1
|
Luu TG, Kim HK. (18)F-Radiolabeled Translocator Protein (TSPO) PET Tracers: Recent Development of TSPO Radioligands and Their Application to PET Study. Pharmaceutics 2022; 14. [PMID: 36432736 DOI: 10.3390/pharmaceutics14112545] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 11/16/2022] [Accepted: 11/17/2022] [Indexed: 11/23/2022] Open
Abstract
Translocator protein 18 kDa (TSPO) is a transmembrane protein in the mitochondrial membrane, which has been identified as a peripheral benzodiazepine receptor. TSPO is generally present at high concentrations in steroid-producing cells and plays an important role in steroid synthesis, apoptosis, and cell proliferation. In the central nervous system, TSPO expression is relatively modest under normal physiological circumstances. However, some pathological disorders can lead to changes in TSPO expression. Overexpression of TSPO is associated with several diseases, such as neurodegenerative diseases, neuroinflammation, brain injury, and cancers. TSPO has therefore become an effective biomarker of related diseases. Positron emission tomography (PET), a non-invasive molecular imaging technique used for the clinical diagnosis of numerous diseases, can detect diseases related to TSPO expression. Several radiolabeled TSPO ligands have been developed for PET. In this review, we describe recent advances in the development of TSPO ligands, and 18F-radiolabeled TSPO in particular, as PET tracers. This review covers pharmacokinetic studies, preclinical and clinical trials of 18F-labeled TSPO PET ligands, and the synthesis of TSPO ligands.
Collapse
|
2
|
Klenner MA, Pascali G, Fraser BH, Darwish TA. Kinetic isotope effects and synthetic strategies for deuterated carbon-11 and fluorine-18 labelled PET radiopharmaceuticals. Nucl Med Biol 2021; 96-97:112-47. [PMID: 33892374 DOI: 10.1016/j.nucmedbio.2021.03.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 03/19/2021] [Accepted: 03/30/2021] [Indexed: 11/22/2022]
Abstract
The deuterium labelling of pharmaceuticals is a useful strategy for altering pharmacokinetic properties, particularly for improving metabolic resistance. The pharmacological effects of such metabolites are often assumed to be negligible during standard drug discovery and are factored in later at the clinical phases of development, where the risks and benefits of the treatment and side-effects can be wholly assessed. This paradigm does not translate to the discovery of radiopharmaceuticals, however, as the confounding effects of radiometabolites can inevitably show in preliminary positron emission tomography (PET) scans and thus complicate interpretation. Consequently, the formation of radiometabolites is crucial to take into consideration, compared to non-radioactive metabolites, and the application of deuterium labelling is a particularly attractive approach to minimise radiometabolite formation. Herein, we provide a comprehensive overview of the deuterated carbon-11 and fluorine-18 radiopharmaceuticals employed in PET imaging experiments. Specifically, we explore six categories of deuterated radiopharmaceuticals used to investigate the activities of monoamine oxygenase (MAO), choline, translocator protein (TSPO), vesicular monoamine transporter 2 (VMAT2), neurotransmission and the diagnosis of Alzheimer's disease; from which we derive four prominent deuteration strategies giving rise to a kinetic isotope effect (KIE) for reducing the rate of metabolism. Synthetic approaches for over thirty of these deuterated radiopharmaceuticals are discussed from the perspective of deuterium and radioisotope incorporation, alongside an evaluation of the deuterium labelling and radiolabelling efficacies across these independent studies. Clinical and manufacturing implications are also discussed to provide a more comprehensive overview of how deuterated radiopharmaceuticals may be introduced to routine practice.
