Design, synthesis, and functional assessment of Cmpd-15 derivatives as negative allosteric modulators for the β2-adrenergic receptor

The β 2 -adrenergic receptor (β 2 AR), a G protein-coupled receptor, is an important therapeutic target. We recently described Cmpd-15, the first small molecule negative allosteric modulator (NAM) for the β 2 AR. Herein we report in details the design, synthesis and structure-activity relationships (SAR) of seven Cmpd-15 derivatives. Furthermore, we provide in a dose-response paradigm, the details of the effects of these derivatives in modulating agonist-induced β 2 AR activities (G-protein-mediated cAMP production and β-arrestin recruitment to the receptor) as well as the binding affinity of an orthosteric agonist in radio-ligand competition binding assay. Our results show that some modifications, including removal of the formamide group in the para -formamido phenylalanine region and bromine in the meta -bromobenzyl methylbenzamide region caused dramatic reduction in the functional activity of Cmpd-15. These SAR results provide valuable insights into the mechanism of action of the NAM Cmpd-15 as well as the basis for future development of more potent and selective modulators for the β 2 AR based on the chemical scaffold of Cmpd-15.