptors. J Nucl Med 2015; 56:586-91. [PMID: 25698783 DOI: 10.2967/jnumed.114.152546] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 01/26/2015] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED PET with selective adenosine 2A receptor (A2A) radiotracers can be used to study a variety of neurodegenerative and neuropsychiatric disorders in vivo and to support drug-discovery studies targeting A2A. The aim of this study was to describe the first in vivo evaluation of (18)F-MNI-444, a novel PET radiotracer for imaging A2A, in healthy human subjects. METHODS Ten healthy human volunteers were enrolled in this study; 6 completed the brain PET studies and 4 participated in the whole-body PET studies. Arterial blood was collected for invasive kinetic modeling of the brain PET data. Noninvasive methods of data quantification were also explored. Test-retest reproducibility was evaluated in 5 subjects. Radiotracer distribution and dosimetry was determined using serial whole-body PET images acquired over 6 h post-radiotracer injection. Urine samples were collected to calculate urinary excretion. RESULTS After intravenous bolus injection, (18)F-MNI-444 rapidly entered the brain and displayed a distribution consistent with known A2A densities in the brain. Binding potentials ranging from 2.6 to 4.9 were measured in A2A-rich regions, with an average test-retest variability of less than 10%. The estimated whole-body radiation effective dose was approximately 0.023 mSv/MBq. CONCLUSION (18)F-MNI-444 is a useful PET radiotracer for imaging A2A in the human brain. The superior in vivo brain kinetic properties of (18)F-MNI-444, compared with previously developed A2A radiotracers, provide the opportunity to foster global use of in vivo A2A PET imaging in neuroscience research.
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Affiliation(s)
- Olivier Barret
- Molecular NeuroImaging, LLC, New Haven, Connecticut; and
| | | | - Christine Vala
- Molecular NeuroImaging, LLC, New Haven, Connecticut; and
| | - David Alagille
- Molecular NeuroImaging, LLC, New Haven, Connecticut; and
| | | | | | - Danna Jennings
- Molecular NeuroImaging, LLC, New Haven, Connecticut; and
| | - Ken Marek
- Molecular NeuroImaging, LLC, New Haven, Connecticut; and
| | - David Russell
- Molecular NeuroImaging, LLC, New Haven, Connecticut; and
| | - John Seibyl
- Molecular NeuroImaging, LLC, New Haven, Connecticut; and
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12
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Barret O, Hannestad J, Alagille D, Vala C, Tavares A, Papin C, Morley T, Fowles K, Lee H, Seibyl J, Tytgat D, Laruelle M, Tamagnan G. Adenosine 2A receptor occupancy by tozadenant and preladenant in rhesus monkeys. J Nucl Med 2014; 55:1712-8. [PMID: 25082853 DOI: 10.2967/jnumed.114.142067] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED Motor symptoms in Parkinson disease (PD) are caused by a loss of dopamine input from the substantia nigra to the striatum. Blockade of adenosine 2A (A(2A)) receptors facilitates dopamine D(2) receptor function. In phase 2 clinical trials, A(2A) antagonists (istradefylline, preladenant, and tozadenant) improved motor function in PD. We developed a new A(2A) PET radiotracer, (18)F-MNI-444, and used it to investigate the relationship between plasma levels and A(2A) occupancy by preladenant and tozadenant in nonhuman primates (NHP). METHODS A series of 20 PET experiments was conducted in 5 adult rhesus macaques. PET data were analyzed with both plasma-input (Logan graphical analysis) and reference-region-based (simplified reference tissue model and noninvasive Logan graphical analysis) methods. Whole-body PET images were acquired for radiation dosimetry estimates. Human pharmacokinetic parameters for tozadenant and preladenant were used to predict A(2A) occupancy in humans, based on median effective concentration (EC(50)) values estimated from the NHP PET measurements. RESULTS (18)F-MNI-444 regional uptake was consistent with A(2A) receptor distribution in the brain. Selectivity was demonstrated by dose-dependent blocking by tozadenant and preladenant. The specific-to-nonspecific ratio was superior to that of other A(2A) PET radiotracers. Pharmacokinetic modeling predicted that tozadenant and preladenant may have different profiles of A(2A) receptor occupancy in humans. CONCLUSION (18)F-MNI-444 appears to be a better PET radiotracer for A(2A) imaging than currently available radiotracers. Assuming that EC(50) in humans is similar to that in NHP, it appears that tozadenant will provide a more sustained A(2A) receptor occupancy than preladenant in humans at clinically tested doses.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Hsiaoju Lee
- Molecular NeuroImaging, LLC, New Haven, Connecticut
| | - John Seibyl
- Molecular NeuroImaging, LLC, New Haven, Connecticut
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13
