Label-free functional selectivity assays

Abstract

G protein-coupled receptors (GPCRs) represent the largest class of drug targets. Ligand-directed functional selectivity or biased agonism opens new possibility for discovering GPCR drugs with better effi cacy and safety profi les. However, quantifi cation of ligand bias is challenging. Herein, we present fi ve different label-free dynamic mass redistribution (DMR) approaches to assess ligand bias acting at the β 2 -adrenergic receptor (β 2 AR). Multiparametric analysis of the DMR agonist profi les reveals divergent pharmacology of a panel of β 2 AR agonists. DMR profi ling using catechol as a conformational probe detects the presence of multiple conformations of the β 2 AR. DMR assays under microfl uidics, together with chemical biology tools, discover ligand-directed desensitization of the receptor. DMR antagonist reverse assays manifest biased antagonism. DMR profi ling using distinct probe-modulated cells detects the biased agonism in the context of self-referenced pharmacological activity map.