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Preller KH, Scholpp J, Wunder A, Rosenbrock H. Neuroimaging Biomarkers for Drug Discovery and Development in Schizophrenia. Biol Psychiatry 2024; 96:666-673. [PMID: 38272287 DOI: 10.1016/j.biopsych.2024.01.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 12/19/2023] [Accepted: 01/14/2024] [Indexed: 01/27/2024]
Abstract
Schizophrenia is a chronic mental illness that affects up to 1% of the population. While efficacious therapies are available for positive symptoms, effective treatment of cognitive and negative symptoms remains an unmet need after decades of research. New developments in the field of neuroimaging are accelerating our knowledge gain regarding the underlying pathophysiology of symptoms in schizophrenia and psychosis spectrum disorders, inspiring new targets for drug development. However, no validated and qualified biomarkers are currently available to support the development of new therapeutics. This review summarizes the current use of neuroimaging technology in clinical drug development for psychotic disorders. As exemplified by drug development programs that target NMDA receptor hypofunction, neuroimaging results play a critical role in target discovery and establishing target engagement and dose selection. Furthermore, pharmacological neuroimaging may provide response biomarkers that allow for early decision making in proof-of-concept studies that leverage pharmacological challenge models in healthy volunteers. That said, while response and predictive biomarkers are starting to be evaluated in patient populations, they continue to play a limited role. Novel approaches to neuroimaging data acquisition and analysis may aid the establishment of biomarkers that are predictive at the individual level in the future. Nevertheless, various gaps in knowledge need to be addressed and biomarkers need to be validated to establish them as "fit for purpose" in drug development.
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Affiliation(s)
- Katrin H Preller
- Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany; Boehringer Ingelheim (Schweiz) GmbH, Basel, Switzerland.
| | - Joachim Scholpp
- Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany
| | - Andreas Wunder
- Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany
| | - Holger Rosenbrock
- Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach an der Riss, Germany
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2
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Frouni I, Kim E, Shaqfah J, Bédard D, Kwan C, Belliveau S, Huot P. [ 3H]-NFPS binding to the glycine transporter 1 in the hemi-parkinsonian rat brain. Exp Brain Res 2024; 242:1203-1214. [PMID: 38526743 PMCID: PMC11078860 DOI: 10.1007/s00221-024-06815-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Accepted: 02/23/2024] [Indexed: 03/27/2024]
Abstract
L-3,4-dihydroxyphenylalanine (L-DOPA) is the main treatment for Parkinson's disease (PD) but with long term administration, motor complications such as dyskinesia are induced. Glycine transporter 1 (GlyT1) inhibition was shown to produce an anti-dyskinetic effect in parkinsonian rats and primates, coupled with an improvement in the anti-parkinsonian action of L-DOPA. The expression of GlyT1 in the brain in the dyskinetic state remains to be investigated. Here, we quantified the levels of GlyT1 across different brain regions using [3H]-NFPS in the presence of Org-25,935. Brain sections were chosen from sham-lesioned rats, L-DOPA-naïve 6-hydroxydopamine (6-OHDA)-lesioned rats and 6-OHDA-lesioned rats exhibiting mild or severe abnormal involuntary movements (AIMs). [3H]-NFPS binding decreased in the ipsilateral and contralateral thalamus, by 28% and 41%, in 6-OHDA-lesioned rats with severe AIMs compared to sham-lesioned animals (P < 0.01 and 0.001). [3H]-NFPS binding increased by 21% in the ipsilateral substantia nigra of 6-OHDA-lesioned rats with severe AIMs compared to 6-OHDA-lesioned rats with mild AIMs (P < 0.05). [3H]-NFPS binding was lower by 19% in the contralateral primary motor cortex and by 20% in the contralateral subthalamic nucleus of 6-OHDA-lesioned rats with mild AIMs animals compared to rats with severe AIMs (both P < 0.05). The severity of AIMs scores positively correlated with [3H]-NFPS binding in the ipsilateral substantia nigra (P < 0.05), ipsilateral entopeduncular nucleus (P < 0.05) and contralateral primary motor cortex (P < 0.05). These data provide an anatomical basis to explain the efficacy of GlyT1 inhibitors in dyskinesia in PD.
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Affiliation(s)
- Imane Frouni
- Département de Pharmacologie et Physiologie, Université de Montréal, Montreal, QC, Canada
- Neurodegenerative Disease Group, Montreal Neurological Institute-Hospital (The Neuro), 3801 University St, Montreal, QC, H3A 2B4, Canada
| | - Esther Kim
- Neurodegenerative Disease Group, Montreal Neurological Institute-Hospital (The Neuro), 3801 University St, Montreal, QC, H3A 2B4, Canada
| | - Judy Shaqfah
- Neurodegenerative Disease Group, Montreal Neurological Institute-Hospital (The Neuro), 3801 University St, Montreal, QC, H3A 2B4, Canada
| | - Dominique Bédard
- Neurodegenerative Disease Group, Montreal Neurological Institute-Hospital (The Neuro), 3801 University St, Montreal, QC, H3A 2B4, Canada
| | - Cynthia Kwan
- Neurodegenerative Disease Group, Montreal Neurological Institute-Hospital (The Neuro), 3801 University St, Montreal, QC, H3A 2B4, Canada
| | - Sébastien Belliveau
- Neurodegenerative Disease Group, Montreal Neurological Institute-Hospital (The Neuro), 3801 University St, Montreal, QC, H3A 2B4, Canada
| | - Philippe Huot
- Département de Pharmacologie et Physiologie, Université de Montréal, Montreal, QC, Canada.
