R-PSOP is a potent and selective nonpeptidic NMUR2 antagonist, exhibiting binding affinity to human and rat NMUR2 with Ki values of 52 nM and 32 nM, respectively. This compound demonstrates moderate central nervous system (CNS) penetration and is valuable in the study of eating disorders, obesity, pain, and stress-related disorders [1].

According to Schild analyses, R-PSOP exhibits functional K_b values of 92 nM for human NMUR2 and 155 nM for rat NMUR2, highlighting its inhibitory effect on intracellular calcium mobilization triggered by NMU-25 in HEK293 cells expressing NMUR2 (the effects of R-PSOP on intracellular calcium mobilization induced by NMU-25 in HEK293 cells expressing human or rat NMUR2) [1]. Furthermore, R-PSOP effectively suppresses the activity initiated by peptide agonists NMU-25, NMU-23, and NMU-8 in these cells. The compound also concentration-dependently diminishes phosphoinositide (PI) turnover stimulated by 10 nM NMU-25 in cells expressing human NMUR2, showing an EC_50 of 5 nM and an IC_50 value of 86 nM [1]. These findings underscore R-PSOP's potent inhibitory effects on specific biochemical responses in human embryonic kidney 293 cells expressing NMUR2.

R-PSOP (10 μL, 50 nmol; intrathecal injection; male Sprague-Dawley rats) reduces nociceptive responses induced by NMU-23 in a spinal reflex setup, indicating its analgesic potential [1].