Activating TP53 by Dual Inhibition of MDMX and MDM2

TP53 is often inactivated by mutations or other mechanisms in human cancers. Recent work has demonstrated that its endogenous inhibitor MDMX (or MDM4) is frequently overexpressed in patients with hematologic malignancies including AML, lymphoid malignancies, as well as other cancers. Pharmacological disruption of the interactions of TP53 with both its endogenous inhibitors (MDMX and MDM2) has long been sought after as an attractive strategy to restore p53-dependent tumor suppressor activity. However, selective targeting of this pathway has previously been limited to MDM2-only small-molecule inhibitors, which lack affinity for MDMX. More recently, pharmacological dual targeting of MDMX/MDM2 has become feasible through stapled peptides and is currently being tested in clinical trials. This presentation will discuss such MDMX/MDM2 dual-targeting strategies as well as new insights into MDMX-mediated mechanisms of tumor progression at the stem cell level, which have emerged from recent studies. Disclosures Steidl: Aileron Therapeutics: Consultancy, Research Funding; Stelexis Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Other: Scientific Co-Founder; Pieries Pharmaceuticals: Consultancy; Celgene: Consultancy; BayerHealthcare: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; GlaxoSmithKline: Research Funding.