- Neurodegenerative Disease Group, Montreal Neurological Institute-Hospital (The Neuro), 3801 University St, Montreal, QC, H3A 2B4, Canada.
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada.
- Movement Disorder Clinic, Division of Neurology, Department of Neurosciences, McGill University Health Centre, Montreal, QC, Canada.
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3
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Hudson AR, Santora VJ, Petroski RE, Almos TA, Anderson G, Barido R, Basinger J, Bellows CL, Bookser BC, Broadbent NJ, Cabebe C, Chai CK, Chen M, Chow S, Chung DM, Heger L, Danks AM, Freestone GC, Gitnick D, Gupta V, Hoffmaster C, Kaplan AP, Kennedy MR, Lee D, Limberis J, Ly K, Mak CC, Masatsugu B, Morse AC, Na J, Neul D, Nikpur J, Renick J, Sebring K, Sevidal S, Tabatabaei A, Wen J, Xia S, Yan Y, Yoder ZW, Zook D, Peters M, Breitenbucher JG. Azetidine-based selective glycine transporter-1 (GlyT1) inhibitors with memory enhancing properties. Bioorg Med Chem Lett 2020; 30:127214. [PMID: 32527538 DOI: 10.1016/j.bmcl.2020.127214] [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: 02/18/2020] [Revised: 04/22/2020] [Accepted: 04/23/2020] [Indexed: 11/24/2022]
Abstract
A strategy to conformationally restrain a series of GlyT1 inhibitors identified potent analogs that exhibited slowly interconverting rotational isomers. Further studies to address this concern led to a series of azetidine-based inhibitors. Compound 26 was able to elevate CSF glycine levels in vivo and demonstrated potency comparable to Bitopertin in an in vivo rat receptor occupancy study. Compound 26 was subsequently shown to enhance memory in a Novel Object Recognition (NOR) behavioral study after a single dose of 0.03 mg/kg, and in a contextual fear conditioning (cFC) study after four QD doses of 0.01-0.03 mg/kg.
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Affiliation(s)
- Andrew R Hudson
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States.
| | - Vincent J Santora
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Robert E Petroski
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Theresa A Almos
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Gary Anderson
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Richard Barido
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Jillian Basinger
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Chris L Bellows
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Brett C Bookser
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Nicola J Broadbent
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Clifford Cabebe
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Chih-Kun Chai
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Mi Chen
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Stephine Chow
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - De Michael Chung
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Lindsay Heger
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Anne M Danks
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Graeme C Freestone
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Dany Gitnick
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Varsha Gupta
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | | | - Alan P Kaplan
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Michael R Kennedy
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Dong Lee
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - James Limberis
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Kiev Ly
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Chi Ching Mak
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Brittany Masatsugu
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Andrew C Morse
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Jim Na
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - David Neul
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - John Nikpur
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Joel Renick
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Kristen Sebring
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Samantha Sevidal
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Ali Tabatabaei
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Jenny Wen
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Shouzhen Xia
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Yingzhuo Yan
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Zachary W Yoder
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Douglas Zook
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - Marco Peters
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
| | - J Guy Breitenbucher
- Dart Neuroscience, 12278 Scripps Summit Dr, San Diego, CA 92131, United States
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4
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Wong DF, Kuwabara H, Horti AG, Roberts JM, Nandi A, Cascella N, Brasic J, Weerts EM, Kitzmiller K, Phan JA, Gapasin L, Sawa A, Valentine H, Wand G, Mishra C, George N, McDonald M, Lesniak W, Holt DP, Azad BB, Dannals RF, Kem W, Freedman R, Gjedde A. Brain PET Imaging of α7-nAChR with [18F]ASEM: Reproducibility, Occupancy, Receptor Density, and Changes in Schizophrenia. Int J Neuropsychopharmacol 2018; 21. [PMID: 29522184 PMCID: PMC6030963 DOI: 10.1093/ijnp/pyy021] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND The α7 nicotinic acetylcholine receptor increasingly has been implicated in normal brain physiology, as well as in neuropsychiatric disorders. The highly cortical distribution of α7 nicotinic acetylcholine receptor suggests a role in cognition. METHODS We expanded the first-in-human PET imaging of α7 nicotinic acetylcholine receptor with [18F]ASEM from 5 to 21 healthy nonsmoking volunteers and added a feasibility study in 6 male patients with schizophrenia. Study aims included: (1) confirmation of test-retest reproducibility of [18F]ASEM binding, (2) demonstration of specificity by competition with DMXB-A, an α7 nicotinic acetylcholine receptor partial agonist, (3) estimation of [18F]ASEM binding potentials and α7 nicotinic acetylcholine receptor density in vivo in humans, and (4) demonstrating the feasibility of studying α7 nicotinic acetylcholine receptor as a target for schizophrenia. RESULTS Test-retest PET confirmed reproducibility (>90%) (variability ≤7%) of [18F]ASEM volume of distribution (VT) estimates in healthy volunteers. Repeated sessions of PET in 5 healthy subjects included baseline and effect of inhibition after oral administration of 150 mg DMXB-A. From reduction of binding potentials, we estimated the dose-dependent occupancy of α7 nicotinic acetylcholine receptor by DMXB-A at 17% to 49% for plasma concentrations at 60 to 200 nM DMXB-A. In agreement with evidence postmortem, α7 nicotinic acetylcholine receptor density averaged 0.67 to 0.82 nM and inhibitor affinity constant averaged 170 to 385 nM. Median VT in a feasibility study of 6 patients with schizophrenia was lower than in healthy volunteers in cingulate cortex, frontal cortex, and hippocampus (P = 0.02, corrected for multiple comparions, Mann-Whitney test). CONCLUSIONS The current results confirm the reproducibility of [18F]ASEM VT estimates and the specificity of the tracer for α7 nicotinic acetylcholine receptor. Preliminary findings from our feasibility study of [18F]ASEM binding in patients with schizophrenia are suggestive and provide guidance for future studies with more subjects.
