The discovery of vibegron, a potent and selective human β₃-AR agonist for the treatment of overactive bladder (OAB), is described. An early-generation clinical β₃-AR agonist MK-0634 (3) exhibited efficacy in humans for the treatment of OAB, but development was discontinued due to unacceptable structure-based toxicity in preclinical species. Optimization of a series of second-generation pyrrolidine-derived β₃-AR agonists included reducing the risk for phospholipidosis, the risk of formation of disproportionate human metabolites, and the risk of formation of high levels of circulating metabolites in preclinical species. These efforts resulted in the discovery of vibegron, which possesses improved druglike properties and an overall superior preclinical profile compared to MK-0634. Structure–activity relationships leading to the discovery of vibegron and a summary of its preclinical profile are described.