PSB-CB5 (CID-85469571) is a compound which acts as an antagonist at the former orphan receptorGPR18, and is the first selective antagonist characterised for this receptor, with an IC50 of 279nM, and good selectivity over related receptors (over 36x selectivity vs CB1 and GPR55, and 14x vs CB2.) As all previously known antagonists for GPR18 also antagonise GPR55, it has been difficult to separate the effects of these two receptor targets, so the discovery of a selective GPR18 antagonist is expected to be useful in research into the actions of this receptor.[1][2][3]
^Rempel V, Atzler K, Behrenswerth A, Karcz T, Schoeder C, Hinz S, et al. (2014). "Bicyclic imidazole-4-one derivatives: a new class of antagonists for the orphan G protein-coupled receptors GPR18 and GPR55". MedChemComm. 5 (5): 632–49. doi:10.1039/C3MD00394A.
^Schoeder CT, Kaleta M, Mahardhika AB, Olejarz-Maciej A, Łażewska D, Kieć-Kononowicz K, Müller CE (July 2018). "Structure-activity relationships of imidazothiazinones and analogs as antagonists of the cannabinoid-activated orphan G protein-coupled receptor GPR18". European Journal of Medicinal Chemistry. 155: 381–397. doi:10.1016/j.ejmech.2018.05.050. PMID29902723. S2CID49214747.