Collapse
|
3
|
Keller T, Krzyczmonik A, Forsback S, Picón FRL, Kirjavainen AK, Takkinen J, Rajander J, Cacheux F, Damont A, Dollé F, Rinne JO, Haaparanta-Solin M, Solin O. Radiosynthesis and Preclinical Evaluation of [ 18F]F-DPA, A Novel Pyrazolo[1,5a]pyrimidine Acetamide TSPO Radioligand, in Healthy Sprague Dawley Rats. Mol Imaging Biol 2017; 19:736-745. [PMID: 28083825 PMCID: PMC5574958 DOI: 10.1007/s11307-016-1040-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
PURPOSE Many neurological conditions result in the overexpression of the translocator protein 18 kDa (TSPO), today recognized as a biomarker for microglial activation and neuroinflammation imaging. The pyrazolo[1,5-a]pyrimidine acetamides are a particularly attractive class of TSPO-specific ligands, prompting the development of several positron emission tomography (PET) radiotracers. This includes F-DPA, a recently reported fluorinated ligand (K i = 1.7 nM), wherein the fluorine atom is directly linked to the phenyl moiety without the presence of an alkyl or alkoxy spacer chain. Reported here is the preparation of [18F]F-DPA using [18F]Selectfluor bis(triflate) and the preliminary evaluation of [18F]F-DPA in healthy rats. Its metabolic profile and biodistribution in rats are compared with that of [18F]DPA-714, a closely related structure. PROCEDURES [18F]F-DPA was synthesized by electrophilic fluorination using [18F]Selectfluor bis(triflate), [18F]DPA-714 was synthesized by conventional nucleophilic fluorination. The biodistribution of both radiotracers was compared in Sprague Dawley rats. Radiometabolites of both radiotracers in plasma and brain homogenates were analyzed by radioTLC. RESULTS The radiochemical yield of [18F]F-DPA was 15 ± 3 % and the specific activity was 7.8 ± 0.4 GBq/μmol. The radiochemical purity exceeded 99 %. The in vivo time activity curves of [18F]F-DPA demonstrate rapid entry into the brain and a concentration equilibrium at 20-30 min after injection. The metabolic profiles at 90 min after radiotracer injection in the plasma show that unchanged [18F]F-DPA and [18F]DPA-714 account for 28.3 ± 6.4 and 11.1 ± 2.6 % of the remaining radioactivity, respectively. In the brain, unchanged [18F]F-DPA accounts for 93.5 ± 2.8 % of the radioactivity; whereas for [18F]DPA-714, this value is 53.6 ± 1.6 %. CONCLUSIONS [18F]Selectfluor bis(triflate) was successfully used to label F-DPA with fluorine-18. The labeling position on the aromatic moiety imparts a higher stability compared to [18F]DPA-714 with regard to in vivo metabolism. [18F]F-DPA is a promising new radiotracer and warrants further investigation in animal models of disease.
Collapse
Affiliation(s)
- Thomas Keller
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Anna Krzyczmonik
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Sarita Forsback
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
- Department of Chemistry, University of Turku, Turku, Finland
| | - Francisco R López Picón
- PET Preclinical Imaging Laboratory, Turku PET Centre, University of Turku, Turku, Finland
- MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Anna K Kirjavainen
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Jatta Takkinen
- PET Preclinical Imaging Laboratory, Turku PET Centre, University of Turku, Turku, Finland
- MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Johan Rajander
- Accelerator Laboratory, Turku PET Centre, Åbo Akademi University, Turku, Finland
| | - Fanny Cacheux
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France
| | | | - Frédéric Dollé
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France
| | - Juha O Rinne
- Turku PET Centre, Division of Clinical Neurosciences, Turku University Hospital, Turku, Finland
| | - Merja Haaparanta-Solin
- PET Preclinical Imaging Laboratory, Turku PET Centre, University of Turku, Turku, Finland
- MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Olof Solin
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland.
- Department of Chemistry, University of Turku, Turku, Finland.
- Accelerator Laboratory, Turku PET Centre, Åbo Akademi University, Turku, Finland.
