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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: 4] [Impact Index Per Article: 2.0] [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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Dosimetry of [⁶⁸Ga]-labeled compounds. Appl Radiat Isot 2012; 76:70-4. [PMID: 22884623 DOI: 10.1016/j.apradiso.2012.06.033] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Revised: 06/06/2012] [Accepted: 06/25/2012] [Indexed: 01/23/2023]
Abstract
This review compiles and analyzes the available dosimetry data of [(68)Ga] labeled compounds. Dosimetry data are given for [(68)Ga]DOTA-NOC, TOC, TATE, and NODAGA-RGDyK. The number of PET-scans with [(68)Ga]DOTA-compounds for imaging neuroendocrine tumors is increasing because [(68)Ga] has a higher affinity to somatostatin receptors (SSTR) in comparison to comparable [(111)In]-compounds. In addition, the better image resolution of the PET images provides improved diagnostics. Despite its widespread use literature on dosimetry of [(68)Ga]-labeled radiopharmaceuticals is sparse. In some cases the description of the underlying methodology is missing or human data are gained from the extrapolation of animal experiments. More and better documented dosimetry data will further promote the use of these promising new agents.
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