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Zhang G, Zhao S, Zhao Z, Jia C, Zhang Y, Xue J, Liu Y, Yang W. Synthesis and Evaluation of 18F-Labeled Phenylpiperazine-like Dopamine D3 Receptor Radioligands for Positron Emission Tomography Imaging. ACS Chem Neurosci 2024; 15:3459-3472. [PMID: 39276340 DOI: 10.1021/acschemneuro.4c00177] [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] [Indexed: 09/17/2024] Open
Abstract
The dopamine D3 receptor (D3R) is important in the pathophysiology of various neuropsychiatric disorders, such as depression, bipolar disorder, schizophrenia, drug addiction, and Parkinson's disease. Positron emission tomography (PET) with innovative radioligands provides an opportunity to assess D3R in vivo and to elucidate D3R-related disease mechanisms. Herein, we present the synthesis of eight 18F-labeled phenylpiperazine-like D3R-selective radioligands possessing good radiochemical purity (>97%), in vitro stability (>95%), and befitting lipophilicity. Based on in vitro binding assays and static microPET studies, the phenylpiperazine-like radioligands [18F]FBPC01 and [18F]FBPC03 were chosen as lead radioligands targeting D3R. Molecular docking further elucidated their binding mechanism. Radiolabeling conditions were optimized and then applied to an automated radiolabeling process, affording products with high specific activity (>112 GBq/μmol). Dynamic rat PET study demonstrated the specific binding of [18F]FBPC01 and [18F]FBPC03 to D3R in the brain ventricles and the pituitary gland. Validated by dynamic PET data analysis, biodistribution study, and metabolism analysis, [18F]FBPC03 exhibited the highest PET signal-to-noise ratio, good D3R-specific binding in the brain ventricles and pituitary gland of rats with few off-target binding, negligible defluorination, and stable brain metabolism, which indicated that [18F]FBPC03 was a promising D3R radioligand.
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Affiliation(s)
- Ge Zhang
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
- School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 10049, China
| | - Shilun Zhao
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing 10049, China
| | - Zuoquan Zhao
- Theranostics and Translational Research Center, Institute of Clinical Medicine, Department of Nuclear Medicine, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, China
| | - Chenhao Jia
- Theranostics and Translational Research Center, Institute of Clinical Medicine, Department of Nuclear Medicine, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, China
| | - Yuxuan Zhang
- Jinan Laboratory of Applied Nuclear Science, Jinan 251401, China
| | - Jingquan Xue
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
- Jinan Laboratory of Applied Nuclear Science, Jinan 251401, China
| | - Yu Liu
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing 10049, China
- Jinan Laboratory of Applied Nuclear Science, Jinan 251401, China
| | - Wenjiang Yang
- Beijing Engineering Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
- Jinan Laboratory of Applied Nuclear Science, Jinan 251401, China
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Shen H, Ma Z, Hans E, Duan Y, Bi GH, Chae YC, Bonifazi A, Battiti FO, Newman AH, Xi ZX, Yang Y. Involvement of dopamine D3 receptor in impulsive choice decision-making in male rats. Neuropharmacology 2024; 257:110051. [PMID: 38917939 PMCID: PMC11401648 DOI: 10.1016/j.neuropharm.2024.110051] [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: 04/13/2024] [Revised: 06/20/2024] [Accepted: 06/21/2024] [Indexed: 06/27/2024]
Abstract
Impulsive decision-making has been linked to impulse control disorders and substance use disorders. However, the neural mechanisms underlying impulsive choice are not fully understood. While previous PET imaging and autoradiography studies have shown involvement of dopamine and D2/3 receptors in impulsive behavior, the roles of distinct D1, D2, and D3 receptors in impulsive decision-making remain unclear. In this study, we used a food reward delay-discounting task (DDT) to identify low- and high-impulsive rats, in which low-impulsive rats exhibited preference for large delayed reward over small immediate rewards, while high-impulsive rats showed the opposite preference. We then examined D1, D2, and D3 receptor gene expression using RNAscope in situ hybridization assays. We found that high-impulsive male rats exhibited lower levels of D2 and D3, and particularly D3, receptor expression in the nucleus accumbens (NAc), with no significant changes in the insular, prelimbic, and infralimbic cortices. Based on these findings, we further explored the role of the D3 receptor in impulsive decision-making. Systemic administration of a selective D3 receptor agonist (FOB02-04) significantly reduced impulsive choices in high-impulsive rats but had no effects in low-impulsive rats. Conversely, a selective D3 receptor antagonist (VK4-116) produced increased both impulsive and omission choices in both groups of rats. These findings suggest that impulsive decision-making is associated with a reduction in D3 receptor expression in the NAc. Selective D3 receptor agonists, but not antagonists, may hold therapeutic potentials for mitigating impulsivity in high-impulsive subjects.
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Affiliation(s)
- Hui Shen
- Neuroimaging Research Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, 21224, USA
| | - Zilu Ma
- Neuroimaging Research Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, 21224, USA
| | - Emma Hans
- Neuroimaging Research Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, 21224, USA
| | - Ying Duan
- Neuroimaging Research Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, 21224, USA
| | - Guo-Hua Bi
- Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, 21224, USA
| | - Yurim C Chae
- Neuroimaging Research Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, 21224, USA
| | - Alessandro Bonifazi
- Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, 21224, USA
| | - Francisco O Battiti
- Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, 21224, USA
| | - Amy Hauck Newman
- Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, 21224, USA
| | - Zheng-Xiong Xi
- Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, 21224, USA.
| | - Yihong Yang
- Neuroimaging Research Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD, 21224, USA.
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Lee JY, Kim HY, Martorano P, Riad A, Taylor M, Luedtke RR, Mach RH. In vitro characterization of [ 125I]HY-3-24, a selective ligand for the dopamine D3 receptor. Front Neurosci 2024; 18:1380009. [PMID: 38655111 PMCID: PMC11036874 DOI: 10.3389/fnins.2024.1380009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 03/14/2024] [Indexed: 04/26/2024] Open
Abstract
Introduction Dopamine D3 receptor (D3R) ligands have been studied for the possible treatment of neurological and neuropsychiatric disorders. However, selective D3R radioligands for in vitro binding studies have been challenging to identify due to the high structural similarity between the D2R and D3R. In a prior study, we reported a new conformationally-flexible benzamide scaffold having a high affinity for D3R and excellent selectivity vs. D2R. In the current study, we characterized the in vitro binding properties of a new radioiodinated ligand, [125I]HY-3-24. Methods In vitro binding studies were conducted in cell lines expressing D3 receptors, rat striatal homogenates, and rat and non-human primate (NHP) brain tissues to measure regional brain distribution of this radioligand. Results HY-3-24 showed high potency at D3R (Ki = 0.67 ± 0.11 nM, IC50 = 1.5 ± 0.58 nM) compared to other D2-like dopamine receptor subtypes (D2R Ki = 86.7 ± 11.9 nM and D4R Ki > 1,000). The Kd (0.34 ± 0.22 nM) and Bmax (38.91 ± 2.39 fmol/mg) values of [125I]HY-3-24 were determined. In vitro binding studies in rat striatal homogenates using selective D2R and D3R antagonists confirmed the D3R selectivity of [125I]HY-3-24. Autoradiography results demonstrated that [125I]HY-3-24 specifically binds to D3Rs in the nucleus accumbens, islands of Calleja, and caudate putamen in rat and NHP brain sections. Conclusion These results suggest that [125I]HY-3-24 appears to be a novel radioligand that exhibits high affinity binding at D3R, with low binding to other D2-like dopamine receptors. It is anticipated that [125I]HY-3-24 can be used as the specific D3R radioligand.
