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Zechner M, Castro Jaramillo CA, Zubler NS, Taddio MF, Mu L, Altmann KH, Krämer SD. In Vitro and In Vivo Evaluation of ABCG2 (BCRP) Inhibitors Derived from Ko143. J Med Chem 2023; 66:6782-6797. [PMID: 37154765 DOI: 10.1021/acs.jmedchem.3c00168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Breast cancer resistance protein (BCRP, ABCG2) is an efflux transporter that plays a crucial role in multidrug resistance to antineoplastic drugs. Ko143, an analogue of the natural product fumitremorgin C, is a potent inhibitor of ABCG2 but is rapidly hydrolyzed to an inactive metabolite in vivo. To identify ABCG2 inhibitors with improved metabolic stability, we have assessed a series of Ko143 analogues for their ability to inhibit ABCG2-mediated transport in ABCG2-transduced MDCK II cells and determined the stability of the most potent compounds in liver microsomes. The most promising analogues were evaluated in vivo by positron emission tomography. In vitro, three of the tested analogues were potent ABCG2 inhibitors and stable in microsomes. In vivo, they increased the distribution of the ABCG2/ABCB1 substrate [11C]tariquidar to the brain both in wild-type (with Abcb1a/b transport blocked by tariquidar) and Abcb1a/b(-/-) mice. One analogue was more potent than Ko143 in both animal models.
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Affiliation(s)
- Melanie Zechner
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Claudia A Castro Jaramillo
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Nadine S Zubler
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Marco F Taddio
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Linjing Mu
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
- Department of Nuclear Medicine, University Hospital Zurich, CH-8091 Zurich, Switzerland
| | - Karl-Heinz Altmann
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Stefanie D Krämer
- Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
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Jewett EM, Någren K, Mock BH, Watkins GL. 30 years of [ 11C]methyl triflate. Appl Radiat Isot 2023; 197:110812. [PMID: 37087867 DOI: 10.1016/j.apradiso.2023.110812] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 03/21/2023] [Accepted: 04/09/2023] [Indexed: 04/25/2023]
Abstract
Some scientific discoveries are well known only to a core group of researchers working on technical subjects. Nevertheless, they open new research directions, allow existing knowledge to be viewed in entirely new and useful ways, or provide a way to make something that was hard or impossible to make before. Carbon-11 methyl triflate ([11C]MeOTf) is one such advance, facilitating the synthesis of many carbon-11 radio tracers and broadening the range of applications of carbon-11 radiochemistry. The year 2022 marked the 30th anniversary of the original paper in Applied Radiation and Isotopes introducing a simple synthesis of [11C]MeOTf from carbon-11 methyl iodide ([11C]MeI) and it also marked the end of the fruitful career and life of the researcher who developed it, Douglas Jewett. It seems fitting to say a few words on how it came to be and how it has helped advance carbon-11 radiochemistry.
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Affiliation(s)
| | - Kjell Någren
- Östre Stationsvej, 36 1TH, 5000, Odense, Denmark
| | - Bruce H Mock
- Indiana University School of Medicine, Indianapolis, IN, 46202, USA
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Production of [ 11C]Carbon Labelled Flumazenil and L-Deprenyl Using the iMiDEV™ Automated Microfluidic Radiosynthesizer. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27248843. [PMID: 36557975 PMCID: PMC9788284 DOI: 10.3390/molecules27248843] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 12/08/2022] [Accepted: 12/09/2022] [Indexed: 12/14/2022]
Abstract
In the last decade, microfluidic techniques have been explored in radiochemistry, and some of them have been implemented in preclinical production. However, these are not suitable and reliable for preparing different types of radiotracers or dose-on-demand production. A fully automated iMiDEV™ microfluidic radiosynthesizer has been introduced and this study is aimed at using of the iMiDEV™ radiosynthesizer with a microfluidic cassette to produce [11C]flumazenil and [11C]L-deprenyl. These two are known PET radioligands for benzodiazepine receptors and monoamine oxidase-B (MAO-B), respectively. Methods were successfully developed to produce [11C]flumazenil and [11C]L-deprenyl using [11C]methyl iodide and [11C]methyl triflate, respectively. The final products 1644 ± 504 MBq (n = 7) and 533 ± 20 MBq (n = 3) of [11C]flumazenil and [11C]L-deprenyl were produced with radiochemical purities were over 98% and the molar activity for [11C]flumazenil and [11C]L-deprenyl was 1912 ± 552 GBq/µmol, and 1463 ± 439 GBq/µmol, respectively, at the end of synthesis. All the QC tests complied with the European Pharmacopeia. Different parameters, such as solvents, bases, methylating agents, precursor concentration, and different batches of cassettes, were explored to increase the radiochemical yield. Synthesis methods were developed using 3-5 times less precursor than conventional methods. The fully automated iMiDEV™ microfluidic radiosynthesizer was successfully applied to prepare [11C]flumazenil and [11C]L-deprenyl.
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Nakamura T, Hiraoka K, Harada R, Matsuzawa T, Ishikawa Y, Funaki Y, Yoshikawa T, Tashiro M, Yanai K, Okamura N. Brain histamine H 1 receptor occupancy after oral administration of desloratadine and loratadine. Pharmacol Res Perspect 2019; 7:e00499. [PMID: 31338198 PMCID: PMC6624455 DOI: 10.1002/prp2.499] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 05/30/2019] [Accepted: 06/10/2019] [Indexed: 01/27/2023] Open
Abstract
Some histamine H1 receptor (H1R) antagonists induce adverse sedative reactions caused by blockade of histamine transmission in the brain. Desloratadine is a second-generation antihistamine for treatment of allergic disorders. Its binding to brain H1Rs, which is the basis of sedative property of antihistamines, has not been examined previously in the human brain by positron emission tomography (PET). We examined brain H1R binding potential ratio (BPR), H1R occupancy (H1RO), and subjective sleepiness after oral desloratadine administration in comparison to loratadine. Eight healthy male volunteers underwent PET imaging with [11C]-doxepin, a PET tracer for H1Rs, after a single oral administration of desloratadine (5 mg), loratadine (10 mg), or placebo in a double-blind crossover study. BPR and H1RO in the cerebral cortex were calculated, and plasma concentrations of loratadine and desloratadine were measured. Subjective sleepiness was quantified by the Line Analogue Rating Scale (LARS) and the Stanford Sleepiness Scale (SSS). BPR was significantly lower after loratadine administration than after placebo (0.504 ± 0.074 vs 0.584 ± 0.059 [mean ± SD], P < 0.05), but BPR after desloratadine administration was not significantly different from BPR after placebo (0.546 ± 0.084 vs 0.584 ± 0.059, P = 0.250). The plasma concentration of loratadine was negatively correlated with BPR in subjects receiving loratadine, but that of desloratadine was not correlated with BPR. Brain H1ROs after desloratadine and loratadine administration were 6.47 ± 10.5% and 13.8 ± 7.00%, respectively (P = 0.103). Subjective sleepiness did not significantly differ among subjects receiving the two antihistamines and placebo. At therapeutic doses, desloratadine did not bind significantly to brain H1Rs and did not induce any significant sedation.
