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Ortore G, Orlandini E, Betti L, Giannaccini G, Mazzoni MR, Camodeca C, Nencetti S. Focus on Human Monoamine Transporter Selectivity. New Human DAT and NET Models, Experimental Validation, and SERT Affinity Exploration. ACS Chem Neurosci 2020; 11:3214-3232. [PMID: 32991141 PMCID: PMC8015229 DOI: 10.1021/acschemneuro.0c00304] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
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The most commonly used antidepressant
drugs are the serotonin transporter
inhibitors. Their effects depend strongly on the selectivity for a
single monoamine transporter compared to other amine transporters
or receptors, and the selectivity is roughly influenced by the spatial
protein structure. Here, we provide a computational study on three
human monoamine transporters, i.e., DAT, NET, and SERT. Starting from
the construction of hDAT and hNET models, whose three-dimensional
structure is unknown, and the prediction of the binding pose for 19
known inhibitors, 3D-QSAR models of three human transporters were
built. The training set variability, which was high in structure and
activity profile, was validated using a set of in-house compounds.
Results concern more than one aspect. First of all, hDAT and hNET
three-dimensional structures were built, validated, and compared to
the hSERT one; second, the computational study highlighted the differences
in binding site arrangement statistically correlated to inhibitor
selectivity; third, the profiling of new inhibitors pointed out a
conservation of the inhibitory activity trend between rabbit and human
SERT with a difference of about 1 order of magnitude; fourth, binding
and functional studies confirmed 4-(benzyloxy)-4-phenylpiperidine 20a–d and 21a–d as potent SERT
inhibitors. In particular, one of the compounds (compound 20b) revealed a higher affinity for SERT than paroxetine in human platelets.
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Affiliation(s)
- Gabriella Ortore
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Elisabetta Orlandini
- Research Center “E. Piaggio”, University of Pisa, Pisa 56122, Italy
- Department of Earth Sciences, University of Pisa, Via Santa Maria 53-55, 56100 Pisa, Italy
| | - Laura Betti
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Gino Giannaccini
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Maria Rosa Mazzoni
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Caterina Camodeca
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Susanna Nencetti
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
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Alluri SR, Kim SW, Volkow ND, Kil KE. PET Radiotracers for CNS-Adrenergic Receptors: Developments and Perspectives. Molecules 2020; 25:molecules25174017. [PMID: 32899124 PMCID: PMC7504810 DOI: 10.3390/molecules25174017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 08/29/2020] [Accepted: 09/01/2020] [Indexed: 12/30/2022] Open
Abstract
Epinephrine (E) and norepinephrine (NE) play diverse roles in our body’s physiology. In addition to their role in the peripheral nervous system (PNS), E/NE systems including their receptors are critical to the central nervous system (CNS) and to mental health. Various antipsychotics, antidepressants, and psychostimulants exert their influence partially through different subtypes of adrenergic receptors (ARs). Despite the potential of pharmacological applications and long history of research related to E/NE systems, research efforts to identify the roles of ARs in the human brain taking advantage of imaging have been limited by the lack of subtype specific ligands for ARs and brain penetrability issues. This review provides an overview of the development of positron emission tomography (PET) radiotracers for in vivo imaging of AR system in the brain.
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Affiliation(s)
- Santosh Reddy Alluri
- University of Missouri Research Reactor, University of Missouri, Columbia, MO 65211-5110, USA;
| | - Sung Won Kim
- Laboratory of Neuroimaging, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-1013, USA;
| | - Nora D. Volkow
- Laboratory of Neuroimaging, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-1013, USA;
- National Institute on Drug Abuse, National Institutes of Health, Bethesda, MD 20892-1013, USA
- Correspondence: (N.D.V.); (K.-E.K.); Tel.: +1-(301)-443-6480 (N.D.V.); +1-(573)-884-7885 (K.-E.K.)
| | - Kun-Eek Kil
- University of Missouri Research Reactor, University of Missouri, Columbia, MO 65211-5110, USA;
- Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, MO 65211, USA
- Correspondence: (N.D.V.); (K.-E.K.); Tel.: +1-(301)-443-6480 (N.D.V.); +1-(573)-884-7885 (K.-E.K.)
