NSI-189 ((4-benzylpiperazin-1-yl)-[2-(3-methylbutylamino)pyridin-3-yl]methanone) is a benzylpiperazine-aminopyridine small molecule, usually studied as its phosphate salt. It was developed on the basis of preclinical data showing stimulation of neurogenesis in human hippocampus-derived neural stem cells in vitro and in mouse hippocampus in vivo. Preclinical research has examined it in rat models of ischaemic stroke, cranial irradiation and type 2 diabetes, and in mouse models of Angelman syndrome and of type 1 and type 2 diabetes. Two clinical trials in major depressive disorder have been published; the phase 1B report carries a published erratum.