ZINC69391, a specific Rac1 inhibitor, interferes with Rac1-GEF interaction by masking Trp56 residue on Rac1 surface. ZINC69391 interferes with the interaction of Rac1 with Dock180 and reduces Rac1-GTP levels. ZINC69391 induces apoptosis, and shows antiproliferative and antimetastatic effects.