Highly Selective Drug-Derived Fluorescent Probes for the Cannabinoid Receptor Type 1 (CBR).

The cannabinoid receptor type 1 (CBR) is pivotal within the endocannabinoid system regulating various signaling cascades with effects in appetite regulation, pain perception, memory formation, and thermoregulation. Still, understanding of CBR's cellular signaling, distribution, and expression dynamics is very fragmentary. Real-time visualization of CBR is crucial for addressing these questions. Selective drug-like CBR ligands with a defined pharmacological profile were investigated for the construction of CBR fluorescent probes using a reverse design-approach. A modular design concept with a diethyl glycine-based building block as the centerpiece allowed for the straightforward synthesis of novel probe candidates. Validated by computational docking studies, radioligand binding, and cAMP assay, this systematic approach allowed for the identification of novel pyrrole-based CBR fluorescent probes. Application in fluorescence-based target-engagement studies and live cell imaging exemplify the great versatility of the tailored CBR probes for investigating CBR localization, trafficking, pharmacology, and its pathological implications.