PSB-SB-487 is an experimental drug which is used as a pharmacological research tool.

It is a coumarin derivative which is an antagonist at the former orphan receptor GPR55.

Unlike older GPR55 antagonists such as O-1918, PSB-SB-487 has good selectivity over the related receptor GPR18, with an IC50 of 113nM at GPR55 vs 12500nM at GPR18.

[1] However it has poorer selectivity over other related receptors, acting as a weak antagonist at CB1 with a Ki of 1170nM, and a partial agonist at CB2 with a Ki of 292nM.

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