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Affiliation(s)
- Tadaho Nakamura
- Division of Pharmacology, Faculty of MedicineTohoku Medical and Pharmaceutical UniversitySendaiJapan
- Department of PharmacologyTohoku University Graduate School of MedicineSendaiJapan
| | - Kotaro Hiraoka
- Cyclotron and Radioisotope CenterTohoku UniversitySendaiJapan
| | - Ryuichi Harada
- Department of PharmacologyTohoku University Graduate School of MedicineSendaiJapan
| | - Takuro Matsuzawa
- Department of PharmacologyTohoku University Graduate School of MedicineSendaiJapan
| | - Yoichi Ishikawa
- Cyclotron and Radioisotope CenterTohoku UniversitySendaiJapan
| | | | - Takeo Yoshikawa
- Department of PharmacologyTohoku University Graduate School of MedicineSendaiJapan
| | - Manabu Tashiro
- Cyclotron and Radioisotope CenterTohoku UniversitySendaiJapan
| | - Kazuhiko Yanai
- Department of PharmacologyTohoku University Graduate School of MedicineSendaiJapan
| | - Nobuyuki Okamura
- Division of Pharmacology, Faculty of MedicineTohoku Medical and Pharmaceutical UniversitySendaiJapan
- Department of PharmacologyTohoku University Graduate School of MedicineSendaiJapan
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5
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Abstract
The application of chemical kinetics is one of the most powerful and versatile tools for investigating reaction mechanisms in complex mixtures. Kinetic studies are commonplace in traditional synthetic chemistry but are seldom used in radiopharmaceutical sciences. When deriving standard reaction rate laws, the focus is normally placed on calculating the chemical concentration of different species over time. In radiopharmaceutical synthesis, the desired product is one of the radioactive components of the mixture. Reaction conditions are optimised to obtain the radioactive product in the highest activity yield. When short-lived radionuclides are used, radioactive decay during the reaction window means that the maximum activity yield does not necessarily coincide with the chemical or decay-corrected radiochemical yields. To account for this difference in the kinetic models, it is shown how standard integrated rate laws can be modified to incorporate the contribution from radioactive decay. An example is then presented to show how radiochemical kinetics can be used to model complex systems, like [18 F]FDG radiosynthesis, that involve parallel or competing reactions at the different chemical scales of the radionuclide and substrate. Increased knowledge of reaction rates, and a more wide-spread application of radiochemical kinetics, can facilitate the development of new radiolabelling reactions. Accurate identification of maximum activity yields using kinetic models also has the potential to improve the optimisation and radiochemical efficiency of all current and future radiopharmaceutical syntheses.
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Affiliation(s)
- Jason P Holland
- University of Zurich, Department of Chemistry, Winterthurerstrasse 190, 8057, Zurich, Switzerland
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Downey J, Bongarzone S, Hader S, Gee AD. In-loop flow [ 11 C]CO 2 fixation and radiosynthesis of N,N'-[ 11 C]dibenzylurea. J Labelled Comp Radiopharm 2018; 61:263-271. [PMID: 28977686 PMCID: PMC5900881 DOI: 10.1002/jlcr.3568] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 08/22/2017] [Accepted: 09/24/2017] [Indexed: 11/11/2022]
Abstract
Cyclotron-produced carbon-11 is a highly valuable radionuclide for the production of positron emission tomography (PET) radiotracers. It is typically produced as relatively unreactive carbon-11 carbon dioxide ([11 C]CO2 ), which is most commonly converted into a more reactive precursor for synthesis of PET radiotracers. The development of [11 C]CO2 fixation methods has more recently enabled the direct radiolabelling of a diverse array of structures directly from [11 C]CO2 , and the advantages afforded by the use of a loop-based system used in 11 C-methylation and 11 C-carboxylation reactions inspired us to apply the [11 C]CO2 fixation "in-loop." In this work, we developed and investigated a new ethylene tetrafluoroethylene (ETFE) loop-based [11 C]CO2 fixation method, enabling the fast and efficient, direct-from-cyclotron, in-loop trapping of [11 C]CO2 using mixed DBU/amine solutions. An optimised protocol was integrated into a proof-of-concept in-loop flow radiosynthesis of N,N'-[11 C]dibenzylurea. This reaction exhibited an average 78% trapping efficiency and a crude radiochemical purity of 83% (determined by radio-HPLC), giving an overall nonisolated radiochemical yield of 72% (decay-corrected) within just 3 minutes from end of bombardment. This proof-of-concept reaction has demonstrated that efficient [11 C]CO2 fixation can be achieved in a low-volume (150 μL) ETFE loop and that this can be easily integrated into a rapid in-loop flow radiosynthesis of carbon-11-labelled products. This new in-loop methodology will allow fast radiolabelling reactions to be performed using cheap/disposable ETFE tubing setup (ideal for good manufacturing practice production) thereby contributing to the widespread usage of [11 C]CO2 trapping/fixation reactions for the production of PET radiotracers.
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Affiliation(s)
- Joseph Downey
- Division of Imaging Sciences and Biomedical EngineeringKing's College LondonLondonUK
| | - Salvatore Bongarzone
- Division of Imaging Sciences and Biomedical EngineeringKing's College LondonLondonUK
| | - Stefan Hader
- Division of Imaging Sciences and Biomedical EngineeringKing's College LondonLondonUK
| | - Antony D. Gee
- Division of Imaging Sciences and Biomedical EngineeringKing's College LondonLondonUK
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Schuller M, Höfner G, Wanner KT. Simultaneous Multiple MS Binding Assays Addressing D 1 and D 2 Dopamine Receptors. ChemMedChem 2017; 12:1585-1594. [PMID: 28776962 DOI: 10.1002/cmdc.201700369] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Revised: 07/27/2017] [Indexed: 01/08/2023]
Abstract
MS Binding Assays are a label-free alternative to radioligand binding assays. They provide basically the same capabilities as the latter, but use a non-labeled reporter ligand instead of a radioligand. In contrast to radioligand binding assays, MS Binding Assays offer-owing to the selectivity of mass spectrometric detection-the opportunity to monitor the binding of different reporter ligands at different targets simultaneously. The present study shows a proof of concept for this strategy as exemplified for MS Binding Assays selectively addressing D1 and D2 dopamine receptors in a single binding experiment. A highly sensitive, rapid and robust LC-ESI-MS/MS quantification method capable of quantifying both SCH23390 and raclopride, selectively addressing D1 and D2 receptors, respectively, was established and validated for this purpose. Based thereon, simultaneous saturation and competition experiments with SCH23390 and raclopride in the presence of both D1 and D2 receptors were performed and analyzed by LC-MS/MS within a single chromatographic cycle. The present study thus demonstrates the feasibility of this strategy and the high versatility of MS Binding Assays that appears to surpass that common for conventional radioligand binding assays.
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Affiliation(s)
- Marion Schuller
- Structural Genomics Consortium and Target Discovery Institute, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, OX3 7FZ, UK
| | - Georg Höfner
- Department of Pharmacy, Center of Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, Munich, Germany
| | - Klaus T Wanner
- Department of Pharmacy, Center of Drug Research, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, Munich, Germany
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8
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Hiraoka K, Tashiro M, Grobosch T, Maurer M, Oda K, Toyohara J, Ishii K, Ishiwata K, Yanai K. Brain histamine H1 receptor occupancy measured by PET after oral administration of levocetirizine, a non-sedating antihistamine. Expert Opin Drug Saf 2014; 14:199-206. [PMID: 25466429 DOI: 10.1517/14740338.2015.989831] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVE Histamine H1 receptor (H1R) antagonists often have sedative side effects, which are caused by the blockade of the neural transmission of the histaminergic neurons. We examined the brain H1R occupancy (H1RO) and the subjective sleepiness of levocetirizine, a new second-generation antihistamine, comparing fexofenadine, another non-sedating antihistamine, as a negative active control. METHODS Eight healthy volunteers underwent positron emission tomography (PET) imaging with [(11)C]doxepin, a PET tracer that specifically binds to H1Rs, after a single oral administration of levocetirizine (5 mg), fexofenadine (60 mg) or placebo in a double-blind crossover study. Binding potential ratios and H1ROs in the cerebral cortices regions were calculated using placebo. Subjective sleepiness was assessed with the Line Analogue Rating Scale and the Stanford Sleepiness Scale. RESULTS There was no significant difference between the mean brain H1RO after levocetirizine administration (8.1%; 95% CI: -9.8 to 26.0%) and fexofenadine administration (-8.0%; 95% CI: -26.7 to 10.6%). Similarly, subjective sleepiness was not significantly different between the two antihistamines and placebo. Neither subjective sleepiness nor plasma concentrations was significantly correlated with the brain H1RO of the two antihistamines. CONCLUSION At therapeutic dose, levocetirizine does not bind significantly to the brain H1Rs and does not induce significant sedation.
