MDM4 and retinoblastoma: Among these 11 compounds, SJ-134433 and SJ-044557 have been found to covalently modify MDMX and thus be abandoned for further investigations, whereas SJ-172550 has been shown to reversibly bind to the p53-binding pocket of MDMX, block the p53-MDMX binding, activate wild-type p53, and induce apoptosis in retinoblastoma cells with MDMX overexpression (94).