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Lovins AR, Miller KA, Buck AK, Ensey DS, Homoelle RK, Murtha MC, Ward NA, Shanahan LA, Gutti G, Shriwas P, McElroy CA, Callam CS, Hadad CM. 4-Amidophenol Quinone Methide Precursors: Effective and Broad-Scope Nonoxime Reactivators of Organophosphorus-Inhibited Cholinesterases and Resurrectors of Organophosphorus-Aged Acetylcholinesterase. ACS Chem Neurosci 2024; 15:1813-1827. [PMID: 38621296 DOI: 10.1021/acschemneuro.4c00011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/17/2024] Open
Abstract
Acetylcholinesterase (AChE) inhibition by organophosphorus (OP) compounds poses a serious health risk to humans. While many therapeutics have been tested for treatment after OP exposure, there is still a need for efficient reactivation against all kinds of OP compounds, and current oxime therapeutics have poor blood-brain barrier penetration into the central nervous system, while offering no recovery in activity from the OP-aged forms of AChE. Herein, we report a novel library of 4-amidophenol quinone methide precursors (QMP) that provide effective reactivation against multiple OP-inhibited forms of AChE in addition to resurrecting the aged form of AChE after exposure to a pesticide or some phosphoramidates. Furthermore, these QMP compounds also reactivate OP-inhibited butyrylcholinesterase (BChE) which is an in vivo, endogenous scavenger of OP compounds. The in vitro efficacies of these QMP compounds were tested for reactivation and resurrection of soluble forms of human AChE and BChE and for reactivation of cholinesterases within human blood as well as blood and brain samples from a humanized mouse model. We identify compound 10c as a lead candidate due to its broad-scope efficacy against multiple OP compounds as well as both cholinesterases. With methylphosphonates, compound 10c (250 μM, 1 h) shows >60% recovered activity from OEt-inhibited AChE in human blood as well as mouse blood and brain, thus highlighting its potential for future in vivo analysis. For 10c, the effective concentration (EC50) is less than 25 μM for reactivation of three different methylphosphonate-inhibited forms of AChE, with a maximum reactivation yield above 80%. Similarly, for OP-inhibited BChE, 10c has EC50 values that are less than 150 μM for two different methylphosphonate compounds. Furthermore, an in vitro kinetic analysis show that 10c has a 2.2- and 92.1-fold superior reactivation efficiency against OEt-inhibited and OiBu-inhibited AChE, respectively, when compared to an oxime control. In addition to 10c being a potent reactivator of AChE and BChE, we also show that 10c is capable of resurrecting (ethyl paraoxon)-aged AChE, which is another current limitation of oximes.
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Affiliation(s)
- Alex R Lovins
- Department of Chemistry and Biochemistry, College of Arts and Sciences, Ohio State University, Columbus, Ohio 43210, United States
| | - Kevin A Miller
- Department of Chemistry and Biochemistry, College of Arts and Sciences, Ohio State University, Columbus, Ohio 43210, United States
| | - Anne K Buck
- Department of Chemistry and Biochemistry, College of Arts and Sciences, Ohio State University, Columbus, Ohio 43210, United States
| | - D Sophia Ensey
- Department of Chemistry and Biochemistry, College of Arts and Sciences, Ohio State University, Columbus, Ohio 43210, United States
| | - Rose K Homoelle
- Department of Chemistry and Biochemistry, College of Arts and Sciences, Ohio State University, Columbus, Ohio 43210, United States
| | - Megan C Murtha
- Department of Chemistry and Biochemistry, College of Arts and Sciences, Ohio State University, Columbus, Ohio 43210, United States
| | - Nathan A Ward
- Department of Chemistry and Biochemistry, College of Arts and Sciences, Ohio State University, Columbus, Ohio 43210, United States
| | - Liam A Shanahan
- Department of Chemistry and Biochemistry, College of Arts and Sciences, Ohio State University, Columbus, Ohio 43210, United States
| | - Gopichand Gutti
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, Ohio State University, Columbus, Ohio 43210, United States
| | - Pratik Shriwas
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, Ohio State University, Columbus, Ohio 43210, United States
| | - Craig A McElroy
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, Ohio State University, Columbus, Ohio 43210, United States
| | - Christopher S Callam
- Department of Chemistry and Biochemistry, College of Arts and Sciences, Ohio State University, Columbus, Ohio 43210, United States
| | - Christopher M Hadad
- Department of Chemistry and Biochemistry, College of Arts and Sciences, Ohio State University, Columbus, Ohio 43210, United States
