The β3 (beta 3) adrenergic receptor agonist or β3-adrenoceptor agonist, also known as β3-AR agonist, are a class of medicine that bind selectively to β3-adrenergic receptors. β3-AR agonists for the treatment of obesity and type 2 diabetes have been in developmental stages within many large pharmaceutical companies since the early 1990s without successfully delivering an anti-obesity product to the market. More recently pharmaceutical companies have developed selective β3-AR agonists targeted at urinary inconsistencies and in 2012 Mirabegron (trade name Myrbetriq and Betmiga) was the first β3-AR agonist to be approved in the United States and Europe for the treatment of overactive bladder (OAB) syndrome. Medical Uses In 2018 only one β3-AR agonist is approved by the European Medicines Agency (EMA) and the Food and drug Administration (FDA) as a medicine. The medicine is called Mirabegron and is used to treat OAB. Urinary bladder Mirabegron is a selective β3-AR agonist that affects the detrusor muscles of the urinary bladder. By stimulation of β3-AR the contraction of the smooth muscles of the bladder is decreased and the bladder can store more volume of urine at a given time. Mirabegron also has an influence on the non-voiding contraction by decreasing the frequency of the contractions. In 2018 two other β3-AR agonists are in clinical trials, vibegron and solabegron. Vibegron is in phase 3 clinical trial and is used to treat OAB. Solabegron is in phase 2b clinical trials to treat OAB in women and in phase 1 clinical trials in men to treat OAB. Obesity and diabetes The β3-AR has been linked to thermogenesis in human skeletal muscles, with studies showing it to be responsible for over 40% of ephedrine-induced thermogenesis. Cardiovascular In March 2016 a study funded by the European Commission began. The study is assessing the efficacy of Mirabegron in prevention of heart failure. In 2018 the study is ongoing and it's expected to conclude in 2020. A selective β1-AR antagonist with additional β3-AR agonist activity, called nebivolol, is one of a few selective B1-AR antagonists known to also cause vasodilation. This peripheral vasodilation is mediated by endothelial nitric oxide release following β3-AR agonism, not by adrenergic receptor blockade. This means nebivolol exerts vasodilatory, cardioprotective effects without the added adrenergic block side effects seen with non-selective beta-blockers that concomitantly lower blood pressure. Nebivolol is therefore approved for hypertension therapy in the United States; however, beta-blockers are still not generally the first