Selective Photoaffinity Probe That Enables Assessment of Cannabinoid CB2 Receptor Expression and Ligand Engagement in Human Cells

Abstract Chemical tools and methods that report on G protein-coupled receptor (GPCR) expression levels and receptor occupancy by small molecules are highly desirable. We report the development of LEI121 as a photoreactive probe to study the type 2 cannabinoid receptor (CB2R), a promising GPCR to treat tissue injury and inflammatory diseases. LEI121 is the first CB2R-selective bifunctional probe that covalently captures CB2R upon photoactivation. An incorporated alkyne serves as ligation handle for the introduction of reporter groups. LEI121 enables target