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Affiliation(s)
- Dean F Wong
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland,Department of Psychiatry and Behavioral Sciences, Baltimore, Maryland,Solomon Snyder Department of Neuroscience, Baltimore, Maryland,Department of Neurology, Baltimore, Maryland,Johns Hopkins University School of Medicine, Baltimore, Maryland,Correspondence: Dean F. Wong, MD, PhD, Radiology, Nuclear Medicine, Johns Hopkins Medical Institutions, JHOC Room 3244, Baltimore, MD ()
| | - Hiroto Kuwabara
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Andrew G Horti
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Joshua M Roberts
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Ayon Nandi
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Nicola Cascella
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland,Sheppard-Pratt Hospital, Baltimore, Maryland
| | - James Brasic
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Elise M Weerts
- Department of Psychiatry and Behavioral Sciences, Baltimore, Maryland
| | - Kelly Kitzmiller
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Jenny A Phan
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland,Department of Biomedicine, Aarhus University, Aarhus, Denmark,Department of Nuclear Medicine and PET Centre, Aarhus University Hospital, Aarhus, Denmark
| | - Lorena Gapasin
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Akira Sawa
- Department of Psychiatry and Behavioral Sciences, Baltimore, Maryland
| | - Heather Valentine
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Gary Wand
- Department of Psychiatry and Behavioral Sciences, Baltimore, Maryland,Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Chakradhar Mishra
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Noble George
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Michael McDonald
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Wojtek Lesniak
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Daniel P Holt
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Babak B Azad
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - Robert F Dannals
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland
| | - William Kem
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland,Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida
| | - Robert Freedman
- Department of Psychiatry, University of Colorado, Aurora, Colorado
| | - Albert Gjedde
- Russell H. Morgan Department of Radiology and Radiological Sciences, Baltimore, Maryland,Department of Nuclear Medicine, University of Southern Denmark, Odense, Denmark
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5
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Affiliation(s)
- Christopher L. Cioffi
- Departments of Basic and Clinical Sciences and Pharmaceutical Sciences, Albany College of Pharmacy and Health Sciences , Albany, NY, USA
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6
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Abstract
Autism spectrum disorder (ASD) is a condition with onset in early childhood characterized by marked deficits in interpersonal interactions and communication and by a restricted and repetitive range of interests and activities. This review points out key recent findings utilizing molecular imaging including magnetic resonance spectroscopy (MRS) and nuclear neuroimaging techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT). MRS indicates an excitatory/inhibitory imbalance in high-functioning autism. Dysfunction of neurotransmitter and glucose metabolism has been demonstrated by PET and SPECT. Levels of serotonin synthesis in typically developing children are approximately twice those of adults; after the age of 5 years, levels decrease to those of adults. In contrast, levels of serotonin synthesis of children with ASD increase between ages 2 and 15 to 1.5-times adult values. The dopamine transporter is increased in the orbitofrontal cortex of men with ASD. The serotonin transporter is reduced in the brains of children, adolescents, and adults with ASD. Reduced serotonin receptors in the thalamus of adults with ASD are associated with communication difficulties. Glucose metabolism is reduced in the brains of people with ASD. Molecular imaging will provide the preliminary data for promising therapeutic interventions.