- Turku PET Centre, University of Turku, Kiinamyllynkatu 4-8, 20520, Turku, Finland.
| |
Collapse
|
4
|
Alam MM, Lee J, Lee SY. Recent Progress in the Development of TSPO PET Ligands for Neuroinflammation Imaging in Neurological Diseases. Nucl Med Mol Imaging 2017; 51:283-296. [PMID: 29242722 DOI: 10.1007/s13139-017-0475-8] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 12/08/2016] [Accepted: 02/06/2017] [Indexed: 12/13/2022] Open
Abstract
Neuroinflammation is heavily associated with various neurological diseases including Alzheimer's disease, Parkinson's disease, multiple sclerosis, and stroke. It is strongly characterized by the activation of microglia which can be visualized using position emission tomography (PET). Traditionally, translocator protein 18 kDa (TSPO) has been the preferred target for imaging the inflammatory progression of the microglial component. TSPO is expressed in the outer mitochondrial membrane and present in very low concentrations in the healthy human brain, but is markedly upregulated in response to brain injury and inflammation. Due to its value as a marker of microglial activation and subsequent utility for evaluating neuroinflammation in CNS disorders, several classes of TSPO radioligands have been developed and evaluated. However, the application of these second-generation TSPO radiotracers has been subject to several limiting factors, including a polymorphism that affects TSPO binding. This review focuses on recent developments in TSPO imaging, as well as current limitations and suggestions for future directions from a medical imaging perspective.
Collapse
Affiliation(s)
- Md Maqusood Alam
- Neuroscience Research Institute, Gachon University, Incheon, 20565 South Korea
| | - Jihye Lee
- Neuroscience Research Institute, Gachon University, Incheon, 20565 South Korea
| | - Sang-Yoon Lee
- Neuroscience Research Institute, Gachon University, Incheon, 20565 South Korea.,Department of Neuroscience, College of Medicine, Gachon University, Incheon, 21936 South Korea
| |
Collapse
|
5
|
Cacheux F, Médran-Navarrete V, Dollé F, Marguet F, Puech F, Damont A. Synthesis and in vitro characterization of novel fluorinated derivatives of the translocator protein 18 kDa ligand CfO-DPA-714. Eur J Med Chem 2016; 125:346-359. [PMID: 27688189 DOI: 10.1016/j.ejmech.2016.09.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 09/07/2016] [Accepted: 09/08/2016] [Indexed: 11/30/2022]
Abstract
The translocator protein 18 kDa (TSPO) is today a validated target for a number of therapeutic applications, but also a well-recognized diagnostic/imaging biomarker for the evaluation of inflammatory related-disease state and progression, prompting the development of specific and dedicated TSPO ligands worldwide. For this purpose, pyrazolo[1,5-a]pyrimidine acetamides constitute a unique class of high affinity and selectivity TSPO ligands; it includes DPA-714, a fluorine-containing derivative that has also been labelled with the positron-emitter fluorine-18, and is nowadays widely used as a Positron Emission Tomography imaging probe. Recently, to prevent defluorination issues encountered in vivo with this tracer, a first series of analogues was reported where the oxygen atom bridging the phenyl ring of the core structure and the fluorinated moiety was replaced with a more robust linkage. Among this new series, CfO-DPA-714 was discovered as a highly promising TSPO ligand. Herein, a novel series of fluorinated analogues of the latter molecule were synthesized and in vitro characterized, where the pharmacomodulation at the amide position of the molecule was explored. Thirteen compounds were thus prepared from a common key-ester intermediate (synthesized in 7 steps from 4-iodobenzoate - 11% overall yield) and a set of commercially available amines and obtained with moderate to good yields (23-81%) and high purities (>95%). With one exception, all derivatives displayed nanomolar to subnanomolar affinity for the TSPO and also high selectivity versus the CBR (Ki (CBR)/Ki (TSPO) > 103). Within this series, three compounds showed better Ki values (0.25, 0.26 and 0.30 nM) than that of DPA-714 (0.91 nM) and CfO-DPA-714 (0.37 nM), and favorable lipophilicity for brain penetration (3.6 < logD7.4 < 4.4). Among these three compounds, the N-methyl-N-propyl amide analogue (9) exhibited similar metabolic stability when compared to CfO-DPA-714 in mouse, rat and human microsomes. Therefore, the latter compound stands out as a promising candidate for drug development or for use as a PET probe, once fluorine-18-labelled, for in vivo neuroinflammation imaging.