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Affiliation(s)
- Ji Youn Lee
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Ho Young Kim
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Paul Martorano
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Aladdin Riad
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Michelle Taylor
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX, United States
| | - Robert R. Luedtke
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX, United States
| | - Robert H. Mach
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
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Tian GL, Hsieh CJ, Taylor M, Lee JY, Luedtke RR, Mach RH. Design and Synthesis of D 3R Bitopic Ligands with Flexible Secondary Binding Fragments: Radioligand Binding and Computational Chemistry Studies. Molecules 2023; 29:123. [PMID: 38202706 PMCID: PMC10779535 DOI: 10.3390/molecules29010123] [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: 10/26/2023] [Revised: 12/20/2023] [Accepted: 12/21/2023] [Indexed: 01/12/2024] Open
Abstract
A series of bitopic ligands based on Fallypride with a flexible secondary binding fragment (SBF) were prepared with the goal of preparing a D3R-selective compound. The effect of the flexible linker ((R,S)-trans-2a-d), SBFs ((R,S)-trans-2h-j), and the chirality of orthosteric binding fragments (OBFs) ((S,R)-trans-d, (S,R)-trans-i, (S,S)-trans-d, (S,S)-trans-i, (R,R)-trans-d, and (R,R)-trans-i) were evaluated in in vitro binding assays. Computational chemistry studies revealed that the interaction of the fragment binding to the SBF increased the distance between the pyrrolidine nitrogen and ASP1103.32 of the D3R, thereby reducing the D3R affinity to a suboptimal level.
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Affiliation(s)
- Gui-Long Tian
- Division of Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; (G.-L.T.); (C.-J.H.)
| | - Chia-Ju Hsieh
- Division of Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; (G.-L.T.); (C.-J.H.)
| | - Michelle Taylor
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA; (M.T.)
| | - Ji Youn Lee
- Division of Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; (G.-L.T.); (C.-J.H.)
| | - Robert R. Luedtke
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA; (M.T.)
| | - Robert H. Mach
- Division of Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; (G.-L.T.); (C.-J.H.)
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Tian GL, Hsieh CJ, Taylor M, Lee JY, Riad AA, Luedtke RR, Mach RH. Synthesis of bitopic ligands based on fallypride and evaluation of their affinity and selectivity towards dopamine D 2 and D 3 receptors. Eur J Med Chem 2023; 261:115751. [PMID: 37688938 PMCID: PMC10841072 DOI: 10.1016/j.ejmech.2023.115751] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 08/08/2023] [Accepted: 08/21/2023] [Indexed: 09/11/2023]
Abstract
The difference in the secondary binding site (SBS) between the dopamine 2 receptor (D2R) and dopamine 3 receptor (D3R) has been used in the design of compounds displaying selectivity for the D3R versus D2R. In the current study, a series of bitopic ligands based on Fallypride were prepared with various secondary binding fragments (SBFs) as a means of improving the selectivity of this benzamide analog for D3R versus D2R. We observed that compounds having a small alkyl group with a heteroatom led to an improvement in D3R versus D2R selectivity. Increasing the steric bulk in the SBF increase the distance between the pyrrolidine N and Asp110, thereby reducing D3R affinity. The best-in-series compound was (2S,4R)-trans-27 which had a modest selectivity for D3R versus D2R and a high potency in the β-arrestin competition assay which provides a measure of the ability of the compound to compete with endogenous dopamine for binding to the D3R. The results of this study identified factors one should consider when designing bitopic ligands based on Fallypride displaying an improved affinity for D3R versus D2R.
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Affiliation(s)
- Gui-Long Tian
- Division of Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Chia-Ju Hsieh
- Division of Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Michelle Taylor
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center-Fort Worth, Texas, TX, 76107, USA
| | - Ji Youn Lee
- Division of Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Aladdin A Riad
- Division of Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Robert R Luedtke
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center-Fort Worth, Texas, TX, 76107, USA
| | - Robert H Mach
- Division of Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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6
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Tang H, Cheng Y, Lou X, Yao H, Xie J, Gu W, Huang X, Liu Y, Lin S, Dai Y, Xue L, Lin X, Wu ZB. DRD2 expression based on 18F-fallypride PET/MR predicts the dopamine agonist resistance of prolactinomas: a pilot study. Endocrine 2023; 80:419-424. [PMID: 36689171 DOI: 10.1007/s12020-023-03310-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Accepted: 01/10/2023] [Indexed: 01/24/2023]
Abstract
PURPOSE The dopamine agonists (DA) have been used widely to treat prolactinomas. However, it is difficult to predict whether the patient will be responsive to DA treatment. METHODS We aimed to investigate whether the in vivo expression of DRD2 based on 18F-fallypride PET/MR could predict the therapeutic effect of DA on prolactinomas. Seven patients with prolactinomas completed 18F-fallypride PET/MR. Among them, three patients underwent surgery and further tumor immunohistochemistry. Imaging findings and immunohistochemical staining were compared with treatment outcomes. RESULTS 18F-fallypride PET/MR was visually positive in 7 of 7 patients, and DRD2 target specificity could be confirmed by immunohistochemical staining. A significantly lower tracer standard uptake value (SUV) could be detected in the resistant patients (n = 3) than in the sensitive patients (n = 4; SUVmean, 4.67 ± 1.32 vs. 13.57 ± 2.42, p < 0.05). DRD2 expression determined by 18F-fallypride PET/MR corresponded with the DA treatment response. CONCLUSION 18F-fallypride PET/MR may be a promising technique for predicting DA response in patients with prolactinoma.
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Affiliation(s)
- Hao Tang
- Department of Neurosurgery, Center of Pituitary Tumor, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Yijun Cheng
- Department of Neurosurgery, Center of Pituitary Tumor, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Xiaohui Lou
- Department of Neurosurgery, Ruian People's Hospital, The Third Affiliated Hospital of Wenzhou Medical University, Ruian, Zhejiang Province, China
| | - Hong Yao
- Department of Neurosurgery, Center of Pituitary Tumor, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Jing Xie
- Department of Pathology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Weiting Gu
- Department of Neurosurgery, Center of Pituitary Tumor, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Xinyun Huang
- Department of Nuclear Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Yanting Liu
- Department of Neurosurgery, Center of Pituitary Tumor, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Shaojian Lin
- Department of Neurosurgery, Center of Pituitary Tumor, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Yuting Dai
- Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Li Xue
- Department of Neurosurgery, Center of Pituitary Tumor, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Xiaozhu Lin
- Department of Nuclear Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
| | - Zhe Bao Wu
- Department of Neurosurgery, Center of Pituitary Tumor, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
- Department of Neurosurgery, First Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325000, China.
