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Sun Y, Ramos-Torres KM, Brugarolas P. Metabolic Stability of the Demyelination Positron Emission Tomography Tracer [ 18F]3-Fluoro-4-Aminopyridine and Identification of Its Metabolites. J Pharmacol Exp Ther 2023; 386:93-101. [PMID: 37024145 PMCID: PMC10289238 DOI: 10.1124/jpet.122.001462] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 03/05/2023] [Accepted: 03/23/2023] [Indexed: 04/08/2023] Open
Abstract
[18F]3-fluoro-4-aminopyridine ([18F]3F4AP) is a positron emission tomography (PET) tracer for imaging demyelination based on the multiple sclerosis drug 4-aminopyridine (4AP, dalfampridine). This radiotracer was found to be stable in rodents and nonhuman primates imaged under isoflurane anesthesia. However, recent findings indicate that its stability is greatly decreased in awake humans and mice. Since both 4AP and isoflurane are metabolized primarily by cytochrome P450 enzymes, particularly cytochrome P450 family 2 subfamily E member 1 (CYP2E1), we postulated that this enzyme may be responsible for the metabolism of 3F4AP. Here, we investigated the metabolism of [18F]3F4AP by CYP2E1 and identified its metabolites. We also investigated whether deuteration, a common approach to increase the stability of drugs, could improve its stability. Our results demonstrate that CYP2E1 readily metabolizes 3F4AP and its deuterated analogs and that the primary metabolites are 5-hydroxy-3F4AP and 3F4AP N-oxide. Although deuteration did not decrease the rate of the CYP2E1-mediated oxidation, our findings explain the diminished in vivo stability of 3F4AP compared with 4AP and further our understanding of when deuteration may improve the metabolic stability of drugs and PET ligands. SIGNIFICANCE STATEMENT: The demyelination tracer [18F]3F4AP was found to undergo rapid metabolism in humans, which could compromise its utility. Understanding the enzymes and metabolic products involved may offer strategies to reduce metabolism. Using a combination of in vitro assays and chemical syntheses, this report shows that cytochrome P450 enzyme CYP2E1 is likely responsible for [18F]3F4AP metabolism, that 4-amino-5-fluoroprydin-3-ol (5-hydroxy-3F4AP, 5OH3F4AP) and 4-amino-3-fluoropyridine 1-oxide (3F4AP N-oxide) are the main metabolites, and that deuteration is unlikely to improve the stability of the tracer in vivo.
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Affiliation(s)
- Yang Sun
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Karla M Ramos-Torres
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Pedro Brugarolas
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
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de Vries EFJ, Elsinga PH, Tsoumpas C. Will extended field-of-view PET/CT depopulate the graveyard of failed PET radiopharmaceuticals? Cancer Imaging 2022; 22:70. [PMID: 36529738 PMCID: PMC9761966 DOI: 10.1186/s40644-022-00510-1] [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: 12/07/2022] [Accepted: 12/08/2022] [Indexed: 12/23/2022] Open
Abstract
With the rapid emergence of extended Field-of-View PET-cameras several new applications for radiopharmaceuticals become within reach. Main reason is the significant increase of the sensitivity of the PET-camera so that much less radioactivity can be administered. Issues that that hampered development or use of PET-radiopharmaceuticals become realistic again. Molar activity requirements can become less strict. New low-yielding radiochemistry methods may become applicable. Carbon-11 labelled compounds can revive and potentially be shipped to nearby PET-facilities. PET-radiopharmaceuticals with slow kinetics in comparison to their half life can still be used. As additional infrastructure and equipment will likely remain unchanged and keep the same sensitivity therefore there will be issues with kinetic modelling requiring analysis of plasma or metabolites samples with lower count rate. Besides the potential revival of failed radiopharmaceuticals, novel challenges are ahead to develop novel radiochemistry based on thus far unsuitable (low yielding or time consuming) reactions.
