In vivo evaluation of carbon-11-labelled non-sarcosine-based glycine transporter 1 inhibitors in mice and conscious monkeys.

INTRODUCTION Glycine transporter 1 (GlyT-1) is an attractive target in positron emission tomography (PET) studies. Here, we report the in vivo evaluation of three carbon-11-labelled non-sarcosine-type GlyT-1 inhibitors--[(11)C]SA1, [(11)C]SA2 and [(11)C]SA3--as novel PET tracers for GlyT-1. METHODS The regional brain distributions of the three compounds in mice were studied at baseline and under receptor-blockade conditions with co-injection of carrier loading or pretreatment with an excess of selective GlyT-1 inhibitors (ALX-5407 and SSR504734). Metabolic stability was investigated by radio high-performance liquid chromatography. Dynamic PET scans in conscious monkeys were performed with/without selective GlyT-1 inhibitors. RESULTS The IC(50) values of SA1, SA2 and SA3 were 9.0, 6400 and 39.7 nM, respectively. The regional brain uptakes of [(11)C]SA1 and [(11)C]SA3 in mice were heterogeneous and consistent with the known distribution of GlyT-1. [(11)C]SA2 showed low and homogeneous uptake in the brain. Most radioactivity in the brain was detected in unchanged form, although peripherally these compounds were degraded. Carrier loading decreased the uptake of [(11)C]SA1 in GlyT-1-rich regions. However, similar reductions were not observed with [(11)C]SA3. Pretreatment with ALX-5407 decreased the uptake of [(11)C]SA1 in GlyT-1-rich regions. In the monkey at baseline, regional brain uptake of [(11)C]SA1 was heterogeneous and consistent with the known GlyT-1 distribution. Pretreatment with selective GlyT-1 inhibitors significantly decreased the distribution volume ratio of [(11)C] SA1 in GlyT-1-rich regions. CONCLUSIONS [(11)C]SA1 has the most suitable profile among the three carbon-11-labelled GlyT-1 inhibitors. Lead optimization of [(11)C]SA1 structure will be required to achieve in vivo selective GlyT-1 imaging.

[1]  B. López-Corcuera,et al.  Glycine transporters: crucial roles of pharmacological interest revealed by gene deletion. , 2005, Trends in pharmacological sciences.

[2]  K. Hashimoto.  Glycine transporter inhibitors as therapeutic agents for schizophrenia. , 2006, Recent patents on CNS drug discovery.

[3]  P. Mallorga,et al.  Pharmacology and expression analysis of glycine transporter GlyT1 with [3H]-(N-[3-(4′-fluorophenyl)-3-(4′phenylphenoxy)propyl])sarcosine , 2003, Neuropharmacology.

[4]  B. Borowsky,et al.  Two glycine transporter variants with distinct localization in the CNS and peripheral tissues are encoded by a common gene , 1993, Neuron.

[5]  J. Coyle,et al.  Glutamatergic mechanisms in schizophrenia. , 2003, Annual review of pharmacology and toxicology.

[6]  D. Javitt.  Glycine transport inhibitors for the treatment of schizophrenia: symptom and disease modification. , 2009, Current opinion in drug discovery & development.

[7]  N. Nelson,et al.  Molecular characterization of four pharmacologically distinct gamma-aminobutyric acid transporters in mouse brain [corrected]. , 1993, The Journal of biological chemistry.

[8]  Nobuko Mataga,et al.  Ketamine increases the striatal N-[11C]methylspiperone binding in vivo: positron emission tomography study using conscious rhesus monkey , 1994, Brain Research.

[9]  K. Hashimoto.  Glycine Transport Inhibitors for the Treatment of Schizophrenia , 2010, The open medicinal chemistry journal.

[10]  Joseph T. Coyle,et al.  The Glutamatergic Dysfunction Hypothesis for Schizophrenia , 1996, Harvard review of psychiatry.

[11]  R N Gunn,et al.  Identification and evaluation of [11C]GSK931145 as a novel ligand for imaging the type 1 glycine transporter with positron emission tomography , 2010, Synapse.

[12]  O. H. Lowry,et al.  Protein measurement with the Folin phenol reagent. , 1951, The Journal of biological chemistry.

[13]  K. Hashimoto.  The NMDA Receptor Hypofunction Hypothesis for Schizophrenia and Glycine Modulatory Sites on the NMDA Receptors as Potential Therapeutic Drugs , 2006 .

[14]  D. Javitt,et al.  Recent advances in the phencyclidine model of schizophrenia. , 1991, The American journal of psychiatry.

[15]  J. Coyle,et al.  The emerging role of glutamate in the pathophysiology and treatment of schizophrenia. , 2001, The American journal of psychiatry.

[16]  C. Giménez,et al.  Molecular biology of glycinergic neurotransmission , 1997, Molecular Neurobiology.

[17]  Cristian Salinas,et al.  A pseudo-reference region method applied to measurement of GlyT1 occupancy in human brain using [11C]GSK931145 and PET , 2010, NeuroImage.

[18]  J. Coyle,et al.  Modulation of N-methyl-D-aspartate receptor function by glycine transport. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[19]  K. Hashimoto,et al.  [11C]CHIBA-1001 as a Novel PET Ligand for α7 Nicotinic Receptors in the Brain: A PET Study in Conscious Monkeys , 2008, PloS one.