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Affiliation(s)
- Brian Jaeho Hwang
- a Department of Neuroscience , Zanvyl Krieger School of Arts and Sciences, Johns Hopkins University , Baltimore , MD , USA
| | - Mona Adel Mohamed
- b Division of Neuroradiology, The Russell H. Morgan Department of Radiology and Radiological Science School of Medicine , Johns Hopkins University , Baltimore , MD , USA
| | - James Robert Brašić
- c Section of High Resolution Brain Positron Emission Tomography Imaging, Division of Nuclear Medicine and Molecular Imaging, The Russell H. Morgan Department of Radiology and Radiological Science , School of Medicine, Johns Hopkins University , Baltimore , MD , USA
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Abstract
As the field of PET has expanded and an ever-increasing number and variety of compounds have been radiolabeled as potential in vivo tracers of biochemistry, transporters have become important primary targets or facilitators of radiotracer uptake and distribution. A transporter can be the primary target through the development of a specific high-affinity radioligand: examples are the multiple high-affinity radioligands for the neuronal membrane neurotransmitter or vesicular transporters, used to image nerve terminals in the brain. The goal of a radiotracer might be to study the function of a transporter through the use of a radiolabeled substrate, such as the application of 3-O-[11C]methyl]glucose to measure rates of glucose transport through the blood-brain barrier. In many cases, transporters are required for radiotracer distributions, but the targeted biochemistries might be unrelated: an example is the use of 2-deoxy-2-[18F]FDG for imaging glucose metabolism, where initial passage of the radiotracer through cell membranes requires the action of specific glucose transporters. Finally, there are transporters such as p-glycoprotein that function to extrude small molecules from tissues, and can effectively work against successful uptake of radiotracers. The diversity of structures and functions of transporters, their importance in human health and disease, and their role in therapeutic drug disposition suggest that in vivo imaging of transporter location and function will continue to be a point of emphasis in PET radiopharmaceutical development. In this review, the variety of transporters and their importance for in vivo PET radiotracer development and application are discussed. Transporters have thus joined the other major protein targets such as G-protein coupled receptors, ligand-gated ion channels, enzymes, and aggregated proteins as of high interest for understanding human health and disease.
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Affiliation(s)
- Michael R Kilbourn
- Department of Radiology, University of Michigan Medical School, Ann Arbor, MI.
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8
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Zheng MQ, Lin SF, Holden D, Naganawa M, Ropchan JR, Najafzaden S, Kapinos M, Tabriz M, Carson RE, Hamill TG, Huang Y. Comparative evaluation of two glycine transporter 1 radiotracers [11C]GSK931145 and [18F]MK-6577 in baboons. Synapse 2015; 70:112-20. [PMID: 26671330 DOI: 10.1002/syn.21879] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2015] [Revised: 12/02/2015] [Accepted: 12/11/2015] [Indexed: 01/24/2023]
Abstract
Glycine transporter type-1 (GlyT1) has been proposed as a target for drug development for schizophrenia. PET imaging with a GlyT1 specific radiotracer will allow for the measurement of target occupancy of GlyT1 inhibitors, and for in vivo investigation of GlyT1 alterations in schizophrenia. We conducted a comparative evaluation of two GlyT1 radiotracers, [(11) C]GSK931145, and [(18) F]MK-6577, in baboons. Two baboons were imaged with [(11) C]GSK931145 and [(18) F]MK-6577. Blocking studies with GSK931145 (0.3 or 0.2 mg/kg) were conducted to determine the level of tracer specific binding. [(11) C]GSK931145 and [(18) F]MK-6577 were synthesized in good yield and high specific activity. Moderately fast metabolism was observed for both tracers, with ∼ 30% of parent at 30 min post-injection. In the brain, both radiotracers showed good uptake and distribution profiles consistent with regional GlyT1 densities. [(18) F]MK-6577 displayed higher uptake and faster kinetics than [(11) C]GSK931145. Time activity curves were well described by the two-tissue compartment model. Regional volume of distribution (VT ) values were higher for [(18) F]MK-6577 than [(11) C]GSK931145. Pretreatment with GSK931145 reduced tracer uptake to a homogeneous level throughout the brain, indicating in vivo binding specificity and lack of a reference region for both radiotracers. Linear regression analysis of VT estimates between tracers indicated higher specific binding for [(18) F]MK-6577 than [(11) C]GSK931145, consistent with higher regional binding potential (BPND ) values of [(18) F]MK-6577 calculated using VT from the baseline scans and non-displaceable distribution volume (VND ) derived from blocking studies. [(18) F]MK-6577 appears to be a superior radiotracer with higher brain uptake, faster kinetics, and higher specific binding signals than [(11) C]GSK931145.
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Affiliation(s)
- Ming-Qiang Zheng
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, PET Center, New Haven, Connecticut
| | - Shu-Fei Lin
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, PET Center, New Haven, Connecticut
| | - Daniel Holden
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, PET Center, New Haven, Connecticut
| | - Mika Naganawa
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, PET Center, New Haven, Connecticut
| | - Jim R Ropchan
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, PET Center, New Haven, Connecticut
| | - Soheila Najafzaden
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, PET Center, New Haven, Connecticut
| | - Michael Kapinos
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, PET Center, New Haven, Connecticut
| | - Mike Tabriz
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, PET Center, New Haven, Connecticut
| | - Richard E Carson
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, PET Center, New Haven, Connecticut
| | - Terence G Hamill
- Discovery Imaging, Merck Research Laboratories, West Point, Pennsylvania
| | - Yiyun Huang
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, PET Center, New Haven, Connecticut
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9
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Measurement of Bmax and Kd with the glycine transporter 1 radiotracer ¹⁸F-MK6577 using a novel multi-infusion paradigm. J Cereb Blood Flow Metab 2015. [PMID: 26198176 PMCID: PMC4671121 DOI: 10.1038/jcbfm.2015.163] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Glycine is a co-agonist of glutamate at the NMDA receptor. Glycine transporter 1 (GlyT1) inhibitors are reported to be potential therapeutic agents for schizophrenia. (18)F-MK6577 is a new positron emission tomography (PET) radiotracer useful for imaging brain GlyT1 and its occupancy in humans. We devised a novel multi-infusion paradigm of radiolabeled and unlabeled compound and an iterative linear/nonlinear alternating fitting method to allow for the determination of in vivo affinity (Kd) and target concentration (Bmax) images, constraining Kd to be uniform across the brain. This paradigm was tested with (18)F-MK6577 in baboons. Voxel-based analysis produced high quality Bmax images and reliable Kd estimates, and also suggested that the nondisplaceable distribution volume (VND) is not uniform throughout the brain. In vivo GlyT1 Kd was estimated to be 1.87 nmol/L for (18)F-MK6577, and the rank order of GlyT1 distribution measured in the baboon brain was: high in the brainstem (133 nmol/L), medium in the cerebellum (83 nmol/L), and low in the cortex (30 nmol/L). These in vivo Kd and Bmax values agreed well with those determined in vitro, thus validating our novel multi-infusion approach.