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Affiliation(s)
- Kotaro Hiraoka
- Tohoku University, Cyclotron and Radioisotope Center, Division of Cyclotron Nuclear Medicine , 6-3, Aoba, Aramaki, Aoba-ku, Sendai, 980-8578 , Japan
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Sai KKS, Fan J, Tu Z, Zerkel P, Mach RH, Kharasch ED. Automated radiochemical synthesis and biodistribution of [¹¹C]l-α-acetylmethadol ([¹¹C]LAAM). Appl Radiat Isot 2014; 91:135-40. [PMID: 24935116 DOI: 10.1016/j.apradiso.2014.05.019] [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: 12/07/2013] [Revised: 03/18/2014] [Accepted: 05/20/2014] [Indexed: 12/25/2022]
Abstract
Long-acting opioid agonists methadone and l-α-acetylmethadol (LAAM) prevent withdrawal in opioid-dependent persons. Attempts to synthesize [(11)C]-methadone for PET evaluation of brain disposition were unsuccessful. Owing, however, to structural and pharmacologic similarities, we aimed to develop [(11)C]LAAM as a PET ligand to probe the brain exposure of long-lasting opioids in humans. This manuscript describes [(11)C]LAAM synthesis and its biodistribution in mice. The radiochemical synthetic strategy afforded high radiochemical yield, purity and specific activity, thereby making the synthesis adaptable to automated modules.
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Affiliation(s)
- Kiran Kumar Solingapuram Sai
- Department of Radiology, Washington University in St. Louis, St. Louis, MO 63110, USA; Department of Radiology, Wake Forest School of Medicine, 1 Medical Center Blvd, Winston Salem, NC 27157, USA
| | - Jinda Fan
- Department of Radiology, Washington University in St. Louis, St. Louis, MO 63110, USA; Department of Radiology, University of Alabama School of Medicine, 720 2nd Ave S, Birmingham, AL 35294, USA
| | - Zhude Tu
- Department of Radiology, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Patrick Zerkel
- Department of Radiology, Washington University in St. Louis, St. Louis, MO 63110, USA
| | - Robert H Mach
- Department of Radiology, Washington University in St. Louis, St. Louis, MO 63110, USA; Department of Radiology, Perelman School of Medicine, University of Pennsylvania, 231 S. 34th Street, Philadelphia, PA 19104, USA
| | - Evan D Kharasch
- Department of Anesthesiology, and Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis, 660 S. Euclid Ave., Campus Box 8054, St. Louis, MO 63110, USA.
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Histamine H₁ receptor occupancy by the new-generation antidepressants fluvoxamine and mirtazapine: a positron emission tomography study in healthy volunteers. Psychopharmacology (Berl) 2013; 230:227-34. [PMID: 23728612 DOI: 10.1007/s00213-013-3146-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 05/08/2013] [Indexed: 10/26/2022]
Abstract
RATIONALE Histamine H₁ antagonists have hypnotic, appetite-promoting, and sedative effects. The affinities of various antidepressants for histamine receptors have only been partially determined in vitro and animal study. Positron emission tomography (PET) can clarify the in vivo dynamics of antidepressants at histamine receptors. OBJECTIVES We performed human PET imaging with [¹¹C]doxepin, a selective PET ligand of the histamine H₁ receptor (H₁R), to study the in vivo affinities of fluvoxamine and mirtazapine for the H₁R. METHODS The subjects were five male healthy Japanese volunteers. We performed cross-randomized PET imaging after single oral administration of fluvoxamine (25mg), mirtazapine (15 mg), or placebo. PET data were analyzed by region-of-interest and voxel-by-voxel analysis. We concurrently measured plasma drug concentrations, using liquid chromatography/tandem mass spectrometry and subjective sleepiness. RESULTS The binding potential ratio of mirtazapine in brain cortex was significantly lower than that of fluvoxamine or placebo. Fluvoxamine did not occupy the H₁R, whereas H₁R occupancy (H₁RO) of mirtazapine reached 80-90 % in the cerebral neocortex. In the voxel-by-voxel analysis, the binding potential of mirtazapine was significantly lower than placebo in the dorsolateral prefrontal cortex, lateral temporal cortex, anterior cingulate gyrus, and posterior cingulate gyrus. The H₁RO of mirtazapine depended on the plasma drug concentration (AUC(0-180 min)) and was related to subjective sleepiness. CONCLUSIONS Our results demonstrate a low affinity of fluvoxamine and a very high affinity of mirtazapine for the human brain H₁R in vivo. This study provides a basis for investigating the efficacy of new-generation antidepressants in central histamine systems.
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Patt M, Solbach C, Habermann B, Schildan A, Baur B, Sabri O. Influence of additives to the formulation of n.c.a. [¹¹C]PiB on sterile filter performance. Appl Radiat Isot 2013; 82:289-92. [PMID: 24128611 DOI: 10.1016/j.apradiso.2013.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/30/2013] [Accepted: 09/11/2013] [Indexed: 10/26/2022]
Abstract
The influence of different additives (PEG 300, PEG 400, PG) to the product solution of [(11)C]PiB was investigated with regard to tracer retention for a number of commonly used sterile filters for aseptic manufacturing of PET-tracers. The effect of the amount of additive with regard to tracer retention and the resulting viscosity of the filtration solution was determined. Recommendations for the individual combinations of filters and amounts of additives suitable for the different filtration methods that are implemented in commercially available synthesis modules are given as well.
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Affiliation(s)
- M Patt
- Department of Nuclear Medicine, University of Leipzig, Liebigstrasse 18, D-04103 Leipzig, Germany.
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12
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Rami-Mark C, Ungersboeck J, Haeusler D, Nics L, Philippe C, Mitterhauser M, Willeit M, Lanzenberger R, Karanikas G, Wadsak W. Reliable set-up for in-loop ¹¹C-carboxylations using Grignard reactions for the preparation of [carbonyl-¹¹C]WAY-100635 and [¹¹C]-(+)-PHNO. Appl Radiat Isot 2013; 82:75-80. [PMID: 23974301 PMCID: PMC3842501 DOI: 10.1016/j.apradiso.2013.07.023] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Revised: 07/22/2013] [Accepted: 07/25/2013] [Indexed: 02/02/2023]
Abstract
Aim of this work was the implementation of a generalized in-loop synthesis for 11C-carboxylations and subsequent 11C-acylations on the TRACERlab FxC Pro platform. The set-up was tested using [carbonyl-11C]WAY-100635 and, for the first time, [11C]-(+)-PHNO. Its general applicability could be demonstrated and both [carbonyl-11C]WAY-100635 and [11C]-(+)-PHNO were prepared with high reliability and satisfying outcome. Generalized method for in-loop 11C-carboxylations implemented. Grignard reactions successfully tested. First in-loop procedure for [11C]-(+)PHNO established. Satisfactory synthesis outcome for both [carbonyl-11C]WAY-100635 and [11C]-(+)PHNO. No distillation for purification of intermediate required.