[20]  J. Storm-Mathisen,et al.  Glycine transporters are differentially expressed among CNS cells , 1995, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[21]  Kenji Hashimoto,et al.  Dysfunction of Glia-Neuron Communication in Pathophysiology of Schizophrenia , 2005 .

[22]  C. Sur,et al.  Glycine Site Modulators and Glycine Transporter-1 Inhibitors as Novel Therapeutic Targets for the Treatment of Schizophrenia , 2005 .

[23]  D. Javitt.  Glycine Transport Inhibitors and the Treatment of Schizophrenia , 2008, Biological Psychiatry.

[24]  R. Depoortère,et al.  Neurochemical, Electrophysiological and Pharmacological Profiles of the Selective Inhibitor of the Glycine Transporter-1 SSR504734, a Potential New Type of Antipsychotic , 2005, Neuropsychopharmacology.

[25]  J. Olney,et al.  Glutamate receptor dysfunction and schizophrenia. , 1995, Archives of general psychiatry.

[26]  A. Belger,et al.  NMDA agonists and antagonists as probes of glutamatergic dysfunction and pharmacotherapies in neuropsychiatric disorders. , 1999, Harvard review of psychiatry.

[27]  S. Kingsmore,et al.  Cloning of the human glycine transporter type 1: molecular and pharmacological characterization of novel isoform variants and chromosomal localization of the gene in the human and mouse genomes. , 1994, Molecular pharmacology.

[28]  Robert B. Innis,et al.  Strategies to Improve Neuroreceptor Parameter Estimation by Linear Regression Analysis , 2002, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[29]  David J. Schlyer,et al.  Graphical Analysis of Reversible Radioligand Binding from Time—Activity Measurements Applied to [N-11C-Methyl]-(−)-Cocaine PET Studies in Human Subjects , 1990, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[30]  H. Schoemaker,et al.  Inhibitors of GlyT1 Affect Glycine Transport via Discrete Binding Sites , 2008, Molecular Pharmacology.

[31]  C. Sur,et al.  The therapeutic potential of glycine transporter-1 inhibitors , 2004, Expert opinion on investigational drugs.

[32]  T. Branchek,et al.  Cloning and expression of a glycine transporter reveal colocalization with NMDA receptors , 1992, Neuron.

[33]  J. Gomeza,et al.  Regional Distribution and Developmental Variation of the Glycine Transporters GLYT1 and GLYT2 in the Rat CNS , 1995, The European journal of neuroscience.

[34]  Hiroyuki Okada,et al.  A high resolution animal PET scanner using compact PS-PMT detectors , 1996 .

[35]  Kenji Hashimoto,et al.  Decreased serum levels of D-serine in patients with schizophrenia: evidence in support of the N-methyl-D-aspartate receptor hypofunction hypothesis of schizophrenia. , 2003, Archives of general psychiatry.

[36]  H. Betz,et al.  Glycine transporters: essential regulators of neurotransmission. , 2005, Trends in biochemical sciences.

[37]  K. Hashimoto,et al.  Glutamate Hypothesis of Schizophrenia and Approach for Possible Therapeutic Drugs , 2004 .

[38]  C. Lindsley,et al.  Progress in the preparation and testing of glycine transporter type-1 (GlyT1) inhibitors. , 2006, Current topics in medicinal chemistry.

[39]  F. Jursky,et al.  Developmental Expression of the Glycine Transporters GLYT1 and GLYT2 in Mouse Brain , 1996, Journal of neurochemistry.

[40]  C. Lindsley,et al.  A novel radioligand for glycine transporter 1: characterization and use in autoradiographic and in vivo brain occupancy studies. , 2008, Nuclear medicine and biology.

[41]  B. Cubelos,et al.  Localization of the GLYT1 glycine transporter at glutamatergic synapses in the rat brain. , 2005, Cerebral cortex.

[42]  R. Vandenberg,et al.  Glycine transport inhibitors as potential antipsychotic drugs , 2001, Expert opinion on therapeutic targets.

[43]  V. Ognyanov,et al.  ALX 5407: a potent, selective inhibitor of the hGlyT1 glycine transporter. , 2001, Molecular pharmacology.

[44]  C. Parsons,et al.  Glycine and N-methyl-D-aspartate receptors: physiological significance and possible therapeutic applications. , 1998, Pharmacological reviews.

[45]  K. Hashimoto,et al.  Protective Effects of N-acetyl-L-cysteine on the Reduction of Dopamine Transporters in the Striatum of Monkeys Treated with Methamphetamine , 2004, Neuropsychopharmacology.

[46]  J. Lowe,et al.  [3H]-(R)-NPTS, a radioligand for the type 1 glycine transporter. , 2003, Bioorganic & medicinal chemistry letters.

[47]  R. Vandenberg,et al.  N[3‐(4′‐fluorophenyl)‐3‐(4′‐phenylphenoxy)propyl]sarcosine (NFPS) is a selective persistent inhibitor of glycine transport , 2001, British journal of pharmacology.

[48]  K. Ishiwata,et al.  Improved synthesis of [11C]SA4503, [11C]MPDX and [11C]TMSX by use of [11C]methyl triflate , 2004, Annals of nuclear medicine.