Collapse
Affiliation(s)
- Fanny Cacheux
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France; Inserm/CEA/Université Paris Sud, UMR 1023, ERL 9218 CNRS, IMIV, Université Paris-Saclay, Orsay, France
| | - Vincent Médran-Navarrete
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France; Inserm/CEA/Université Paris Sud, UMR 1023, ERL 9218 CNRS, IMIV, Université Paris-Saclay, Orsay, France
| | - Frédéric Dollé
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France; Inserm/CEA/Université Paris Sud, UMR 1023, ERL 9218 CNRS, IMIV, Université Paris-Saclay, Orsay, France
| | | | | | - Annelaure Damont
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France; Inserm/CEA/Université Paris Sud, UMR 1023, ERL 9218 CNRS, IMIV, Université Paris-Saclay, Orsay, France.
| |
Collapse
|
6
|
Damont A, Médran-Navarrete V, Cacheux F, Kuhnast B, Pottier G, Bernards N, Marguet F, Puech F, Boisgard R, Dollé F. Novel Pyrazolo[1,5-a]pyrimidines as Translocator Protein 18 kDa (TSPO) Ligands: Synthesis, in Vitro Biological Evaluation, [(18)F]-Labeling, and in Vivo Neuroinflammation PET Images. J Med Chem 2015; 58:7449-64. [PMID: 26280386 DOI: 10.1021/acs.jmedchem.5b00932] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
A series of novel pyrazolo[1,5-a]pyrimidines, closely related to N,N-diethyl-2-(2-(4-(2-fluoroethoxy)phenyl)-5,7-dimethylpyrazolo[1,5-a]pyrimidin-3-yl)acetamide (2, DPA-714), were synthesized and biologically in vitro evaluated for their potential to bind the translocator protein 18 kDa (TSPO), a protein today recognized as an early biomarker of neuroinflammatory processes. This series is composed of fluoroalkyl- and fluoroalkynyl- analogues, prepared from a common iodinated intermediate via Sonogashira coupling reactions. All derivatives displayed subnanomolar affinity for the TSPO (0.37 to 0.86 nM), comparable to that of 2 (0.91 nM). Two of them were radiolabeled with fluorine-18, and their biodistribution was investigated by in vitro autoradiography and positron emission tomography (PET) imaging on a rodent model of neuroinflammation. Brain uptake and local accumulation of both compounds in the AMPA-mediated lesion confirm their potential as in vivo PET-radiotracers. In particular, [(18)F]23 exhibited a significantly higher ipsi- to contralateral ratio at 60 min than the parent molecule [(18)F]2 in vivo.
Collapse
Affiliation(s)
- Annelaure Damont
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France.,Inserm/CEA/Université Paris Sud, UMR 1023-ERL 9218 CNRS, IMIV, Orsay, France
| | - Vincent Médran-Navarrete
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France.,Inserm/CEA/Université Paris Sud, UMR 1023-ERL 9218 CNRS, IMIV, Orsay, France
| | - Fanny Cacheux
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France.,Inserm/CEA/Université Paris Sud, UMR 1023-ERL 9218 CNRS, IMIV, Orsay, France
| | - Bertrand Kuhnast
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France.,Inserm/CEA/Université Paris Sud, UMR 1023-ERL 9218 CNRS, IMIV, Orsay, France
| | - Géraldine Pottier
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France.,Inserm/CEA/Université Paris Sud, UMR 1023-ERL 9218 CNRS, IMIV, Orsay, France
| | - Nicholas Bernards
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France.,Inserm/CEA/Université Paris Sud, UMR 1023-ERL 9218 CNRS, IMIV, Orsay, France
| | | | | | - Raphaël Boisgard
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France.,Inserm/CEA/Université Paris Sud, UMR 1023-ERL 9218 CNRS, IMIV, Orsay, France
| | - Frédéric Dollé
- CEA, I2BM, Service Hospitalier Frédéric Joliot, Orsay, France.,Inserm/CEA/Université Paris Sud, UMR 1023-ERL 9218 CNRS, IMIV, Orsay, France
| |
Collapse
|
7
|
Damont A, Marguet F, Puech F, Dollé F. Synthesis and in vitro characterization of novel fluorinated derivatives of the TSPO 18 kDa ligand SSR180575. Eur J Med Chem 2015. [DOI: 10.1016/j.ejmech.2015.07.033] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
