Rafabegron (also known as TAK-677 ) is an indole derivative patented by Dainippon Pharmaceutical Co., Ltd., as antidiabetics and antiobesity agent. Rafabegron asts as beta3-adrenergic agonist. In preclinical studies Rafabegron reduced the total weight of white adipose tissues by reducing the size of the adipocytes, an effect associated with the normalization of tumor necrosis factor-alpha and leptin expression levels in micce. The levels of uncoupling protein (UCP)-1 mRNA in brown adipose tissue were increased threefold. Rafabegron caused a marked increase (20- to 80-fold) in the expression of UCP-1 in white adipose tissues. In clinical trials. Rafabegron has no effect on 24-h respiratory quotient or fat oxidation but does slightly increase 24-h energy expenditure at the highest dose. The acute studies showed large interindividual variability in plasma concentrations of Rafabegron indicating some possible problems with bioavailability and therefore efficacy. Based on these data further development was discontinued.