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Affiliation(s)
- Christina Rami-Mark
- Radiochemistry and Biomarker Development Unit, Department of Biomedical Imaging and Image-guided Therapy, Division of Nuclear Medicine, Medical University of Vienna, A-1090 Vienna, Austria; Department of Inorganic Chemistry, University of Vienna, A-1090 Vienna, Austria
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13
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Improved HPLC purification strategy for [11C]raclopride and [11C]DASB leading to high radiochemical yields and more practical high quality radiopharmaceutical formulations. Appl Radiat Isot 2013; 78:62-7. [DOI: 10.1016/j.apradiso.2013.04.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 02/19/2013] [Accepted: 04/05/2013] [Indexed: 11/21/2022]
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Shao X, Schnau PL, Fawaz MV, Scott PJH. Enhanced radiosyntheses of [¹¹C]raclopride and [¹¹C]DASB using ethanolic loop chemistry. Nucl Med Biol 2012; 40:109-16. [PMID: 23123138 DOI: 10.1016/j.nucmedbio.2012.09.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 09/25/2012] [Accepted: 09/28/2012] [Indexed: 10/27/2022]
Abstract
INTRODUCTION To improve the synthesis and quality control of carbon-11 labeled radiopharmaceuticals, we report the fully automated loop syntheses of [¹¹C]raclopride and [¹¹C]DASB using ethanol as the only organic solvent for synthesis module cleaning, carbon-11 methylation, HPLC purification, and reformulation. METHODS Ethanolic loop chemistry is fully automated using a GE TRACERLab FX(C-Pro) synthesis module, and is readily adaptable to any other carbon-11 synthesis apparatus. Precursors (1 mg) were dissolved in ethanol (100 μL) and loaded into the HPLC loop. [¹¹C]MeOTf was passed through the HPLC loop and then the labeled products were purified by semi-preparative HPLC and reformulated into ethanolic saline. RESULTS Both [¹¹C]raclopride (3.7% RCY; >95% RCP; SA=20831 Ci/mmol; n=64) and [¹¹C]DASB, both with (3.0% RCY; >95% RCP; SA=15152Ci/mmol; n=9) and without (3.0% RCY; >95% RCP; SA=10931 Ci/mmol; n=3) sodium ascorbate, have been successfully prepared using the described methodology. Doses are suitable for human use and the described methods are now employed for routine clinical production of both radiopharmaceuticals at the University of Michigan. CONCLUSIONS Ethanolic loop chemistry is a powerful technique for preparing [¹¹C]raclopride and [¹¹C]DASB, and we are in the process of adapting it for other carbon-11 radiopharmaceuticals prepared in our laboratories ([¹¹C]PMP, [¹¹C]PBR28 etc.).
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Affiliation(s)
- Xia Shao
- Department of Radiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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Fully automated and reproducible radiosynthesis of high specific activity [¹¹C]raclopride and [¹¹C]Pittsburgh compound-B using the combination of two commercial synthesizers. Nucl Med Commun 2012; 32:1011-7. [PMID: 21897309 DOI: 10.1097/mnm.0b013e32834b45a3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
INTRODUCTION The use of ¹¹C-labeled radiotracers in routine positron emission tomography studies is dependent on the production capability of radiochemistry laboratories. Therefore, considerable efforts are being focused on the development of fast, efficient, and robust methods for the preparation of such radiotracers. METHODS The fully automated syntheses of [¹¹C]raclopride and [¹¹C]Pittsburgh compound-B (PIB) starting from cyclotron-produced [¹¹C]CH4 are reported. [¹¹C]methyl iodide and [¹¹C]methyl triflate were produced in the TRACERlab FXC Pro synthesis box. Methylation reactions and the final formulation were performed using the AutoLoop (captive solvent method) and the ReFORM-plus systems, respectively. RESULTS [¹¹C]raclopride (n=30) and [¹¹C]PIB (n=24) were synthesized by O-[¹¹C]-methylation and N-[¹¹C]-methylation of (S)-O-desmethylraclopride and 6-OH-BTA-0 using [¹¹C]methyl iodide and [¹¹C]methyl triflate, respectively. Good radiochemical yields (51.3 ± 11.2 and 32.9 ± 6.6%, referred to as [¹¹C]methyl iodide, decay corrected) and specific activities (109 ± 20 and 143 ± 26 GBq/µmol) were obtained for [¹¹C]raclopride and [¹¹C]PIB, respectively, in a fully automated process. Radiochemical purity was higher than 99% in all cases. CONCLUSION The fast, robust and fully automated processes reported here allow [¹¹C]raclopride and [¹¹C]PIB synthesis with good radiochemical yields and high specific activities. Consecutive productions can be performed with minimal intervention on the synthesis modules and minimal exposure to radiation.
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Lodi F, Malizia C, Castellucci P, Cicoria G, Fanti S, Boschi S. Synthesis of oncological [11C]radiopharmaceuticals for clinical PET. Nucl Med Biol 2011; 39:447-60. [PMID: 22172394 DOI: 10.1016/j.nucmedbio.2011.10.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 10/14/2011] [Accepted: 10/22/2011] [Indexed: 01/05/2023]
Abstract
Positron emission tomography (PET) is a nuclear medicine modality which provides quantitative images of biological processes in vivo at the molecular level. Several PET radiopharmaceuticals labeled with short-lived isotopes such as (18)F and (11)C were developed in order to trace specific cellular and molecular pathways with the aim of enhancing clinical applications. Among these [(11)C]radiopharmaceuticals are N-[(11)C]methyl-choline ([(11)C]choline), l-(S-methyl-[(11)C])methionine ([(11)C]methionine) and 1-[(11)C]acetate ([(11)C]acetate), which have gained an important role in oncology where the application of 2-[(18)F]fluoro-2-deoxy-d-glucose ([(18)F]FDG) is suboptimal. Nevertheless, the production of these radiopharmaceuticals did not reach the same level of standardization as for [(18)F]FDG synthesis. This review describes the most recent developments in the synthesis of the above-mentioned [(11)C]radiopharmaceuticals aiming to increase the availability and hence the use of [(11)C]choline, [(11)C]methionine and [(11)C]acetate in clinical practice.
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Affiliation(s)
- Filippo Lodi
- PET Radiopharmacy, Nuclear Medicine Unit, Azienda Ospedaliero Universitaria di Bologna, Policlinico S. Orsola-Malpighi, Bologna, Italy.
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Shao X, Hoareau R, Runkle AC, Tluczek LJM, Hockley BG, Henderson BD, Scott PJH. Highlighting the versatility of the Tracerlab synthesis modules. Part 2: fully automated production of [11C]-labeled radiopharmaceuticals using a Tracerlab FXC-Pro. J Labelled Comp Radiopharm 2011. [DOI: 10.1002/jlcr.1937] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Xia Shao
- Department of Radiology; The University of Michigan School of Medicine; Ann Arbor; MI; 48109; USA
| | - Raphaël Hoareau
- Department of Radiology; The University of Michigan School of Medicine; Ann Arbor; MI; 48109; USA
| | - Adam C. Runkle
- Department of Radiology; The University of Michigan School of Medicine; Ann Arbor; MI; 48109; USA
| | - Louis J. M. Tluczek
- Department of Radiology; The University of Michigan School of Medicine; Ann Arbor; MI; 48109; USA
| | - Brian G. Hockley
- Department of Radiology; The University of Michigan School of Medicine; Ann Arbor; MI; 48109; USA
| | - Bradford D. Henderson
- Department of Radiology; The University of Michigan School of Medicine; Ann Arbor; MI; 48109; USA
| | - Peter J. H. Scott
- Department of Radiology; The University of Michigan School of Medicine; Ann Arbor; MI; 48109; USA
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Next-day residual sedative effect after nighttime administration of an over-the-counter antihistamine sleep aid, diphenhydramine, measured by positron emission tomography. J Clin Psychopharmacol 2010; 30:694-701. [PMID: 21105284 DOI: 10.1097/jcp.0b013e3181fa8526] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Antihistamines often are self-administered at night as over-the-counter (OTC) sleep aids, but their next-day residual sedative effect has never been evaluated using a reliable quantitative method such as positron emission tomography (PET). We performed a double-blind, placebo-controlled, crossover study in which we evaluated the residual effect the next day after nighttime administration of diphenhydramine, a commonly used OTC sleep aid, in terms of brain H₁ receptor occupancy (H₁RO) measured using ¹¹C-doxepin-PET. We also compared the results of diphenhydramine with those of bepotastine, a second-generation antihistamine. Eight healthy adult male subjects underwent PET measurement the morning (11:00) after random oral administration of diphenhydramine (50 mg), bepotastine (10 mg), or placebo the night before (23:00). Binding potential ratios and H₁ROs were calculated in different brain regions of interest such as the cingulate gyrus, frontotemporal cortex, and cerebellum. Subjective sleepiness and plasma drug concentration also were measured. Calculation of binding potential ratios revealed significantly lower values for diphenhydramine than for bepotastine or placebo in all regions of interest (P < 0.01). Cortical mean H₁RO after diphenhydramine treatment was 44.7% compared with 16.6% for bepotastine treatment (P < 0.01). Subjective sleepiness was not significantly different among the subjects treated with each test drug or the placebo. In conclusion, the next-day residual sedative effect after nighttime administration of the OTC sleep aid diphenhydramine was verified for the first time by direct PET measurement of H₁RO. Taking into account the possible hangover effect of OTC antihistamine sleep aids, care needs to be taken during their administration.