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Hayes TR, Chao CK, Blecha JE, Huynh TL, VanBrocklin HF, Zinn KR, Gerdes JM, Thompson CM. [ 11C]Paraoxon: Radiosynthesis, Biodistribution and In Vivo Positron Emission Tomography Imaging in Rat. J Pharmacol Exp Ther 2024; 388:333-346. [PMID: 37770203 PMCID: PMC10801775 DOI: 10.1124/jpet.123.001832] [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: 07/07/2023] [Revised: 08/31/2023] [Accepted: 09/05/2023] [Indexed: 10/03/2023] Open
Abstract
Synthesis of the acetylcholinesterase inhibitor paraoxon (POX) as a carbon-11 positron emission tomography tracer ([11C]POX) and profiling in live rats is reported. Naïve rats intravenously injected with [11C]POX showed a rapid decrease in parent tracer to ∼1%, with an increase in radiolabeled serum proteins to 87% and red blood cells (RBCs) to 9%. Protein and RBC leveled over 60 minutes, reflecting covalent modification of proteins by [11C]POX. Ex vivo biodistribution and imaging profiles in naïve rats had the highest radioactivity levels in lung followed by heart and kidney, and brain and liver the lowest. Brain radioactivity levels were low but observed immediately after injection and persisted over the 60-minute experiment. This showed for the first time that even low POX exposures (∼200 ng tracer) can rapidly enter brain. Rats given an LD50 dose of nonradioactive paraoxon at the LD50 20 or 60 minutes prior to [11C]POX tracer revealed that protein pools were blocked. Blood radioactivity at 20 minutes was markedly lower than naïve levels due to rapid protein modification by nonradioactive POX; however, by 60 minutes the blood radioactivity returned to near naïve levels. Live rat tissue imaging-derived radioactivity values were 10%-37% of naïve levels in nonradioactive POX pretreated rats at 20 minutes, but by 60 minutes the area under the curve (AUC) values had recovered to 25%-80% of naïve. The live rat imaging supported blockade by nonradioactive POX pretreatment at 20 minutes and recovery of proteins by 60 minutes. SIGNIFICANCE STATEMENT: Paraoxon (POX) is an organophosphorus (OP) compound and a powerful prototype and substitute for OP chemical warfare agents (CWAs) such as sarin, VX, etc. To study the distribution and penetration of POX into the central nervous system (CNS) and other tissues, a positron emission tomography (PET) tracer analog, carbon-11-labeled paraoxon ([11C]POX), was prepared. Blood and tissue radioactivity levels in live rats demonstrated immediate penetration into the CNS and persistent radioactivity levels in tissues indicative of covalent target modification.
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Affiliation(s)
- Thomas R Hayes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - Chih-Kai Chao
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - Joseph E Blecha
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - Tony L Huynh
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - Henry F VanBrocklin
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - Kurt R Zinn
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - John M Gerdes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - Charles M Thompson
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
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Gentzsch C, Hoffmann M, Ohshima Y, Nose N, Chen X, Higuchi T, Decker M. Synthesis and Initial Characterization of a Selective, Pseudo-irreversible Inhibitor of Human Butyrylcholinesterase as PET Tracer. ChemMedChem 2021; 16:1427-1437. [PMID: 33645891 PMCID: PMC8247983 DOI: 10.1002/cmdc.202000942] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/19/2021] [Indexed: 02/06/2023]
Abstract
The enzyme butyrylcholinesterase (BChE) represents a promising target for imaging probes to potentially enable early diagnosis of neurodegenerative diseases like Alzheimer's disease (AD) and to monitor disease progression in some forms of cancer. In this study, we present the design, facile synthesis, in vitro and preliminary ex vivo and in vivo evaluation of a morpholine-based, selective inhibitor of human BChE as a positron emission tomography (PET) tracer with a pseudo-irreversible binding mode. We demonstrate a novel protecting group strategy for 18 F radiolabeling of carbamate precursors and show that the inhibitory potency as well as kinetic properties of our unlabeled reference compound were retained in comparison to the parent compound. In particular, the prolonged duration of enzyme inhibition of such a morpholinocarbamate motivated us to design a PET tracer, possibly enabling a precise mapping of BChE distribution.
