MDMX/MDM2-IN-2 is a potent p53-MDM2/MDMX dual inhibitors with K i s of 0.23 μM and 2.45 μM for MDM2 and MDMX, respectively. MDMX/MDM2-IN-2 inhibits the binding of p53 and MDM2 proteins. MDMX/MDM2-IN-2 restores the function of p53 and enables cell cycle arrest and apoptosis. MDMX/MDM2-IN-2 inhibits cell migration and invasion. MDMX/MDM2-IN-2 has antitumor activity.