The orally available hydrochloride salt of pyrrolidine-3-carboxylic acid with potential antineoplastic activity. As a selective antagonist of the endothelin-A (ETA) receptor, atrasentan binds selectively to the ETA receptor, which may result in inhibition of endothelin-induced angiogenesis and tumor cell proliferation. Check for active clinical trials using this agent. (NCI Thesaurus)