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Affiliation(s)
- Christian Gentzsch
- Pharmaceutical and Medicinal ChemistryInstitute of Pharmacy and Food ChemistryJulius-Maximilians-University of WürzburgAm Hubland97074WürzburgGermany
| | - Matthias Hoffmann
- Pharmaceutical and Medicinal ChemistryInstitute of Pharmacy and Food ChemistryJulius-Maximilians-University of WürzburgAm Hubland97074WürzburgGermany
| | - Yasuhiro Ohshima
- Comprehensive Heart Failure CenterUniversity Hospital of WürzburgAm Schwarzenberg 1597078WürzburgGermany
- Department of Nuclear MedicineUniversity Hospital of WürzburgOberdürrbacher Straße 697080WürzburgGermany
| | - Naoko Nose
- Graduate School of MedicineDentistry and Pharmaceutical SciencesOkayama University2-5-1 Shikata-cho, Kita-kuOkayamaJapan
| | - Xinyu Chen
- Department of Nuclear MedicineUniversity Hospital of AugsburgStenglinstraße 286156AugsburgGermany
- Comprehensive Heart Failure CenterUniversity Hospital of WürzburgAm Schwarzenberg 1597078WürzburgGermany
- Department of Nuclear MedicineUniversity Hospital of WürzburgOberdürrbacher Straße 697080WürzburgGermany
| | - Takahiro Higuchi
- Comprehensive Heart Failure CenterUniversity Hospital of WürzburgAm Schwarzenberg 1597078WürzburgGermany
- Department of Nuclear MedicineUniversity Hospital of WürzburgOberdürrbacher Straße 697080WürzburgGermany
- Graduate School of MedicineDentistry and Pharmaceutical SciencesOkayama University2-5-1 Shikata-cho, Kita-kuOkayamaJapan
| | - Michael Decker
- Pharmaceutical and Medicinal ChemistryInstitute of Pharmacy and Food ChemistryJulius-Maximilians-University of WürzburgAm Hubland97074WürzburgGermany
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Hayes TR, Chao CK, Blecha JE, Huynh TL, Zinn KR, Thompson CM, Gerdes JM, VanBrocklin HF. Biological Distribution and Metabolic Profiles of Carbon-11 and Fluorine-18 Tracers of VX- and Sarin-Analogs in Sprague-Dawley Rats. Chem Res Toxicol 2020; 34:63-69. [PMID: 33373198 PMCID: PMC7818893 DOI: 10.1021/acs.chemrestox.0c00237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Organophosphorus esters (OPs) were originally developed as pesticides but were repurposed as easily manufactured, inexpensive, and highly toxic chemical warfare agents. Acute OP toxicity is primarily due to inhibition of acetylcholinesterase (AChE), an enzyme in the central and peripheral nervous system. OP inhibition of AChE can be reversed using oxime reactivators but many show poor CNS penetration, indicating a need for new clinically viable reactivators. However, challenges exist on how to best measure restored AChE activity in vivo and assess the reactivating agent efficacy. This work reports the development of molecular imaging tools using radiolabeled OP analog tracers that are less toxic to handle in the laboratory, yet inhibit AChE in a similar fashion to the actual OPs. Carbon-11 and fluorine-18 radiolabeled analog tracers of VX and sarin OP agents were prepared. Following intravenous injection in normal Sprague-Dawley rats (n = 3-4/tracer), the tracers were evaluated and compared using noninvasive microPET/CT imaging, biodistribution assay, and arterial blood analyses. All showed rapid uptake and stable retention in brain, heart, liver, and kidney tissues determined by imaging and biodistribution. Lung uptake of the sarin analog tracers was elevated, 2-fold and 4-fold higher uptake at 5 and 30 min, respectively, compared to that for the VX analog tracers. All tracers rapidly bound to red blood cells (RBC) and blood proteins as measured in the biodistribution and arterial blood samples. Analysis of the plasma soluble activity (nonprotein/cell bound activity) showed only 1-6% parent tracer and 88-95% of the activity in the combined solid fractions (RBC and protein bound) as early as 0.5 min post injection. Multivariate analysis of tracer production yield, molar activity, brain uptake, brain area under the curve over 0-15 min, and the amount of parent tracer in the plasma at 5 min revealed the [18F]VX analog tracer had the most favorable values for each metric. This tracer was considered the more optimal tracer relative to the other tracers studied and suitable for future in vivo OP exposure and reactivation studies.
