Highly Selective Drug-Derived Fluorescent Probes for the Cannabinoid Receptor Type 1 (CB₁R)

The cannabinoid receptor type 1 (CB₁R) is pivotal within the endocannabinoid system regulating various signaling cascades with effects in appetite regulation, pain perception, memory formation, and thermoregulation. Still, understanding of CB₁R's cellular signaling, distribution, and expression dynamics is very fragmentary. Real-time visualization of CB₁R is crucial for addressing these questions. Selective drug-like CB₁R ligands with a defined pharmacological profile were investigated for the construction of CB₁R 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 CB₁R fluorescent probes. Application in fluorescence-based target-engagement studies and live cell imaging exemplify the great versatility of the tailored CB₁R probes for investigating CB₁R localization, trafficking, pharmacology, and its pathological implications.