AT-121

AT-121 is a dual μ-opioid and nociceptin receptor partial agonist (Kis = 16.49 and 3.67 nM, respectively). It stimulates [35S]GTPγS binding to cell membranes expressing μ-opioid or nociceptin receptors (EC50s = 19.6 and 34.7 nM, respectively). AT-121 (0.003-0.03 mg/kg) decreases capsaicin-induced thermal allodynia without increasing scratching activity in rhesus monkeys in a dose-dependent manner. It lacks reinforcing effects, a marker of abuse potential, and reduces oxycodone, but not food pellet, reinforcement in a drug self-administration assay in rhesus monkeys when administered at doses ranging from 0.3 to 10 μg/kg per injection. AT-121 (0.01 or 0.03 mg/kg) does not induce hyperalgesia, a marker of tolerance development, in rhesus monkeys.