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10
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Gunn RN, Slifstein M, Searle GE, Price JC. Quantitative imaging of protein targets in the human brain with PET. Phys Med Biol 2015; 60:R363-411. [DOI: 10.1088/0031-9155/60/22/r363] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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11
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Castner SA, Murthy NV, Ridler K, Herdon H, Roberts BM, Weinzimmer DP, Huang Y, Zheng MQ, Rabiner EA, Gunn RN, Carson RE, Williams GV, Laruelle M. Relationship between glycine transporter 1 inhibition as measured with positron emission tomography and changes in cognitive performances in nonhuman primates. Neuropsychopharmacology 2014; 39:2742-9. [PMID: 24487737 PMCID: PMC4200505 DOI: 10.1038/npp.2014.4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 11/04/2013] [Accepted: 12/13/2013] [Indexed: 01/22/2023]
Abstract
Several lines of evidence suggest that schizophrenia is associated with deficits in glutamatergic transmission at the N-methyl-d-aspartate (NMDA) receptors. Glycine is a NMDA receptor co-agonist, and extracellular levels of glycine are regulated in the forebrain by the glycine type-1 transporters (GlyT-1). GlyT-1 inhibitors elevate extracellular glycine and thus potentiate NMDA transmission. This mechanism represents a promising new avenue for the treatment of schizophrenia. Here, the recently introduced positron emission tomography radiotracer [11C]GSK931145 was used to quantify the relationship between occupancy of GlyT-1 by a GlyT-1 inhibitor, Org 25935, and its impact on spatial working memory performances in rhesus monkeys. The effect of Org 25935 on working memory was assessed both in control conditions and during a state of relative NMDA hypofunction induced by ketamine administration, at a dose selected for each animal to reduce task performance by about 50%. Under control conditions, Org 25935 had no effect on working memory at GlyT-1 occupancies lower than 75% and significantly impaired working memory at occupancies higher than 75%. Under ketamine conditions, Org 25935 reversed the deficit in working memory induced by ketamine and did so optimally in the 40-70% GlyT-1 occupancy range. The results confirm the efficacy of this mechanism to correct working memory deficits associated with NMDA hypofunction. These data also suggest the existence of an inverted-U dose-response curve in the potential therapeutic effect of this class of compounds.
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Affiliation(s)
- S A Castner
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - N V Murthy
- Neurosciences Centre for Excellence in Drug Discovery, GlaxoSmithKline, Harlow, UK
| | - K Ridler
- Clinical Imaging Centre, GlaxoSmithKline, Hammersmith Hospital–Imperial College, London, UK
| | - H Herdon
- Neurosciences Centre for Excellence in Drug Discovery, GlaxoSmithKline, Harlow, UK
| | - B M Roberts
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - D P Weinzimmer
- Department of Radiology, Yale University School of Medicine, New Haven, CT, USA
| | - Y Huang
- Department of Radiology, Yale University School of Medicine, New Haven, CT, USA
| | - M Q Zheng
- Department of Radiology, Yale University School of Medicine, New Haven, CT, USA
| | - E A Rabiner
- Clinical Imaging Centre, GlaxoSmithKline, Hammersmith Hospital–Imperial College, London, UK
| | - R N Gunn
- Clinical Imaging Centre, GlaxoSmithKline, Hammersmith Hospital–Imperial College, London, UK
| | - R E Carson
- Department of Radiology, Yale University School of Medicine, New Haven, CT, USA
| | - G V Williams
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - M Laruelle
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA,Neurosciences Centre for Excellence in Drug Discovery, GlaxoSmithKline, Harlow, UK,Department of Radiology, Yale University School of Medicine, New Haven, CT, USA,UCB Pharma, Braine-l'Alleud, Brussels, Belgium,UCB Pharma, Chemin du Foriest, Braine-l'Alleud 1420, Belgium, Tel: +1 914 316 0923, Fax: +322 386 2550, E-mail:
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12
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Joshi AD, Sanabria-Bohórquez SM, Bormans G, Koole M, De Hoon J, Van Hecken A, Depre M, De Lepeleire I, Van Laere K, Sur C, Hamill TG. Characterization of the novel GlyT1 PET tracer [18F]MK-6577 in humans. Synapse 2014; 69:33-40. [PMID: 25196464 DOI: 10.1002/syn.21782] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 07/06/2014] [Accepted: 07/26/2014] [Indexed: 01/05/2023]
Abstract
