IRL-1620 acetate is an effective and selective agonist of Endothelin B receptor (ETB) with a Ki of 16 pM which is more selective than ETA with a Ki of 19 μM.

IRL-1620 acetate is 60 times more selective for the ETB receptor than ET-3 (KiETA/ KiETB=1900)[3].

IRL-1620 acetate improves both acquisition (learning) and retention (memory) on the water maze task and enhances angiogenic and neurogenic remodeling. Rats treated with IRL-1620 acetate significantly reduces the cognitive impairment induced by Aβ. IRL-1620 acetate treatment enhances the number of blood vessels labeled with VEGF compared to vehicle treatment[1]. IRL-1620 acetate, restores analgesic tolerance to morphine and oxycodone, but it does not affect morphine and oxycodone induced decrease in NGF/PI3K expression. IRL-1620 acetate attenuates opioid tolerance without the involvement of NGF/PI3K pathway[2]. IRL-1620 acetate (1-100 nM) induces contractions of the guinea pig trachea. The effective concentration that produces 30 % of 60 mM KCI-induced contraction is estimated to be 28 nM for IRL 1620[3]. IRL-1620 acetate (1-100 nM) increases cytosolic Ca2+ in the vascular endothelium ([Ca]E) with little effect on resting muscle tone, and relaxes the norepinephrine-stimulated tone with an increase in [Ca]E, in rat aorta[3].