NGB 2904 (hydrochloride) is a potent, selective, orally active and brain-penetrated antagonist of dopamine D3 receptor, with a Ki of 1.4 nM. NGB 2904 hydrochloride shows selectivity for D3 over D2, 5-HT2, α1, D4, D1 and D5 receptors (Kis=217, 223, 642, >5000, >10000 and >10000 nM, respectively). NGB 2904 hydrochloride antagonizes Quinpirole-stimulated mitogenesis.