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López-Picón FR, Kirjavainen AK, Forsback S, Takkinen JS, Peters D, Haaparanta-Solin M, Solin O. In vivo characterization of a novel norepinephrine transporter PET tracer [ 18F]NS12137 in adult and immature Sprague-Dawley rats. Am J Cancer Res 2019; 9:11-19. [PMID: 30662550 PMCID: PMC6332804 DOI: 10.7150/thno.29740] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 11/16/2018] [Indexed: 12/31/2022] Open
Abstract
Norepinephrine modulates cognitive processes such as working and episodic memory. Pathological changes in norepinephrine and norepinephrine transporter (NET) function and degeneration of the locus coeruleus produce irreversible impairments within the whole norepinephrine system, disrupting cognitive processes. Monitoring these changes could enhance diagnostic accuracy and support development of novel therapeutic components for several neurodegenerative diseases. Thus, we aimed to develop a straightforward nucleophilic fluorination method with high molar activity for the novel NET radiotracer [18F]NS12137 and to demonstrate the ability of [18F]NS12137 to quantify changes in NET expression. Methods: We applied an 18F-radiolabeling method in which a brominated precursor was debrominated by nucleophilic 18F-fluorination in dimethyl sulfoxide. Radiolabeling was followed by a deprotection step, purification, and formulation of the radiotracer. The [18F]NS12137 brain uptake and distribution were studied with in vivo PET/CT and ex vivo autoradiography using both adult and immature Sprague-Dawley rats because postnatal NET expression peaks at 10-20 days post birth. The NET specificity for the tracer was demonstrated by pretreatment of the animals with nisoxetine, which is well-known to have a high affinity for NET. Results: [18F]NS12137 was successfully synthesized with radiochemical yields of 18.6±5.6%, radiochemical purity of >99%, and molar activity of >500 GBq/μmol at the end of synthesis. The in vivo [18F]NS12137 uptake showed peak standard uptake values (SUV) of over 1.5 (adult) and 2.2 (immature) in the different brain regions. Peak SUV/30 min and peak SUV/60 min ratios were calculated for the different brain regions of the adult and immature rats, with a peak SUV/60 min ratio of more than 4.5 in the striatum of adult rats. As expected, in vivo studies demonstrated uptake of the tracer in brain areas rich in NET, particularly thalamus, neocortex, and striatum, and remarkably also in the locus coeruleus, a quite small volume for imaging with PET. The uptake was significantly higher in immature rats compared to the adult animals. Ex vivo studies using autoradiography showed very strong specific binding in NET-rich areas such as the locus coeruleus and the bed nucleus of the stria terminalis, and high binding in larger grey matter areas such as the neocortex and striatum. The uptake of [18F]NS12137 was dramatically reduced both in vivo and ex vivo by pretreatment with nisoxetine, demonstrating the specificity of binding. Conclusions: [18F]NS12137 was synthesized in good yield and high molar activity and demonstrated the characteristics of a good radiotracer, such as good brain penetration, fast washout, and high specific binding to NET.
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Kirjavainen AK, Forsback S, López-Picón FR, Marjamäki P, Takkinen J, Haaparanta-Solin M, Peters D, Solin O. 18F-labeled norepinephrine transporter tracer [ 18F]NS12137: radiosynthesis and preclinical evaluation. Nucl Med Biol 2017; 56:39-46. [PMID: 29172120 DOI: 10.1016/j.nucmedbio.2017.10.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 10/11/2017] [Accepted: 10/16/2017] [Indexed: 01/16/2023]
Abstract
INTRODUCTION Several psychiatric and neurodegenerative diseases are associated with malfunction of brain norepinephrine transporter (NET). However, current clinical evaluations of NET function are limited by the lack of sufficiently sensitive methods of detection. To this end, we have synthesized exo-3-[(6-[18F]fluoro-2-pyridyl)oxy]-8-azabicyclo[3.2.1]-octane ([18F]NS12137) as a radiotracer for positron emission tomography (PET) and have demonstrated that it is highly specific for in vivo detection of NET-rich regions of rat brain tissue. METHODS We applied two methods of electrophilic, aromatic radiofluorination of the precursor molecule, exo-3-[(6-trimethylstannyl-2-pyridyl)oxy]-8-azabicyclo-[3.2.1]octane-8-carboxylate: (1) direct labeling with [18F]F2, and (2) labeling with [18F]Selectfluor, a derivative of [18F]F2, using post-target produced [18F]F2. The time-dependent distribution of [18F]NS12137 in brain tissue of healthy, adult Sprague-Dawley rats was determined by ex vivo autoradiography. The specificity of [18F]NS12137 binding was demonstrated on the basis of competitive binding by nisoxetine, a known NET antagonist of high specificity. RESULTS [18F]NS12137 was successfully synthesized with radiochemical yields of 3.9% ± 0.3% when labeled with [18F]F2 and 10.2% ± 2.7% when labeled with [18F]Selectfluor. The molar activity of radiotracer was 8.8 ± 0.7 GBq/μmol with [18F]F2 labeling and 6.9 ± 0.4 GBq/μmol with [18F]Selectfluor labeling at the end of synthesis of [18F]NS12137. Uptake of [18F]NS12137 in NET-rich areas in rat brain was demonstrated with the locus coeruleus (LCoe) having the highest regional uptake. Prior treatment of rats with nisoxetine showed no detectable [18F]NS12137 in the LCoe. Analyses of whole brain samples for radiometabolites showed only the parent compound [18F]NS12137. Uptake of 18F-radioactivity in bone increased with time. CONCLUSIONS The two electrophilic 18F-labeling methods proved to be suitable for synthesis of [18F]NS12137 with the [18F]Selectfluor method providing an approximate three-fold higher yield than the [18F]F2 method. As an electrostatically neutral radiotracer [18F]NS12137 crosses the blood-brain barrier and enabled specific labeling of NET-rich regions of rat brain tissue with the highest concentration in the LCoe.