Decreased glutamatergic neurotransmission is hypothesized to be involved in the pathophysiology of schizophrenia. Inhibition of glycine transporter Type-1 (GlyT1) reuptake is expected to increase the glutamatergic neurotransmission and may serve as treatment for cognitive and negative symptoms of schizophrenia. In this article, we present human data from a novel GlyT1 PET tracer, [(18) F]MK-6577. In the process of developing a GlyT1 inhibitor therapeutic, a PET tracer can assist in determining the dose with a high probability of sufficiently testing the mechanism of action. This article reports the human PET studies with [(18) F]MK-6577 for measuring GlyT1 receptor availability at baseline in normal human subjects and occupancy with a GlyT1 inhibitor, MK-2637. Studies were also performed to measure radiation burden and the baseline test-retest (T-RT) variability of the tracer. The effective dose from sequential whole-body dosimetry scans in three male subjects was estimated to be 24.5 ± 2.9 µSV/MBq (mean ± SD). The time-activity curves from T-RT scans modeled satisfactorily using a two tissue compartmental model. The tracer uptake was highest in the pons (VT = 6.7 ± 0.9, BPND = 4.1 ± 0.43) and lowest in the cortex (VT = 2.1 ± 0.5, BPND = 0.60 ± 0.23). VT T-RT variability measured in three subjects was <12% on average. The occupancy scans performed in a cohort of 15 subjects indicated absence of a reference region. The in vivo potency (Occ50 ) of MK-2637 was determined using two methods: A: Lassen plot with a population input function (Occ50 = 106 nM, SE = 20 nM) and B: pseudo reference tissue model using cortex as the pseudo reference region (Occ50 = 141 nM, SE = 21 nM).
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13
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Kim E, Howes OD, Kapur S. Molecular imaging as a guide for the treatment of central nervous system disorders. DIALOGUES IN CLINICAL NEUROSCIENCE 2014. [PMID: 24174903 PMCID: PMC3811103 DOI: 10.31887/dcns.2013.15.3/ekim] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Molecular imaging techniques have a number of advantages for research into the pathophysiology and treatment of central nervous system (CNS) disorders. Firstly, they provide a noninvasive means of characterizing physiological processes in the living brain, enabling molecular alterations to be linked to clinical changes. Secondly, the pathophysiological target in a given CNS disorder can be measured in animal models and in experimental human models in the same way, which enables translational research. Moreover, as molecular imaging facilitates the detection of functional change which precedes gross pathology, it is particularly useful for the early diagnosis and treatment of CNS disorders. This review considers the application of molecular imaging to CNS disorders focusing on its potential to inform the development and evaluation of treatments. We focus on schizophrenia, Parkinson's disease, depression, and dementia as major CNS disorders. We also review the potential of molecular imaging to guide new drug development for CNS disorders.
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Affiliation(s)
- Euitae Kim
- Department of Neuropsychiatry, Seoul National University Bundang Hospital, Gyeonggi-do 463-707, Korea
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14
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Poels EMP, Kegeles LS, Kantrowitz JT, Slifstein M, Javitt DC, Lieberman JA, Abi-Dargham A, Girgis RR. Imaging glutamate in schizophrenia: review of findings and implications for drug discovery. Mol Psychiatry 2014; 19:20-9. [PMID: 24166406 DOI: 10.1038/mp.2013.136] [Citation(s) in RCA: 144] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2013] [Revised: 08/25/2013] [Accepted: 09/09/2013] [Indexed: 12/11/2022]
Abstract
Currently, all treatments for schizophrenia (SCZ) function primarily by blocking D(2)-type dopamine receptors. Given the limitations of these medications, substantial efforts have been made to identify alternative neurochemical targets for treatment development in SCZ. One such target is brain glutamate. The objective of this article is to review and synthesize the proton magnetic resonance spectroscopy ((1)H MRS) and positron emission tomography (PET)/single-photon emission computed tomography (SPECT) investigations that have examined glutamatergic indices in SCZ, including those of modulatory compounds such as glutathione (GSH) and glycine, as well as data from ketamine challenge studies. The reviewed (1)H MRS and PET/SPECT studies support the theory of hypofunction of the N-methyl-D-aspartate receptor (NMDAR) in SCZ, as well as the convergence between the dopamine and glutamate models of SCZ. We also review several advances in MRS and PET technologies that have opened the door for new opportunities to investigate the glutamate system in SCZ and discuss some ways in which these imaging tools can be used to facilitate a greater understanding of the glutamate system in SCZ and the successful and efficient development of new glutamate-based treatments for SCZ.