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7
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Free RB, Nilson AN, Boldizsar NM, Doyle TB, Rodriguiz RM, Pogorelov VM, Machino M, Lee KH, Bertz JW, Xu J, Lim HD, Dulcey AE, Mach RH, Woods JH, Lane JR, Shi L, Marugan JJ, Wetsel WC, Sibley DR. Identification and Characterization of ML321: A Novel and Highly Selective D 2 Dopamine Receptor Antagonist with Efficacy in Animal Models That Predict Atypical Antipsychotic Activity. ACS Pharmacol Transl Sci 2023; 6:151-170. [PMID: 36654757 PMCID: PMC9841785 DOI: 10.1021/acsptsci.2c00202] [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: 10/18/2022] [Indexed: 12/31/2022]
Abstract
We have developed and characterized a novel D2R antagonist with exceptional GPCR selectivity - ML321. In functional profiling screens of 168 different GPCRs, ML321 showed little activity beyond potent inhibition of the D2R and to a lesser extent the D3R, demonstrating excellent receptor selectivity. The D2R selectivity of ML321 may be related to the fact that, unlike other monoaminergic ligands, ML321 lacks a positively charged amine group and adopts a unique binding pose within the orthosteric binding site of the D2R. PET imaging studies in non-human primates demonstrated that ML321 penetrates the CNS and occupies the D2R in a dose-dependent manner. Behavioral paradigms in rats demonstrate that ML321 can selectively antagonize a D2R-mediated response (hypothermia) while not affecting a D3R-mediated response (yawning) using the same dose of drug, thus indicating exceptional in vivo selectivity. We also investigated the effects of ML321 in animal models that are predictive of antipsychotic efficacy in humans. We found that ML321 attenuates both amphetamine- and phencyclidine-induced locomotor activity and restored pre-pulse inhibition (PPI) of acoustic startle in a dose-dependent manner. Surprisingly, using doses that were maximally effective in both the locomotor and PPI studies, ML321 was relatively ineffective in promoting catalepsy. Kinetic studies revealed that ML321 exhibits slow-on and fast-off receptor binding rates, similar to those observed with atypical antipsychotics with reduced extrapyramidal side effects. Taken together, these observations suggest that ML321, or a derivative thereof, may exhibit ″atypical″ antipsychotic activity in humans with significantly fewer side effects than observed with the currently FDA-approved D2R antagonists.
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Affiliation(s)
- R. Benjamin Free
- Molecular
Neuropharmacology Section, National Institute of Neurological Disorders
and Stroke, Intramural Research Program, National Institutes of Health, 35 Convent Drive, MSC-3723, Bethesda, Maryland20892, United States
| | - Ashley N. Nilson
- Molecular
Neuropharmacology Section, National Institute of Neurological Disorders
and Stroke, Intramural Research Program, National Institutes of Health, 35 Convent Drive, MSC-3723, Bethesda, Maryland20892, United States
| | - Noelia M. Boldizsar
- Molecular
Neuropharmacology Section, National Institute of Neurological Disorders
and Stroke, Intramural Research Program, National Institutes of Health, 35 Convent Drive, MSC-3723, Bethesda, Maryland20892, United States
| | - Trevor B. Doyle
- Molecular
Neuropharmacology Section, National Institute of Neurological Disorders
and Stroke, Intramural Research Program, National Institutes of Health, 35 Convent Drive, MSC-3723, Bethesda, Maryland20892, United States
| | - Ramona M. Rodriguiz
- Department
of Psychiatry and Behavioral Sciences, Mouse Behavioral and Neuroendocrine
Analysis Core Facility, Duke University
Medical Center, 354 Sands Building, 303 Research Drive, Durham, North Carolina27710, United States
| | - Vladimir M. Pogorelov
- Department
of Psychiatry and Behavioral Sciences, Mouse Behavioral and Neuroendocrine
Analysis Core Facility, Duke University
Medical Center, 354 Sands Building, 303 Research Drive, Durham, North Carolina27710, United States
| | - Mayako Machino
- Computational
Chemistry and Molecular Biophysics Section, Molecular Targets and
Medications Discovery Branch, National Institute on Drug Abuse, Intramural
Research Program, National Institutes of
Health, 333 Cassell Drive, Baltimore, Maryland21224, United
States
| | - Kuo Hao Lee
- Computational
Chemistry and Molecular Biophysics Section, Molecular Targets and
Medications Discovery Branch, National Institute on Drug Abuse, Intramural
Research Program, National Institutes of
Health, 333 Cassell Drive, Baltimore, Maryland21224, United
States
| | - Jeremiah W. Bertz
- Department
of Pharmacology, University of Michigan
Medical School, 1150 W. Medical Center Dr., Ann Arbor, Michigan48109, United States
| | - Jinbin Xu
- Division
of Radiological Sciences, Department of Radiology, Mallinckrodt Institute
of Radiology, Washington University School
of Medicine, St. Louis, Missouri63110, United States
| | - Herman D. Lim
- Drug Discovery
Biology, Monash Institute of Pharmaceutical Sciences, Monash University, 399 Royal Parade, Parkville, VIC3052, Australia
| | - Andrés E. Dulcey
- Division
of Pre-Clinical Innovation, National Center for Advancing Translational
Sciences, National Institutes of Health, 9800 Medical Center Drive, Rockville, Maryland20850, United States
| | - Robert H. Mach
- Department
of Radiology, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, Pennsylvania19104, United States
| | - James H. Woods
- Department
of Pharmacology, University of Michigan
Medical School, 1150 W. Medical Center Dr., Ann Arbor, Michigan48109, United States
| | - J Robert Lane
- Centre
of Membrane Proteins and Receptors, Universities
of Birmingham and Nottingham, NottinghamNG7 2UH, United Kingdom
| | - Lei Shi
- Computational
Chemistry and Molecular Biophysics Section, Molecular Targets and
Medications Discovery Branch, National Institute on Drug Abuse, Intramural
Research Program, National Institutes of
Health, 333 Cassell Drive, Baltimore, Maryland21224, United
States
| | - Juan J. Marugan
- Division
of Pre-Clinical Innovation, National Center for Advancing Translational
Sciences, National Institutes of Health, 9800 Medical Center Drive, Rockville, Maryland20850, United States
| | - William C. Wetsel
- Department
of Psychiatry and Behavioral Sciences, Mouse Behavioral and Neuroendocrine
Analysis Core Facility, Duke University
Medical Center, 354 Sands Building, 303 Research Drive, Durham, North Carolina27710, United States
- Departments
of Neurobiology and Cell Biology, Duke University
Medical Center, 354 Sands Building, 303 Research Drive, Durham, North Carolina27710, United States
| | - David R. Sibley
- Molecular
Neuropharmacology Section, National Institute of Neurological Disorders
and Stroke, Intramural Research Program, National Institutes of Health, 35 Convent Drive, MSC-3723, Bethesda, Maryland20892, United States
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8
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Ji L, Fang Y, Tang J, Liu C, Huang C, Hu Q, Li Q, Chen Z. Synthesis and biological evaluation of 18F-labelled dopamine D 3 receptor selective ligands. Bioorg Med Chem Lett 2022; 62:128630. [PMID: 35182773 DOI: 10.1016/j.bmcl.2022.128630] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 02/13/2022] [Accepted: 02/14/2022] [Indexed: 12/29/2022]
Abstract
The dopamine D3 receptor (D3R) is highly expressed in the limbic regions of the brain and closely related to a variety of neurological disorders including Parkinson's disease, schizophrenia and drug-seeking behavior. In vivo imaging of D3R with radio-labelled tracers and positron emission tomography (PET) has become a powerful technique in related disorders. In this study, we synthesized three novel aromatically 18F-labelled phenylpiperazine-like D3R selective radioactive ligands ([18F]5b, [18F]8b and [18F]11b) and developed a simple, rapid and efficient 18F-labelling method by condition optimization. Radiosynthesis of [18F]5b, [18F]8b and [18F]11b was achieved by 18F-fluorination from nitroarene precursors. Final radiochemical purities of [18F]5b, [18F]8b and [18F]11b solution were > 99% and remained good stability (> 98% for up to 6 h) in PBS and FBS. PET imaging and cellular binding studies revealed that [18F]8b had a higher D3R affinity than [18F]5b and [18F]11b. Autoradiography and biodistribution studies of the brain showed that [18F]8b had medium intensity specific accumulation in the striatum and cortex. Meanwhile, the low skeletal uptake of [18F]8b revealed a good in vivo stability with negligible defluorination. These results indicated that [18F]8b might be a potential 18F-labelled D3R PET imaging agent.