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Affiliation(s)
- Anna K Kirjavainen
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland.
| | - Sarita Forsback
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland; Department of Chemistry, University of Turku, Turku, Finland
| | - Francisco R López-Picón
- Preclinical Imaging, Turku PET Centre, University of Turku, Turku, Finland; Medicity Research Laboratory, University of Turku, Turku, Finland
| | | | - Jatta Takkinen
- Preclinical Imaging, Turku PET Centre, University of Turku, Turku, Finland; Medicity Research Laboratory, University of Turku, Turku, Finland
| | - Merja Haaparanta-Solin
- Preclinical Imaging, Turku PET Centre, University of Turku, Turku, Finland; Medicity Research Laboratory, University of Turku, Turku, Finland
| | - Dan Peters
- DanPET AB, Malmö, Sweden; Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
| | - Olof Solin
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland; Department of Chemistry, University of Turku, Turku, Finland; Accelerator Laboratory, Åbo Akademi University, Turku, Finland
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5
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Shahzad D, Faisal M, Rauf A, Huang JH. Synthetic Story of a Blockbuster Drug: Reboxetine, a Potent Selective Norepinephrine Reuptake Inhibitor. Org Process Res Dev 2017. [DOI: 10.1021/acs.oprd.7b00265] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Danish Shahzad
- Department
of Chemistry, Quaid-i-Azam University, 45320 Islamabad, Pakistan
| | - Muhammad Faisal
- Department
of Chemistry, Quaid-i-Azam University, 45320 Islamabad, Pakistan
| | - Ameema Rauf
- Department
of Chemistry, University of Wah, Wah Cantt, Pakistan
| | - Jian-hua Huang
- School
of Pharmacy, Hunan University of Chinese Medicine, Changsha 410208, China
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Wang P, Fu T, Zhang X, Yang F, Zheng G, Xue W, Chen Y, Yao X, Zhu F. Differentiating physicochemical properties between NDRIs and sNRIs clinically important for the treatment of ADHD. Biochim Biophys Acta Gen Subj 2017; 1861:2766-2777. [PMID: 28757337 DOI: 10.1016/j.bbagen.2017.07.022] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 07/23/2017] [Accepted: 07/26/2017] [Indexed: 12/25/2022]
Abstract
BACKGROUND Drugs available for treating attention-deficit hyperactivity disorder (ADHD) are mainly selective norepinephrine (sNRIs) and dual norepinephrine-dopamine (NDRIs) reuptake inhibitors. The major problem of sNRIs lines in their delayed onset of action and partial- or non-responses, which makes NDRIs distinguished in drug efficacy. Understanding of the differential binding modes of these 2 types of drugs to their corresponding targets can give great insights into the discovery of privileged drug-like scaffolds with improved efficacy. So far, no such study has been carried out. METHODS A combinatorial computational strategy, integrating homology modeling, molecular docking, molecular dynamics (MD) and binding free energy calculation, was employed to analyze the binding modes of 8 clinically important ADHD drugs in their targets. RESULTS Binding modes of 2 types of ADHD drugs (sNRIs and NDRIs) in their targets was identified for the first time by MD simulation, and 15 hot spot residues were discovered as crucial for NDRIs' binding in hNET and hDAT. Comparing to sNRIs, a clear reduction in the hydrophobic property of NDRIs' one functional group was observed, and the depth of drugs' aromatic ring stretched into the pocket of both targets was further identified as key contributors to drugs' selectivity. CONCLUSIONS The hydrophobic property of NDRI ADHD drugs' one functional group contributes to their selectivity when bind hNET and hDAT. GENERAL SIGNIFICANCE These results provide insights into NDRI ADHD drugs' binding mechanisms, which could be utilized as structural blueprints for assessing and discovering more efficacious drugs for ADHD therapy.
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Affiliation(s)
- Panpan Wang
- Innovative Drug Research and Bioinformatics Group, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China; College of Chemistry and Pharmaceutical Engineering, Huanghuai University, Zhumadian 463000, China; School of Pharmaceutical Sciences and Collaborative Innovation Center for Brain Science, Chongqing University, Chongqing 401331, China
| | - Tingting Fu
- Innovative Drug Research and Bioinformatics Group, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China; School of Pharmaceutical Sciences and Collaborative Innovation Center for Brain Science, Chongqing University, Chongqing 401331, China
| | - Xiaoyu Zhang
- Innovative Drug Research and Bioinformatics Group, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China; School of Pharmaceutical Sciences and Collaborative Innovation Center for Brain Science, Chongqing University, Chongqing 401331, China
| | - Fengyuan Yang
- Innovative Drug Research and Bioinformatics Group, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China; School of Pharmaceutical Sciences and Collaborative Innovation Center for Brain Science, Chongqing University, Chongqing 401331, China
| | - Guoxun Zheng
- Innovative Drug Research and Bioinformatics Group, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China; School of Pharmaceutical Sciences and Collaborative Innovation Center for Brain Science, Chongqing University, Chongqing 401331, China
| | - Weiwei Xue
- School of Pharmaceutical Sciences and Collaborative Innovation Center for Brain Science, Chongqing University, Chongqing 401331, China.
| | - Yuzong Chen
- Bioinformatics and Drug Design Group, Department of Pharmacy, National University of Singapore, Singapore 117543, Singapore
| | - Xiaojun Yao
- State Key Laboratory of Applied Organic Chemistry, Department of Chemistry, Lanzhou University, Lanzhou 730000, China
| | - Feng Zhu
- Innovative Drug Research and Bioinformatics Group, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China; School of Pharmaceutical Sciences and Collaborative Innovation Center for Brain Science, Chongqing University, Chongqing 401331, China.
