Structure- based identification of a G protein-biased allosteric modulator of cannabinoid receptor CB1

Cannabis sativa is known for its therapeutic benefit in various diseases including pain relief by targeting cannabinoid receptors. The primary component of cannabis, A 9 - tetrahydrocannabinol (THC), and other agonists engage the orthosteric site of CB1, activating both Gi and (3- arrestin signaling pathways. The activation of diverse pathways could result in on - target side effects and cannabis addiction, which may hinder therapeutic potential. A significant challenge in pharmacology is the design of a ligand that can modulate specific signaling of CB1. By leveraging insights from the structure-function selectivity relationship (SFSR), we have identified Gi signaling- biased agonist - allosteric modulators (ago - BAMs). Further, two cryoelectron microscopy (cryo - EM) structures reveal the binding mode of ago - BAM at the extrahelical allosteric site of CB1. Combining mutagenesis and pharmacological studies, we elucidated the detailed mechanism of ago - BAM - mediated biased signaling. Notably, ago - BAM CB - 05 demonstrated analgesic efficacy with fewer side effects, minimal drug toxicity and no cannabis addiction in mouse pain models. In summary, our finding not only suggests that ago - BAMs of CB1 provide a potential nonopioid strategy for pain management but also sheds light on BAM identification for GPCRs.