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Affiliation(s)
- Linyang Ji
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, School of Pharmacy, Xuzhou Medical University, Xuzhou 221004, China
| | - Yi Fang
- NHC Key Laboratory of Nuclear Medicine, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi 214063, 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
| | - Caiyun Huang
- School of Pharmaceutical Science, Inner Mongolia Medical University, Hohhot 010110, China
| | - Qianyue Hu
- Department of Radiopharmaceuticals, School of Pharmacy, Nanjing Medical University, Nanjing 211166, China
| | - Qingming Li
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, School of Pharmacy, Xuzhou Medical University, Xuzhou 221004, 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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9
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Kiss B, Krámos B, Laszlovszky I. Potential Mechanisms for Why Not All Antipsychotics Are Able to Occupy Dopamine D 3 Receptors in the Brain in vivo. Front Psychiatry 2022; 13:785592. [PMID: 35401257 PMCID: PMC8987915 DOI: 10.3389/fpsyt.2022.785592] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 02/25/2022] [Indexed: 11/29/2022] Open
Abstract
Dysfunctions of the dopaminergic system are believed to play a major role in the core symptoms of schizophrenia such as positive, negative, and cognitive symptoms. The first line of treatment of schizophrenia are antipsychotics, a class of medications that targets several neurotransmitter receptors in the brain, including dopaminergic, serotonergic, adrenergic and/or muscarinic receptors, depending on the given agent. Although the currently used antipsychotics display in vitro activity at several receptors, majority of them share the common property of having high/moderate in vitro affinity for dopamine D2 receptors (D2Rs) and D3 receptors (D3Rs). In terms of mode of action, these antipsychotics are either antagonist or partial agonist at the above-mentioned receptors. Although D2Rs and D3Rs possess high degree of homology in their molecular structure, have common signaling pathways and similar in vitro pharmacology, they have different in vivo pharmacology and therefore behavioral roles. The aim of this review, with summarizing preclinical and clinical evidence is to demonstrate that while currently used antipsychotics display substantial in vitro affinity for both D3Rs and D2Rs, only very few can significantly occupy D3Rs in vivo. The relative importance of the level of endogenous extracellular dopamine in the brain and the degree of in vitro D3Rs receptor affinity and selectivity as determinant factors for in vivo D3Rs occupancy by antipsychotics, are also discussed.
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Affiliation(s)
- Béla Kiss
- Pharmacological and Drug Safety Research, Gedeon Richter Plc., Budapest, Hungary
| | - Balázs Krámos
- Spectroscopic Research Department, Gedeon Richter Plc., Budapest, Hungary
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10
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D3 Receptors and PET Imaging. Curr Top Behav Neurosci 2022; 60:251-275. [PMID: 35711027 DOI: 10.1007/7854_2022_374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
This chapter encapsulates a short introduction to positron emission tomography (PET) imaging and the information gained by using this technology to detect changes of the dopamine 3 receptor (D3R) at the molecular level in vivo. We will discuss available D3R radiotracers, emphasizing [11C]PHNO. The focus, however, will be on PET findings in conditions including substance abuse, obesity, traumatic brain injury, schizophrenia, Parkinson's disease, and aging. Finally, there is a discussion about progress in producing next-generation selective D3R radiotracers.
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11
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Bidesi NSR, Vang Andersen I, Windhorst AD, Shalgunov V, Herth MM. The role of neuroimaging in Parkinson's disease. J Neurochem 2021; 159:660-689. [PMID: 34532856 PMCID: PMC9291628 DOI: 10.1111/jnc.15516] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 09/09/2021] [Accepted: 09/10/2021] [Indexed: 11/29/2022]
Abstract
Parkinson's disease (PD) is a neurodegenerative disorder that affects millions of people worldwide. Two hallmarks of PD are the accumulation of alpha-synuclein and the loss of dopaminergic neurons in the brain. There is no cure for PD, and all existing treatments focus on alleviating the symptoms. PD diagnosis is also based on the symptoms, such as abnormalities of movement, mood, and cognition observed in the patients. Molecular imaging methods such as magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), and positron emission tomography (PET) can detect objective alterations in the neurochemical machinery of the brain and help diagnose and study neurodegenerative diseases. This review addresses the application of functional MRI, PET, and SPECT in PD patients. We provide an overview of the imaging targets, discuss the rationale behind target selection, the agents (tracers) with which the imaging can be performed, and the main findings regarding each target's state in PD. Molecular imaging has proven itself effective in supporting clinical diagnosis of PD and has helped reveal that PD is a heterogeneous disorder, which has important implications for the development of future therapies. However, the application of molecular imaging for early diagnosis of PD or for differentiation between PD and atypical parkinsonisms has remained challenging. The final section of the review is dedicated to new imaging targets with which one can detect the PD-related pathological changes upstream from dopaminergic degeneration. The foremost of those targets is alpha-synuclein. We discuss the progress of tracer development achieved so far and challenges on the path toward alpha-synuclein imaging in humans.