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Positron Emission Tomography: Basic Principles, New Applications, and Studies Under Anesthesia. Int Anesthesiol Clin 2016; 54:109-28. [PMID: 26655512 DOI: 10.1097/aia.0000000000000090] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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8
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Stehouwer JS, Goodman MM. Fluorine-18 Radiolabeled PET Tracers for Imaging Monoamine Transporters: Dopamine, Serotonin, and Norepinephrine. PET Clin 2016; 4:101-28. [PMID: 20216936 DOI: 10.1016/j.cpet.2009.05.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
This review focuses on the development of fluorine-18 radiolabeled PET tracers for imaging the dopamine transporter (DAT), serotonin transporter (SERT), and norepinephrine transporter (NET). All successful DAT PET tracers reported to date are members of the 3β-phenyl tropane class and are synthesized from cocaine. Currently available carbon-11 SERT PET tracers come from both the diphenylsulfide and 3β-phenyl nortropane class, but so far only the nortropanes have found success with fluorine-18 derivatives. NET imaging has so far employed carbon-11 and fluorine-18 derivatives of reboxetine but due to defluorination of the fluorine-18 derivatives further research is still necessary.
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Adhikarla V, Zeng F, Votaw JR, Goodman MM, Nye JA. Compartmental modeling of [(11)C]MENET binding to the norepinephrine transporter in the healthy human brain. Nucl Med Biol 2016; 43:318-23. [PMID: 27150035 DOI: 10.1016/j.nucmedbio.2016.02.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 02/24/2016] [Accepted: 02/24/2016] [Indexed: 11/24/2022]
Abstract
INTRODUCTION Dysregulation of the noradrenergic system has been implicated in a number of neurological conditions such as Parkinson's and Alzheimer's. [(11)C]MENET is a novel PET radiotracer with high affinity and selectivity for the norepinephrine transporter. The applicability of different kinetic models on [(11)C]MENET PET image quantification in healthy population is evaluated. METHODS Six healthy volunteers (mean age: 54years) were recruited for the study, five of whom underwent arterial sampling for measurement of the input function. Ninety minute dynamic PET scans were obtained on a high resolution research tomograph with 15mCi of [(11)C]MENET injected at the scan start time. Regions of interest were delineated on the PET scan aided by the corresponding MRI image for anatomical guidance. Distribution volumes and their ratios (DVRs) with respect to the occipital reference tissue were calculated using the full arterial model (FAM), the simplified reference tissue model (SRTM) and the multilinear reference tissue model (MRTM2). RESULTS Among the FAMs, the single-tissue model was found to be statistically superior to the two-tissue model. [(11)C]MENET focal uptake was observed in the NET-rich regions of the brainstem and subcortical regions including the thalamus, locus cereleus and the raphe nuclei. Highest DVRs were observed in the locus cereleus (mean±standard deviation: 1.39±0.25) and red nucleus (1.35±0.25). DVRs of the thalamus were in good agreement between FAM (1.26±0.13), SRTM (1.23±0.15) and MRTM2 (1.21±0.14). Comparing the FAM to the SRTM and MRTM2, DVRs were underestimated in the thalamus by 3 and 4% on average, respectively. CONCLUSION The single-tissue compartmental model was sufficient in describing the [(11)C]MENET kinetics in the healthy human brain. SRTM and MRTM2 present themselves as attractive options for estimating NET DVR using an occipital reference region.
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Affiliation(s)
- Vikram Adhikarla
- Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, 30322, USA.
| | - Fanxing Zeng
- Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, 30322, USA
| | - John R Votaw
- Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, 30322, USA
| | - Mark M Goodman
- Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, 30322, USA
| | - Jonathon A Nye
- Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, 30322, USA.
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Chaturvedi S, Mishra AK. Small Molecule Radiopharmaceuticals - A Review of Current Approaches. Front Med (Lausanne) 2016; 3:5. [PMID: 26942181 PMCID: PMC4763069 DOI: 10.3389/fmed.2016.00005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 01/15/2016] [Indexed: 12/24/2022] Open
Abstract
Radiopharmaceuticals are an integral component of nuclear medicine and are widely applied in diagnostics and therapy. Though widely applied, the development of an “ideal” radiopharmaceutical can be challenging. Issues such as specificity, selectivity, sensitivity, and feasible chemistry challenge the design and synthesis of radiopharmaceuticals. Over time, strategies to address the issues have evolved by making use of new technological advances in the fields of biology and chemistry. This review presents the application of few advances in design and synthesis of radiopharmaceuticals. The topics covered are bivalent ligand approach and lipidization as part of design modifications for enhanced selectivity and sensitivity and novel synthetic strategies for optimized chemistry and radiolabeling of radiopharmaceuticals.
