EHT1864 is a small molecule inhibitor of the Rac family of GTPase, used in Rac1, Rac1b, Rac2 and Rac3, which is the most potent for Rac1, whether binding affinity or stimulating nucleotide release. In the NIH 3t3 fibroblast of mouse, EHT1864 decreased by 80% the formation of PDGF induced pseudopodia. EHT1864 can completely inhibit the formation of Rac1 and PAK-RBD complexes at 50μM concentrations, leading to the release of nucleotides from Rac1. EHT1864 can also inhibit the reassociation of EDTA or Tiam1-induced nucleotides with Rac1. Furthermore, EHT1864 inhibits Rac1-induced cell transformation and inhibits 80% of the colony-forming activity.