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Affiliation(s)
- Natasha S R Bidesi
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Ida Vang Andersen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Albert D Windhorst
- Radiology and Nuclear Medicine, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Vladimir Shalgunov
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Matthias M Herth
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.,Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen, Denmark
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12
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Lee B, Taylor M, Griffin SA, McInnis T, Sumien N, Mach RH, Luedtke RR. Evaluation of Substituted N-Phenylpiperazine Analogs as D3 vs. D2 Dopamine Receptor Subtype Selective Ligands. Molecules 2021; 26:molecules26113182. [PMID: 34073405 PMCID: PMC8198181 DOI: 10.3390/molecules26113182] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 05/19/2021] [Accepted: 05/21/2021] [Indexed: 11/20/2022] Open
Abstract
N-phenylpiperazine analogs can bind selectively to the D3 versus the D2 dopamine receptor subtype despite the fact that these two D2-like dopamine receptor subtypes exhibit substantial amino acid sequence homology. The binding for a number of these receptor subtype selective compounds was found to be consistent with their ability to bind at the D3 dopamine receptor subtype in a bitopic manner. In this study, a series of the 3-thiophenephenyl and 4-thiazolylphenyl fluoride substituted N-phenylpiperazine analogs were evaluated. Compound 6a was found to bind at the human D3 receptor with nanomolar affinity with substantial D3 vs. D2 binding selectivity (approximately 500-fold). Compound 6a was also tested for activity in two in-vivo assays: (1) a hallucinogenic-dependent head twitch response inhibition assay using DBA/2J mice and (2) an L-dopa-dependent abnormal involuntary movement (AIM) inhibition assay using unilateral 6-hydroxydopamine lesioned (hemiparkinsonian) rats. Compound 6a was found to be active in both assays. This compound could lead to a better understanding of how a bitopic D3 dopamine receptor selective ligand might lead to the development of pharmacotherapeutics for the treatment of levodopa-induced dyskinesia (LID) in patients with Parkinson’s disease.
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Affiliation(s)
- Boeun Lee
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; (B.L.); (R.H.M.)
| | - Michelle Taylor
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center-Fort Worth, Fort Worth, TX 76107, USA; (M.T.); (S.A.G.); (T.M.); (N.S.)
| | - Suzy A. Griffin
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center-Fort Worth, Fort Worth, TX 76107, USA; (M.T.); (S.A.G.); (T.M.); (N.S.)
| | - Tamara McInnis
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center-Fort Worth, Fort Worth, TX 76107, USA; (M.T.); (S.A.G.); (T.M.); (N.S.)
| | - Nathalie Sumien
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center-Fort Worth, Fort Worth, TX 76107, USA; (M.T.); (S.A.G.); (T.M.); (N.S.)
| | - Robert H. Mach
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; (B.L.); (R.H.M.)
| | - Robert R. Luedtke
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center-Fort Worth, Fort Worth, TX 76107, USA; (M.T.); (S.A.G.); (T.M.); (N.S.)
- Correspondence:
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13
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Interaction of Ligands for PET with the Dopamine D3 Receptor: In Silico and In Vitro Methods. Biomolecules 2021; 11:biom11040529. [PMID: 33918451 PMCID: PMC8065765 DOI: 10.3390/biom11040529] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 03/25/2021] [Accepted: 03/31/2021] [Indexed: 12/28/2022] Open
Abstract
[18F]Fallypride and [18F]Fluortriopride (FTP) are two different PET radiotracers that bind with sub-nanomolar affinity to the dopamine D3 receptor (D3R). In spite of their similar D3 affinities, the two PET ligands display very different properties for labeling the D3R in vivo: [18F]Fallypride is capable of binding to D3R under "baseline" conditions, whereas [18F]FTP requires the depletion of synaptic dopamine in order to image the receptor in vivo. These data suggest that [18F]Fallypride is able to compete with synaptic dopamine for binding to the D3R, whereas [18F]FTP is not. The goal of this study was to conduct a series of docking and molecular dynamic simulation studies to identify differences in the ability of each molecule to interact with the D3R that could explain these differences with respect to competition with synaptic dopamine. Competition studies measuring the ability of each ligand to compete with dopamine in the β-arrestin assay were also conducted. The results of the in silico studies indicate that FTP has a weaker interaction with the orthosteric binding site of the D3R versus that of Fallypride. The results of the in silico studies were also consistent with the IC50 values of each compound in the dopamine β-arrestin competition assays. The results of this study indicate that in silico methods may be able to predict the ability of a small molecule to compete with synaptic dopamine for binding to the D3R.
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Prasad K, de Vries EFJ, Elsinga PH, Dierckx RAJO, van Waarde A. Allosteric Interactions between Adenosine A 2A and Dopamine D 2 Receptors in Heteromeric Complexes: Biochemical and Pharmacological Characteristics, and Opportunities for PET Imaging. Int J Mol Sci 2021; 22:ijms22041719. [PMID: 33572077 PMCID: PMC7915359 DOI: 10.3390/ijms22041719] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 02/02/2021] [Accepted: 02/03/2021] [Indexed: 12/17/2022] Open
Abstract
Adenosine and dopamine interact antagonistically in living mammals. These interactions are mediated via adenosine A2A and dopamine D2 receptors (R). Stimulation of A2AR inhibits and blockade of A2AR enhances D2R-mediated locomotor activation and goal-directed behavior in rodents. In striatal membrane preparations, adenosine decreases both the affinity and the signal transduction of D2R via its interaction with A2AR. Reciprocal A2AR/D2R interactions occur mainly in striatopallidal GABAergic medium spiny neurons (MSNs) of the indirect pathway that are involved in motor control, and in striatal astrocytes. In the nucleus accumbens, they also take place in MSNs involved in reward-related behavior. A2AR and D2R co-aggregate, co-internalize, and co-desensitize. They are at very close distance in biomembranes and form heteromers. Antagonistic interactions between adenosine and dopamine are (at least partially) caused by allosteric receptor–receptor interactions within A2AR/D2R heteromeric complexes. Such interactions may be exploited in novel strategies for the treatment of Parkinson’s disease, schizophrenia, substance abuse, and perhaps also attention deficit-hyperactivity disorder. Little is known about shifting A2AR/D2R heteromer/homodimer equilibria in the brain. Positron emission tomography with suitable ligands may provide in vivo information about receptor crosstalk in the living organism. Some experimental approaches, and strategies for the design of novel imaging agents (e.g., heterobivalent ligands) are proposed in this review.
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Affiliation(s)
- Kavya Prasad
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
- Correspondence: (K.P.); (A.v.W.); Tel.: +31-50-3613215
| | - Erik F. J. de Vries
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
| | - Philip H. Elsinga
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
| | - Rudi A. J. O. Dierckx
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
- Department of Diagnostic Sciences, Ghent University Faculty of Medicine and Health Sciences, C.Heymanslaan 10, 9000 Gent, Belgium
| | - Aren van Waarde
- Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713GZ Groningen, The Netherlands; (E.F.J.d.V.); (P.H.E.); (R.A.J.O.D.)
- Correspondence: (K.P.); (A.v.W.); Tel.: +31-50-3613215
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15
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Abstract
![]()
Developing
drugs for the central nervous system (CNS) requires
fine chemical modifications, as a strict balance between size and
lipophilicity is necessary to improve the permeability through the
blood-brain barrier (BBB).
