In a preclinical study, researchers identified and characterized 18 new compounds (agonists) that activate bitter taste receptor subtype TAS2R5 to promote relaxation of human airway smooth muscle cells. The cross-disciplinary team found 1,10 phenanthroline-5,6-dione (T5-8 for short) was 1,000 times more potent than some of the other bronchodilator agonists tested, and it demonstrated marked effectiveness in human airway smooth muscle cells grown in the laboratory.