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Affiliation(s)
- Thomas R Hayes
- Department of Radiology and Biomedical Imaging, University of California at San Francisco, San Francisco, California 94143, United States
| | - Chih-Kai Chao
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, United States
| | - Joseph E Blecha
- Department of Radiology and Biomedical Imaging, University of California at San Francisco, San Francisco, California 94143, United States
| | - Tony L Huynh
- Department of Radiology and Biomedical Imaging, University of California at San Francisco, San Francisco, California 94143, United States
| | - Kurt R Zinn
- Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering; Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan 48824, United States
| | - Charles M Thompson
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, United States
| | - John M Gerdes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, United States
| | - Henry F VanBrocklin
- Department of Radiology and Biomedical Imaging, University of California at San Francisco, San Francisco, California 94143, United States
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Hayes TR, Blecha JE, Chao CK, Huynh TL, VanBrocklin HF, Zinn KR, Taylor PW, Gerdes JM, Thompson CM. Positron emission tomography evaluation of oxime countermeasures in live rats using the tracer O-(2-[ 18 F]fluoroethyl)-O-(p-nitrophenyl)methylphosphonate [ 18 F]-VXS. Ann N Y Acad Sci 2020; 1479:180-195. [PMID: 32436233 DOI: 10.1111/nyas.14363] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 04/13/2020] [Accepted: 04/17/2020] [Indexed: 11/27/2022]
Abstract
Oxime antidotes regenerate organophosphate-inhibited acetylcholinesterase (AChE). Although they share a common mechanism of AChE reactivation, the rate and amount of oxime that enters the brain are critical to the efficacy, a process linked to the oxime structure and charge. Using a platform based on the organophosphate [18 F]-VXS as a positron emission tomography tracer for active AChE, the in vivo distribution of [18 F]-VXS was evaluated after an LD50 dose (250 μg/kg) of the organophosphate paraoxon (POX) and following oximes as antidotes. Rats given [18 F]-VXS tracer alone had significantly higher radioactivity (two- to threefold) in the heart and lung than rats given LD50 POX at 20 or 60 min prior to [18 F]-VXS. When rats were given LD50 POX followed by 2-PAM (cationic), RS194b (ionizable), or monoisonitrosoacetone (MINA) (neutral), central nervous system (CNS) radioactivity returned to levels at or above untreated naive rats (no POX), whereas CNS radioactivity did not increase in rats given the dication oximes HI-6 or MMB-4. MINA showed a significant, pairwise increase in CNS brain radioactivity compared with POX-treated rats. This new in vivo dynamic platform using [18 F]-VXS tracer measures and quantifies peripheral and CNS relative changes in AChE availability after POX exposure and is suitable for comparing oxime delivery and AChE reactivation in rats.
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Affiliation(s)
- Thomas R Hayes
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California
| | - Joseph E Blecha
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California
| | - Chih-Kai Chao
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana
| | - Tony L Huynh
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California
| | - Henry F VanBrocklin
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, California
| | - Kurt R Zinn
- Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering, Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan
| | - Palmer W Taylor
- Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California at San Diego, La Jolla, California
| | - John M Gerdes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana
| | - Charles M Thompson
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana
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Hayes TR, Blecha JE, Thompson CM, Gerdes JM, VanBrocklin HF. Divergent synthesis of organophosphate [ 11C]VX- and [ 11C]Sarin-surrogates from a common set of starting materials. Appl Radiat Isot 2019; 151:182-186. [PMID: 31202183 DOI: 10.1016/j.apradiso.2019.05.033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Revised: 05/09/2019] [Accepted: 05/23/2019] [Indexed: 11/27/2022]
Abstract
Radiolabeled 1-[11C]ethyl, 4-nitrophenyl methylphosphonate (VX surrogate) and 2-[11C]-propanyl, 4-nitrophenyl methylphosphonate (sarin surrogate) were developed as organophosphate (OP) tracers. The [11C]ethyl- and [11C]isopropyl-iodide radiolabeled synthons were obtained by temperature controlled, in loop reactions of [11C]CO2 with MeMgBr followed by reduction with LiAlH4, then reaction with HI. Distillation of the [11C]alkyl iodides into a solution of hydrogen (4-nitrophenyl)methylphosphonate and cesium carbonate afforded the desired tracers in >95% radiochemical purity, yields from [11C]CO2 of 1-3% and 1.7-15.1 GBq/mmol molar activities.
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Affiliation(s)
- Thomas R Hayes
- Department of Radiology and Biomedical Imaging, University of California - San Francisco, 185 Berry St. Suite 350, San Francisco, CA, 94107, United States
| | - Joseph E Blecha
- Department of Radiology and Biomedical Imaging, University of California - San Francisco, 185 Berry St. Suite 350, San Francisco, CA, 94107, United States
| | - Charles M Thompson
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT, 59812, United States
| | - John M Gerdes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT, 59812, United States
| | - Henry F VanBrocklin
- Department of Radiology and Biomedical Imaging, University of California - San Francisco, 185 Berry St. Suite 350, San Francisco, CA, 94107, United States.