In this context, morpholine and its analogues represent valuable heterocycles,
due to their conformational and physicochemical properties. In fact,
the presence of a weak basic nitrogen atom and of an oxygen atom at
the opposite position provides a peculiar pKa value and a flexible conformation to the ring, thus allowing
it to take part in several lipophilic–hydrophilic interactions,
and to improve blood solubility and brain permeability of the overall
structure. In CNS-active compounds, morpholines are used (1) to enhance
the potency through molecular interactions, (2) to act as a scaffold
directing the appendages in the correct position, and (3) to modulate
pharmacokinetic/pharmacodynamic (PK/PD) properties. In this perspective,
selected morpholine-containing CNS drug candidates are discussed to
reveal the active pharmacophores accountable for the (1) modulation
of receptors involved in mood disorders and pain, (2) bioactivity
toward enzymes and receptors responsible for neurodegenerative diseases,
and (3) inhibition of enzymes involved in the pathology of CNS tumors.
The medicinal chemistry/pharmacological activity of morpholine derivatives
is discussed, in the effort to highlight the importance of morpholine
ring interactions in the active site of different targets, particularly
reporting binding features retrieved from PDB data, when available.
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Affiliation(s)
- Elena Lenci
- Department of Chemistry “Ugo Schiff”, University of Florence, via della Lastruccia 13, 50019 Sesto Fiorentino, Florence, Italy
| | - Lorenzo Calugi
- Department of Chemistry “Ugo Schiff”, University of Florence, via della Lastruccia 13, 50019 Sesto Fiorentino, Florence, Italy
| | - Andrea Trabocchi
- Department of Chemistry “Ugo Schiff”, University of Florence, via della Lastruccia 13, 50019 Sesto Fiorentino, Florence, Italy
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16
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Kilbourn MR. 11C- and 18F-Radiotracers for In Vivo Imaging of the Dopamine System: Past, Present and Future. Biomedicines 2021; 9:108. [PMID: 33499179 PMCID: PMC7912183 DOI: 10.3390/biomedicines9020108] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 01/17/2021] [Accepted: 01/19/2021] [Indexed: 12/17/2022] Open
Abstract
The applications of positron emission tomography (PET) imaging to study brain biochemistry, and in particular the aspects of dopamine neurotransmission, have grown significantly over the 40 years since the first successful in vivo imaging studies in humans. In vivo PET imaging of dopaminergic functions of the central nervous system (CNS) including dopamine synthesis, vesicular storage, synaptic release and receptor binding, and reuptake processes, are now routinely used for studies in neurology, psychiatry, drug abuse and addiction, and drug development. Underlying these advances in PET imaging has been the development of the unique radiotracers labeled with positron-emitting radionuclides such as carbon-11 and fluorine-18. This review focuses on a selection of the more accepted and utilized PET radiotracers currently available, with a look at their past, present and future.
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Affiliation(s)
- Michael R Kilbourn
- Department of Radiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA
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17
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Reilly SW, Riad AA, Hsieh CJ, Sahlholm K, Jacome DA, Griffin S, Taylor M, Weng CC, Xu K, Kirschner N, Luedtke RR, Parry C, Malhotra S, Karanicolas J, Mach RH. Leveraging a Low-Affinity Diazaspiro Orthosteric Fragment to Reduce Dopamine D 3 Receptor (D 3R) Ligand Promiscuity across Highly Conserved Aminergic G-Protein-Coupled Receptors (GPCRs). J Med Chem 2019; 62:5132-5147. [PMID: 31021617 DOI: 10.1021/acs.jmedchem.9b00412] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Previously, we reported a 3-(2-methoxyphenyl)-9-(3-((4-methyl-5-phenyl-4 H-1,2,4-triazol-3-yl)thio)propyl)-3,9-diazaspiro[5.5]undecane (1) compound with excellent dopamine D3 receptor (D3R) affinity (D3R Ki = 12.0 nM) and selectivity (D2R/D3R ratio = 905). Herein, we present derivatives of 1 with comparable D3R affinity (32, D3R Ki = 3.2 nM, D2R/D3R ratio = 60) and selectivity (30, D3R Ki = 21.0 nM, D2R/D3R ratio = 934). Fragmentation of 1 revealed orthosteric fragment 5a to express an unusually low D3R affinity ( Ki = 2.7 μM). Compared to piperazine congener 31, which retains a high-affinity orthosteric fragment (5d, D3R Ki = 23.9 nM), 1 was found to be more selective for the D3R among D1- and D2-like receptors and exhibited negligible off-target interactions at serotoninergic and adrenergic G-protein-coupled receptors (GPCRs), common off-target sites for piperazine-containing D3R scaffolds. This study provides a unique rationale for implementing weakly potent orthosteric fragments into D3R ligand systems to minimize drug promiscuity at other aminergic GPCR sites.
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Affiliation(s)
- Sean W Reilly
- Department of Radiology , Perelman School of Medicine, University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Aladdin A Riad
- Department of Radiology , Perelman School of Medicine, University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Chia-Ju Hsieh
- Department of Radiology , Perelman School of Medicine, University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Kristoffer Sahlholm
- Department of Radiology , Perelman School of Medicine, University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Daniel A Jacome
- Department of Systems Pharmacology and Translational Therapeutics , University of Pennsylvania , 421 Curie Boulevard , Philadelphia , Pennsylvania 19104 , United States
| | - Suzy Griffin
- Department of Pharmacology and Neuroscience , University of North Texas Health Science Center , 3500 Camp Bowie Boulevard , Fort Worth , Texas 76107 , United States
| | - Michelle Taylor
- Department of Pharmacology and Neuroscience , University of North Texas Health Science Center , 3500 Camp Bowie Boulevard , Fort Worth , Texas 76107 , United States
| | - Chi-Chang Weng
- Department of Radiology , Perelman School of Medicine, University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Kuiying Xu
- Department of Radiology , Perelman School of Medicine, University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Nathan Kirschner
- Department of Radiology , Perelman School of Medicine, University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Robert R Luedtke
- Department of Pharmacology and Neuroscience , University of North Texas Health Science Center , 3500 Camp Bowie Boulevard , Fort Worth , Texas 76107 , United States
| | - Christopher Parry
- Program in Molecular Therapeutics , Fox Chase Cancer Center , 333 Cottman Avenue , Philadelphia , Pennsylvania 19111 , United States
| | - Shipra Malhotra
- Program in Molecular Therapeutics , Fox Chase Cancer Center , 333 Cottman Avenue , Philadelphia , Pennsylvania 19111 , United States
| | - John Karanicolas
- Program in Molecular Therapeutics , Fox Chase Cancer Center , 333 Cottman Avenue , Philadelphia , Pennsylvania 19111 , United States
| | - Robert H Mach
- Department of Radiology , Perelman School of Medicine, University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
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18
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Hayatshahi HS, Xu K, Griffin SA, Taylor M, Mach RH, Liu J, Luedtke RR. Analogues of Arylamide Phenylpiperazine Ligands To Investigate the Factors Influencing D3 Dopamine Receptor Bitropic Binding and Receptor Subtype Selectivity. ACS Chem Neurosci 2018; 9:2972-2983. [PMID: 30010318 DOI: 10.1021/acschemneuro.8b00142] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
We have previously reported on the ability of arylamide phenylpiperazines to bind selectively to the D3 versus the D2 dopamine receptor subtype. For these studies, we used LS-3-134 as the prototypic arylamide phenylpiperazine ligand because it binds with high affinity at D3 dopamine receptor (0.17 nM) and exhibits >150-fold D3 vs D2 receptor binding selectivity. Our goal was to investigate how the composition and size of the nonaromatic ring structure at the piperazine position of substituted phenylpiperazine analogues might influence binding affinity at the human D2 and D3 dopamine receptors. Two factors were identified as being important for determining the binding affinity of bitropic arylamide phenylpiperazines at the dopamine D3 receptor subtype. One factor was the strength of the salt bridge between the highly conserved residue Asp3.32 with the protonated nitrogen of the nonaromatic ring at the piperazine position. The second factor was the configuration of the unbound ligand in an aqueous solution. These two factors were found to be related to the logarithm of the affinities using a simple correlation model, which could be useful when designing high affinity subtype selective bitropic ligands. While this model is based upon the interaction of arylamide phenylpiperazines with the D2 and D3 D2-like dopamine receptor subtypes, it provides insights into the complexity of the factors that define a bitropic mode of the binding at GPCRs.
