PSB-CB5
# PSB-CB5

PSB-CB5 (CID-85469571) is a compound which acts as an antagonist at the former orphan receptor GPR18, and is the first selective antagonist characterised for this receptor, with an $IC_{50}$ of 279nM, and good selectivity over related receptors (over 36x selectivity vs $CB_1$ and GPR55, and 14x vs $CB_2.)$ 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.