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Affiliation(s)
- E. F. J. de Vries
- grid.4494.d0000 0000 9558 4598Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, Hanzeplein 1, Groningen, 9713GZ The Netherlands
| | - P. H. Elsinga
- grid.4494.d0000 0000 9558 4598Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, Hanzeplein 1, Groningen, 9713GZ The Netherlands
| | - C. Tsoumpas
- grid.4494.d0000 0000 9558 4598Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, Hanzeplein 1, Groningen, 9713GZ The Netherlands
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Cao S, Tang J, Liu C, Fang Y, Ji L, Xu Y, Chen Z. Synthesis and Biological Evaluation of [ 18F]FECNT-d 4 as a Novel PET Agent for Dopamine Transporter Imaging. Mol Imaging Biol 2021; 23:733-744. [PMID: 33851345 DOI: 10.1007/s11307-021-01603-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 03/21/2021] [Accepted: 04/02/2021] [Indexed: 11/27/2022]
Abstract
PURPOSE The dopamine transporter (DAT) is a marker of the occurrence and development of Parkinson's disease (PD) and other diseases with nigrostriatal degeneration. 2β-Carbomethoxy-3β-(4-chlorophenyl)-8-(2-[18F]-fluoroethyl)nortropane ([18F]FECNT), an 18F-labelled tropane derivative, was reported to be a useful positron-emitting probe for DAT. However, the rapid formation of brain-penetrating radioactive metabolites is an impediment to the proper quantitation of DAT in PET studies with [18F]FECNT. Deuterium-substituted analogues have presented better in vivo stability to reduce metabolites. This study aimed to synthesize a deuterium-substituted DAT radiotracer, [18F]FECNT-d4, and to make a preliminary investigation of its properties as a DAT tracer in vivo. PROCEDURES The ligand [18F]FECNT-d4 was obtained by one-step radiolabelling reaction. The lipophilicity was measured by the shake-flask method. Binding properties of [18F]FECNT-d4 were estimated by in vitro binding assay, biodistribution, and microPET imaging in rats. In vivo stability of [18F]FECNT-d4 was estimated by radio-HPLC. RESULTS [18F]FECNT-d4 was synthesized at an average activity yield of 46 ± 17 % (n = 15) and the molar activity was 67 ± 12 GBq/μmol. The deuterated tracer showed suitable lipophilicity and the ability to penetrate the blood-brain barrier (brain uptake of 1.72 % ID at 5 min). [18F]FECNT-d4 displayed a high binding affinity for DAT comparable to that of [18F]FECNT in rat striatum homogenates. Biodistribution results in normal rats showed that [18F]FECNT-d4 exhibited a higher ratio of the target to non-target (striatum/cerebellum) at 15 min post administration (5.00 ± 0.44 vs 3.84 ± 0.24 for [18F]FECNT-d4 vs [18F]FECNT). MicroPET imaging studies of [18F]FECNT-d4 in normal rats showed that the ligand selectively localized to DAT-rich striatal regions and the accumulation could be blocked with DAT inhibitor. Furthermore, in the unilateral PD model rat, a significant reduction of the signal was found in the lesioned side relative to the unlesioned side. Striatal standardized uptake value of [18F]FECNT-d4 remained ~4.02 in the striatum between 5 and 20 min, whereas that of [18F]FECNT fell rapidly from 4.11 to 2.95. Radio-HPLC analysis of the plasma demonstrated better in vivo stability of [18F]FECNT-d4 than [18F]FECNT. CONCLUSION The deuterated compound [18F]FECNT-d4 may serve as a promising PET imaging agent to assess DAT-related disorders.
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Affiliation(s)
- Shanshan Cao
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, School of Pharmacy, Xuzhou Medical University, Xuzhou, 221004, China
| | - Jie Tang
- NHC Key Laboratory of Nuclear Medicine, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, 214063, China
| | - Chunyi Liu
- NHC Key Laboratory of Nuclear Medicine, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, 214063, China
| | - Yi Fang
- NHC Key Laboratory of Nuclear Medicine, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, 214063, China
| | - Linyang Ji
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, School of Pharmacy, Xuzhou Medical University, Xuzhou, 221004, China
| | - Yingjiao Xu
- NHC Key Laboratory of Nuclear Medicine, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, 214063, China
| | - Zhengping Chen
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, School of Pharmacy, Xuzhou Medical University, Xuzhou, 221004, China. .,NHC Key Laboratory of Nuclear Medicine, Jiangsu Key Laboratory of Molecular Nuclear Medicine, Jiangsu Institute of Nuclear Medicine, Wuxi, 214063, China.
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Laube M, Gassner C, Neuber C, Wodtke R, Ullrich M, Haase-Kohn C, Löser R, Köckerling M, Kopka K, Kniess T, Hey-Hawkins E, Pietzsch J. Deuteration versus ethylation - strategies to improve the metabolic fate of an 18F-labeled celecoxib derivative. RSC Adv 2020; 10:38601-38611. [PMID: 35517533 PMCID: PMC9057277 DOI: 10.1039/d0ra04494f] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 10/11/2020] [Indexed: 12/14/2022] Open
Abstract
The inducible isoenzyme cyclooxygenase-2 (COX-2) is closely associated with chemo-/radioresistance and poor prognosis of solid tumors. Therefore, COX-2 represents an attractive target for functional characterization of tumors by positron emission tomography (PET). In this study, the celecoxib derivative 3-([18F]fluoromethyl)-1-[4-(methylsulfonyl)phenyl]-5-(p-tolyl)-1H-pyrazole ([18F]5a) was chosen as a lead compound having a reported high COX-2 inhibitory potency and a potentially low carbonic anhydrase binding tendency. The respective deuterated analog [D2,18F]5a and the fluoroethyl-substituted derivative [18F]5b were selected to study the influence of these modifications with respect to COX inhibition potency in vitro and metabolic stability of the radiolabeled tracers in vivo. COX-2 inhibitory potency was found to be influenced by elongation of the side chain but, as expected, not by deuteration. An automated radiosynthesis comprising 18F-fluorination and purification under comparable conditions provided the radiotracers [18F]5a,b and [D2,18F]5a in good radiochemical yields (RCY) and high radiochemical purity (RCP). Biodistribution and PET studies comparing all three compounds revealed bone accumulation of 18F-activity to be lowest for the ethyl derivative [18F]5b. However, the deuterated analog [D2,18F]5a turned out to be the most stable compound of the three derivatives studied here. Time-dependent degradation of [18F]5a,b and [D2,18F]5a after incubation in murine liver microsomes was in accordance with the data on metabolism in vivo. Furthermore, metabolites were identified based on UPLC-MS/MS. The aim of this study is to investigate the influence of deuteration and elongation on an 18F-labeled COX-2 inhibitor with focus on metabolic stability to develop suitable COX-2 targeting radiotracers.![]()
