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Xiong M, Lubberink M, Appel L, Fang XT, Danfors T, Kumlien E, Antoni G. Evaluation of [ 11C]UCB-A positron emission tomography in human brains. EJNMMI Res 2024; 14:56. [PMID: 38884834 PMCID: PMC11183037 DOI: 10.1186/s13550-024-01117-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Accepted: 06/02/2024] [Indexed: 06/18/2024] Open
Abstract
BACKGROUND In preclinical studies, the positron emission tomography (PET) imaging with [11C]UCB-A provided promising results for imaging synaptic vesicle protein 2A (SV2A) as a proxy for synaptic density. This paper reports the first-in-human [11C]UCB-A PET study to characterise its kinetics in healthy subjects and further evaluate SV2A-specific binding. RESULTS Twelve healthy subjects underwent 90-min baseline [11C]UCB-A scans with PET/MRI, with two subjects participating in an additional blocking scan with the same scanning procedure after a single dose of levetiracetam (1500 mg). Our results indicated abundant [11C]UCB-A brain uptake across all cortical regions, with slow elimination. Kinetic modelling of [11C]UCB-A PET using various compartment models suggested that the irreversible two-tissue compartment model best describes the kinetics of the radioactive tracer. Accordingly, the Patlak graphical analysis was used to simplify the analysis. The estimated SV2A occupancy determined by the Lassen plot was around 66%. Significant specific binding at baseline and comparable binding reduction as grey matter precludes the use of centrum semiovale as reference tissue. CONCLUSIONS [11C]UCB-A PET imaging enables quantifying SV2A in vivo. However, its slow kinetics require a long scan duration, which is impractical with the short half-life of carbon-11. Consequently, the slow kinetics and complicated quantification methods may restrict its use in humans.
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Affiliation(s)
- Mengfei Xiong
- Molecular Imaging and Medical Physics, Department of Surgical Sciences, Uppsala University, Entrance 70, 75185, Uppsala, Sweden.
| | - Mark Lubberink
- Molecular Imaging and Medical Physics, Department of Surgical Sciences, Uppsala University, Entrance 70, 75185, Uppsala, Sweden
| | - Lieuwe Appel
- Molecular Imaging and Medical Physics, Department of Surgical Sciences, Uppsala University, Entrance 70, 75185, Uppsala, Sweden
| | - Xiaotian Tsong Fang
- Molecular Imaging and Medical Physics, Department of Surgical Sciences, Uppsala University, Entrance 70, 75185, Uppsala, Sweden
- Julius Clinical BV, Zeist, The Netherlands
| | - Torsten Danfors
- Molecular Imaging and Medical Physics, Department of Surgical Sciences, Uppsala University, Entrance 70, 75185, Uppsala, Sweden
| | - Eva Kumlien
- Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| | - Gunnar Antoni
- Department of Medicinal Chemistry, Uppsala University, Uppsala, Sweden
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Vogler L, Ballweg A, Bohr B, Briel N, Wind K, Antons M, Kunze LH, Gnörich J, Lindner S, Gildehaus FJ, Baumann K, Bartenstein P, Boening G, Ziegler SI, Levin J, Zwergal A, Höglinger GU, Herms J, Brendel M. Assessment of synaptic loss in mouse models of β-amyloid and tau pathology using [ 18F]UCB-H PET imaging. Neuroimage Clin 2023; 39:103484. [PMID: 37541098 PMCID: PMC10407951 DOI: 10.1016/j.nicl.2023.103484] [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: 01/09/2023] [Revised: 07/24/2023] [Accepted: 07/25/2023] [Indexed: 08/06/2023]
Abstract
OBJECTIVE In preclinical research, the use of [18F]Fluorodesoxyglucose (FDG) as a biomarker for neurodegeneration may induce bias due to enhanced glucose uptake by immune cells. In this study, we sought to investigate synaptic vesicle glycoprotein 2A (SV2A) PET with [18F]UCB-H as an alternative preclinical biomarker for neurodegenerative processes in two mouse models representing the pathological hallmarks of Alzheimer's disease (AD). METHODS A total of 29 PS2APP, 20 P301S and 12 wild-type mice aged 4.4 to 19.8 months received a dynamic [18F]UCB-H SV2A-PET scan (14.7 ± 1.5 MBq) 0-60 min post injection. Quantification of tracer uptake in cortical, cerebellar and brainstem target regions was implemented by calculating relative volumes of distribution (VT) from an image-derived-input-function (IDIF). [18F]UCB-H binding was compared across all target regions between transgenic and wild-type mice. Additional static scans were performed in a subset of mice to compare [18F]FDG and [18F]GE180 (18 kDa translocator protein tracer as a surrogate for