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Affiliation(s)
- E M P Poels
- 1] Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA [2] New York State Psychiatric Institute, New York, NY, USA
| | - L S Kegeles
- 1] Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA [2] New York State Psychiatric Institute, New York, NY, USA
| | - J T Kantrowitz
- 1] Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA [2] New York State Psychiatric Institute, New York, NY, USA
| | - M Slifstein
- 1] Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA [2] New York State Psychiatric Institute, New York, NY, USA
| | - D C Javitt
- 1] Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA [2] New York State Psychiatric Institute, New York, NY, USA
| | - J A Lieberman
- 1] Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA [2] New York State Psychiatric Institute, New York, NY, USA
| | - A Abi-Dargham
- 1] Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA [2] New York State Psychiatric Institute, New York, NY, USA [3] Department of Radiology, Columbia University College of Physicians and Surgeons, New York, NY, USA
| | - R R Girgis
- 1] Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY, USA [2] New York State Psychiatric Institute, New York, NY, USA
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15
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GlyT-1 Inhibitors: From Hits to Clinical Candidates. SMALL MOLECULE THERAPEUTICS FOR SCHIZOPHRENIA 2014. [DOI: 10.1007/7355_2014_53] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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16
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Cioffi CL. Modulation of NMDA receptor function as a treatment for schizophrenia. Bioorg Med Chem Lett 2013; 23:5034-44. [PMID: 23916256 DOI: 10.1016/j.bmcl.2013.07.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 07/03/2013] [Accepted: 07/13/2013] [Indexed: 11/30/2022]
Abstract
Schizophrenia is a devastating mental illness that afflicts nearly 1% of the world's population. Currently available antipsychotics treat positive symptoms, but are largely ineffective at addressing negative symptoms and cognitive dysfunction. Thus, improved pharmacotherapies that treat all aspects of the disease remain a critical unmet need. There is mounting evidence that links NMDA receptor hypofunction and the expression of schizophrenia, and numerous drug discovery programs have developed agents that directly or indirectly potentiate NMDA receptor-mediated neurotransmission. Several compounds have emerged that show promise for treating all symptom sub-domains in both preclinical models and clinical studies, and we will review recent developments in many of these areas.
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17
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Glycine transporter type 1 occupancy by bitopertin: a positron emission tomography study in healthy volunteers. Neuropsychopharmacology 2013; 38:504-12. [PMID: 23132267 PMCID: PMC3547202 DOI: 10.1038/npp.2012.212] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Deficient N-methyl-D-aspartate (NMDA) receptor transmission is thought to underlie schizophrenia. An approach for normalizing glutamate neurotransmission by enhancing NMDA receptor transmission is to increase glycine availability by inhibiting the glycine transporter type 1 (GlyT1). This study investigated the relationship between the plasma concentration of the glycine reuptake inhibitor bitopertin (RG1678) and brain GlyT1 occupancy. Healthy male volunteers received up to 175 mg bitopertin once daily, for 10-12 days. Three positron emission tomography scans, preceded by a single intravenous infusion of ∼30 mCi [(11)C]RO5013853, were performed: at baseline, on the last day of bitopertin treatment, and 2 days after drug discontinuation. Eighteen subjects were enrolled. At baseline, regional volume of distribution (V(T)) values were highest in the pons, thalamus, and cerebellum (1.7-2.7 ml/cm(3)) and lowest in cortical areas (∼0.8 ml/cm(3)). V(T) values were reduced to a homogeneous level following administration of 175 mg bitopertin. Occupancy values derived by a two-tissue five-parameter (2T5P) model, a simplified reference tissue model (SRTM), and a pseudoreference tissue model (PRTM) were overall comparable. At steady state, the relationship between bitopertin plasma concentration and GlyT1 occupancy derived by the 2T5P model, SRTM, and PRTM exhibited an EC(50) of ∼190, ∼200, and ∼130 ng/ml, respectively. E(max) was ∼92% independently of the model used. Bitopertin plasma concentration was a reliable predictor of occupancy because the concentration-occupancy relationship was superimposable at steady state and 2 days after drug discontinuation. These data allow understanding of the concentration-occupancy-efficacy relationship of bitopertin and support dose selection of future molecules.
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18
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Beyoğlu D, Idle JR. The glycine deportation system and its pharmacological consequences. Pharmacol Ther 2012; 135:151-67. [PMID: 22584143 PMCID: PMC3665358 DOI: 10.1016/j.pharmthera.2012.05.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 04/27/2012] [Indexed: 12/13/2022]
Abstract
The glycine deportation system is an essential component of glycine catabolism in man whereby 400 to 800mg glycine per day are deported into urine as hippuric acid. The molecular escort for this deportation is benzoic acid, which derives from the diet and from gut microbiota metabolism of dietary precursors. Three components of this system, involving hepatic and renal metabolism, and renal active tubular secretion help regulate systemic and central nervous system levels of glycine. When glycine levels are pathologically high, as in congenital nonketotic hyperglycinemia, the glycine deportation system can be upregulated with pharmacological doses of benzoic acid to assist in normalization of glycine homeostasis. In congenital urea cycle enzymopathies, similar activation of the glycine deportation system with benzoic acid is useful for the excretion of excess nitrogen in the form of glycine. Drugs which can substitute for benzoic acid as substrates for the glycine deportation system have adverse reactions that may involve perturbations of glycine homeostasis. The cancer chemotherapeutic agent ifosfamide has an unacceptably high incidence of encephalopathy. This would appear to arise as a result of the production of toxic aldehyde metabolites which deplete ATP production and sequester NADH in the mitochondrial matrix, thereby inhibiting the glycine deportation system and causing de novo glycine synthesis by the glycine cleavage system. We hypothesize that this would result in hyperglycinemia and encephalopathy. This understanding may lead to novel prophylactic strategies for ifosfamide encephalopathy. Thus, the glycine deportation system plays multiple key roles in physiological and neurotoxicological processes involving glycine.