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Tavares AAS, Batis JC, Papin C, Jennings D, Alagille D, Russell DS, Vala C, Lee H, Baldwin RM, Zubal IG, Marek KL, Seibyl JP, Barret O, Tamagnan GD. Kinetic modeling, test-retest, and dosimetry of 123I-MNI-420 in humans. J Nucl Med 2013; 54:1760-7. [PMID: 23970369 DOI: 10.2967/jnumed.113.119933] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED In vivo imaging of adenosine 2A receptors (A2A) in the brain has attracted significant interest from the scientific community, because studies have shown that dysregulation of these receptors is implicated in a variety of neurodegenerative and psychiatric disorders, including Parkinson and Huntington diseases. This work aimed to describe the kinetic properties, test-retest results, and dosimetry estimates of (123)I-MNI-420, a SPECT radiotracer for the in vivo imaging of A2A in the brain. METHODS Nine healthy human subjects were enrolled in this study; 7 completed (123)I-MNI-420 brain SPECT studies, and 2 participated in whole-body planar imaging evaluating (123)I-MNI-420 biodistribution and dosimetry. For 3 of the brain SPECT studies, arterial blood was collected for invasive modeling. Noninvasive models were also explored, including Logan graphical analysis and simplified reference tissue models. Test-retest reliability was assessed in 4 subjects. To evaluate radiotracer biodistribution and dosimetry, serial whole-body images were acquired immediately after injection and at selected time points after injection. Urine samples were collected over a period of 21 h to calculate urinary excretion. RESULTS (123)I-MNI-420 rapidly entered the human brain and displayed uptake consistent with known A2A densities. At pseudoequilibrium (reached at 90 min after radiotracer injection), stable target-to-cerebellum ratios of around 1.4-2.0 were determined. Binding potentials around 0.8-1.2 were estimated using different kinetic models and the cerebellum as the reference region. Average test-retest variability in the striatum was 4.8%, 3.5%, and 6.5% for the simplified reference tissue model, Logan graphical analysis, and standardized uptake value ratio methods, respectively. The estimated radiation effective dose determined from whole-body studies was 0.036 mSv/MBq. CONCLUSION The data indicate that (123)I-MNI-420 is a useful SPECT radiotracer for imaging A2A in the brain and has radiation doses that would allow for multiple scans in the same research subject each year. The availability of (123)I-MNI-420 offers the possibility of investigating A2A activity in specific conditions and evaluating drug occupancy for A2A candidate therapeutics.
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14
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Tavares AADS, Batis J, Barret O, Alagille D, Vala C, Kudej G, Koren A, Cosgrove KP, Nice K, Kordower JH, Seibyl J, Tamagnan GD. In vivo evaluation of [(123)I]MNI-420: a novel single photon emission computed tomography radiotracer for imaging of adenosine 2A receptors in brain. Nucl Med Biol 2013; 40:403-9. [PMID: 23332393 DOI: 10.1016/j.nucmedbio.2012.12.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 11/24/2012] [Accepted: 12/03/2012] [Indexed: 01/08/2023]
Abstract
INTRODUCTION Dysregulation of adenosine 2A (A2A) receptor function in brain has been implicated in multiple psychiatric and neurodegenerative disorders, including schizophrenia and Parkinson's disease, making the development of an imaging agent to study A2A receptors in both healthy brain and disease states desirable. In this study, [(123)I]MNI-420 was evaluated as a potential single photon emission computed tomography (SPECT) radiotracer for imaging A2A receptors in brain. METHODS Two adult male monkeys (Macaca fascicularis) and three adult female baboons (Papio anubis) were anesthetized and imaged on Neurofocus SPECT cameras. Baboons underwent baseline and displacement studies using varying doses of caffeine (2.0-20mg/kg). Baseline and pre-blocking experiments with multiple doses of preladenant (0.01-1.2mg/kg), a highly selective A2A antagonist, were performed in cynomolgus monkeys. RESULTS Following bolus intravenous (i.v.) injection, [(123)I]MNI-420 rapidly entered the non-human primate brain. The regional brain accumulation of [(123)I]MNI-420 matched the known distribution of A2A receptors in brain (highest in the striatum). Striatum to cerebellum ratios and binding potentials of around 3.0-3.5 and 2.0-2.5, respectively, were measured in monkey and baboon brain. A dose-dependent occupancy was observed following i.v. injection of caffeine at pseudo-equilibrium conditions during displacement experiments. Pre-treatment with preladenant blocked specific binding in A2A rich regions in a dose-dependent fashion. CONCLUSIONS The data indicate that [(123)I]MNI-420 holds promise as a SPECT radiotracer for imaging A2A receptors in brain and further evaluation is warranted, in order to determine its utility as a SPECT radiotracer for imaging of A2A in brain.
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