8
|
Cheung YY, Nickels ML, Tang D, Buck JR, Manning HC. Facile synthesis of SSR180575 and discovery of 7-chloro-N,N,5-trimethyl-4-oxo-3(6-[(18)F]fluoropyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide, a potent pyridazinoindole ligand for PET imaging of TSPO in cancer. Bioorg Med Chem Lett 2014; 24:4466-4471. [PMID: 25172419 PMCID: PMC4163096 DOI: 10.1016/j.bmcl.2014.07.091] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 07/29/2014] [Accepted: 07/31/2014] [Indexed: 10/24/2022]
Abstract
A novel synthesis of the translocator protein (TSPO) ligand 7-chloro-N,N,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide (SSR180575, 3) was achieved in four steps from commercially available starting materials. Focused structure-activity relationship development about the pyridazinoindole ring at the N3 position led to the discovery of 7-chloro-N,N,5-trimethyl-4-oxo-3(6-fluoropyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide (14), a novel ligand of comparable affinity. Radiolabeling with fluorine-18 ((18)F) yielded 7-chloro-N,N,5-trimethyl-4-oxo-3(6-[(18)F]fluoropyridin-2-yl)-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide ([(18)F]-14) in high radiochemical yield and specific activity. In vivo studies of [(18)F]-14 revealed this agent as a promising probe for molecular imaging of glioma.
Collapse
Affiliation(s)
- Yiu-Yin Cheung
- Vanderbilt University Institute of Imaging Science (VUIIS), Vanderbilt University Medical Center, Nashville, TN 37232, United States
| | - Michael L Nickels
- Vanderbilt University Institute of Imaging Science (VUIIS), Vanderbilt University Medical Center, Nashville, TN 37232, United States; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN 37232, United States
| | - Dewei Tang
- Vanderbilt University Institute of Imaging Science (VUIIS), Vanderbilt University Medical Center, Nashville, TN 37232, United States; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN 37232, United States
| | - Jason R Buck
- Vanderbilt University Institute of Imaging Science (VUIIS), Vanderbilt University Medical Center, Nashville, TN 37232, United States; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN 37232, United States
| | - H Charles Manning
- Vanderbilt University Institute of Imaging Science (VUIIS), Vanderbilt University Medical Center, Nashville, TN 37232, United States; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN 37232, United States; Program in Chemical and Physical Biology, Vanderbilt University Medical Center, Nashville, TN 37232, United States; Vanderbilt-Ingram Cancer Center (VICC), Vanderbilt University Medical Center, Nashville, TN 37232, United States; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37232, United States; Department of Neurosurgery, Vanderbilt University Medical Center, Nashville, TN 37232, United States
| |
Collapse
|
9
|
Damont A, Roeda D, Dollé F. The potential of carbon-11 and fluorine-18 chemistry: illustration through the development of positron emission tomography radioligands targeting the translocator protein 18 kDa. J Labelled Comp Radiopharm 2013; 56:96-104. [DOI: 10.1002/jlcr.2992] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 07/18/2012] [Accepted: 11/06/2012] [Indexed: 11/05/2022]
Affiliation(s)
- Annelaure Damont
- CEA, I2BM, Service Hospitalier Frédéric Joliot; 4 place du Général Leclerc; F-91406; Orsay; France
| | - Dirk Roeda
- CEA, I2BM, Service Hospitalier Frédéric Joliot; 4 place du Général Leclerc; F-91406; Orsay; France
| | - Frédéric Dollé
- CEA, I2BM, Service Hospitalier Frédéric Joliot; 4 place du Général Leclerc; F-91406; Orsay; France
| |
Collapse
|
10
|
