Potent and selective NOP receptor antagonist (IC50 values are 0.27, 2500, 6700 and > 10000 nM for NOP, κ-, μ- and δ-receptors respectively). Inhibits nociceptin-induced stimulation of [35S]-GTPγS binding and Ca2+ mobilization in CHO cells in vitro and antagonizes NOP agonist-induced reduction in locomotor activity in vivo. Brain penetrant.