Translational potential of allosteric modulators targeting the cannabinoid CB receptor.

The cannabinoid type-1 (CB) receptor, a G-protein-coupled receptor, is an attractive target for drug discovery due to its involvement in many physiological processes. Historically, drug discovery efforts targeting the CB receptor have focused on the development of orthosteric ligands that interact with the active site to which endogenous cannabinoids bind. Research performed over the last several decades has revealed substantial difficulties in translating CB orthosteric ligands into druggable candidates. The difficulty is mainly due to the adverse effects associated with orthosteric CB ligands. Recent discoveries of allosteric CB modulators provide tremendous opportunities to develop CB ligands with novel mechanisms of action; these ligands may potentially improve the pharmacological effects and enhance drug safety in treating the disorders by regulating the functions of the CB receptor. In this paper, we review and summarize the complex pharmacological profiles of each class of CB allosteric modulators, the development of new classes of CB allosteric modulators and the results from in vivo assessments of their therapeutic value.