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Affiliation(s)
- Hamed S. Hayatshahi
- Department of Pharmaceutical Sciences, University of North Texas System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, Texas 76107, United States
| | - Kuiying Xu
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Suzy A. Griffin
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, Texas 76107, United States
| | - Michelle Taylor
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, Texas 76107, United States
| | - Robert H. Mach
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Jin Liu
- Department of Pharmaceutical Sciences, University of North Texas System College of Pharmacy, University of North Texas Health Science Center, Fort Worth, Texas 76107, United States
| | - Robert R. Luedtke
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, Texas 76107, United States
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19
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Liow JS, Morse CL, Lu S, Frankland M, Tye GL, Zoghbi SS, Gladding RL, Shaik AB, Innis RB, Newman AH, Pike VW. [ O- methyl- 11C] N-(4-(4-(3-Chloro-2-methoxyphenyl)-piperazin-1-yl)butyl)-1 H-indole-2-carboxamide ([ 11C]BAK4-51) Is an Efflux Transporter Substrate and Ineffective for PET Imaging of Brain D₃ Receptors in Rodents and Monkey. Molecules 2018; 23:molecules23112737. [PMID: 30360553 PMCID: PMC6278341 DOI: 10.3390/molecules23112737] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 10/15/2018] [Accepted: 10/18/2018] [Indexed: 11/16/2022] Open
Abstract
Selective high-affinity antagonists for the dopamine D₃ receptor (D₃R) are sought for treating substance use disorders. Positron emission tomography (PET) with an effective D₃R radioligand could be a useful tool for the development of such therapeutics by elucidating pharmacological specificity and target engagement in vivo. Currently, a D₃R-selective radioligand does not exist. The D₃R ligand, N-(4-(4-(3-chloro-2-methoxyphenyl)piperazin-1-yl)butyl)-1H-indole-2-carboxamide (BAK4-51, 1), has attractive properties for PET radioligand development, including full antagonist activity, very high D₃R affinity, D₃R selectivity, and moderate lipophilicity. We labeled 1 with the positron-emitter carbon-11 (t1/2 = 20.4 min) in the methoxy group for evaluation as a radioligand in animals with PET. However, [11C]1 was found to be an avid substrate for brain efflux transporters and lacked D₃R-specific signal in rodent and monkey brain in vivo.
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Affiliation(s)
- Jeih-San Liow
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Room B3C346, 10 Center Drive, Bethesda, MD 20892, USA.
| | - Cheryl L Morse
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Room B3C346, 10 Center Drive, Bethesda, MD 20892, USA.
| | - Shuiyu Lu
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Room B3C346, 10 Center Drive, Bethesda, MD 20892, USA.
| | - Michael Frankland
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Room B3C346, 10 Center Drive, Bethesda, MD 20892, USA.
| | - George L Tye
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Room B3C346, 10 Center Drive, Bethesda, MD 20892, USA.
| | - Sami S Zoghbi
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Room B3C346, 10 Center Drive, Bethesda, MD 20892, USA.
| | - Robert L Gladding
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Room B3C346, 10 Center Drive, Bethesda, MD 20892, USA.
| | - Anver B Shaik
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA.
| | - Robert B Innis
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Room B3C346, 10 Center Drive, Bethesda, MD 20892, USA.
| | - Amy H Newman
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA.
| | - Victor W Pike
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Room B3C346, 10 Center Drive, Bethesda, MD 20892, USA.
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Doot RK, Dubroff JG, Scheuermann JS, Labban KJ, Cai J, Hsieh CJ, Li S, Lee H, Schubert EK, Hou C, Sheffer R, Schmitz A, Xu K, Mach RH. Validation of gallbladder absorbed radiation dose reduction simulation: human dosimetry of [ 18F]fluortriopride. EJNMMI Phys 2018; 5:21. [PMID: 30294746 PMCID: PMC6174116 DOI: 10.1186/s40658-018-0219-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 06/05/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND [18F]Fluortriopride (FTP) was developed as a dopamine D3-selective radiotracer, thought to be important to neurobiological reward pathways and implicated in drug addiction, Parkinson's disease, and schizophrenia. Preclinical radiation dosimetry studies found the gallbladder wall received the highest dose. A gallbladder dose reduction intervention was simulated using a novel reduction model for healthy adults following fatty-meal consumption. The goals of this study were to assess whole body FTP human dosimetry and determine the feasibility of reducing absorbed dose to the gallbladder wall. RESULTS Effective dose without a fatty meal was 0.022 ± 0.002 mSv/MBq (± standard deviation) with highest organ dose of 0.436 ± 0.178 mSv/MBq to the gallbladder wall (n = 10). Predicted gallbladder dose reduction with fatty meal consumed was 67.4% (n = 10). Meal consumption by four repeat volunteers decreased average gallbladder dose by 71.3% (n = 4) compared to the original ten volunteers. CONCLUSIONS Observed effective doses were adequately low to continue studying FTP uptake in humans. Validated dosimetry simulations indicate up to a 71% reduction in gallbladder dose can be achieved by employing intrinsic physiology to contract the gallbladder via fatty meal ingestion. This methodology for predicting gallbladder absorbed dose reduction from fatty meal consumption can be applied to other radiopharmaceuticals and radiotherapies.