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Thompson CM, Gerdes JM, VanBrocklin HF. Positron emission tomography studies of organophosphate chemical threats and oxime countermeasures. Neurobiol Dis 2019; 133:104455. [PMID: 31022458 DOI: 10.1016/j.nbd.2019.04.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 03/28/2019] [Accepted: 04/19/2019] [Indexed: 01/31/2023] Open
Abstract
There is a unique in vivo interplay involving the mechanism of inactivation of acetylcholinesterase (AChE) by toxic organophosphorus (OP) compounds and the restoration of AChE activity by oxime antidotes. OP compounds form covalent adducts to this critical enzyme target and oximes are introduced to directly displace the OP from AChE. For the most part, the in vivo inactivation of AChE leading to neurotoxicity and antidote-based therapeutic reversal of this mechanism are well understood, however, these molecular-level events have not been evaluated by dynamic imaging in living systems at millimeter resolution. A deeper understanding of these critically, time-dependent mechanisms is needed to develop new countermeasures. To address this void and to help accelerate the development of new countermeasures, positron-emission tomography (PET) has been investigated as a unique opportunity to create platform technologies to directly examine the interdependent toxicokinetic/pharmacokinetic and toxicodynamic/pharmacodynamic features of OPs and oximes in real time within live animals. This review will cover two first-in-class PET tracers representing an OP and an oxime antidote, including their preparation, requisite pharmacologic investigations, mechanistic interpretations, biodistribution and imaging.
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Affiliation(s)
- Charles M Thompson
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT 59812, USA.
| | - John M Gerdes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT 59812, USA
| | - Henry F VanBrocklin
- Department of Radiology and Biomedical Imaging, University of California, San Francisco 185 Berry St. Suite 350, San Francisco, CA 94107, USA
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Hayes TR, Thompson CM, Blecha JE, Gerdes JM, VanBrocklin HF. Radiosynthesis of O-(1-[ 18 F]fluoropropan-2-yl)-O-(4-nitrophenyl)methylphosphonate: A novel PET tracer surrogate of sarin. J Labelled Comp Radiopharm 2018; 61:1089-1094. [PMID: 30347484 DOI: 10.1002/jlcr.3688] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 10/05/2018] [Accepted: 10/15/2018] [Indexed: 11/09/2022]
Abstract
O-(1-Fluoropropan-2-yl)-O-(4-nitrophenyl) methylphosphonate is a reactive organophosphate ester (OP) developed as a surrogate of the chemical warfare agent sarin that forms a similar covalent adduct at the active site serine of acetylcholinesterase. The radiolabeled O-(1-[18 F]fluoropropan-2-yl)-O-(4-nitrophenyl) methylphosphonate ([18 F] fluorosarin surrogate) has not been previously prepared. In this paper, we report the first radiosynthesis of this tracer from the reaction of bis-(4-nitrophenyl) methylphosphonate with 1-[18 F]fluoro-2-propanol in the presence of DBU. The 1-[18 F]fluoro-2-propanol was prepared by reaction of propylene sulfite with Kryptofix 2.2.2 and [18 F] fluoride ion. The desired tracer O-(1-[18 F]fluoropropan-2-yl)-O-(4-nitrophenyl) methylphosphonate was obtained in a >98% radiochemical purity with a 2.4% ± 0.6% yield (n = 5, 65 minutes from start of synthesis) based on starting [18 F] fluoride ion and a molar activity of 49.9 GBq/μmol (1.349 ± 0.329 Ci/μmol, n = 3). This new facile radiosynthesis routinely affords sufficient quantities of [18 F] fluorosarin surrogate in high radiochemical purity, which will further enable the tracer development as a novel radiolabeled OP acetylcholinesterase inhibitor for assessment of OP modes of action with PET imaging in vivo.
