This superior efficacy of MBQ-168 may be attributed to MBQ-167’s poor solubility, pH sensitivity, or fluorescence interference due to the intrinsic fluorescence spectra of MBQ-167 rather than diminished efficacy because both MBQ-167 and MBQ-168 inhibit Rac activation from breast cancer cell lysates to a similar extent. This evidence concerns the gene AKT1 and breast cancer.