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Rommel D, Abarca-Quinones J, Bol A, Peeters F, Lhommel R, Lonneux M, Labar D, Gregoire V, Duprez T. Early monitoring of external radiation therapy by [18F]-fluoromethylcholine positron emission tomography and 3-T proton magnetic resonance spectroscopy: an experimental study in a rodent rhabdomyosarcoma model. Nucl Med Biol 2010; 37:645-53. [DOI: 10.1016/j.nucmedbio.2010.03.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 02/23/2010] [Accepted: 03/08/2010] [Indexed: 01/04/2023]
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Kikuchi A, Takeda A, Okamura N, Tashiro M, Hasegawa T, Furumoto S, Kobayashi M, Sugeno N, Baba T, Miki Y, Mori F, Wakabayashi K, Funaki Y, Iwata R, Takahashi S, Fukuda H, Arai H, Kudo Y, Yanai K, Itoyama Y. In vivo visualization of alpha-synuclein deposition by carbon-11-labelled 2-[2-(2-dimethylaminothiazol-5-yl)ethenyl]-6-[2-(fluoro)ethoxy]benzoxazole positron emission tomography in multiple system atrophy. Brain 2010; 133:1772-8. [PMID: 20430832 DOI: 10.1093/brain/awq091] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The histopathological hallmark of multiple system atrophy is the appearance of intracellular inclusion bodies, named glial cytoplasmic inclusions, which are mainly composed of alpha-synuclein fibrils. In vivo visualization of alpha-synuclein deposition should be used for the diagnosis and assessment of therapy and severity of pathological progression in multiple system atrophy. Because 2-[2-(2-dimethylaminothiazol-5-yl)ethenyl]-6-[2-(fluoro)ethoxy] benzoxazole could stain alpha-synuclein-containing glial cytoplasmic inclusions in post-mortem brains, we compared the carbon-11-labelled 2-[2-(2-dimethylaminothiazol-5-yl)ethenyl]-6-[2-(fluoro)ethoxy] benzoxazole positron emission tomography findings of eight multiple system atrophy cases to those of age-matched normal controls. The positron emission tomography data demonstrated high distribution volumes in the subcortical white matter (uncorrected P < 0.001), putamen and posterior cingulate cortex (uncorrected P < 0.005), globus pallidus, primary motor cortex and anterior cingulate cortex (uncorrected P < 0.01), and substantia nigra (uncorrected P < 0.05) in multiple system atrophy cases compared to the normal controls. They were coincident with glial cytoplasmic inclusion-rich brain areas in multiple system atrophy and thus, carbon-11-labelled 2-[2-(2-dimethylaminothiazol-5-yl)ethenyl]-6-[2-(fluoro)ethoxy] benzoxazole positron emission tomography is a promising surrogate marker for monitoring intracellular alpha-synuclein deposition in living brains.
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Affiliation(s)
- Akio Kikuchi
- Department of Neurology, Graduate School of Medicine, Tohoku University, Sendai, 980-8574 Japan
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Rodent rhabdomyosarcoma: comparison between total choline concentration at H-MRS and [18F]-fluoromethylcholine uptake at PET using accurate methods for collecting data. Mol Imaging Biol 2009; 12:415-23. [PMID: 19937391 DOI: 10.1007/s11307-009-0283-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Revised: 08/18/2009] [Accepted: 10/08/2009] [Indexed: 10/20/2022]
Abstract
PURPOSE To compare choline concentration/amount at proton magnetic resonance spectroscopy (H-MRS) and [18F]-fluoromethylcholine (FCH) uptake at positron emission tomography (PET) in a tumour animal model. PROCEDURES Twenty-two rats bearing grafted syngenic rhabdomyosarcoma in both thighs were examined on a 3T MR system and on a small animal PET system. Total choline concentration was measured on proton MR spectra using a so-called 'best internal fitting' volume of interest. Choline uptake was expressed as mean and maximum standardized uptake value (SUV and SUVmax, respectively) and as the percent of injected dose (%ID) after tumour delineation on fused PET-MR images. Data sets were displayed on standard scatter plots. RESULTS Thirty-six tumours were available for analysis. The area under the curve of the 3.2 ppm choline peak ranged from 69 to 476 (mean, 192) in arbitrary units. Mean SUV values ranged from 0.05 to 0.49 (mean, 0.19) and the %ID from 0.05 to 2.28 (mean, 0.54). Scatter plots failed to reveal quantitative relationship between choline concentration and uptake. Empirically data-driven cut-off lines applied to choline amount (choline concentration x tumour volume) versus choline uptake suggested a paradoxically negative relationship. CONCLUSION Total choline concentration did not correlate with FCH uptake in a tumour experimental model. A negative feedback of high values of total choline amount on cellular FCH uptake seemed to be present.
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Tashiro M, Kato M, Miyake M, Watanuki S, Funaki Y, Ishikawa Y, Iwata R, Yanai K. Dose dependency of brain histamine H(1) receptor occupancy following oral administration of cetirizine hydrochloride measured using PET with [11C]doxepin. Hum Psychopharmacol 2009; 24:540-8. [PMID: 19697300 DOI: 10.1002/hup.1051] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
AIMS The strength of sedation due to antihistamines can be evaluated using positron emission tomography (PET). The purpose of the present study is to measure histamine H(1) receptor (H(1)R) occupancy following oral administration of cetirizine (10 and 20 mg) in order to examine dose dependency. METHODS Fifteen healthy male volunteers (age range, 20-35 years) were divided into 3 subgroups and were studied following single oral administration of cetirizine at 10 mg (n = 5) and 20 mg (n = 5) or hydroxyzine at 30 mg (n = 5) using PET with 11C-doxepin. Each subject was scanned also following the administration of placebo. Binding potential and H(1)RO values were calculated in the prefrontal and anterior cingulate cortices. Subjective sleepiness was also measured, and the correlation to H(1)RO was examined for each antihistamine. RESULTS The averaged H(1)ROs of cetirizine 10 mg, 20 mg, and hydroxyzine 30 mg in the prefrontal and cingulate cortices was 12.6%, 25.2%, and 67.6%, respectively. The H(1)RO of hydroxyzine 30 mg correlated well with subjective sleepiness (p < 0.001); however, those of cetirizine 10 and 20 mg showed no correlation with subjective sleepiness. CONCLUSION It was demonstrated that the brain penetration of orally administered cetirizine was dose-dependent. Cetirizine 10 mg, with its low H(1)RO and thus minimal sedation, could be more safely used than cetirizine 20 mg for the treatment of various allergic disorders.
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Affiliation(s)
- Manabu Tashiro
- Division of Cyclotron Nuclear Medicine, Tohoku University, Sendai, Miyagi, Japan.
