IRL-1620 TFA

IRL-1620 (TFA) is a potent and selective endothelin receptor type B (ETB) agonist with a Ki of 16 pM[1].

IRL-1620 (TFA) is the most potent and specific ligand for the ETB receptor (KiETA/ KiETB=120,000) as judged by the Ki values for ETA (19 μM) and ETB (16 PM) receptors[1]. IRL-1620 (TFA) is 60 times more selective for the ETB receptor than ET-3 (KiETA/ KiETB=1,900)[1].

IRL-1620 (TFA) (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[1]. IRL-1620 (TFA) (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,[1]. IRL-1620 (TFA) improves both acquisition (learning) and retention (memory) on the water maze task and enhances angiogenic and neurogenic remodeling. Rats treated with IRL-1620 significantly reduces the cognitive impairment induced by Aβ. IRL-1620 treatment enhances the number of blood vessels labeled with VEGF compared to vehicle treatment[2].IRL-1620 (TFA), restores analgesic tolerance to morphine and oxycodone, but it does not affect morphine and oxycodone induced decrease in NGF/PI3K expression. IRL-1620 attenuates opioid tolerance without the involvement of NGF/PI3K pathway[3].

[1]. Takai M, et al. A potent and specific agonist, Suc-[Glu9,Ala11,15]-endothelin-1(8-21), IRL 1620, for the ETB receptor. Biochem Biophys Res Commun. 1992 Apr 30;184(2):953-9. [2]. Briyal S, et al. Stimulation of endothelin B receptors by IRL-1620 decreases the progression of Alzheimer's disease. Neuroscience. 2015 Aug 20;301:1-11. [3]. Gulati S, et al. Attenuation of opioid tolerance by ETB receptor agonist, IRL-1620, is independent of an accompanied decrease in nerve growth factor in mice. Heliyon. 2017 Jun 7;3(6):e00317.