This paper describes the discovery of a new non-peptide endothelin A (ETA) selective ligand, 2, 4-dibenzyloxybenzoic acid 3, which inhibits the binding of [125I] ET-1 to ETA receptors with an IC50 of 9 μM (ET-1= endothelin-1). Optimisation of 3 resulted in compound 52 which had an IC50 of 1 μM. One of the analogues of 3, compound 15, was examined in a functional assay and shown to antagonise ET-1-induced contraction of rat aorta. The ...