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Affiliation(s)
- Shubhra Chaturvedi
- Division of Cyclotron and Radiopharmaceutical Sciences, Institute of Nuclear Medicine and Allied Sciences, Defence Research and Development Organisation , Delhi , India
| | - Anil K Mishra
- Division of Cyclotron and Radiopharmaceutical Sciences, Institute of Nuclear Medicine and Allied Sciences, Defence Research and Development Organisation , Delhi , India
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11
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Rami-Mark C, Berroterán-Infante N, Philippe C, Foltin S, Vraka C, Hoepping A, Lanzenberger R, Hacker M, Mitterhauser M, Wadsak W. Radiosynthesis and first preclinical evaluation of the novel norepinephrine transporter pet-ligand [(11)C]ME@HAPTHI. EJNMMI Res 2015; 5:113. [PMID: 26061602 PMCID: PMC4467816 DOI: 10.1186/s13550-015-0113-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 05/22/2015] [Indexed: 11/16/2022] Open
Abstract
Background The norepinephrine transporter (NET) has been demonstrated to be relevant to a multitude of neurological, psychiatric and cardiovascular pathologies. Due to the wide range of possible applications for PET imaging of the NET together with the limitations of currently available radioligands, novel PET tracers for imaging of the cerebral NET with improved pharmacological and pharmacodynamic properties are needed. Methods The present study addresses the radiosynthesis and first preclinical evaluation of the novel NET PET tracer [11C]Me@HAPTHI by describing its affinity, selectivity, metabolic stability, plasma free fraction, blood–brain barrier (BBB) penetration and binding behaviour in in vitro autoradiography. Results [11C]Me@HAPTHI was prepared and displayed outstanding affinity and selectivity as well as excellent in vitro metabolic stability, and it is likely to penetrate the BBB. Moreover, selective NET binding in in vitro autoradiography was observed in human brain and rat heart tissue samples. Conclusions All preclinical results and radiosynthetic key-parameters indicate that the novel benzothiadiazole dioxide-based PET tracer [11C]Me@HAPTHI is a feasible and improved NET radioligand and might prospectively facilitate clinical NET imaging. Electronic supplementary material The online version of this article (doi:10.1186/s13550-015-0113-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Christina Rami-Mark
- Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, Vienna, Austria,
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Doi H. Pd-mediated rapid cross-couplings using [11C]methyl iodide: groundbreaking labeling methods in11C radiochemistry. J Labelled Comp Radiopharm 2015; 58:73-85. [DOI: 10.1002/jlcr.3253] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 11/28/2014] [Accepted: 11/28/2014] [Indexed: 11/11/2022]
Affiliation(s)
- Hisashi Doi
- Labeling Chemistry Team; Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies (CLST); 6-7-3 Minatojima-minamimachi, Chuo-ku Kobe Hyogo 650-0047 Japan
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13
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Suzuki M, Doi H, Koyama H, Zhang Z, Hosoya T, Onoe H, Watanabe Y. Pd0-Mediated Rapid Cross-Coupling Reactions, the RapidC-[11C]Methylations, Revolutionarily Advancing the Syntheses of Short-Lived PET Molecular Probes. CHEM REC 2014; 14:516-41. [DOI: 10.1002/tcr.201400002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Indexed: 11/12/2022]
Affiliation(s)
- Masaaki Suzuki
- National Center for Geriatrics and Gerontology; 35 Gengo Morioka-cho Obu-shi Aichi 474-8511 Japan
| | - Hisashi Doi
- Division of Bio-Function Dynamics Imaging; Riken Center for Life Science Technologies (CLST); 6-7-3 Minatojima-minamimachi Chuo-ku Kobe 650-0047 Japan
| | - Hiroko Koyama
- Division of Regeneration and Advanced Medical Science; Graduate School of Medicine; Gifu University; 1-1 Yanagido Gifu 501-1194 Japan
| | - Zhouen Zhang
- Division of Bio-Function Dynamics Imaging; Riken Center for Life Science Technologies (CLST); 6-7-3 Minatojima-minamimachi Chuo-ku Kobe 650-0047 Japan
| | - Takamitsu Hosoya
- Division of Regeneration and Advanced Medical Science; Graduate School of Medicine; Gifu University; 1-1 Yanagido Gifu 501-1194 Japan
| | - Hirotaka Onoe
- Division of Bio-Function Dynamics Imaging; Riken Center for Life Science Technologies (CLST); 6-7-3 Minatojima-minamimachi Chuo-ku Kobe 650-0047 Japan
| | - Yasuyoshi Watanabe
- Division of Bio-Function Dynamics Imaging; Riken Center for Life Science Technologies (CLST); 6-7-3 Minatojima-minamimachi Chuo-ku Kobe 650-0047 Japan
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14
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Zhou J, Yeung YY. Synthesis of Reboxetine Intermediate and Carnitine Acetyltransferase Inhibitor via NBS-Induced Electrophilic Multicomponent Reaction. J Org Chem 2014; 79:4644-9. [DOI: 10.1021/jo500609a] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Jing Zhou
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
| | - Ying-Yeung Yeung
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
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Chin BB, Kronauge JF, Femia FJ, Chen J, Maresca KP, Hillier S, Petry NA, James OG, Oldan JD, Armor T, Stubbs JB, Stabin MG, Babich JW. Phase-1 clinical trial results of high-specific-activity carrier-free 123I-iobenguane. J Nucl Med 2014; 55:765-71. [PMID: 24627436 DOI: 10.2967/jnumed.113.124057] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED A first-in-human phase 1 clinical study was performed on 12 healthy adults with a high-specific-activity carrier-free formulation of (123)I-iobenguane. Clinical data are presented on the behavior of this receptor-targeting imaging agent. METHODS Whole-body and thoracic planar and SPECT imaging were performed over 48 h for calculation of tissue radiation dosimetry and for evaluation of clinical safety and efficacy. RESULTS A reference clinical imaging database acquired over time for healthy men and women injected with high-specific-activity (123)I-iobenguane showed organ distribution and whole-body retention similar to those of conventional (123)I-iobenguane. The heart-to-mediastinum ratios for the high-specific-activity formulation were statistically higher than for conventional formulations, and the predicted radiation dosimetry estimations for some organs varied significantly from those based on animal distributions. CONCLUSION Human normal-organ kinetics, radiation dosimetry, clinical safety, and imaging efficacy provide compelling evidence for the use of high-specific-activity (123)I-iobenguane.