Boutin H, Prenant C, Maroy R, Galea J, Greenhalgh AD, Smigova A, Cawthorne C, Julyan P, Wilkinson SM, Banister SD, Brown G, Herholz K, Kassiou M, Rothwell NJ. [18F]DPA-714: direct comparison with [11C]PK11195 in a model of cerebral ischemia in rats. PLoS One 2013; 8:e56441. [PMID: 23418569 PMCID: PMC3572061 DOI: 10.1371/journal.pone.0056441] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 01/11/2013] [Indexed: 12/11/2022] Open
Abstract
Purpose Neuroinflammation is involved in several brain disorders and can be monitored through expression of the translocator protein 18 kDa (TSPO) on activated microglia. In recent years, several new PET radioligands for TSPO have been evaluated in disease models. [18F]DPA-714 is a TSPO radiotracer with great promise; however results vary between different experimental models of neuroinflammation. To further examine the potential of [18F]DPA-714, it was compared directly to [11C]PK11195 in experimental cerebral ischaemia in rats. Methods Under anaesthesia, the middle cerebral artery of adult rats was occluded for 60 min using the filament model. Rats were allowed recovery for 5 to 7 days before one hour dynamic PET scans with [11C]PK11195 and/or [18F]DPA-714 under anaesthesia. Results Uptake of [11C]PK11195 vs [18F]DPA-714 in the ischemic lesion was similar (core/contralateral ratio: 2.84±0.67 vs 2.28±0.34 respectively), but severity of the brain ischemia and hence ligand uptake in the lesion appeared to vary greatly between animals scanned with [11C]PK11195 or with [18F]DPA-714. To solve this issue of inter-individual variability, we performed a direct comparison of [11C]PK11195 and [18F]DPA-714 by scanning the same animals sequentially with both tracers within 24 h. In this direct comparison, the core/contralateral ratio (3.35±1.21 vs 4.66±2.50 for [11C]PK11195 vs [18F]DPA-714 respectively) showed a significantly better signal-to-noise ratio (1.6 (1.3–1.9, 95%CI) fold by linear regression) for [18F]DPA-714. Conclusions In a clinically relevant model of neuroinflammation, uptake for both radiotracers appeared to be similar at first, but a high variability was observed in our model. Therefore, to truly compare tracers in such models, we performed scans with both tracers in the same animals. By doing so, our result demonstrated that [18F]DPA-714 displayed a higher signal-to-noise ratio than [11C]PK11195. Our results suggest that, with the longer half-life of [18F] which facilitates distribution of the tracer across PET centre, [18F]DPA-714 is a good alternative for TSPO imaging.
Collapse
Affiliation(s)
- Hervé Boutin
- Faculty of Medical and Human Sciences, University of Manchester, Manchester, United Kingdom.
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Ching AS, Kuhnast B, Damont A, Roeda D, Tavitian B, Dollé F. Current paradigm of the 18-kDa translocator protein (TSPO) as a molecular target for PET imaging in neuroinflammation and neurodegenerative diseases. Insights Imaging 2012; 3:111-9. [PMID: 22696004 DOI: 10.1007/s13244-011-0128-x] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 06/18/2011] [Accepted: 09/09/2011] [Indexed: 11/08/2022] Open
Abstract
Neuroinflammation is a process characterised by drastic changes in microglial morphology and by marked upregulation of the 18-kDa translocator protein (TSPO) on the mitochondria. The continual increase in incidence of neuroinflammation and neurodegenerative diseases poses a major health issue in many countries, requiring more innovative diagnostic and monitoring tools. TSPO expression may constitute a biomarker for brain inflammation that could be monitored by using TSPO tracers as neuroimaging agents. From medical imaging perspectives, this review focuses on the current concepts related to the TSPO, and discusses briefly on the status of its PET imaging related to neuroinflammation and neurodegenerative diseases in humans.