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Cheung MK, Ho CL. A simple, versatile, low-cost and remotely operated apparatus for [11C]acetate, [11C]choline, [11C]methionine and [11C]PIB synthesis. Appl Radiat Isot 2009; 67:581-9. [DOI: 10.1016/j.apradiso.2008.08.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2008] [Revised: 07/17/2008] [Accepted: 08/26/2008] [Indexed: 10/21/2022]
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Yoshizawa M, Tashiro M, Fukudo S, Yanai K, Utsumi A, Kano M, Karahasi M, Endo Y, Morisita J, Sato Y, Adachi M, Itoh M, Hongo M. Increased brain histamine H1 receptor binding in patients with anorexia nervosa. Biol Psychiatry 2009; 65:329-35. [PMID: 18814859 DOI: 10.1016/j.biopsych.2008.08.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Revised: 08/04/2008] [Accepted: 08/04/2008] [Indexed: 11/17/2022]
Abstract
BACKGROUND The central histaminergic neuron system modulates various brain functions, including eating behavior. We hypothesized that women have higher density of histamine H1 receptor (H1R) in the limbic system than men and that the density of central H1R is increased in patients with anorexia nervosa (AN). METHODS Subjects were 12 female AN patients, 12 healthy female subjects, and 11 healthy male subjects. Positron emission tomography with H1R radioligand [(11)C]doxepin was performed on all subjects and regions of interest based analysis was conducted to evaluate brain H1R binding potential (BP). Abnormal eating behavior, depression, and anxiety of subjects were evaluated using the Eating Attitude Test-26 (EAT-26), Self-Rating Depression Scale (SDS), and State-Trait Anxiety Inventory (STAI), respectively. RESULTS Binding potential of [(11)C]doxepin in female subjects was significantly higher than that in male subjects at the following brain sites: amygdala, hippocampus, medial prefrontal cortex, orbitofrontal cortex, and temporal cortex. Anorexia nervosa patients showed significantly higher BP of [(11)C]doxepin in the amygdala and lentiform nucleus than the control female subjects. In AN patients, BP of [(11)C]doxepin in the amygdala and thalamus negatively correlated with EAT-26 scores. There was a significant negative correlation between BP of [(11)C]doxepin and SDS or STAI scores in the amygdala, anterior cingulate cortex, and orbitofrontal cortex of AN patients. CONCLUSIONS These findings support the hypothesis that women have higher H1R density in the limbic system than men and suggest that AN patients may have higher expression of H1R in the limbic brain, particularly in the amygdala.
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Affiliation(s)
- Masahiko Yoshizawa
- Department of Psychosomatic Medicine, Tohoku University School of Medicine, Japan
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Shao X, Kilbourn MR. A simple modification of GE tracerlab FX C Pro for rapid sequential preparation of [11C]carfentanil and [11C]raclopride. Appl Radiat Isot 2008; 67:602-5. [PMID: 19162491 DOI: 10.1016/j.apradiso.2008.12.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Revised: 12/05/2008] [Accepted: 12/09/2008] [Indexed: 11/16/2022]
Abstract
A simple modification of the GE Tracerlab FX C Pro system which enabled performance of both solvent capture (loop method) and conventional solution phase [(11)C]methylation in the same module is described. By the quick setup and automated method, [(11)C]carfentanil and [(11)C]raclopride could be prepared in rapid succession without opening the hot cell. The radiochemical yields were over 40% and 30% (decay-corrected and based on [(11)C]methyl iodide) for [(11)C]carfentanil and [(11)C]raclopride, respectively. The radiochemical purities were greater than 95% and specific activities over 5 Ci/mmol for both tracers. The modification is extremely easy and can be utilized for multiple syntheses of other (11)C-labeled radiopharmaceuticals in a fast and reliable manner.
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Affiliation(s)
- Xia Shao
- Department of Radiology, University of Michigan, Ann Arbor, MI 48109, USA.
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Miller P, Long N, Vilar R, Gee A. Synthese von11C-,18F-,15O- und13N-Radiotracern für die Positronenemissionstomographie. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200800222] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Miller P, Long N, Vilar R, Gee A. Synthesis of11C,18F,15O, and13N Radiolabels for Positron Emission Tomography. Angew Chem Int Ed Engl 2008; 47:8998-9033. [DOI: 10.1002/anie.200800222] [Citation(s) in RCA: 726] [Impact Index Per Article: 45.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Arai T, Zhang MR, Ogawa M, Fukumura T, Kato K, Suzuki K. Efficient and reproducible synthesis of [1-11C]acetyl chloride using the loop method. Appl Radiat Isot 2008; 67:296-300. [PMID: 19028105 DOI: 10.1016/j.apradiso.2008.09.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 07/14/2008] [Accepted: 09/19/2008] [Indexed: 11/15/2022]
Abstract
[1-(11)C]Acetyl chloride ([(11)C]AcCl), an important [(11)C]acylating agent, was synthesized by reacting [(11)C]CO(2) with methylmagnesium bromide coated on the inner surface of a polyethylene loop (loop method). By optimizing the reaction conditions and synthesis parameters, [1-(11)C]phenylacetate and [1-(11)C]benzylacetate were produced from [(11)C]AcCl in high radiochemical yield and specific activity.
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Affiliation(s)
- Takuya Arai
- Department of Molecular Probes, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
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Automated radiosynthesis of the Pittsburg compound-B using a commercial synthesizer. Nucl Med Commun 2008; 29:920-6. [DOI: 10.1097/mnm.0b013e328304e0e1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Tashiro M, Duan X, Kato M, Miyake M, Watanuki S, Ishikawa Y, Funaki Y, Iwata R, Itoh M, Yanai K. Brain histamine H1 receptor occupancy of orally administered antihistamines, bepotastine and diphenhydramine, measured by PET with 11C-doxepin. Br J Clin Pharmacol 2008; 65:811-21. [PMID: 18410464 DOI: 10.1111/j.1365-2125.2008.03143.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT 'Bepotastine besilate' is a novel second-generation antihistamine developed in Japan and its antiallergic effects have already been demonstrated by various studies. However, only a few clinical studies regarding its sedative property are available. In addition, histamine H(1) receptor occupancy (H(1)RO) of this new antihistamine has never been measured by positron emission tomography (PET). WHAT THIS STUDY ADDS This paper provides the first measurement result of cerebral H(1)RO of bepotastine besilate (approximately 15%) as determined by PET. This result is in accordance with the clinical classification of bepotastine as a second-generation antihistamine. In addition, the relationship between subjective sleepiness and cerebral H(1)RO of this second-generation antihistamine is demonstrated for the first time using a placebo-controlled crossover study design. AIMS Antihistamines are frequently used for treating various allergic diseases, but often induce sedation. The degree of sedation can be evaluated by measuring histamine H(1) receptor occupancy (H(1)RO) in the brain using positron emission tomography (PET). The aim was to measure H(1)RO of bepotastine, a new second-generation antihistamine, and to compare it with that of diphenhydramine. METHODS Eight healthy male volunteers (mean age +/- SD 24.4 +/- 3.3 years) were studied after single oral administration of bepotastine (10 mg), diphenhydramine (30 mg) or placebo, by PET imaging with (11)C-doxepin in a crossover study design. Binding potential ratio and H(1)ROs were calculated using placebo data and were compared between bepotastine and diphenhydramine in the anterior and posterior cingulate gyri (ACG and PCG, respectively), superior and inferior frontal cortices (SFC and IFC, respectively), orbitofrontal cortex (OFC), insular cortex (IC), lateral and medial temporal cortices (LTC and MTC, respectively), parietal cortex (PC), occipital cortex (OC) and sensorimotor cortex (SMC). Plasma concentration of each antihistamine was measured, and its correlation to H(1)RO was examined. RESULTS H(1)RO after bepotastine treatment was significantly lower than that after diphenhydramine treatment in all cortical regions (P < 0.001). Mean H(1)ROs of bepotastine and diphenhydramine were 14.7% and 56.4%, respectively. H(1)ROs of both bepotastine and diphenhydramine correlated to their respective drug plasma concentration (P < 0.001). CONCLUSION Oral bepotastine (10 mg), with its relatively low H(1)RO and thus minimal sedation, has the potential for use as a mildly or slightly sedative antihistamine in the treatment of various allergic disorders.
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Affiliation(s)
- Manabu Tashiro
- Division of Cyclotron Nuclear Medicine, Cyclotron and Radioisotope Centre, Tohoku University, Sendai, Miyagi, Japan.
