The search for opioid analgesics with limited tolerance liability

Abstract

Reducing the well-known side effects of opioids prescribed to treat chronic pain remains unresolved, despite extensive research in this field. Among several options to tackle this problem the synthesis of multifunctional compounds containing hybridized structures gained a lot of interest. Recently, extensively investigated are combinations of opioid agonist and antagonist pharmacophores embodied in a single molecule. To this end, agonism at the μ opioid receptor (MOR) with simultaneous antagonism at the δ opioid receptor (DOR) emerged as a promising avenue to obtaining novel analogs devoid of serious adverse effects associated with morphine-based analgesics. In this review we covered up-to-date research on the synthesis of peptide-based ligands with MOR agonist/DOR antagonist profile.

Keywords: Antinociceptive activity; G protein-coupled receptors; Mixed-efficacy opioid ligands; Peptidomimetics; Tolerance.