High affinity and selective urotensin II (UT) receptor antagonist (pKi values are 9.14, 9.28, 9.34, 9.64 and 9.66 at monkey, human, mouse, cat and rat recombinant receptors respectively). Exhibits selectivity for UT receptors over a range of GPCRs, ion channels, enzymes and neurotransmitter transporters. Supresses human urotensin-II (hU-II)-induced contraction of isolated rat aorta in vitro and ex vivo. Inhibits the hU-II-induced increase in mean blood pressure in vivo. Orally active. Purity 98%. MW (observed): 617.95