Ro 46-2005 is a novel synthetic non-peptide endothelin receptor antagonist, inhibits the specific binding of 125I-ET-1 to human vascular smooth muscle cells (ETA receptor) with IC50 of 220 nM. IC50 value: 220 nM (ETA) [2] Target: Endothelin in vitro: Ro 46-2005 proves to be equipotent (IC50 200-500 nM) for inhibition of [125I]ET-1 binding on the two known ET receptor subtypes (ETA and ETB). Ro 46-2005 also inhibits the functional consequences of ET-1 stimulation: the ET-l-induced release of arachidonic acid from rat mesangial cells was inhibited with an IC50 of 1.8 μM.