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Affiliation(s)
- Thomas R Hayes
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA
| | - Charles M Thompson
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT, USA
| | - Joseph E Blecha
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA
| | - John M Gerdes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT, USA
| | - Henry F VanBrocklin
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA
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Chao CK, Balasubramanian N, Gerdes JM, Thompson CM. The inhibition, reactivation and mechanism of VX-, sarin-, fluoro-VX and fluoro-sarin surrogates following their interaction with HuAChE and HuBuChE. Chem Biol Interact 2018; 291:220-227. [PMID: 29920286 PMCID: PMC6061941 DOI: 10.1016/j.cbi.2018.06.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 05/20/2018] [Accepted: 06/15/2018] [Indexed: 10/14/2022]
Abstract
In this study, the mechanisms of HuAChE and HuBChE inhibition by Me-P(O) (OPNP) (OR) [PNP = p-nitrophenyl; R = CH2CH3, CH2CH2F, OCH(CH3)2, OCH(CH3) (CH2F)] representing surrogates and fluoro-surrogates of VX and sarin were studied by in vitro kinetics and mass spectrometry. The in vitro measures showed that the VX- and fluoro-VX surrogates were relatively strong inhibitors of HuAChE and HuBChE (ki ∼ 105-106 M-1min-1) and underwent spontaneous and 2-PAM-mediated reactivation within 30 min. The sarin surrogates were weaker inhibitors of HuAChE and HuBChE (ki ∼ 104-105 M-1min-1), and in general did not undergo spontaneous reactivation, although HuAChE adducts were partially reactivatable at 18 h using 2-PAM. The mechanism of HuAChE and HuBChE inhibition by the surrogates was determined by Q-TOF and MALDI-TOF mass spectral analyses. The surrogate-adducted proteins were trypsin digested and the active site-containing peptide bearing the OP-modified serine identified by Q-TOF as triply- and quadruply-charged ions representing the respective increase in mass of the attached OP moiety. Correspondingly, monoisotopic ions of the tryptic peptides representing the mass increase of the OP-adducted peptide was identified by MALDI-TOF. The mass spectrometry analyses validated the identity of the OP moiety attached to HuAChE or HuBChE as MeP(O) (OR)-O-serine peptides (loss of the PNP leaving group) via mechanisms consistent with those found with chemical warfare agents. MALDI-TOF MS analyses of the VX-modified peptides versus time showed a steady reduction in adduct versus parent peptide (reactivation), whereas the sarin-surrogate-modified peptides remained largely intact over the course of the experiment (24 h). Overall, the presence of a fluorine atom on the surrogate modestly altered the rate constants of inhibition and reactivation, however, the mechanism of inhibition (ejection of PNP group) did not change.
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Affiliation(s)
- Chih-Kai Chao
- Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT, 59812, United States
| | | | - John M Gerdes
- Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT, 59812, United States
| | - Charles M Thompson
- Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT, 59812, United States.
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10
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Abstract
Hydrolytic enzymes are a large class of biological catalysts that play a vital role in a plethora of critical biochemical processes required to maintain human health. However, the expression and/or activity of these important enzymes can change in many different diseases and therefore represent exciting targets for the development of positron emission tomography (PET) and single-photon emission computed tomography (SPECT) radiotracers. This review focuses on recently reported radiolabeled substrates, reversible inhibitors, and irreversible inhibitors investigated as PET and SPECT tracers for imaging hydrolytic enzymes. By learning from the most successful examples of tracer development for hydrolytic enzymes, it appears that an early focus on careful enzyme kinetics and cell-based studies are key factors for identifying potentially useful new molecular imaging agents.
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Affiliation(s)
- Brian P Rempel
- 1 Department of Science, Augustana Faculty, University of Alberta, Edmonton, Alberta, Canada
| | - Eric W Price
- 2 Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Christopher P Phenix
- 2 Department of Chemistry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.,3 Biomarker Discovery, Thunder Bay Regional Health Research Institute, Thunder Bay, Ontario, Canada
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11
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Neumann KD, Thompson CM, Blecha JE, Gerdes JM, VanBrocklin HF. An improved radiosynthesis of O-(2-[ 18 F]fluoroethyl)-O-(p-nitrophenyl)methylphosphonate: A first-in-class cholinesterase PET tracer. J Labelled Comp Radiopharm 2017; 60:337-342. [PMID: 28406525 DOI: 10.1002/jlcr.3511] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 03/31/2017] [Accepted: 04/05/2017] [Indexed: 11/06/2022]
Abstract
O-(2-Fluoroethyl)-O-(p-nitrophenyl) methylphosphonate 1 is an organophosphate cholinesterase inhibitor that creates a phosphonyl-serine covalent adduct at the enzyme active site blocking cholinesterase activity in vivo. The corresponding radiolabeled O-(2-[18 F]fluoroethyl)-O-(p-nitrophenyl) methylphosphonate, [18 F]1, has been previously prepared and found to be an excellent positron emission tomography imaging tracer for assessment of cholinesterases in live brain, peripheral tissues, and blood. However, the previously reported [18 F]1 tracer synthesis was slow even with microwave acceleration, required high-performance liquid chromatography separation of the tracer from impurities, and gave less optimal radiochemical yields. In this paper, we report a new synthetic approach to circumvent these shortcomings that is reliant on the facile reactivity of bis-(O,O-p-nitrophenyl) methylphosphonate, 2, with 2-fluoroethanol in the presence of DBU. The cold synthesis was successfully translated to provide a more robust radiosynthesis. Using this new strategy, the desired tracer, [18 F]1, was obtained in a non-decay-corrected radiochemical yield of 8 ± 2% (n = 7) in >99% radiochemical and >95% chemical purity with a specific activity of 3174 ± 345 Ci/mmol (EOS). This new facile radiosynthesis routinely affords highly pure quantities of [18 F]1, which will further enable tracer development of OP cholinesterase inhibitors and their evaluation in vivo.
