Synthesis and characterization in monkey of [11C]SP203 as a radioligand for imaging brain metabotropic glutamate 5 receptors.

Purpose [18F]SP203 (3-fluoro-5-(2-(2-([18F]fluoromethyl)-thiazol-4-yl)ethynyl)benzonitrile) is an effective high-affinity and selective radioligand for imaging metabotropic 5 receptors (mGluR5) in human brain with PET. To provide a radioligand that may be used for more than one scanning session in the same subject in a single day, we set out to label SP203 with shorter-lived 11C (t 1/2 = 20.4 min) and to characterize its behavior as a radioligand with PET in the monkey.