Selective inhibitor of Rac1-GEF interaction. Prevents Rac1 activation by Rac-specific guanine nucleotide exchange factors (GEFs) TrioN and Tiam1 (IC50 ~ 50 μM) without affecting Cdc42 or RhoA activation. Inhibits Rac1-mediated cell functions and is reported to reverse tumor cell phenotyes in prostate cancer cells.