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Huang YY, Chang LT, Shen HY, Chen YH, Tzen KY, Shiue CY, Hsin LW. Synthesis and evaluation of 2-(2'-((dimethylamino)methyl)-4'-(2-fluoroethoxy-substituted)phenylthio)benzenamine derivatives as potential positron emission tomography imaging agents for serotonin transporters. Bioorg Chem 2020; 97:103654. [PMID: 32088418 DOI: 10.1016/j.bioorg.2020.103654] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 01/30/2020] [Accepted: 02/05/2020] [Indexed: 10/25/2022]
Abstract
A series of diphenylsulfide derivatives with various substitutions at the 4-position on phenyl ring A and different lengths of the 2-fluoroethoxy-substituted side-chain at the 4'-position on ring B were synthesized and evaluated as potential positron emission tomography (PET) imaging agents for serotonin transporters (SERT). These ligands exhibited high SERT binding affinities (Ki = 0.11-1.3 nM) and the 4-methyl-substituted (4-Me) compounds 7a and 8a displayed excellent selectivity for SERT versus norepinephrine transporters (NET) (392- and 700-fold, respectively). In the parallel artificial membrane permeability assay (PAMPA), these ligands demonstrated moderate to high brain penetration, and the 4-Me analogs showed higher BBB permeability than the corresponding 4-F analogs. The 2-fluoroethoxy-substituted ligands showed higher metabolic stability and lower lipophilicity than 4-F-ADAM. [18F]7a-c were readily prepared using an automatic synthesizer and exhibited significant uptake and slow washout in rat brains. At 120 min after iv injection, [18F]7a exhibited the highest uptake in the midbrain, whereas [18F]7b exhibited the highest uptake in the hypothalamus and midbrain. After treatment with citalopram, a SERT-selective ligand, the uptake of [18F]7a in the hypothalamus and striatum was significantly decreased. The potent and highly selective SERT binding and the selective and reversible accumulation in SERT-rich brain regions suggested that [18F]7a is a promising lead for the further development of novel [18F]-labeled PET imaging agents for SERT binding sites in the brain.
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Affiliation(s)
- Ya-Yao Huang
- PET Center, Department of Nuclear Medicine, National Taiwan University Hospital, 7, Chung-Shan S. Road, Taipei, Taiwan
| | - Li-Te Chang
- School of Pharmacy, College of Medicine, National Taiwan University, 17, Xuzhou Road, Room 936, Taipei 10055, Taiwan
| | - Hsin-Yi Shen
- School of Pharmacy, College of Medicine, National Taiwan University, 17, Xuzhou Road, Room 936, Taipei 10055, Taiwan
| | - Ying-Heng Chen
- School of Pharmacy, College of Medicine, National Taiwan University, 17, Xuzhou Road, Room 936, Taipei 10055, Taiwan
| | - Kai-Yuan Tzen
- PET Center, Department of Nuclear Medicine, National Taiwan University Hospital, 7, Chung-Shan S. Road, Taipei, Taiwan
| | - Chyng-Yann Shiue
- PET Center, Department of Nuclear Medicine, National Taiwan University Hospital, 7, Chung-Shan S. Road, Taipei, Taiwan.
| | - Ling-Wei Hsin
- School of Pharmacy, College of Medicine, National Taiwan University, 17, Xuzhou Road, Room 936, Taipei 10055, Taiwan; Center for Innovative Therapeutics Discovery, National Taiwan University, 17, Xuzhou Road, Room 936, Taipei 10055, Taiwan.
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Zhang Y, Liu F, Xiao H, Yao X, Li G, Choi SR, Ploessl K, Zha Z, Zhu L, Kung HF. Fluorine-18 labeled diphenyl sulfide derivatives for imaging serotonin transporter (SERT) in the brain. Nucl Med Biol 2018; 66:1-9. [PMID: 30096380 DOI: 10.1016/j.nucmedbio.2018.06.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 06/15/2018] [Accepted: 06/28/2018] [Indexed: 02/06/2023]
Abstract
OBJECTIVES Serotonin transporters (SERT) play an important role in controlling serotonin concentration in the synaptic cleft and in managing postsynaptic signal transduction. Inhibitors of SERT binding are well known as selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine, sertraline, paroxetine, and escitalopram, that are commonly prescribed antidepressants. Positron emission tomography (PET) and single photon emission tomography (SPECT) imaging agents targeting SERT may be useful for studying its function and providing a tool for monitoring drug treatment. METHODS A series of novel 18F-labeled diphenyl sulfide derivatives were prepared and tested for their binding affinity. Among them, 2-((2-((dimethylamino)-methyl)-4-(2-(2-fluoroethoxy)ethoxy)phenyl)thio)aniline, 1, which showed excellent binding toward serotonin transporter (SERT) in the brain (Ki = 0.09 nM), was selected for further evaluation. An active OTs intermediate, 7, was treated with [18F]F-/K222 to provide [18F]1 in one step and in high radiochemical yields. This new SERT targeting agent was evaluated in rats by biodistribution studies and animal PET imaging studies. RESULTS The radiolabeling reaction led to the desired [18F]1. After HPLC purification no-carrier-added [18F]1 was obtained (radiochemical yield, 23-47% (n = 10,); radiochemical purity >99%; molar activity, 15-28 GBq/μmol). Biodistribution studies with [18F]1 showed good brain uptake (1.04% dose/g at 2 min post-injection), high uptake into the hypothalamus (1.55% dose/g at 30 min), and a high target-to-non-target (hypothalamus to cerebellum) ratio of 6.1 at 120 min post-injection. A PET imaging study in normal rats showed excellent uptake in the midbrain and thalamus regions known to be rich in SERT binding sites at 60 min after iv injection. Chasing experiment with escitalopram (iv, 2 mg/kg) in a rat at 60 min after iv injection caused a noticeable reduction in the regional radioactivity and the target-to-non-target ratio, suggesting binding by [18F]1 was highly specific and reversible for SERT binding sites in the brain. CONCLUSIONS A novel diphenyl sulfide derivative, [18F]1 for SERT imaging was successfully prepared and evaluated. Results suggest that this new chemical entity is targeting SERT binding sites in the brain, and it is a suitable candidate for future commercial development.
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Affiliation(s)
- Yan Zhang
- Key Laboratory of Radiopharmaceuticals (College of Chemistry), Beijing Normal University, Ministry of Education, Beijing, 100875, China
| | - Futao Liu
- Key Laboratory of Radiopharmaceuticals (College of Chemistry), Beijing Normal University, Ministry of Education, Beijing, 100875, China; Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Hao Xiao
- Key Laboratory of Radiopharmaceuticals (College of Chemistry), Beijing Normal University, Ministry of Education, Beijing, 100875, China
| | - Xinyue Yao
- Key Laboratory of Radiopharmaceuticals (College of Chemistry), Beijing Normal University, Ministry of Education, Beijing, 100875, China
| | - Genxun Li
- Key Laboratory of Radiopharmaceuticals (College of Chemistry), Beijing Normal University, Ministry of Education, Beijing, 100875, China
| | - Seok Rye Choi
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Karl Ploessl
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Zhihao Zha
- Beijing Institute for Brain Disorders, Capital Medical University, Beijing, 100069, China
| | - Lin Zhu
- Key Laboratory of Radiopharmaceuticals (College of Chemistry), Beijing Normal University, Ministry of Education, Beijing, 100875, China; Beijing Institute for Brain Disorders, Capital Medical University, Beijing, 100069, China.
| | - Hank F Kung
- Beijing Institute for Brain Disorders, Capital Medical University, Beijing, 100069, China; Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104, USA.
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