microglial activation) standardized uptake values (SUV) with [18F]UCB-H binding at different ages. Following the final scan, a subset of mouse brains was immunohistochemically stained with synaptic markers for gold standard validation of the PET results. RESULTS [18F]UCB-H binding in all target regions was significantly reduced in 8-months old P301S transgenic mice when compared to wild-type controls (temporal lobe: p = 0.014; cerebellum: p = 0.0018; brainstem: p = 0.0014). Significantly lower SV2A tracer uptake was also observed in 13-months (temporal lobe: p = 0.0080; cerebellum: p = 0.006) and 19-months old (temporal lobe: p = 0.0042; cerebellum: p = 0.011) PS2APP transgenic versus wild-type mice, whereas the brainstem revealed no significantly altered [18F]UCB-H binding. Immunohistochemical analyses of post-mortem mouse brain tissue confirmed the SV2A PET findings. Correlational analyses of [18F]UCB-H and [18F]FDG using Pearson's correlation coefficient revealed a significant negative association in the PS2APP mouse model (R = -0.26, p = 0.018). Exploratory analyses further stressed microglial activation as a potential reason for this inverse relationship, since [18F]FDG and [18F]GE180 quantification were positively correlated in this cohort (R = 0.36, p = 0.0076). CONCLUSION [18F]UCB-H reliably depicts progressive synaptic loss in PS2APP and P301S transgenic mice, potentially qualifying as a more reliable alternative to [18F]FDG as a biomarker for assessment of neurodegeneration in preclinical research.
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Affiliation(s)
- Letizia Vogler
- Department of Nuclear Medicine, University Hospital of Munich, Ludwig-Maximilians-University (LMU) Munich, Munich, Germany
| | - Anna Ballweg
- Department of Nuclear Medicine, University Hospital of Munich, Ludwig-Maximilians-University (LMU) Munich, Munich, Germany
| | - Bernd Bohr
- Department of Nuclear Medicine, University Hospital of Munich, Ludwig-Maximilians-University (LMU) Munich, Munich, Germany
| | - Nils Briel
- Center for Neuropathology, LMU Munich, Munich, Germany
| | - Karin Wind
- Department of Nuclear Medicine, University Hospital of Munich, Ludwig-Maximilians-University (LMU) Munich, Munich, Germany
| | - Melissa Antons
- Department of Nuclear Medicine, University Hospital of Munich, Ludwig-Maximilians-University (LMU) Munich, Munich, Germany
| | - Lea H Kunze
- Department of Nuclear Medicine, University Hospital of Munich, Ludwig-Maximilians-University (LMU) Munich, Munich, Germany
| | - Johannes Gnörich
- Department of Nuclear Medicine, University Hospital of Munich, Ludwig-Maximilians-University (LMU) Munich, Munich, Germany
| | - Simon Lindner
- Department of Nuclear Medicine, University Hospital of Munich, Ludwig-Maximilians-University (LMU) Munich, Munich, Germany
| | - Franz-Josef Gildehaus
- Department of Nuclear Medicine, University Hospital of Munich, Ludwig-Maximilians-University (LMU) Munich, Munich, Germany
| | - Karlheinz Baumann
- Roche Pharma Research and Early Development, Neuroscience Discovery, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Basel, Switzerland
| | - Peter Bartenstein
- Department of Nuclear Medicine, University Hospital of Munich, Ludwig-Maximilians-University (LMU) Munich, Munich, Germany
| | - Guido Boening
- Department of Nuclear Medicine, University Hospital of Munich, Ludwig-Maximilians-University (LMU) Munich, Munich, Germany
| | - Sibylle I Ziegler
- Department of Nuclear Medicine, University Hospital of Munich, Ludwig-Maximilians-University (LMU) Munich, Munich, Germany
| | - Johannes Levin
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany; Munich Cluster for Systems Neurology (SyNergy), Munich, Germany; Department of Neurology, University Hospital of Munich, LMU Munich, Munich, Germany
| | - Andreas Zwergal
- Department of Neurology, University Hospital of Munich, LMU Munich, Munich, Germany; German Center for Vertigo and Balance Disorders (DSGZ), University Hospital of Munich, LMU Munich, Munich, Germany
| | - Günter U Höglinger
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany; Department of Neurology, University Hospital of Munich, LMU Munich, Munich, Germany
| | - Jochen Herms
- Center for Neuropathology, LMU Munich, Munich, Germany
| | - Matthias Brendel
- Department of Nuclear Medicine, University Hospital of Munich, Ludwig-Maximilians-University (LMU) Munich, Munich, Germany; German Center for Neurodegenerative Diseases (DZNE), Munich, Germany; Munich Cluster for Systems Neurology (SyNergy), Munich, Germany.
