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Aguero C, Dhaynaut M, Amaral AC, Moon SH, Neelamegam R, Scapellato M, Carazo-Casas C, Kumar S, El Fakhri G, Johnson K, Frosch MP, Normandin MD, Gómez-Isla T. Head-to-head comparison of [ 18F]-Flortaucipir, [ 18F]-MK-6240 and [ 18F]-PI-2620 postmortem binding across the spectrum of neurodegenerative diseases. Acta Neuropathol 2024; 147:25. [PMID: 38280071 PMCID: PMC10822013 DOI: 10.1007/s00401-023-02672-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 12/19/2023] [Accepted: 12/19/2023] [Indexed: 01/29/2024]
Abstract
We and others have shown that [18F]-Flortaucipir, the most validated tau PET tracer thus far, binds with strong affinity to tau aggregates in Alzheimer's (AD) but has relatively low affinity for tau aggregates in non-AD tauopathies and exhibits off-target binding to neuromelanin- and melanin-containing cells, and to hemorrhages. Several second-generation tau tracers have been subsequently developed. [18F]-MK-6240 and [18F]-PI-2620 are the two that have garnered most attention. Our recent data indicated that the binding pattern of [18F]-MK-6240 closely parallels that of [18F]-Flortaucipir. The present study aimed at the direct comparison of the autoradiographic binding properties and off-target profile of [18F]-Flortaucipir, [18F]-MK-6240 and [18F]-PI-2620 in human tissue specimens, and their potential binding to monoamine oxidases (MAO). Phosphor-screen and high resolution autoradiographic patterns of the three tracers were studied in the same postmortem tissue material from AD and non-AD tauopathies, cerebral amyloid angiopathy, synucleopathies, transactive response DNA-binding protein 43 (TDP-43)-frontotemporal lobe degeneration and controls. Our results show that the three tracers show nearly identical autoradiographic binding profiles. They all strongly bind to neurofibrillary tangles in AD but do not seem to bind to a significant extent to tau aggregates in non-AD tauopathies pointing to their limited utility for the in vivo detection of non-AD tau lesions. None of them binds to lesions containing β-amyloid, α-synuclein or TDP-43 but they all show strong off-target binding to neuromelanin and melanin-containing cells, as well as weaker binding to areas of hemorrhage. The autoradiographic binding signals of the three tracers are only weakly displaced by competing concentrations of selective MAO-B inhibitor deprenyl but not by MAO-A inhibitor clorgyline suggesting that MAO enzymes do not appear to be a significant binding target of any of them. These findings provide relevant insights for the correct interpretation of the in vivo behavior of these three tau PET tracers.
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Affiliation(s)
- Cinthya Aguero
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
| | - Maeva Dhaynaut
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Ana C Amaral
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
| | - S-H Moon
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Ramesh Neelamegam
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Margaret Scapellato
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
| | - Carlos Carazo-Casas
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
| | - Sunny Kumar
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
| | - Georges El Fakhri
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Keith Johnson
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Matthew P Frosch
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA
- C.S. Kubik Laboratory for Neuropathology, Massachusetts General Hospital, Boston, MA, USA
| | - Marc D Normandin
- Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
| | - Teresa Gómez-Isla
- MassGeneral Institute for NeuroDegenerative Disease, Charlestown, MA, USA.
- Department of Neurology, Massachusetts General Hospital, WACC Suite 715, 15th Parkman St., Boston, MA, 02114, USA.
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Zhou Y, Li J, Nordberg A, Ågren H. Dissecting the Binding Profile of PET Tracers to Corticobasal Degeneration Tau Fibrils. ACS Chem Neurosci 2021; 12:3487-3496. [PMID: 34464084 PMCID: PMC8447187 DOI: 10.1021/acschemneuro.1c00536] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
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Alzheimer’s
disease and primary tauopathies are characterized
by the presence of tau pathology in brain. Several tau positron emission
tomography (PET) tracers have been developed and studied in Alzheimer’s
disease (AD), but there is still a lack of 4R-tau specific tracers
for non-AD tauopathies. We here present the first computational study
on the binding profiles of four tau different PET tracers, PI2620,
CBD2115, PM-PBB3, and MK6240, to corticobasal degeneration (CBD) tau.
The in silico results showed different preferences
for the various binding sites on the 4R fibril, and especially an
entry site, a concave site, and a core site showed high binding affinity
to these tracers. The core site and entry site both showed higher
binding affinity than the surface sites, but the tracers were less
likely to enter these sites. PI2620, CBD2115, and PM-PBB3 all showed
higher binding affinities to CBD tau than the 3R/4R tracer MK6240.
The same strategy has also been applied to AD tau fibrils, and significant
differences in selectivity of binding sites were also observed. A
higher binding affinity was observed for CBD2115 and PM-PBB3 to AD
tau compared to PI2620. None of the studied tracers showed a selectivity
for 4R compared to 3R/4R tau. This study clearly shows that identified
binding sites from cryo-EM with low resolution can be further refined
by metadynamics simulations in order to provide atomic resolution
of the binding modes as well as of the thermodynamic properties.
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Affiliation(s)
- Yang Zhou
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
| | - Junhao Li
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
| | - Agneta Nordberg
- Division of Clinical Geriatrics, Center for Alzheimer Research, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, 141 84, Stockholm, Sweden
- Theme Aging Karolinska University Hospital, S-141 86 Stockholm, Sweden
| | - Hans Ågren
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
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