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Affiliation(s)
- Bennett B Chin
- Department of Radiology, Duke University Medical Center, Durham, North Carolina
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16
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Zeng F, Voll RJ, Crowe RJ, Waldrep MS, Dolph KB, Goodman MM. An improved synthesis of [11C]MENET via Suzuki coupling with [11C]methyl iodide. J Labelled Comp Radiopharm 2013; 56:307-9. [PMID: 24285377 DOI: 10.1002/jlcr.3047] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Revised: 03/08/2013] [Accepted: 03/13/2013] [Indexed: 11/10/2022]
Abstract
[(11) C]MENET, a promising norepinephrine transporter imaging agent, was prepared by Suzuki cross coupling of 1 mg N-t-Boc pinacolborate precursor with [(11) C]CH3 I in DMF using palladium complex generated in situ from Pd2 (dba)3 and (o-CH3 C6 H4 )3 P together with K2 CO3 as the co-catalyst, followed by deprotection with trifluoroacetic acid. This improved radiolabeling method provided [(11) C]MENET in high radiochemical yield at end of synthesis (EOS, 51 ± 3%, decay-corrected from end of (11) CH3 I synthesis, n = 6), moderate specific activity (1.5-1.9 Ci/µmol at EOS), and high radiochemical (>98%) and chemical purity (>98%) in a synthesis time of 60 ± 5 min from the end of bombardment.
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Affiliation(s)
- Fanxing Zeng
- Department of Radiology and Imaging Sciences, Emory University, 1841 Clifton Road NE, Atlanta, GA, 30329, USA
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Alstrup AKO, Smith DF. Anaesthesia for positron emission tomography scanning of animal brains. Lab Anim 2013; 47:12-8. [PMID: 23349451 DOI: 10.1258/la.2012.011173] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Positron emission tomography (PET) provides a means of studying physiological and pharmacological processes as they occur in the living brain. Mice, rats, dogs, cats, pigs and non-human primates are often used in studies using PET. They are commonly anaesthetized with ketamine, propofol or isoflurane in order to prevent them from moving during the imaging procedure. The use of anaesthesia in PET studies suffers, however, from the drawback of possibly altering central neuromolecular mechanisms. As a result, PET findings obtained in anaesthetized animals may fail to correctly represent normal properties of the awake brain. Here, we review findings of PET studies carried out either in both awake and anaesthetized animals or in animals given at least two different anaesthetics. Such studies provide a means of estimating the extent to which anaesthesia affects the outcome of PET neuroimaging in animals. While no final conclusion can be drawn concerning the 'best' general anaesthetic for PET neuroimaging in laboratory animals, such studies provide findings that can enhance an understanding of neurobiological mechanisms in the living brain.
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Affiliation(s)
- Aage Kristian Olsen Alstrup
- Department of Nuclear Medicine and PET Centre, Aarhus University Hospitals, Nørrebrogade 44, 10G, DK-8000 Aarhus C, Denmark.
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Tavares AADS, Barret O, Batis J, Alagille D, Koren A, Papin C, Kudej G, Nice K, Kordower JH, Cosgrove KP, Kloczynski T, Brenner E, Seibyl J, Tamagnan G. Kinetic modeling and occupancy measures of the norepinephrine transporters in baboons using single photon emission computed tomography with (123)I-INER. Synapse 2012; 67:30-41. [PMID: 23042643 DOI: 10.1002/syn.21613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Accepted: 10/01/2012] [Indexed: 11/11/2022]
Abstract
This study aims to investigate the pharmacokinetics of a recently developed radiotracer for imaging of the norepinephrine transporter (NET) in baboon brain, (123)I-INER, using single photon emission computed tomography (SPECT). In addition, it also aims to determine NET occupancy by atomoxetine and reboxetine, two selective norepinephrine reuptake inhibitors, using (123)I-INER in baboons. Baseline and preblocking studies with a high dose of atomoxetine (0.85 mg/kg) were conducted in three baboons using SPECT with (123)I-INER administered as a bolus. Kinetic modeling analysis was investigated for different models, namely invasive and reference tissue models. Bolus plus constant infusion experiments with displacement at equilibrium using six different doses of atomoxetine (0.03-0.85 mg/kg) and four different doses of reboxetine (0.5-3.0 mg/kg) were carried out in several baboons to obtain occupancy measurements as a function of dose for the two NET selective drugs. Results showed that reference tissue models can be used to estimate binding potential values and occupancy measures of (123)I-INER in different brain regions. In addition, the apparent volume of distribution was estimated by dividing concentration in tissue by the concentration in blood at 3 hours postinjection. After administration of atomoxetine or reboxetine, a dose-dependent occupancy was observed in brain regions known to contain high densities of NET. In conclusion, pharmacokinetic properties of (123) I-INER were successfully described, and obtained results may be used to simplify future data acquisition and image processing. Dose-dependent NET occupancy for two selective norepinephrine reuptake inhibitors was successfully measured in vivo in baboon brain using SPECT and (123) I-INER.