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Rossi R, Arjmand S, Bærentzen SL, Gjedde A, Landau AM. Synaptic Vesicle Glycoprotein 2A: Features and Functions. Front Neurosci 2022; 16:864514. [PMID: 35573314 PMCID: PMC9096842 DOI: 10.3389/fnins.2022.864514] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 04/05/2022] [Indexed: 01/05/2023] Open
Abstract
In recent years, the field of neuroimaging dramatically moved forward by means of the expeditious development of specific radioligands of novel targets. Among these targets, the synaptic vesicle glycoprotein 2A (SV2A) is a transmembrane protein of synaptic vesicles, present in all synaptic terminals, irrespective of neurotransmitter content. It is involved in key functions of neurons, focused on the regulation of neurotransmitter release. The ubiquitous expression in gray matter regions of the brain is the basis of its candidacy as a marker of synaptic density. Following the development of molecules derived from the structure of the anti-epileptic drug levetiracetam, which selectively binds to SV2A, several radiolabeled markers have been synthetized to allow the study of SV2A distribution with positron emission tomography (PET). These radioligands permit the evaluation of in vivo changes of SV2A distribution held to be a potential measure of synaptic density in physiological and pathological conditions. The use of SV2A as a biomarker of synaptic density raises important questions. Despite numerous studies over the last decades, the biological function and the expressional properties of SV2A remain poorly understood. Some functions of SV2A were claimed, but have not been fully elucidated. While the expression of SV2A is ubiquitous, stronger associations between SV2A and Υ amino butyric acid (GABA)-ergic rather than glutamatergic synapses were observed in some brain structures. A further issue is the unclear interaction between SV2A and its tracers, which reflects a need to clarify what really is detected with neuroimaging tools. Here, we summarize the current knowledge of the SV2A protein and we discuss uncertain aspects of SV2A biology and physiology. As SV2A expression is ubiquitous, but likely more strongly related to a certain type of neurotransmission in particular circumstances, a more extensive knowledge of the protein would greatly facilitate the analysis and interpretation of neuroimaging results by allowing the evaluation not only of an increase or decrease of the protein level, but also of the type of neurotransmission involved.
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Affiliation(s)
- Rachele Rossi
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Department of Nuclear Medicine and PET Center, Aarhus University Hospital, Aarhus, Denmark
| | - Shokouh Arjmand
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Simone Larsen Bærentzen
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Department of Nuclear Medicine and PET Center, Aarhus University Hospital, Aarhus, Denmark
| | - Albert Gjedde
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark.,Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
| | - Anne M Landau
- Translational Neuropsychiatry Unit, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Department of Nuclear Medicine and PET Center, Aarhus University Hospital, Aarhus, Denmark
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Zheng C, Holden D, Zheng MQ, Pracitto R, Wilcox KC, Lindemann M, Felchner Z, Zhang L, Tong J, Fowles K, Finnema SJ, Nabulsi N, Carson RE, Huang Y, Cai Z. A metabolically stable PET tracer for imaging synaptic vesicle protein 2A: synthesis and preclinical characterization of [ 18F]SDM-16. Eur J Nucl Med Mol Imaging 2022; 49:1482-1496. [PMID: 34761284 PMCID: PMC8940841 DOI: 10.1007/s00259-021-05597-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 10/17/2021] [Indexed: 11/01/2022]
Abstract
PURPOSE To quantify the synaptic vesicle glycoprotein 2A (SV2A) changes in the whole central nervous system (CNS) under pathophysiological conditions, a high affinity SV2A PET radiotracer with improved in vivo stability is desirable to minimize the potential confounding effect of radiometabolites. The aim of this study was to develop such a PET tracer based on the molecular scaffold of UCB-A, and evaluate its pharmacokinetics, in vivo stability, specific binding, and nonspecific binding signals in nonhuman primate brains, in comparison with [11C]UCB-A, [11C]UCB-J, and [18F]SynVesT-1. METHODS The racemic SDM-16 (4-(3,5-difluorophenyl)-1-((2-methyl-1H-imidazol-1-yl)methyl)pyrrolidin-2-one) and its two enantiomers were synthesized and assayed for in vitro binding affinities to human SV2A. We synthesized the enantiopure [18F]SDM-16 using the corresponding enantiopure arylstannane precursor. Nonhuman primate brain PET scans were performed on FOCUS 220 scanners. Arterial blood was drawn for the measurement of plasma free fraction (fP), radiometabolite analysis, and construction of the plasma input function. Regional time-activity curves (TACs) were fitted with the one-tissue compartment (1TC) model to obtain the volume of distribution (VT). Nondisplaceable binding potential (BPND) was calculated using either the nondisplaceable volume of distribution (VND) or the centrum semiovale (CS) as the reference region. RESULTS SDM-16 was synthesized in 3 steps with 44% overall yield and has the highest affinity (Ki = 0.9 nM) to human SV2A among all reported SV2A ligands. [18F]SDM-16 was prepared in about 20% decay-corrected radiochemical yield within 90 min, with greater than 99% radiochemical and enantiomeric purity. This radiotracer displayed high specific binding in monkey brains and was metabolically more stable than the other SV2A PET tracers. The fP of [18F]SDM-16 was 69%, which was higher than those of [11C]UCB-J (46%), [18F]SynVesT-1 (43%), [18F]SynVesT-2 (41%), and [18F]UCB-H (43%). The TACs were well described with the 1TC. The averaged test-retest variability (TRV) was 7 ± 3%, and averaged absolute TRV (aTRV) was 14 ± 7% for the analyzed brain regions. CONCLUSION We have successfully synthesized a novel SV2A PET tracer [18F]SDM-16, which has the highest SV2A binding affinity and metabolical stability among published SV2A PET tracers. The [18F]SDM-16 brain PET images showed superb contrast between gray matter and white matter. Moreover, [18F]SDM-16 showed high specific and reversible binding in the NHP brains, allowing for the reliable and sensitive quantification of SV2A, and has potential applications in the visualization and quantification of SV2A beyond the brain.
