Description: A-123189 is a novel, selective and potent α1D antagonists in both the α1 clonal cell lines and in in vitro tissue strips. It shares with BMY7378 and SNAP8719 the common structural features of a substituted phenylpiperazine and a heterocycle attached via a two-carbon linker. The 5-phenyl substitution on the heterocyclic attachment was shown to impart the α1D selectivity. A-123189 exhibits potent antagonism in the α1D functional model, the rat aorta and shows ∼100-fold selectivity over the rat vas deferens and spleen. A-123189 displays over 100-fold greater potency in the rat aorta than BMY7378. Relative to BMY7378, A-123189 is less α1d selective in their binding affinities.