Functionalized Cannabinoid Subtype 2 Receptor Ligands: Fluorescent, PET, Photochromic and Covalent Molecular Probes

Cannabinoid subtype 2 receptors (CB(2)Rs) are G protein‐coupled receptors (GPCRs) belonging to the endocannabinoid system, a complex network of signalling pathways leading to the regulation of key physiological processes. Interestingly, CB(2)Rs are strongly up‐regulated in pathological conditions correlated with the onset of inflammatory events like cancer and neurodegenerative diseases. Therefore, CB(2)Rs represent an important biological target for therapeutic as well as diagnostic purposes. No CB(2)R‐selective drugs are yet on the market, thus underlining a that deeper comprehension of CB(2)Rs’ complex activation pathways and their role in the regulation of diseases is needed. Herein, we report an overview of pharmacological and imaging tools such as fluorescent, positron emission tomography (PET), photochromic and covalent selective CB(2)R ligands. These molecular probes can be used in vitro as well as in vivo to investigate and explore the unravelled role(s) of CB(2)Rs, and they can help to design suitable CB(2)R‐targeted drugs.