Developing new PET tracers to image the growth hormone secretagogue receptor 1a (GHS-R1a)

The growth hormone secretagogue receptor 1a (GHS-R1a) is the orphan G-protein-coupled receptor, and its endogenous ligand is ghrelin. GHS-R1a contributes to regulation of glucose homeostasis, memory and learning, food addiction, and neuroprotection. Several PET tracers for GHS-R1a have been developed, but none have been reported to be clinically applicable to GHS-R1a imaging. In this study, we developed three new PET tracers for GHS-R1a: ¹⁸F-labeled 6-(4-chlorophenyl)-3-((1-(2-fluoroethyl)piperidin-3-yl)methyl)-2-(o-tolyl)quinazolin-4(3H)-one (1), ¹¹C-labeled 6-(4-chlorophenyl)-3-((1-(2-methoxyethyl)piperidin-3-yl)methyl)-2-(o-tolyl)quinazolin-4(3H)-one (2), and ¹¹C-labeled (S)-(4-(1H-indole-6-carbonyl)-3-methylpiperazin-1-yl)(4′-methoxy-[1,1′-biphenyl]-4-yl)methanone (3).