CK-666 (442633-00-3) is a potent, selective and reversible inhibitor of ARP2/3 complex (actin related proteins 2 and 3) with an IC50?= 4 μM for human ARP2/3.1?Blocks actin nucleation and radically alters lamellipodial actin architecture, suspended cell shape and the cell spreading process.2 CK-666 attenuates BBB dysfunction induced by methamphetamine.3?It is an important new tool for studying actin assembly and the diverse range of actin-related processes in normal4 and pathophysiology5.