rel-SB-612111 hydrochloride is a novel and potent human opiate receptor-like orphan receptor (ORL-1) antagonist with a high affinity for hORL-1 ( K i =0.33 nM). rel-SB-612111 hydrochloride exhibits selectivity for μ-, κ- and δ-receptors with K i values of 57.6 nM, 160.5 nM and 2109 nM, respecticely. rel-SB-612111 hydrochloride effectively antagonizes the pronociceptive action of Nociceptin in an acute pain model.