Rapid identification of dual p53-MDM2/MDMX interaction inhibitors through virtual screening and hit-based substructure search

Abstract

Multi-target agents have garnered great interest over the past decade for their favorable therapeutic efficacy and drug resistance profiles. Recently, dual inhibition of the p53 tumor suppressor interaction with its two negative regulators MDM2 and MDMX has become an attractive anticancer approach as it can induce sustained MDM2/MDMX antagonism and robust p53 activation. However, small molecule inhibitors with dual specificity against MDM2 and MDMX are difficult to design and are still scarce. To identify novel scaffolds for dual inhibition of the p53-MDM2/MDMX interactions, we developed two five-point pharmacophore models for filtering the 2012 National Cancer Institute database, from which molecular docking was conducted to identify dual inhibitors. We found 38 virtual hits and subjected them to a fluorescence polarization-based competitive binding assay, resulting in 10 active compounds of different scaffolds. To further expand the chemical diversity of the initial hits, we performed a hit-based substructure search and identified NSC148171 from pharmacophore 1 as the most potent dual-specificity inhibitor with K_i values for MDM2 and MDMX at 0.62 and 4.6 μM. All hits were subjected to inhibition assay of cancer cellular vitality and showed anti-proliferative activity roughly correlated with their K_i values. This work not only yields several novel scaffolds for further structural and functional optimization of dual-specificity inhibitors of the p53-MDM2/MDMX interactions, but also showcases the power of our computational methods for small molecule anticancer drug discovery.