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Varnäs K, Nag S, Halldin C, Farde L. PET Evaluation of the Novel F-18 Labeled Reversible Radioligand [ 18F]GEH200449 for Detection of Monoamine Oxidase-B in the Non-Human Primate Brain. ACS Chem Neurosci 2023; 14:3206-3211. [PMID: 37587571 PMCID: PMC10485887 DOI: 10.1021/acschemneuro.3c00332] [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: 05/15/2023] [Accepted: 08/07/2023] [Indexed: 08/18/2023] Open
Abstract
Positron emission tomography (PET) using radioligands for the enzyme monoamine oxidase B (MAO-B) is increasingly applied as a marker for astrogliosis in neurodegenerative disorders. In the present study, a novel reversible fluorine-18 labeled MAO-B compound, [18F]GEH200449, was evaluated as a PET radioligand in non-human primates. PET studies of [18F]GEH200449 at baseline showed brain exposure (maximum concentration: 3.4-5.2 SUV; n = 5) within the range of that for suitable central nervous system radioligands and a regional distribution consistent with the known localization of MAO-B. Based on the quantitative assessment of [18F]GEH200449 data using the metabolite-corrected arterial plasma concentration as input function, the Logan graphical analysis was selected as the preferred method of quantification. The binding of [18F]GEH200449, as calculated based on regional estimates of the total distribution volume, was markedly inhibited (occupancy >80%) by the administration of the selective MAO-B ligands L-deprenyl (0.5 and 1.0 mg/kg) or rasagiline (0.75 mg/kg) prior to radioligand injection. Radioligand binding was displaceable by the administration of L-deprenyl (0.5 mg/kg) at 25 min after radioligand injection, thus supporting reversible binding to MAO-B. These observations support that [18F]GEH200449 is a reversible MAO-B radioligand suitable for applied studies in humans.
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Affiliation(s)
- Katarina Varnäs
- Karolinska Institutet,
Department
of Clinical Neuroscience, Center for Psychiatry Research and Stockholm
County Council, BioClinicum J:15, Visionsgatan 4, SE-171
64 Solna, Sweden
| | - Sangram Nag
- Karolinska Institutet,
Department
of Clinical Neuroscience, Center for Psychiatry Research and Stockholm
County Council, BioClinicum J:15, Visionsgatan 4, SE-171
64 Solna, Sweden
| | - Christer Halldin
- Karolinska Institutet,
Department
of Clinical Neuroscience, Center for Psychiatry Research and Stockholm
County Council, BioClinicum J:15, Visionsgatan 4, SE-171
64 Solna, Sweden
| | - Lars Farde
- Karolinska Institutet,
Department
of Clinical Neuroscience, Center for Psychiatry Research and Stockholm
County Council, BioClinicum J:15, Visionsgatan 4, SE-171
64 Solna, Sweden
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Harada R, Furumoto S, Kudo Y, Yanai K, Villemagne VL, Okamura N. Imaging of Reactive Astrogliosis by Positron Emission Tomography. Front Neurosci 2022; 16:807435. [PMID: 35210989 PMCID: PMC8862631 DOI: 10.3389/fnins.2022.807435] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 01/14/2022] [Indexed: 11/13/2022] Open
Abstract
Many neurodegenerative diseases are neuropathologically characterized by neuronal loss, gliosis, and the deposition of misfolded proteins such as β-amyloid (Aβ) plaques and tau tangles in Alzheimer’s disease (AD). In postmortem AD brains, reactive astrocytes and activated microglia are observed surrounding Aβ plaques and tau tangles. These activated glial cells secrete pro-inflammatory cytokines and reactive oxygen species, which may contribute to neurodegeneration. Therefore, in vivo imaging of glial response by positron emission tomography (PET) combined with Aβ and tau PET would provide new insights to better understand the disease process, as well as aid in the differential diagnosis, and monitoring glial response disease-specific therapeutics. There are two promising targets proposed for imaging reactive astrogliosis: monoamine oxidase-B (MAO-B) and imidazoline2 binding site (I2BS), which are predominantly expressed in the mitochondrial membranes of astrocytes and are upregulated in various neurodegenerative conditions. PET tracers targeting these two MAO-B and I2BS have been evaluated in humans. [18F]THK-5351, which was originally designed to target tau aggregates in AD, showed high affinity for MAO-B and clearly visualized reactive astrocytes in progressive supranuclear palsy (PSP). However, the lack of selectivity of [18F]THK-5351 binding to both MAO-B and tau, severely limits its clinical utility as a biomarker. Recently, [18F]SMBT-1 was developed as a selective and reversible MAO-B PET tracer via compound optimization of [18F]THK-5351. In this review, we summarize the strategy underlying molecular imaging of reactive astrogliosis and clinical studies using MAO-B and I2BS PET tracers.