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Lim KS, Kwon JS, Jang IJ, Jeong JM, Lee JS, Kim HW, Kang WJ, Kim JR, Cho JY, Kim E, Yoo SY, Shin SG, Yu KS. Modeling of Brain D2 Receptor Occupancy-Plasma Concentration Relationships with a Novel Antipsychotic, YKP1358, Using Serial PET Scans in Healthy Volunteers. Clin Pharmacol Ther 2007; 81:252-8. [PMID: 17259948 DOI: 10.1038/sj.clpt.6100049] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
YKP1358 is a novel serotonin (5-HT(2A)) and dopamine (D(2)) antagonist that, in preclinical studies, fits the general profile of an atypical antipsychotic. We conducted a D(2) receptor occupancy study with YKP1358 in healthy volunteers using positron emission tomography (PET) to measure the D(2) receptor occupancy of YKP1358 and to characterize its relationship to plasma drug concentrations. A single oral dose, parallel group, dose-escalation (100, 200, and 250 mg) study was performed in 10 healthy male volunteers with the PET radiotracer [(11)C]raclopride. The D(2) receptor occupancy of striatum was measured pre-dose, and at 2, 5, and 10 h after YKP1358 administration. Serial blood samples were taken for measurement of plasma YKP1358 concentrations. D(2) receptor occupancy by YKP1358 increased to 53-83% at 2 h, and then decreased afterwards, ranging from 40-64% at 5 h to 20-51% at 10 h. The YKP1358 dose-plasma concentration relationship exhibited extensive variability, but there was a good relationship between plasma concentrations and D(2) receptor occupancy that was well predicted by a sigmoid E(max) model using nonlinear mixed effects modeling. To our knowledge, this is the first study in which the relationship between plasma concentration and the biomarker of D(2) receptor occupancy was modeled using nonlinear mixed effects modeling. It is anticipated that these results will be useful in estimating for subsequent studies the initial doses of YKP1358 required to achieve a therapeutically effective range of D(2) receptor occupancy.
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Affiliation(s)
- K S Lim
- Department of Pharmacology and Clinical Pharmacology Unit, Seoul National University College of Medicine and Hospital, Seoul, Korea
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Wuest F, Berndt M, Kniess T. Carbon-11 labeling chemistry based upon [11C]methyl iodide. ERNST SCHERING RESEARCH FOUNDATION WORKSHOP 2007:183-213. [PMID: 17172156 DOI: 10.1007/978-3-540-49527-7_7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Radiochemistry with the short-lived positron emitter 11C (half-life 20.38 min) represents special challenges in terms of synthesis time and labeling techniques. The recent developments in 11C radiochemistry have steadily expanded the number of 11C labeled compounds. This chapter addresses selected chemical and technical aspects of 11C chemistry based on the readily available labeling precursors [11 C]methyl iodide and, to a lesser extent, [11C]methyl triflate. Special emphasis is placed on heteroatom methylation reactions and 11C-C bond formations.
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Affiliation(s)
- F Wuest
- PET Tracer Department, Institute of Bioinorganic and Radiopharmaceutical Chemistry, Research Centre Rossendorf, Dresden, Germany.
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Fei X, Mock BH, DeGrado TR, Wang J, Glick‐Wilson BE, Sullivan ML, Hutchins GD, Zheng Q. An Improved Synthesis of PET Dopamine D2 Receptors Radioligand [11C]Raclopride. SYNTHETIC COMMUN 2006. [DOI: 10.1081/scc-120034174] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Xiangshu Fei
- a Department of Radiology , Indiana University School of Medicine , 1345 West 16th Street, L‐3 Room 202, Indianapolis, Indiana, 46202‐2111, USA
| | - Bruce H. Mock
- a Department of Radiology , Indiana University School of Medicine , 1345 West 16th Street, L‐3 Room 202, Indianapolis, Indiana, 46202‐2111, USA
| | - Timothy R. DeGrado
- a Department of Radiology , Indiana University School of Medicine , 1345 West 16th Street, L‐3 Room 202, Indianapolis, Indiana, 46202‐2111, USA
| | - Ji‐Quan Wang
- a Department of Radiology , Indiana University School of Medicine , 1345 West 16th Street, L‐3 Room 202, Indianapolis, Indiana, 46202‐2111, USA
| | - Barbara E. Glick‐Wilson
- a Department of Radiology , Indiana University School of Medicine , 1345 West 16th Street, L‐3 Room 202, Indianapolis, Indiana, 46202‐2111, USA
| | - Michael L. Sullivan
- a Department of Radiology , Indiana University School of Medicine , 1345 West 16th Street, L‐3 Room 202, Indianapolis, Indiana, 46202‐2111, USA
| | - Gary D. Hutchins
- a Department of Radiology , Indiana University School of Medicine , 1345 West 16th Street, L‐3 Room 202, Indianapolis, Indiana, 46202‐2111, USA
| | - Qi‐Huang Zheng
- a Department of Radiology , Indiana University School of Medicine , 1345 West 16th Street, L‐3 Room 202, Indianapolis, Indiana, 46202‐2111, USA
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Tashiro M, Mochizuki H, Sakurada Y, Ishii K, Oda K, Kimura Y, Sasaki T, Ishiwata K, Yanai K. Brain histamine H receptor occupancy of orally administered antihistamines measured by positron emission tomography with (11)C-doxepin in a placebo-controlled crossover study design in healthy subjects: a comparison of olopatadine and ketotifen. Br J Clin Pharmacol 2006; 61:16-26. [PMID: 16390347 PMCID: PMC1884984 DOI: 10.1111/j.1365-2125.2005.02514.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
AIMS The strength of sedation due to antihistamines can be evaluated by using positron emission tomography (PET). The purpose of the present study is to measure histamine H(1) receptor (H(1)R) occupancy due to olopatadine, a new second-generation antihistamine and to compare it with that of ketotifen. METHODS Eight healthy males (mean age 23.5 years-old) were studied following single oral administration of olopatadine 5 mg or ketotifen 1 mg using PET with (11)C-doxepin in a placebo-controlled crossover study design. Binding potential ratio and H(1)R occupancy were calculated and were compared between olopatadine and ketotifen in the medial prefrontal (MPFC), dorsolateral prefrontal (DLPFC), anterior cingulate (ACC), insular (IC), temporal (TC), parietal (PC), occipital cortices (OC). Plasma drug concentration was measured, and correlation of AUC to H(1)R occupancy was examined. RESULTS H(1)R occupancy after olopatadine treatment was significantly lower than that after ketotifen treatment in the all cortical regions (P < 0.001). Mean H(1)R occupancies for olopatadine and ketotifen were, respectively: MPFC, 16.7 vs. 77.7; DLPFC, 14.1 vs. 85.9; ACC, 14.7 vs. 76.1; IC, 12.8 vs. 69.7; TC, 12.5 vs. 66.5; PC, 13.9 vs. 65.8; and OC, 19.5 vs. 60.6. Overall cortical mean H(1)R occupancy of olopatadine and ketotifen were 15% and 72%, respectively. H(1)R occupancy of both drugs correlated well with their respective drug plasma concentrations (P < 0.001). CONCLUSION It is suggested that 5 mg oral olopatadine, with its low H(1)R occupancy and thus minimal sedation, could safely be used an antiallergic treatment for various allergic disorders. Abbreviations histamine H(1) receptor (H(1)R), histamine H(1) receptor occupancy (H(1)RO), dopamine D(2) receptor (D(2)R), positron emission tomography (PET), blood-brain barrier (BBB), binding potential ratio (BPR), distribution volume (DV).
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Affiliation(s)
- Manabu Tashiro
- Department of Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
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35
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Ishikawa Y, Iwata R, Furumoto S, Pascali C, Bogni A, Kubota K, Ishiwata K. Simple automated preparation of O-[11C]methyl-l-tyrosine for routine clinical use. Appl Radiat Isot 2005; 63:55-61. [PMID: 15866448 DOI: 10.1016/j.apradiso.2005.01.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Revised: 01/15/2005] [Accepted: 01/21/2005] [Indexed: 11/16/2022]
Abstract
The previously reported preparation of O-[(11)C]methyl-l-tyrosine ([(11)C]MT), a promising tumor imaging agent, has been now considerably simplified and automated. Main changes were the use of [(11)C]methyl iodide ([(11)C]MeI) in the reaction with l-tyrosine disodium and the use of solid phase extraction on commercially available cartridges instead of HPLC for the final purification. An injectable saline solution of [(11)C]MT was obtained within 30 min after EOB with radiochemical yield of ca. 60% (decay-corrected, based on [(11)C]MeI). Radiochemical purity was over 97%. The automated preparation was carried out using a miniature module employing manifold valves.
