The synthesis and preclinical evaluation in rhesus monkey of [18F]MK-6577 and [11C]CMPyPB glycine transporter 1 positron emission tomography radiotracers

• Published in: Synapse (New York, N.Y.) Vol. 65; no. 4; pp. 261 - 270
• Main Authors: Hamill, Terence G., Eng, Waisi, Jennings, Andrew, Lewis, Richard, Thomas, Steven, Wood, Suzanne, Street, Leslie, Wisnoski, David, Wolkenberg, Scott, Lindsley, Craig, Sanabria-BohÓRquez, Sandra M., Patel, Shil, Riffel, Kerry, Ryan, Christine, Cook, Jacquelynn, Sur, Cyrille, Burns, H. Donald, Hargreaves, Richard
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.04.2011
• Subjects: Alkylation; Animals; Aromatics; autoradiography; Benzamides - blood; Benzamides - chemical synthesis; Brain slice preparation; Carbon Radioisotopes - blood; carbon-11; Cell Line; Cerebellum; Computed tomography; Cortex (frontal); Drug Evaluation, Preclinical - methods; Fluorine Radioisotopes - blood; fluorine-18; Glycine Plasma Membrane Transport Proteins - blood; Glycine Plasma Membrane Transport Proteins - metabolism; Glycine transporter; glycine transporter type 1; GlyT1; Humans; Macaca mulatta; Metabolites; Neostriatum; Neuroimaging; Pons; Positron emission tomography; positron emission tomography (PET); Positron-Emission Tomography - methods; Pyridines - blood; Pyridines - chemical synthesis; rhesus monkey; Substantia grisea; Sulfonamides - blood; Sulfonamides - chemical synthesis; Synapses; Thalamus; Tracers
• ISSN: 0887-4476; 1098-2396; 1098-2396
• DOI: 10.1002/syn.20842

Two positron emission tomography radiotracers for the glycine transporter 1 (GlyT1) are reported here. Each radiotracer is a propylsulfonamide‐containing benzamide and was labeled with either carbon‐11 or fluorine‐18. [11C]CMPyPB was synthesized by the alkylation of a 3‐hydroxypyridine precursor using [11C]MeI, and [18F]MK‐6577 was synthesized by a nucleophilic aromatic substitution reaction using a 2‐chloropyridine precursor. Each tracer shows good uptake into rhesus monkey brain with the expected distribution of highest uptake in the pons, thalamus, and cerebellum and lower uptake in the striatum and gray matter of the frontal cortex. In vivo blockade and chase studies of [18F]MK‐6577 showed a large specific signal and reversible binding. In vitro autoradiographic studies with [18F]MK‐6577 showed a large specific signal in both rhesus monkey and human brain slices and a distribution consistent with the in vivo results and those reported in the literature. In vivo metabolism studies in rhesus monkeys demonstrated that only more‐polar metabolites are formed for each tracer. Of these two tracers, [18F]MK‐6577 was more extensively characterized and is a promising clinical positron emission tomography tracer for imaging GlyT1 and for measuring GlyT1 occupancy of therapeutic compounds. Synapse, 2011. © 2010 Wiley‐Liss, Inc.