Discovery of SHR0687, a Highly Potent and Peripheral Nervous System-Restricted KOR Agonist.

Analgesics with no abuse liability are highly demanded in the market. KOR agonists have been proved to be strong analgesics without MOR agonist-related side effects, such as respiratory depression, tolerance, and dependence liability; however, activation of KOR in the central nervous system (CNS) may cause sedation and anxiety. It has been reported that peripheral KOR activation produces comparable bioactivity without CNS-related side effects. Herein, we designed and synthesized a novel tetrapeptide (SHR0687), which was shown to be a highly potent KOR agonist with excellent selectivity over other opioid receptors, such as MOR and DOR. In addition, SHR0687 displayed favorable PK profiles across species, as well as robust efficacy in a rat carrageenan-induced pain model. Notably, SHR0687 exhibited negligible blood-brain barrier penetration, which was meaningful in minimizing CNS-related side effects.