Discovery of a Highly Selective and Potent κ Opioid Receptor Agonist from -Cyclopropylmethyl-7α-phenyl-6,14-endoethanotetrahydronorthebaines with Reduced Central Nervous System (CNS) Side Effects Navigated by the Message-Address Concept.

Effective and safe analgesics represent an unmet medical need for the treatment of acute and chronic pain. A series of -cyclopropylmethyl-7α-phenyl-6,14-endoethanotetrahydronorthebaines were designed, synthesized, and assayed, leading to the discovery of a benzylamine derivative (compound , SLL-039) as a highly selective and potent κ opioid agonist (κ, = 0.47 nM, κ/μ = 682, κ/δ = 283), which was confirmed by functional assays and antinociceptive assays . The effect could be blocked by pretreatment with the selective κ antagonist nor-BNI. Moreover, this compound did not induce sedation, a common dose limiting effect of κ opioid receptor agonists, at its analgesic dose compared to U50,488H. The dissociation of sedation/antinociception found in SLL-039 was assumed to be correlated with the occupation of its benzamide motif in a unique subsite involving V118, W124, and E209.