Application of Fluorine- And Nitrogen-Walk Approaches: Defining the Structural and Functional Diversity of 2-Phenylindole Class of CB1 Receptor Positive Allosteric Modulators

Cannabinoid 1 receptor (CB1R) allosteric ligands hold far-reaching therapeutic promise. We report application of fluoro- and nitrogen-walk approaches to enhance the drug-like properties of GAT211, a prototype CB1R allosteric agonist-positive allosteric modulator (ago-PAM). Several analogs exhibited improved functional potency (cAMP, arrestin2), metabolic stability, and aqueous solubility. Two key analogs, GAT591 (6r) and GAT593 (6s), exhibited augmented allosteric-agonist and PAM activities in neuronal cultures, improved metabolic stability, and enhanced orthosteric agonist binding (CP55,940). Both also exhibited good analgesic potency in the CFA inflammatory-pain model with longer duration of action over GAT211 while devoid of adverse cannabimimetic effects. Another analog, GAT592 (9j), exhibited moderate ago-PAM potency and improved aqueous solubility with therapeutic reduction of intraocular pressure in murine glaucoma models. The SAR findings and the enhanced allosteric activity in this class of allo...