1-Oxa-4,9-diazaspiro[5.5]undecan-3-one, 9-[2-(2,5-difluorophenyl)ethyl]-4-ethyl-2-methyl-, hydrochloride (1:1), (2R)-

EST73502 hydrochloride is a selective, orally active and blood-brain barrier (BBB) penetrant dual μ-opioid receptor (MOR) agonist and σ1 receptor (σ1R) antagonist, with Kis of 64 nM and 118 nM for MOR and σ1R, respectively. EST73502 hydrochloride has antinociceptive activity[1]. EST73502 hydrochloride (10-40 mg/kg; p.o.) shows a dose-response analgesic effect reaching a maximum of 64% and an EC50 of 14 mg/kg in the paw pressure test in CD1 male mice[1].EST73502 hydrochloride (5 mg/kg; i.p.; twice a day; for 10 days) attenuates partial sciatic nerve ligation (PSNL)-induced mechanical allodynia in male CD1 mice[1].

[1]. Mónica García, et al. Discovery of EST73502, a Dual μ-Opioid Receptor Agonist and σ 1 Receptor Antagonist Clinical Candidate for the Treatment of Pain. J Med Chem. 2020 Oct 16.