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Affiliation(s)
- Kiel D Neumann
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Charles M Thompson
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT, USA
| | - Joseph E Blecha
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - John M Gerdes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT, USA
| | - Henry F VanBrocklin
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
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12
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van der Born D, Pees A, Poot AJ, Orru RVA, Windhorst AD, Vugts DJ. Fluorine-18 labelled building blocks for PET tracer synthesis. Chem Soc Rev 2017; 46:4709-4773. [DOI: 10.1039/c6cs00492j] [Citation(s) in RCA: 113] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
This review presents a comprehensive overview of the synthesis and application of fluorine-18 labelled building blocks since 2010.
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Affiliation(s)
- Dion van der Born
- Department of Radiology & Nuclear Medicine
- VU University Medical Center
- 1081 HV Amsterdam
- The Netherlands
| | - Anna Pees
- Department of Radiology & Nuclear Medicine
- VU University Medical Center
- 1081 HV Amsterdam
- The Netherlands
| | - Alex J. Poot
- Department of Radiology & Nuclear Medicine
- VU University Medical Center
- 1081 HV Amsterdam
- The Netherlands
| | - Romano V. A. Orru
- Department of Chemistry and Pharmaceutical Sciences and Amsterdam Institute for Molecules
- Medicines & Systems (AIMMS)
- VU University Amsterdam
- Amsterdam
- The Netherlands
| | - Albert D. Windhorst
- Department of Radiology & Nuclear Medicine
- VU University Medical Center
- 1081 HV Amsterdam
- The Netherlands
| | - Danielle J. Vugts
- Department of Radiology & Nuclear Medicine
- VU University Medical Center
- 1081 HV Amsterdam
- The Netherlands
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13
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Chao CK, Ahmed SK, Gerdes JM, Thompson CM. Novel Organophosphate Ligand O-(2-Fluoroethyl)-O-(p-Nitrophenyl)Methylphosphonate: Synthesis, Hydrolytic Stability and Analysis of the Inhibition and Reactivation of Cholinesterases. Chem Res Toxicol 2016; 29:1810-1817. [PMID: 27551891 PMCID: PMC5575788 DOI: 10.1021/acs.chemrestox.6b00160] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The organophosphate O-(2-fluoroethyl)-O-(p-nitrophenyl) methyphosphonate 1 is the first-in-class, fluorine-18 radiolabeled organophosphate inhibitor ([18F]1) of acetylcholinesterase (AChE). In rats, [18F]1 localizes in AChE rich regions of the brain and other tissues where it likely exists as the (CH3)(18FCH2CH2O)P(O)-AChE adduct (ChE-1). Characterization of this adduct would define the inhibition mechanism and subsequent postinhibitory pathways and reactivation rates. To validate this adduct, the stability (hydrolysis) of 1 and ChE-1 reactivation rates were determined. Base hydrolysis of 1 yields p-nitrophenol and (CH3) (FCH2CH2O)P(O)OH with pseudo first order rate constants (kobsd) at pH 7.4 (PBS) of 3.25 × 10-4 min-1 (t1/2 = 35.5 h) at 25 °C and 8.70 × 10-4 min-1 (t1/2 = 13.3 h) at 37 °C. Compound 1 was a potent inhibitor of human acetylcholinesterase (HuAChE; ki = 7.5 × 105 M-1 min-1), electric eel acetylcholinesterase (EEAChE) (ki = 3.0 × 106 M-1 min-1), and human serum butyrylcholinesterase (HuBChE; 1.95 × 105 M-1 min-1). Spontaneous and oxime-mediated reactivation rates for the (CH3) (FCH2CH2O)P(O)-serine ChE adducts using 2-PAM (10 μM) were (a) HuAChE 8.8 × 10-5 min-1 (t1/2 = 131.2 h) and 2.41 × 10-2 min-1 (t1/2 = 0.48 h), (b) EEAChE 9.32 × 10-3 min-1 (t1/2 = 1.24 h) and 3.33 × 10-2 min-1 (t1/2 = 0.35 h), and (c) HuBChE 1.16 × 10-4 min-1 (t1/2 = 99.6 h) and 4.19 × 10-2 min-1 (t1/2 = 0.27 h). All ChE-1 adducts undergo rapid and near complete restoration of enzyme activity following addition of 2-PAM (30 min), and no aging was observed for either reactivation process. The fast reactivation rates and absence of aging of ChE-1 adducts are explained on the basis of the electron-withdrawing fluorine group that favors the nucleophilic reactivation processes but disfavors cation-based dealkylation aging mechanisms. Therefore, the likely fate of radiolabeled compound 1 in vivo is the formation of (CH3)(FCH2CH2O)P(O)-serine adducts and monoacid (CH3)(FCH2CH2O)P(O)OH from hydrolysis and reactivation.
