G protein-coupled receptors (GPCRs) are one of the largest group of therapeutic targets in cardiovascular disease. For instance, GPCRs such as ?-adrenergic receptors and angiotensin type I receptors are the targets of a variety of widely used medications in the treatment of heart failure. Ligands for GPCRs are characterized as agonists: those that stabilize a receptor conformation that promote activation of heterotrimeric G proteins to generate second-messenger signaling; or antagonists that block such activation. However, work over the past 2 decades, in a large part emanating from the laboratories of investigators on this proposal, has shown that ligands stabilize distinct active receptor conformations to selectivity engage, or ?bias?, the receptor toward either G protein or other transducers such as ?-arrestin, to induce distinct subset of signaling pathways. This concept of ligand-dependent functional selectivity is known as biased signaling. While the majority of GPCR ligands target orthosteric binding sites, i.e., the binding site of the endogenous ligand, an emerging important area of receptor biology and drug development is the identity of ligands that bind to allosteric, or topographically distinct, sites on receptors. The objective of this R01 renewal is to identify, characterize, and translate novel ligands that function as allosteric modulators on the ?1AR thereby generating new medicinal molecules targeting one of the most important receptors in the cardiovascular system. In this proposal, we aim to test that hypothesis that we can identify and develop novel ligands that function as biased allosteric modulators for the ?1AR thereby generating a whole new family of medicinal molecules for heart failure.