High Affinity Fluorescent Probe for Proteinase-Activated Receptor 2 (PAR2)
ACS Medicinal Chemistry Letters
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© 2019 American Chemical Society. PAR2 is a proteolytically activated G protein-coupled receptor (GPCR) that is implicated in various cancers and inflammatory diseases. Ligands with low nanomolar affinity for PAR2 have been developed, but there is a paucity of research on the development of PAR2-targeting imaging probes. Here, we report the development of seven novel PAR2-targeting compounds. Four of these compounds are highly potent and selective PAR2-targeting peptides (EC50 = 10 to 23 nM) that have a primary amine handle available for facile conjugation to various imaging components. We describe a peptide of the sequence Isox-Cha-Chg-ARK(Sulfo-Cy5)-NH2 as the most potent and highest affinity PAR2-selective fluorescent probe reported to date (EC50 = 16 nM, KD = 38 nM). This compound has a greater than 10-fold increase in potency and binding affinity for PAR2 compared to the leading previously reported probe and is conjugated to a red-shifted fluorophore, enabling in vitro and in vivo studies.