Fully automated radiosynthesis of [18F]FCPPC for imaging microglia with PET.

Abstract

Colony-stimulating factor 1 receptor (CSF1R) is almost exclusively expressed on microglia in the human brain and thus, has promise as a biomarker for imaging microglia density as a proxy for neuroinflammation. [¹¹C]CPPC is a radiotracer with selective affinity to CSF1R, and has been evaluated for in-human microglia PET imaging. The flourine-18 labeled CPPC derivative, 5-cyano-N-(4-(4-(2-[¹⁸F]fluoroethyl)piperazin-1-yl)-2-(piperidin-1-yl)phenyl)furan-2-carboxamide ([¹⁸F]FCPPC), was previously synthesized, however, with a low radiochemical yield using manual radiosynthesis. In this work, we report a fully automated radiosynthesis of [¹⁸F]FCPPC on a Synthra RNplus research module. In a total synthesis time of 50 min, [¹⁸F]FCPPC was obtained in decay corrected radiochemical yields of 26.8 ± 0.1% (n = 3) with >99% radiochemical purities. Quality control testing showed that [¹⁸F]FCPPC met all release criteria. In sum, we report the first fully automated radiosynthesis of [¹⁸F]FCPPC, a promising radiopharmaceutical for imaging microglia in humans.