Lesopitron (E-4424) is a selective full agonist of the 5-HT1A receptor which is structurally related to the azapirones. In 2001 it was under development by Esteve as an anxiolytic for the treatment of generalized anxiety disorder (GAD). It made it to phase II clinical trials but was apparently discontinued as no new information on lesopitron has surfaced since.
Enpiprazole (INN, BAN) is an anxiolytic drug of the phenylpiperazine group that was never marketed. It produces anxiolytic-like effects in animals, though these effects appear to be biphasic and may reverse at high doses. It is known to produce ortho-chlorophenylpiperazine (oCPP) as a metabolite.