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Affiliation(s)
- Markus Laube
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Cemena Gassner
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany .,Faculty of Chemistry and Food Chemistry, School of Science, Technische Universität Dresden Mommsenstrasse 4 D-01062 Dresden Germany
| | - Christin Neuber
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Robert Wodtke
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Martin Ullrich
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Cathleen Haase-Kohn
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Reik Löser
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Martin Köckerling
- University of Rostock, Institute of Chemistry, Department of Inorganic Solid State Chemistry Albert-Einstein-Str. 3a D-18059 Rostock Germany
| | - Klaus Kopka
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Torsten Kniess
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany
| | - Evamarie Hey-Hawkins
- Leipzig University, Faculty of Chemistry and Mineralogy, Institute of Inorganic Chemistry Johannisallee 29 D-04103 Leipzig Germany
| | - Jens Pietzsch
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research Bautzner Landstrasse 400 01328 Dresden Germany .,Faculty of Chemistry and Food Chemistry, School of Science, Technische Universität Dresden Mommsenstrasse 4 D-01062 Dresden Germany
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Ghosh KK, Padmanabhan P, Yang CT, Mishra S, Halldin C, Gulyás B. Dealing with PET radiometabolites. EJNMMI Res 2020; 10:109. [PMID: 32997213 PMCID: PMC7770856 DOI: 10.1186/s13550-020-00692-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Accepted: 09/07/2020] [Indexed: 02/08/2023] Open
Abstract
Abstract Positron emission tomography (PET) offers the study of biochemical,
physiological, and pharmacological functions at a cellular and molecular level.
The performance of a PET study mostly depends on the used radiotracer of
interest. However, the development of a novel PET tracer is very difficult, as
it is required to fulfill a lot of important criteria. PET radiotracers usually
encounter different chemical modifications including redox reaction, hydrolysis,
decarboxylation, and various conjugation processes within living organisms. Due
to this biotransformation, different chemical entities are produced, and the
amount of the parent radiotracer is declined. Consequently, the signal measured
by the PET scanner indicates the entire amount of radioactivity deposited in the
tissue; however, it does not offer any indication about the chemical disposition
of the parent radiotracer itself. From a radiopharmaceutical perspective, it is
necessary to quantify the parent radiotracer’s fraction present in the tissue.
Hence, the identification of radiometabolites of the radiotracers is vital for
PET imaging. There are mainly two reasons for the chemical identification of PET
radiometabolites: firstly, to determine the amount of parent radiotracers in
plasma, and secondly, to rule out (if a radiometabolite enters the brain) or
correct any radiometabolite accumulation in peripheral tissue. Besides,
radiometabolite formations of the tracer might be of concern for the PET study,
as the radiometabolic products may display considerably contrasting distribution
patterns inside the body when compared with the radiotracer itself. Therefore,
necessary information is needed about these biochemical transformations to
understand the distribution of radioactivity throughout the body. Various
published review articles on PET radiometabolites mainly focus on the sample
preparation techniques and recently available technology to improve the
radiometabolite analysis process. This article essentially summarizes the
chemical and structural identity of the radiometabolites of various radiotracers
including [11C]PBB3,
[11C]flumazenil,
[18F]FEPE2I, [11C]PBR28,
[11C]MADAM, and
(+)[18F]flubatine. Besides, the importance of
radiometabolite analysis in PET imaging is also briefly summarized. Moreover,
this review also highlights how a slight chemical modification could reduce the
formation of radiometabolites, which could interfere with the results of PET
imaging. Graphical abstract ![]()
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Affiliation(s)
- Krishna Kanta Ghosh
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore
| | - Parasuraman Padmanabhan
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore.
| | - Chang-Tong Yang
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore.,Department of Nuclear Medicine and Molecular Imaging, Radiological Sciences Division, Singapore General Hospital, Outram Road, Singapore, 169608, Singapore.,Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Sachin Mishra
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore
| | - Christer Halldin
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore.,Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden
| | - Balázs Gulyás
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, 59 Nanyang Drive, Singapore, 636921, Singapore. .,Department of Clinical Neuroscience, Center for Psychiatry Research, Karolinska Institutet and Stockholm County Council, SE-171 76, Stockholm, Sweden.
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