Ro 46-8443 is the first non-peptide endothelin ETB receptor selective antagonist. Ro 46-8443 displays an at least 100-fold selectivity for ETB (IC50: 34-69 nM) over ETA receptors (IC50: 6800 nM)[1][2].
[1]. Breu V, et al. In vitro characterisation of Ro 46-8443, the first non-peptide antagonist selective for the endothelin ETB receptor. FEBS Lett. 1996;383(1-2):37-41. [2]. Clozel M, et al. The role of ETB receptors in normotensive and hypertensive rats as revealed by the non-peptide selective ETB receptor antagonist Ro 46-8443. FEBS Lett. 1996;383(1-2):42-45.