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Tavares AAS, Jobson NK, Dewar D, Sutherland A, Pimlott SL, Batis J, Barret O, Seibyl J, Tamagnan G. Iodine-123 labeled reboxetine analogues for imaging of noradrenaline transporter in brain using single photon emission computed tomography. Synapse 2012; 66:923-30. [PMID: 22807144 DOI: 10.1002/syn.21585] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 06/25/2012] [Accepted: 07/08/2012] [Indexed: 11/07/2022]
Abstract
Preliminary investigation of the radioiodinated (S,S)-reboxetine analogue, (123) I-INER, in baboons showed this tracer to have promise for imaging the noradrenaline transporter (NAT) using single photon emission computed tomography (SPECT). More recently, the radioiodinated (R,S)-stereoisomer of (123) I-INER, (123) I-NKJ64, has been synthesized and preliminary evaluation in rats has been reported. This article reports the brain distribution and pharmacokinetic properties of (123) I-NKJ64 in baboons and compares results with (123) I-INER data in the same species. SPECT studies were conducted in two ovariectomized adult female baboons using two different protocols: (1) bolus of (123) I-INER or (123) I-NKJ64; and (2) bolus plus constant infusion of (123) I-NKJ64 with reboxetine (2.0 mg/kg) administration at equilibrium. Following bolus injection, both radiotracers rapidly and avidly entered the baboon brain. The regional brain accumulation of (123) I-NKJ64 did not match the known distribution of NAT in baboon brain, contrasting with previous results obtained in rats. Conversely, the regional distribution of (123) I-INER was consistent with known distribution of NAT in baboon brain. No displacement of (123) I-NKJ64 was observed following administration of reboxetine. This contrasts with previous data obtained for (123) I-INER, where 60% of specific binding was displaced by a lower dose of reboxetine. These data suggest that (123) I-NKJ64 may lack affinity and selectivity for NAT in baboon brain and (123) I-INER is the most promising iodinated reboxetine analogue developed to date for in vivo imaging of NAT in brain using SPECT. This study highlights the importance of species differences during radiotracer development and the stereochemical configuration of analogues of reboxetine in vivo.
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Affiliation(s)
- Adriana Alexandre S Tavares
- Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, G12 8QQ, United Kingdom.
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Fluorinated molecules in the diagnosis and treatment of neurodegenerative diseases. Future Med Chem 2011; 1:821-33. [PMID: 21426082 DOI: 10.4155/fmc.09.85] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The use of fluorinated molecules as drugs and imaging agents for CNS disorders has been studied extensively over the years. Incorporating a fluorine atom into the structure of a drug changes its physiochemical properties and can thereby lead to much more desirable pharmacokinetic and pharmacodynamic properties. This change can help to facilitate blood-brain barrier permeability, which is a critical matter for drugs intended for CNS activities. Fluorine incorporation into structures of drugs for the treatment of neurodegenerative diseases has been an attractive field for drug discovery. Such incorporation can greatly influence the physicochemical properties, metabolic stability and receptor binding affinity of the resulting molecule. Some studies have shown that when a proton was substituted with fluorine, the binding or inhibitory potency was greatly increased. The fluorine-18 isotope, (18)F, is utilized in detection and diagnosis of neurodegenerative diseases, whereas (19)F compounds are used in the treatment of these diseases and in MRI. (18)F is widely used in PET imaging because it offers the advantage of a longer half-life compared with other radionuclides. It is used for imaging various receptors and transporters that have been linked to neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease and multiple system atrophy. Fluorine plays an important role in the diagnosis and treatment of many CNS diseases, including neurodegenerative disorders. The use of fluorine in the diagnosis and treatment of neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, will be discussed in this review.
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Pascali G, Nannavecchia G, Pitzianti S, Salvadori PA. Dose-on-demand of diverse 18F-fluorocholine derivatives through a two-step microfluidic approach. Nucl Med Biol 2011; 38:637-44. [DOI: 10.1016/j.nucmedbio.2011.01.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2010] [Revised: 01/22/2011] [Accepted: 01/23/2011] [Indexed: 10/18/2022]
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Tavares AAS, Jobson NK, Dewar D, Sutherland A, Pimlott SL. Development of the radiosynthesis of high-specific-activity 123I-NKJ64. Nucl Med Biol 2011; 38:493-500. [PMID: 21531286 DOI: 10.1016/j.nucmedbio.2010.11.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 10/15/2010] [Accepted: 11/04/2010] [Indexed: 11/28/2022]
Abstract
INTRODUCTION (123)I-NKJ64, a reboxetine analogue, is currently under development as a potential novel single photon emission computed tomography radiotracer for imaging the noradrenaline transporter in brain. This study describes the development of the radiosynthesis of (123)I-NKJ64, highlighting the advantages and disadvantages, pitfalls and solutions encountered while developing the final radiolabelling methodology. METHODS The synthesis of (123)I-NKJ64 was evaluated using an electrophilic iododestannylation method, where a Boc-protected trimethylstannyl precursor was radioiodinated using peracetic acid as an oxidant and deprotection was investigated using either trifluoroacetic acid (TFA) or 2 M hydrochloric acid (HCl). RESULTS Radioiodination of the Boc-protected trimethylstannyl precursor was achieved with an incorporation yield of 92±6%. Deprotection with 2 M HCl produced (123)I-NKJ64 with the highest radiochemical yield of 98.05±1.63% compared with 83.95±13.24% with TFA. However, the specific activity of the obtained (123)I-NKJ64 was lower when measured after using 2 M HCl (0.15±0.23 Ci/μmol) as the deprotecting agent in comparison to TFA (1.76±0.60 Ci/μmol). Further investigation of the 2 M HCl methodology found a by-product, identified as the deprotected proto-destannylated precursor, which co-eluted with (123)I-NKJ64 during the high-performance liquid chromatography (HPLC) purification. CONCLUSIONS The radiosynthesis of (123)I-NKJ64 was achieved with good isolated radiochemical yield of 68% and a high specific activity of 1.8 Ci/μmol. TFA was found to be the most suitable deprotecting agent, since 2 M HCl generated a by-product that could not be fully separated from (123)I-NKJ64 using the HPLC methodology investigated. This study highlights the importance of HPLC purification and accurate measurement of specific activity while developing new radiosynthesis methodologies.