Collapse
|
12
|
Moerman L, Dumolyn C, Boon P, De Vos F. The influence of mass of [11C]-laniquidar and [11C]-N-desmethyl-loperamide on P-glycoprotein blockage at the blood-brain barrier. Nucl Med Biol 2011; 39:121-5. [PMID: 21958857 DOI: 10.1016/j.nucmedbio.2011.06.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Revised: 06/17/2011] [Accepted: 06/22/2011] [Indexed: 01/16/2023]
Abstract
INTRODUCTION An earlier report suggested that mass amount of PET tracers could be an important factor in brain uptake mediated by P-glycoprotein. Thereby, this study investigated the influence of mass dose of laniquidar, desmethyl-loperamide and loperamide on the P-glycoprotein-mediated brain uptake of, respectively, [(11)C]-laniquidar and [(11)C]-N-desmethyl-loperamide ([(11)C]-dLop). METHODS Wild-type (WT) mice were injected intravenously with solutions of 5.6 MBq [(11)C]-laniquidar (either no carrier added or 60 mg/kg laniquidar added) or with 5.0-7.4 MBq [(11)C]-dLop (either no carrier added or 3 mg/kg desmethyl loperamide). Mice were killed, and brain and blood were collected, weighted and counted for radioactivity. Mdr1a(-/-) knockout mice were incorporated as the control group. RESULTS Injection of (11)C-laniquidar (no carrier added) in WT mice resulted in a statistical significant lower brain uptake (0.7±0.2 %ID/g) compared to the carrier-added formulation (60 mg/kg laniquidar) (3.1±0.3 %ID/g) (P=.004), while no statistical difference could be observed between formulations of [(11)C]-dLop. The [(11)C]-laniquidar and [(11)C]-dLop blood concentrations were not significantly different between the tested formulations in WT mice. In control animals, no effect of mass amount on brain uptake of both tracers could be demonstrated. CONCLUSIONS These results demonstrate the bivalent character of laniquidar, acting as a substrate at low doses and as a blocking agent for P-glycoprotein transport in the brain at higher doses. In comparison, no difference was observed in [(11)C]-dLop uptake between carrier- and no-carrier-added formulations, which confirms that desmethyl-loperamide is a substrate of P-glycoprotein at the blood-brain barrier.
Collapse
|
13
|
Chauveau F, Boutin H, Van Camp N, Thominiaux C, Hantraye P, Rivron L, Marguet F, Castel MN, Rooney T, Benavides J, Dollé F, Tavitian B. In vivo imaging of neuroinflammation in the rodent brain with [11C]SSR180575, a novel indoleacetamide radioligand of the translocator protein (18 kDa). Eur J Nucl Med Mol Imaging 2011; 38:509-14. [PMID: 20936410 DOI: 10.1007/s00259-010-1628-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Accepted: 09/09/2010] [Indexed: 10/19/2022]
Abstract
PURPOSE Neuroinflammation is involved in neurological disorders through the activation of microglial cells. Imaging of neuroinflammation with radioligands for the translocator protein (18 kDa) (TSPO) could prove to be an attractive biomarker for disease diagnosis and therapeutic evaluation. The indoleacetamide-derived 7-chloro-N,N,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide, SSR180575, is a selective high-affinity TSPO ligand in human and rodents with neuroprotective effects. METHODS Here we report the radiolabelling of SSR180575 with (11)C and in vitro and in vivo imaging in an acute model of neuroinflammation in rats. RESULTS The image contrast and the binding of [(11)C]SSR180575 are higher than that obtained with the isoquinoline-based TSPO radioligand, [(11)C]PK11195. Competition studies demonstrate that [(11)C]SSR180575 has high specific binding for the TSPO. CONCLUSION [(11)C]SSR180575 is the first PET radioligand for the TSPO based on an indoleacetamide scaffold designed for imaging neuroinflammation in animal models and in the clinic.
Collapse
|