Bragsin2 is a potent, selective and noncompetitive nucleotide exchange factor BRAG2 inhibitor, with an IC50 of 3 μM. Bragsin2 binds at the interface between the PH domain of BRAG2 and the lipid bilayer, leads BRAG2 unable to activate lipidated Arf GTPase. Bragsin2 affects breast cancer stem cells.