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Affiliation(s)
- Chao Zheng
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06520, USA
| | - Daniel Holden
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06520, USA
| | - Ming-Qiang Zheng
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06520, USA
| | - Richard Pracitto
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06520, USA
| | - Kyle C Wilcox
- Translational Imaging, AbbVie Inc, North Chicago, IL, 60064, USA
| | - Marcel Lindemann
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06520, USA
| | - Zachary Felchner
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06520, USA
| | - Li Zhang
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06520, USA
| | - Jie Tong
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06520, USA
| | - Krista Fowles
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06520, USA
| | - Sjoerd J Finnema
- Translational Imaging, AbbVie Inc, North Chicago, IL, 60064, USA
| | - Nabeel Nabulsi
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06520, USA
| | - Richard E Carson
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06520, USA
| | - Yiyun Huang
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06520, USA
| | - Zhengxin Cai
- PET Center, Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, 06520, USA.
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Toyonaga T, Fesharaki-Zadeh A, Strittmatter SM, Carson RE, Cai Z. PET Imaging of Synaptic Density: Challenges and Opportunities of Synaptic Vesicle Glycoprotein 2A PET in Small Animal Imaging. Front Neurosci 2022; 16:787404. [PMID: 35345546 PMCID: PMC8957200 DOI: 10.3389/fnins.2022.787404] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 02/14/2022] [Indexed: 12/02/2022] Open
Abstract
The development of novel PET imaging agents for synaptic vesicle glycoprotein 2A (SV2A) allowed for the in vivo detection of synaptic density changes, which are correlated with the progression and severity of a variety of neuropsychiatric diseases. While multiple ongoing clinical investigations using SV2A PET are expanding its applications rapidly, preclinical SV2A PET imaging in animal models is an integral component of the translation research and provides supporting and complementary information. Herein, we overview preclinical SV2A PET studies in animal models of neurodegenerative disorders and discuss the opportunities and practical challenges in small animal SV2A PET imaging. At the Yale PET Center, we have conducted SV2A PET imaging studies in animal models of multiple diseases and longitudinal SV2A PET allowed us to evaluate synaptic density dynamics in the brains of disease animal models and to assess pharmacological effects of novel interventions. In this article, we discuss key considerations when designing preclinical SV2A PET imaging studies and strategies for data analysis. Specifically, we compare the brain imaging characteristics of available SV2A tracers, i.e., [11C]UCB-J, [18F]SynVesT-1, [18F]SynVesT-2, and [18F]SDM-16, in rodent brains. We also discuss the limited spatial resolution of PET scanners for small brains and challenges of kinetic modeling. We then compare different injection routes and estimate the maximum throughput (i.e., number of animals) per radiotracer synthesis by taking into account the injectable volume for each injection method, injected mass, and radioactivity half-lives. In summary, this article provides a perspective for designing and analyzing SV2A PET imaging studies in small animals.
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Affiliation(s)
- Takuya Toyonaga
- Positron Emission Tomography (PET) Center, Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States
| | - Arman Fesharaki-Zadeh
- Psychiatry, Yale School of Medicine, New Haven, CT, United States
- Neurology, Yale School of Medicine, New Haven, CT, United States
| | - Stephen M. Strittmatter
- Neurology, Yale School of Medicine, New Haven, CT, United States
- Neuroscience, Yale School of Medicine, New Haven, CT, United States
| | - Richard E. Carson
- Positron Emission Tomography (PET) Center, Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States
| | - Zhengxin Cai
- Positron Emission Tomography (PET) Center, Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States
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