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Affiliation(s)
- Robert K Doot
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
| | - Jacob G Dubroff
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Joshua S Scheuermann
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Kyle J Labban
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Jenny Cai
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Chia-Ju Hsieh
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Shihong Li
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Hsiaoju Lee
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Erin K Schubert
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Catherine Hou
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Regan Sheffer
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Alexander Schmitz
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Kuiying Xu
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Robert H Mach
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
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Maia TV, Conceição VA. Dopaminergic Disturbances in Tourette Syndrome: An Integrative Account. Biol Psychiatry 2018; 84:332-344. [PMID: 29656800 DOI: 10.1016/j.biopsych.2018.02.1172] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 02/04/2018] [Accepted: 02/25/2018] [Indexed: 12/28/2022]
Abstract
Tourette syndrome (TS) is thought to involve dopaminergic disturbances, but the nature of those disturbances remains controversial. Existing hypotheses suggest that TS involves 1) supersensitive dopamine receptors, 2) overactive dopamine transporters that cause low tonic but high phasic dopamine, 3) presynaptic dysfunction in dopamine neurons, or 4) dopaminergic hyperinnervation. We review evidence that contradicts the first two hypotheses; we also note that the last two hypotheses have traditionally been considered too narrowly, explaining only small subsets of findings. We review all studies that have used positron emission tomography and single-photon emission computerized tomography to investigate the dopaminergic system in TS. The seemingly diverse findings from those studies have typically been interpreted as pointing to distinct mechanisms, as evidenced by the various hypotheses concerning the nature of dopaminergic disturbances in TS. We show, however, that the hyperinnervation hypothesis provides a simple, parsimonious explanation for all such seemingly diverse findings. Dopaminergic hyperinnervation likely causes increased tonic and phasic dopamine. We have previously shown, using a computational model of the role of dopamine in basal ganglia, that increased tonic dopamine and increased phasic dopamine likely increase the propensities to express and learn tics, respectively. There is therefore a plausible mechanistic link between dopaminergic hyperinnervation and TS via increased tonic and phasic dopamine. To further bolster this argument, we review evidence showing that all medications that are effective for TS reduce signaling by tonic dopamine, phasic dopamine, or both.
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Affiliation(s)
- Tiago V Maia
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal.
| | - Vasco A Conceição
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
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Abstract
Dopamine D3 receptors have key roles in behavioral reward, addiction, Parkinson's disease, and schizophrenia, and there is interest in studying their role in these disorders using PET. However, current PET radiotracers for studying D3 receptors in humans all bind to both D2 and D3 due to similarities between the two receptors. Selective D2 and D3 radioligands would aid investigation of the differences between D2 and D3 circuitry in the central nervous system. While there are currently in vitro measures of ligand D3/D2 selectivity, there is a need for an in vivo PET measure of D3/D2 selectivity. This review discusses current PET imaging of dopamine D2/D3 receptors and proposes methodology for quantitating in vivo selectivity of probes for PET imaging of dopamine D3 receptors.
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Affiliation(s)
- Robert K Doot
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
| | - Jacob G Dubroff
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Kyle J Labban
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Robert H Mach
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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Nebel N, Strauch B, Maschauer S, Lasch R, Rampp H, Fehler SK, Bock LR, Hübner H, Gmeiner P, Heinrich MR, Prante O. [ 18F]Fluorophenylazocarboxylates: Design and Synthesis of Potential Radioligands for Dopamine D3 and μ-Opioid Receptor. ACS OMEGA 2017; 2:8649-8659. [PMID: 29479577 PMCID: PMC5819854 DOI: 10.1021/acsomega.7b01374] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 11/16/2017] [Indexed: 06/08/2023]
Abstract
18F-Labeled building blocks from the type of [18F]fluorophenylazocarboxylic-tert-butyl esters offer a rapid, mild, and reliable method for the 18F-fluoroarylation of biomolecules. Two series of azocarboxamides were synthesized as potential radioligands for dopamine D3 and the μ-opioid receptor, revealing compounds 3d and 3e with single-digit and sub-nanomolar affinity for the D3 receptor and compound 4c with only micromolar affinity for the μ-opioid receptor, but enhanced selectivity for the μ-subtype in comparison to the lead compound AH-7921. A "minimalist procedure" without the use of a cryptand and base for the preparation of 4-[18F]fluorophenylazocarboxylic-tert-butyl ester [18F]2a was established, together with the radiosynthesis of methyl-, methoxy-, and phenyl-substituted derivatives ([18F]2b-f). With the substituted [18F]fluorophenylazocarbylates in hand, two prototype azocarboxylates radioligands were synthesized by 18F-fluoroarylation, namely the methoxy azocarboxamide [18F]3d as the D3 receptor radioligand and [18F]4a as a prototype structure of the μ-opioid receptor radioligand. By introducing the new series of [18F]fluorophenylazocarboxylic-tert-butyl esters, the method of 18F-fluoroarylation was significantly expanded, thereby demonstrating the versatility of 18F-labeled phenylazocarboxylates for the design of potential radiotracers for positron emission tomography .
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Affiliation(s)
- Natascha Nebel
- Department
of Nuclear Medicine, Molecular Imaging and Radiochemistry, Friedrich Alexander University Erlangen-Nürnberg
(FAU), Schwabachanlage
6, Erlangen D-91054, Germany
| | - Brigitte Strauch
- Department
of Nuclear Medicine, Molecular Imaging and Radiochemistry, Friedrich Alexander University Erlangen-Nürnberg
(FAU), Schwabachanlage
6, Erlangen D-91054, Germany
| | - Simone Maschauer
- Department
of Nuclear Medicine, Molecular Imaging and Radiochemistry, Friedrich Alexander University Erlangen-Nürnberg
(FAU), Schwabachanlage
6, Erlangen D-91054, Germany
| | - Roman Lasch
- Department
of Chemistry and Pharmacy, Medicinal Chemistry, Emil Fischer Center, Friedrich Alexander University Erlangen-Nürnberg
(FAU), Schuhstrasse 19, Erlangen D-91052, Germany
| | - Hannelore Rampp
- Department
of Chemistry and Pharmacy, Medicinal Chemistry, Emil Fischer Center, Friedrich Alexander University Erlangen-Nürnberg
(FAU), Schuhstrasse 19, Erlangen D-91052, Germany
| | - Stefanie K. Fehler
- Department
of Chemistry and Pharmacy, Medicinal Chemistry, Emil Fischer Center, Friedrich Alexander University Erlangen-Nürnberg
(FAU), Schuhstrasse 19, Erlangen D-91052, Germany
| | - Leonard R. Bock
- Department
of Chemistry and Pharmacy, Medicinal Chemistry, Emil Fischer Center, Friedrich Alexander University Erlangen-Nürnberg
(FAU), Schuhstrasse 19, Erlangen D-91052, Germany
| | - Harald Hübner
- Department
of Chemistry and Pharmacy, Medicinal Chemistry, Emil Fischer Center, Friedrich Alexander University Erlangen-Nürnberg
(FAU), Schuhstrasse 19, Erlangen D-91052, Germany
| | - Peter Gmeiner
- Department
of Chemistry and Pharmacy, Medicinal Chemistry, Emil Fischer Center, Friedrich Alexander University Erlangen-Nürnberg
(FAU), Schuhstrasse 19, Erlangen D-91052, Germany
| | - Markus R. Heinrich
- Department
of Chemistry and Pharmacy, Medicinal Chemistry, Emil Fischer Center, Friedrich Alexander University Erlangen-Nürnberg
(FAU), Schuhstrasse 19, Erlangen D-91052, Germany
| | - Olaf Prante
- Department
of Nuclear Medicine, Molecular Imaging and Radiochemistry, Friedrich Alexander University Erlangen-Nürnberg
(FAU), Schwabachanlage
6, Erlangen D-91054, Germany
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