Bragsin2 is a hydration resistant cell penetrant, potent and selective noncompetitive inhibitor of ArfGEF BRAG2 (Afr guanine nucleotide exchange factor BRAG2) that inhibits Arf GTPase activation in vitro and in cells. It binds to pleckstrin homology (PH) domain of BRAG2 and misposition BRAG2 on the membrane. Bragsin2 disrupt the function of the yeast ArfGEF Sec7p. Bragsin2 suppresses tumorsphere formation of some breast cancer stem cell lines including SUM149 and S68.