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Affiliation(s)
- Ryuichi Harada
- Department of Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Japan
- *Correspondence: Ryuichi Harada,
| | - Shozo Furumoto
- Cyclotron and Radioisotope Center, Tohoku University, Sendai, Japan
| | - Yukitsuka Kudo
- Department of New Therapeutics Innovation for Alzheimer’s and Dementia, Institute of Development and Aging, Tohoku University, Sendai, Japan
| | - Kazuhiko Yanai
- Department of Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Victor L. Villemagne
- Department of Molecular Imaging and Therapy, Austin Health, Melbourne, VIC, Australia
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States
| | - Nobuyuki Okamura
- Division of Pharmacology, Faculty of Medicine, Tohoku Medical and Pharmaceutical University, Sendai, Japan
- Nobuyuki Okamura,
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Harada R, Shimizu Y, Du Y, Ishikawa Y, Iwata R, Kudo Y, Yanai K, Okamura N, Furumoto S. The Role of Chirality of [ 18F]SMBT-1 in Imaging of Monoamine Oxidase-B. ACS Chem Neurosci 2022; 13:322-329. [PMID: 35049267 DOI: 10.1021/acschemneuro.1c00655] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
(S)-(2-Methylpyrid-5-yl)-6-[(3-[18F]fluoro-2-hydroxy)propoxy]quinoline ([18F]SMBT-1) was recently developed as a novel class of selective and reversible monoamine oxidase-B (MAO-B) tracers for in vivo imaging of reactive astrogliosis via positron emission tomography. To investigate the effect of the chirality of [18F]SMBT-1 on tracer performance, we synthesized (S)-[18F]6 ([18F]SMBT-1) and (R)-[18F]6 and compared their binding properties, pharmacokinetics, and metabolism. (S)-6 showed higher binding affinity to MAO-B and lower binding affinity to MAO-A than (R)-6, demonstrating a higher selectivity ratio (MAO-B/MAO-A). A pharmacokinetic study in mice demonstrated that both (S)-[18F]6 and (R)-[18F]6 showed sufficient initial brain uptake. However, (S)-[18F]6 was cleared significantly faster from the body. An abundant sulfoconjugate metabolite M2 was observed in plasma for (S)-[18F]6 but not for (R)-[18F]6. In vitro sulfation assays confirmed that (S)-6 was more reactive than (R)-6, consistent with the in vivo findings. Mefenamic acid, a selective sulfotransferase 1A1 (SULT1A1) inhibitor, strongly inhibited the in vitro sulfation of (S)-6 by mouse liver fractions, human liver cytosol fractions, and human recombinant SULT1A1 enzyme. Genetic polymorphisms of SULT1A1 did not affect the sulfation of (S)-6 in vitro. In conclusion, (S)-[18F]6 had a more favorable binding affinity and binding selectivity for MAO-B than (R)-[18F]6. Additionally, (S)-[18F]6 also possessed better pharmacological and metabolic properties than (R)-[18F]6. These results suggest that (S)-[18F]6 ([18F]SMBT-1) is a promising candidate for application in the imaging of MAO-B in vivo.
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Affiliation(s)
- Ryuichi Harada
- Department of Pharmacology, Graduate School of Medicine, Tohoku University, 2-1 Seiryomachi, Aobaku, Sendai 980-8575, Japan
- Department of New Therapeutics Innovation for Alzheimer’s and Dementia, Institute of Development Aging and Cancer (IDAC), Tohoku University, 2-1 Seiryomachi, Aobaku, Sendai 980-8575, Japan
| | - Yuki Shimizu
- Cyclotron and Radioisotope Center (CYRIC), Tohoku University, 6-3 Aoba, Aramaki, Aobaku, Sendai 980-8578, Japan
| | - Yiqing Du
- Department of Pharmacology, Graduate School of Medicine, Tohoku University, 2-1 Seiryomachi, Aobaku, Sendai 980-8575, Japan
| | - Yoichi Ishikawa
- Cyclotron and Radioisotope Center (CYRIC), Tohoku University, 6-3 Aoba, Aramaki, Aobaku, Sendai 980-8578, Japan
| | - Ren Iwata
- Cyclotron and Radioisotope Center (CYRIC), Tohoku University, 6-3 Aoba, Aramaki, Aobaku, Sendai 980-8578, Japan
| | - Yukitsuka Kudo
- Department of New Therapeutics Innovation for Alzheimer’s and Dementia, Institute of Development Aging and Cancer (IDAC), Tohoku University, 2-1 Seiryomachi, Aobaku, Sendai 980-8575, Japan
| | - Kazuhiko Yanai
- Department of Pharmacology, Graduate School of Medicine, Tohoku University, 2-1 Seiryomachi, Aobaku, Sendai 980-8575, Japan
| | - Nobuyuki Okamura
- Division of Pharmacology, Faculty of Medicine, Tohoku Medical and Pharmaceutical University, 1-15-1 Fukumuro, Miyaginoku, Sendai 983-8536, Japan
| | - Shozo Furumoto
- Cyclotron and Radioisotope Center (CYRIC), Tohoku University, 6-3 Aoba, Aramaki, Aobaku, Sendai 980-8578, Japan
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