YM-254890 is a novel Gαq/11 inhibitor,1 U46619-induced platelet aggregation is inhibited but phorbol ester- or ionophore-induced aggregation is not2 (IC50 = 0.1-0.2 µM)1. It blocks Pasteurella multocida toxin-mediated activation of Gαq.3 A highly useful new tool for studying Gαq/11-coupled receptor signaling and resulting cellular events.4