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Affiliation(s)
- Adriana Alexandre S Tavares
- Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, G12 8QQ Glasgow, UK.
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Tavares AAS, Jobson NK, Dewar D, Sutherland A, Pimlott SL. ¹²³I-NKJ64: a novel single photon emission computed tomography radiotracer for imaging the noradrenaline transporter in brain. Synapse 2010; 65:658-67. [PMID: 21157929 DOI: 10.1002/syn.20895] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Accepted: 11/17/2010] [Indexed: 11/11/2022]
Abstract
Dysregulation of noradrenergic function has been implicated in a variety of psychiatric and neurodegenerative disorders, including depression and Alzheimer's disease. The noradrenaline transporter (NAT) is a major target for antidepressant drugs, including reboxetine, a selective noradrenaline reuptake inhibitor. Therefore, the development of a radiotracer for imaging of the NAT is desirable. In this study, NKJ64, a novel iodinated analog of reboxetine, was radiolabeled and evaluated as a potential single photon emission computerized tomography (SPECT) radiotracer for imaging the NAT in brain. Biological evaluation of the novel radiotracer, ¹²³/¹²⁵I-NKJ64, was carried out in rats using: in vitro ligand binding assays; in vitro and ex vivo autoradiography; in vivo biodistribution studies and ex vivo pharmacological blocking studies. ¹²⁵I-NKJ64 displayed saturable binding with high affinity for NAT in cortical homogenates (K(D) = 4.82 ± 0.87 nM, mean ± SEM, n = 3). In vitro and ex vivo autoradiography showed the regional distribution of ¹²³I-NKJ64 binding to be consistent with the known density of NAT in brain. Following i.v. injection there was rapid uptake of ¹²³I-NKJ64 in brain, with maximum uptake of 2.93% ± 0.14% (mean ± SEM, n = 3) of the injected dose. The specific to nonspecific ratio (locus coeruleus:caudate putamen) of ¹²³I-NKJ64 uptake measured by ex vivo autoradiography was 2.8 at 30 min post i.v. injection. The prior administration of reboxetine significantly reduced the accumulation of ¹²³I-NKJ64 in the locus coeruleus (>50% blocking). The data indicate that further evaluation of ¹²³I-NKJ64 in nonhuman primates is warranted in order to determine its utility as a SPECT radiotracer for imaging of NAT in brain.
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Affiliation(s)
- Adriana Alexandre S Tavares
- Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, G128QQ Glasgow, Scotland, United Kingdom.
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Shobo M, Kondo Y, Yamada H, Mihara T, Yamamoto N, Katsuoka M, Harada K, Ni K, Matsuoka N. Norzotepine, a Major Metabolite of Zotepine, Exerts Atypical Antipsychotic-Like and Antidepressant-Like Actions through Its Potent Inhibition of Norepinephrine Reuptake. J Pharmacol Exp Ther 2010; 333:772-81. [DOI: 10.1124/jpet.110.166264] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Suzuki M, Doi H. Pd0-Mediated Rapid C-[11C]Methylations and C-[18F]Fluoromethylations: Revolutionary New Methodologies for the Synthesis of Short-Lived PET Molecular Probes. J SYN ORG CHEM JPN 2010. [DOI: 10.5059/yukigoseikyokaishi.68.1195] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Nguyen VL, Pichika R, Bhakta PH, Kant R, Mukherjee J. (R)-N-Methyl-3-(3'-[F]fluoropropyl)phenoxy)-3-phenylpropanamine (F-MFP3) as a potential PET imaging agent for norepinephrine transporter. J Labelled Comp Radiopharm 2010; 53:172-177. [PMID: 20495670 DOI: 10.1002/jlcr.1744] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A decline of norepinephrine transporter (NET) level is associated with several psychiatric and neurological disorders. Therefore positron emission tomography (PET) imaging agents are greatly desired to study the NET pathway. We have developed a C-fluoropropyl analog of nisoxetine: (R)-N-methyl-3-(3'-[(18)F]fluoropropyl)phenoxy)-3-phenylpropanamine ((18)F-MFP3) as a new potential PET radiotracer for NET with the advantage of the longer half-life of fluorine-18 (110 min compared with carbon-11 (20 min). Synthesis of (R)-N-methyl-3-(3'-fluoropropyl)phenoxy)-3-phenylpropanamine (MFP3) was achieved in five steps starting from (S)-N-methyl-3-ol-3-phenylpropanamine in approx. 3-5% overall yields. In vitro binding affinity of nisoxetine and MFP3 in rat brain homogenates labeled with (3)H-nisoxetine gave Ki values of 8.02 nM and 23 nM, respectively. For radiosynthesis of (18)F-MFP3, fluorine-18 was incorporated into a tosylate precursor, followed by the deprotection of the N-BOC-protected amine group with a 15% decay corrected yield in 2.5 h. Reverse-phase chromatographic purification provided (18)F-MFP3 in specific activities of >2000 Ci/mmol. Fluorine-18 labeled (18)F-MFP3 has been produced in modest radiochemical yields and in high specific activities. Evaluation of (18)F-MFP3 in animal imaging studies is in progress in order to validate this new fluorine-18 radiotracer for PET imaging of NET.
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Affiliation(s)
- Vivien L Nguyen
- Department of Psychiatry and Human Behavior, University of California, Irvine, CA, USA
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