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Affiliation(s)
- Diren Beyoğlu
- Hepatology Research Group, Department of Clinical Research, University of Bern, 3010 Bern, Switzerland
| | - Jeffrey R. Idle
- Hepatology Research Group, Department of Clinical Research, University of Bern, 3010 Bern, Switzerland
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19
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Borroni E, Zhou Y, Ostrowitzki S, Alberati D, Kumar A, Hainzl D, Hartung T, Hilton J, Dannals RF, Wong DF. Pre-clinical characterization of [11C]R05013853 as a novel radiotracer for imaging of the glycine transporter type 1 by positron emission tomography. Neuroimage 2011; 75:291-300. [PMID: 22178811 DOI: 10.1016/j.neuroimage.2011.11.090] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 11/24/2011] [Accepted: 11/30/2011] [Indexed: 11/19/2022] Open
Abstract
A specific positron emission tomography (PET) radiotracer for the glycine transporter type 1 (GlyT1) would constitute an imaging biomarker to investigate the distribution of GlyT1 in normal individuals and those with neuropsychiatric disorders. In addition it could demonstrate the ability of a novel drug to reach its target in the brain and enable receptor occupancy studies, thus facilitating drug development. In this article we describe the evaluation in non-human primates of two candidate PET radiotracers ([(11)C]RO5013852 and [(11)C]RO5013853) previously characterized in the rat. Both radiotracers showed acceptable uptake in the baboon brain and heterogeneous distribution consistent with that reported for GlyT1. In vivo blockade studies with two specific glycine reuptake inhibitors (GRIs), RO5013853 and bitopertin (RG1678, reduced uptake of both tracers to homogenous levels across brain regions and demonstrated specificity of the signal. [(11)C]RO5013853 showed a larger specific signal and slightly higher brain uptake and was therefore selected for further characterization. Quantitative compartmental analysis of PET data showed that the 2-tissue compartment model with 5 parameters was the most appropriate to describe the kinetics of [(11)C]RO5013853. Two additional methods were used: a) the Logan graphical analysis using plasma input and, b) a linear parametric imaging approach with the 2-tissue compartmental model. These produced VT estimates of comparable magnitude, namely, pons, thalamus and cerebellum>caudate, putamen and cortical regions. High resolution autoradiography with tritiated RO5013853 was used to confirm the binding pattern observed by PET. In vivo metabolism studies in the baboon demonstrated the formation of a single, radiolabeled metabolite more polar than the parent compound. Finally, [(11)C]RO5013853 was used to quantify the degree of cerebral GlyT1 occupancy observed in the baboon following oral administration of bitopertin, a selective GRI presently in Phase III clinical trial. Plasma concentrations of approximately 150-300 ng/mL were estimated to produce 50% GlyT1 occupancy in the thalamus, the cerebellum and the pons. [(11)C]RO5013853 is a promising radiotracer for in vivo imaging of the GlyT1. It can be easily radiolabeled, exhibits moderate metabolism, displays a good specific signal, and is suitable for receptor occupancy studies of therapeutic compounds that target the GlyT1. The successful characterization of [(11)C]RO5013853 in healthy volunteers is presented in this NeuroImage issue (Wong et al., 2013).
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Affiliation(s)
- Edilio Borroni
- Neuroscience Department, Pharmaceutical Division, F. Hoffmann-La Roche Ltd, CH-4070 Basel, Switzerland.
| | - Yun Zhou
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD 21287-0807, USA
| | - Susanne Ostrowitzki
- Neuroscience Department, Pharmaceutical Division, F. Hoffmann-La Roche Ltd, CH-4070 Basel, Switzerland
| | - Daniela Alberati
- Neuroscience Department, Pharmaceutical Division, F. Hoffmann-La Roche Ltd, CH-4070 Basel, Switzerland
| | - Anil Kumar
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD 21287-0807, USA
| | - Dominik Hainzl
- Nonclinical Safety Department, Pharmaceutical Division, F. Hoffmann-La Roche Ltd, CH-4070 Basel, Switzerland
| | - Thomas Hartung
- Process Research & Synthesis Department, Pharmaceutical Division, F. Hoffmann-La Roche Ltd, CH-4070 Basel, Switzerland
| | - John Hilton
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD 21287-0807, USA
| | - Robert F Dannals
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD 21287-0807, USA
| | - Dean F Wong
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD 21287-0807, USA; Department of Psychiatry, The Johns Hopkins University School of Medicine, 601 N. Caroline St., JHOC, Baltimore, MD 21287-0807, USA; Department of Neuroscience, The Johns Hopkins University School of Medicine, 601 N. Caroline St., JHOC, Baltimore, MD 21287-0807, USA; Department of Environmental Health Sciences, The Johns Hopkins University School of Medicine, 601 N. Caroline St., JHOC, Baltimore, MD 21287-0807, USA; Honorary Professor of Neuroscience and Pharmacology, University of Copenhagen, Denmark
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