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Cao S, Tang J, Liu C, Fang Y, Ji L, Xu Y, Chen Z. Synthesis and Biological Evaluation of [ 18F]FECNT-d 4 as a Novel PET Agent for Dopamine Transporter Imaging. Mol Imaging Biol 2021; 23:733-744. [PMID: 33851345 DOI: 10.1007/s11307-021-01603-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 03/21/2021] [Accepted: 04/02/2021] [Indexed: 11/27/2022]
Abstract
PURPOSE The dopamine transporter (DAT) is a marker of the occurrence and development of Parkinson's disease (PD) and other diseases with nigrostriatal degeneration. 2β-Carbomethoxy-3β-(4-chlorophenyl)-8-(2-[18F]-fluoroethyl)nortropane ([18F]FECNT), an 18F-labelled tropane derivative, was reported to be a useful positron-emitting probe for DAT. However, the rapid formation of brain-penetrating radioactive metabolites is an impediment to the proper quantitation of DAT in PET studies with [18F]FECNT. Deuterium-substituted analogues have presented better in vivo stability to reduce metabolites. This study aimed to synthesize a deuterium-substituted DAT radiotracer, [18F]FECNT-d4, and to make a preliminary investigation of its properties as a DAT tracer in vivo. PROCEDURES The ligand [18F]FECNT-d4 was obtained by one-step radiolabelling reaction. The lipophilicity was measured by the shake-flask method. Binding properties of [18F]FECNT-d4 were estimated by in vitro binding assay, biodistribution, and microPET imaging in rats. In vivo stability of [18F]FECNT-d4 was estimated by radio-HPLC. RESULTS [18F]FECNT-d4 was synthesized at an average activity yield of 46 ± 17 % (n = 15) and the molar activity was 67 ± 12 GBq/μmol. The deuterated tracer showed suitable lipophilicity and the ability to penetrate the blood-brain barrier (brain uptake of 1.72 % ID at 5 min). [18F]FECNT-d4 displayed a high binding affinity for DAT comparable to that of [18F]FECNT in rat striatum homogenates. Biodistribution results in normal rats showed that [18F]FECNT-d4 exhibited a higher ratio of the target to non-target (striatum/cerebellum) at 15 min post administration (5.00 ± 0.44 vs 3.84 ± 0.24 for [18F]FECNT-d4 vs [18F]FECNT). MicroPET imaging studies of [18F]FECNT-d4 in normal rats showed that the ligand selectively localized to DAT-rich striatal regions and the accumulation could be blocked with DAT inhibitor. Furthermore, in the unilateral PD model rat, a significant reduction of the signal was found in the lesioned side relative to the unlesioned side. Striatal standardized uptake value of [18F]FECNT-d4 remained ~4.02 in the striatum between 5 and 20 min, whereas that of [18F]FECNT fell rapidly from 4.11 to 2.95. Radio-HPLC analysis of the plasma demonstrated better in vivo stability of [18F]FECNT-d4 than [18F]FECNT. CONCLUSION The deuterated compound [18F]FECNT-d4 may serve as a promising PET imaging agent to assess DAT-related disorders.
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Affiliation(s)
- Shanshan Cao
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, School of Pharmacy, Xuzhou Medical University, Xuzhou, 221004, China
| | - Jie Tang
- NHC Key Laboratory of Nuclear Medicine, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, 214063, China
| | - Chunyi Liu
- NHC Key Laboratory of Nuclear Medicine, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, 214063, China
| | - Yi Fang
- NHC Key Laboratory of Nuclear Medicine, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, 214063, China
| | - Linyang Ji
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, School of Pharmacy, Xuzhou Medical University, Xuzhou, 221004, China
| | - Yingjiao Xu
- NHC Key Laboratory of Nuclear Medicine, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, 214063, China
| | - Zhengping Chen
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, School of Pharmacy, Xuzhou Medical University, Xuzhou, 221004, China. .,NHC Key Laboratory of Nuclear Medicine, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, 214063, China.
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Ghosh KK, Padmanabhan P, Yang CT, Mishra S, Halldin C, Gulyás B. Dealing with PET radiometabolites. EJNMMI Res 2020; 10:109. [PMID: 32997213 PMCID: PMC7770856 DOI: 10.1186/s13550-020-00692-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Accepted: 09/07/2020] [Indexed: 02/08/2023] Open
Abstract
Abstract Positron emission tomography (PET) offers the study of biochemical,
physiological, and pharmacological functions at a cellular and molecular level.
The performance of a PET study mostly depends on the used radiotracer of
interest. However, the development of a novel PET tracer is very difficult, as
it is required to fulfill a lot of important criteria. PET radiotracers usually
encounter different chemical modifications including redox reaction, hydrolysis,
decarboxylation, and various conjugation processes within living organisms. Due
to this biotransformation, different chemical entities are produced, and the
amount of the parent radiotracer is declined. Consequently, the signal measured
by the PET scanner indicates the entire amount of radioactivity deposited in the
tissue; however, it does not offer any indication about the chemical disposition
of the parent radiotracer itself. From a radiopharmaceutical perspective, it is
necessary to quantify the parent radiotracer’s fraction present in the tissue.
Hence, the identification of radiometabolites of the radiotracers is vital for
PET imaging. There are mainly two reasons for the chemical identification of PET
radiometabolites: firstly, to determine the amount of parent radiotracers in
plasma, and secondly, to rule out (if a radiometabolite enters the brain) or
correct any radiometabolite accumulation in peripheral tissue. Besides,
radiometabolite formations of the tracer might be of concern for the PET study,
as the radiometabolic products may display considerably contrasting distribution
patterns inside the body when compared with the radiotracer itself. Therefore,
necessary information is needed about these biochemical transformations to
understand the distribution of radioactivity throughout the body. Various
published review articles on PET radiometabolites mainly focus on the sample
preparation techniques and recently available technology to improve the
radiometabolite analysis process. This article essentially summarizes the
chemical and structural identity of the radiometabolites of various radiotracers
including [11C]PBB3,
[11C]flumazenil,
[18F]FEPE2I, [11C]PBR28,
[11C]MADAM, and
(+)[18F]flubatine. Besides, the importance of
radiometabolite analysis in PET imaging is also briefly summarized. Moreover,
this review also highlights how a slight chemical modification could reduce the
formation of radiometabolites, which could interfere with the results of PET
imaging. Graphical abstract ![]()
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Affiliation(s)
- Krishna Kanta Ghosh
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore
| | - Parasuraman Padmanabhan
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore.
| | - Chang-Tong Yang
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore.,Department of Nuclear Medicine and Molecular Imaging, Radiological Sciences Division, Singapore General Hospital, Outram Road, Singapore, 169608, Singapore.,Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Sachin Mishra
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore
| | - Christer Halldin
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore.,Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden
| | - Balázs Gulyás
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore. .,Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden.
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