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Affiliation(s)
- Chih-Kai Chao
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, United States
| | - S. Kaleem Ahmed
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, United States
- Center for Neuromolecular Research, Drug Discovery Division, Southern Research Institute, Birmingham, Alabama 35205, United States
| | - John M. Gerdes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, United States
- Center for Neuromolecular Research, Drug Discovery Division, Southern Research Institute, Birmingham, Alabama 35205, United States
| | - Charles M. Thompson
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812, United States
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14
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Sawatzky E, Al-Momani E, Kobayashi R, Higuchi T, Samnick S, Decker M. A Novel Way To Radiolabel Human Butyrylcholinesterase for Positron Emission Tomography through Irreversible Transfer of the Radiolabeled Moiety. ChemMedChem 2016; 11:1540-50. [DOI: 10.1002/cmdc.201600223] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 05/30/2016] [Indexed: 11/07/2022]
Affiliation(s)
- Edgar Sawatzky
- Pharmaceutical and Medicinal Chemistry; Institute of Pharmacy and Food Chemistry; Julius Maximilian University Würzburg; Am Hubland 97074 Würzburg Germany
| | - Ehab Al-Momani
- Experimental Nuclear Medicine; Center of Inner Medicine; University Hospital Würzburg; OberdürrbacherStrasse 6 97080 Würzburg Germany
| | - Ryohei Kobayashi
- Experimental Nuclear Medicine; Center of Inner Medicine; University Hospital Würzburg; OberdürrbacherStrasse 6 97080 Würzburg Germany
| | - Takahiro Higuchi
- Experimental Nuclear Medicine; Center of Inner Medicine; University Hospital Würzburg; OberdürrbacherStrasse 6 97080 Würzburg Germany
| | - Samuel Samnick
- Experimental Nuclear Medicine; Center of Inner Medicine; University Hospital Würzburg; OberdürrbacherStrasse 6 97080 Würzburg Germany
| | - Michael Decker
- Pharmaceutical and Medicinal Chemistry; Institute of Pharmacy and Food Chemistry; Julius Maximilian University Würzburg; Am Hubland 97074 Würzburg Germany
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15
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Kniess T, Laube M, Brust P, Steinbach J. 2-[18F]Fluoroethyl tosylate – a versatile tool for building18F-based radiotracers for positron emission tomography. MEDCHEMCOMM 2015. [DOI: 10.1039/c5md00303b] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The review highlights the role of 2-[18F]fluoroethyltosylate ([18F]FETs) in PET radiotracer design since it is a preferred labeling reagent according to its high reactivity to phenolic, amine, thiophenolic and carboxylic functions.
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Affiliation(s)
- Torsten Kniess
- Helmholtz-Zentrum Dresden-Rossendorf
- Institute of Radiopharmaceutical Cancer Research
- Dresden
- Germany
| | - Markus Laube
- Helmholtz-Zentrum Dresden-Rossendorf
- Institute of Radiopharmaceutical Cancer Research
- Dresden
- Germany
| | - Peter Brust
- Helmholtz-Zentrum Dresden-Rossendorf
- Institute of Radiopharmaceutical Cancer Research
- Dresden
- Germany
| | - Jörg Steinbach
- Helmholtz-Zentrum Dresden-Rossendorf
- Institute of Radiopharmaceutical Cancer Research
- Dresden
- Germany
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