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Affiliation(s)
- Yoichi Ishikawa
- CYRIC Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
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36
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Solbach C, Uebele M, Reischl G, Machulla HJ. Efficient radiosynthesis of carbon-11 labelled uncharged Thioflavin T derivatives using [11C]methyl triflate for beta-amyloid imaging in Alzheimer's Disease with PET. Appl Radiat Isot 2005; 62:591-5. [PMID: 15701414 DOI: 10.1016/j.apradiso.2004.09.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2004] [Revised: 09/01/2004] [Accepted: 09/19/2004] [Indexed: 11/19/2022]
Abstract
The synthesis of carbon-11 amino function labelled uncharged Thioflavin T derivatives is known to be performed by reaction of the demethyl-precursors with [11C]methyl iodide but the labelling yields are only mediocre. The use of [11C]methyl triflate improved the radiochemical yield of three potential beta-amyloid imaging PET-radiotracers significantly. Performance of the labelling reaction by reacting the corresponding precursor molecules with [11C]methyl triflate for 1 min at 80 degrees C led to radiochemical yields of 44+/-10% (n=5) for [11C]6-Me-BTA-1, 68+/-4% (n=10) for [11C]BTA-1 and 58+/-2% (n=5) for [11C]6-OH-BTA-1 with respect to [11C]methyl triflate. In production runs (60 min, 50 microA) up to 6500 MBq (mean: 4000+/-1900 MBq) of [11C]6-Me-BTA-1, 7900 MBq (mean: 6000+/-1000 MBq) of [11C]BTA-1 and 7100 MBq (mean: 6300+/-600 MBq) of [11C]6-OH-BTA-1 could be obtained ready for intravenous injection. The radiochemical purity was >95% with specific activities in the range of 80-120 GBq/micromol (EOS) within a total synthesis time of less than 40 min after EOB.
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Affiliation(s)
- C Solbach
- Radiopharmacy, PET-Center, University Hospital Tübingen, Roentgenweg 15, D-72076 Tübingen, Germany
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37
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Studenov AR, Jivan S, Adam MJ, Ruth TJ, Buckley KR. Studies of the mechanism of the in-loop synthesis of radiopharmaceuticals. Appl Radiat Isot 2004; 61:1195-201. [PMID: 15388110 DOI: 10.1016/j.apradiso.2004.05.051] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2003] [Revised: 05/06/2004] [Accepted: 05/06/2004] [Indexed: 11/30/2022]
Abstract
A series of experiments were performed to better understand the mechanism of the In-loop [11C]CH3I-methylation. The timing of [11C]CH3I delivery is critical for the high yield of radiolabeling since in-loop radioactivity trapping is reversible. Trapped radioactivity escapes faster from a Tefzel loop compared to a PEEK- or stainless steel loop. Up to 50% of delivered radioactivity may be concentrated at the loop origin (representing 8.1% of the total loop volume). A five-fold reduction of the reaction solvent volume and/or precursor amount may lead to a decrease of the product radiochemical yield either by lowering the in-loop radioactivity trapping or by diminishing conversion of [11C]CH3I into the product.
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Affiliation(s)
- Andrei R Studenov
- TRIUMF, PET Group, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Canada.
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38
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Abstract
Factors that place constraints on radio-chemists who are seeking to design and develop radiopharmaceuticals for PET imaging studies include the short half-lives of 11C and 18F, minimum radiochemical yield and specific activity requirements, and high radiation fields that are associated with multi-Curie quantities of PET radionuclides. Nevertheless, during the past 20 years, considerable progress has been made in the development and application of a variety of PET radiotracers for a range of imaging studies in human subjects. We have highlighted a few areas of radiochemistry that focused on PET radiotracers that are described in this issue. Although the number of PET radiotracers synthesized is in the hundreds [6], much work remains to develop specific and useful PET radiotracers for a host of new and exciting noninvasive imaging applications.
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Affiliation(s)
- N Scott Mason
- Positron Emission Tomography Facility, Department of Radiology, University of Pittsburgh, B-938, UPMC Presbyterian, 200 Lothrop Street, Pittsburgh, PA 15213-2582, USA.
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39
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Schweiger L, Craib S, Welch A, Sharp P. Radiosynthesis of [N-methyl-11C]methylene blue. J Labelled Comp Radiopharm 2003. [DOI: 10.1002/jlcr.784] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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40
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Funaki Y, Kato M, Iwata R, Sakurai E, Sakurai E, Tashiro M, Ido T, Yanai K. Evaluation of the binding characteristics of [5-(11)C-methoxy]Donepezil in the rat brain for in vivo visualization of acetylcholinesterase. J Pharmacol Sci 2003; 91:105-12. [PMID: 12686754 DOI: 10.1254/jphs.91.105] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Donepezil, an acetylcholinesterase (AChE) inhibitor, has not been evaluated for its binding characteristics using a radioactive tracer, although its inhibitory action on AChE has been studied. The aim of this research is to examine whether AChE can be visualized in vivo and in vitro with [(11)C]donepezil. [5-(11)C-methoxy]Donepezil was synthesized by O-methylation using [(11)C]methyl triflate. The binding of [(11)C]donepezil to brain homogenates was higher in the brain stem and striatum, and it was lowest in the cerebellum. The in vitro autoradiographic study successfully demonstrated the specific binding of [(11)C]donepezil to AChE in the rat brain. The IC(50) value of binding was approximately 10 nM, which is comparable to the reported value for inhibiting enzyme activity (6 nM). Saturation experiments revealed that the B(max) and K(d) of [(11)C]donepezil binding in vitro are 65 fmol/mg tissue and 39.8 nM, respectively. In accordance with the in vitro bindings, the in vivo distribution of [(11)C]donepezil was heterogeneous in the rat brain. In the blocking experiments, the heterogeneous distribution disappeared in the presence of a large amount of unlabeled donepezil. These data suggest that [5-(11)C-methoxy]donepezil can be potentially useful to image AChE non-invasively in the human brain by positron emission tomography.
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41
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Iwata R, Furumoto S, Pascali C, Bogni A, Ishiwata K. Radiosynthesis ofO-[11C]methyl-L-tyrosine andO-[18F]Fluoromethyl-L-tyrosine as potential PET tracers for imaging amino acid transport. J Labelled Comp Radiopharm 2003. [DOI: 10.1002/jlcr.696] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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42
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Studenov AR, Jivan S, Buckley KR, Adam MJ. Efficientin-loop synthesis of high specific radioactivity [11C]carfentanil. J Labelled Comp Radiopharm 2003. [DOI: 10.1002/jlcr.722] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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43
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Wegman TD, Maas B, Elsinga PH, Vaalburg W. An improved method for the preparation of [11C]verapamil. Appl Radiat Isot 2002; 57:505-7. [PMID: 12361330 DOI: 10.1016/s0969-8043(02)00143-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
This paper describes an improved preparation of [11C]verapamil by reaction of [11C]methyl triflate with desmethylverapamil. The optimal reaction temperature, amount of precursor and reaction time were assessed. With this method [11C]verapamil can be prepared with a reproducible radiochemical yield of 66 +/- 4% (EOB, based on [11C]methyltriflate). Total synthesis time was 60 min. Radiochemical purity was >99% and specific activities varied between 5 and 30TBq/mmol.
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Affiliation(s)
- T D Wegman
- Positron Emission Tomography Center, Groningen University Hospital, The Netherlands.
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44
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Luurtsema G, Windhorst AD, Mooijer MP, Herscheid JD, Lammertsma AA, Franssen EJ. Fully automated high yield synthesis of (R)- and (S)-[11C]verapamil for measuring P-glycoprotein function with positron emission tomography. J Labelled Comp Radiopharm 2002. [DOI: 10.1002/jlcr.632] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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45
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Iwata R, Pascali C, Bogni A, Yanai K, Kato M, Ido T, Ishiwata K. A combined loop-SPE method for the automated preparation of [11C]doxepin. J Labelled Comp Radiopharm 2002. [DOI: 10.1002/jlcr.557] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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