Discovery of a Novel Chemical Scaffold for Dual MDM2 and MDM4 Inhibition

Abstract p53 is frequently inactivated through overexpression of MDM2 and MDM4, highlighting the need for effective MDM2/MDM4 dual inhibitors. In this work, an MDM2/MDM4-based virtual screening led to the identification of etrasimod as dual MDM2/MDM4 inhibitor. Guided by structural insights, rational modification of the cyclopentyl substituent afforded a series of six cyclopenta[b]indole derivatives designed to improve interactions in the hydrophobic Leu-26 pocket in both proteins. This optimization resulted in enhanced dual inhibitory activity, with the most potent analogue bearing a 3,4-dichlorophenyl substituent exhibiting IC50 values of 1.6 μM (MDM2) and 2.6 μM (MDM4) in binding assays. Moreover, mechanistic studies in SJSA-1 cells demonstrated a significant increase in p53 steady-state protein levels, as well as cleaved caspase-3 and cleaved PARP, consistent with p53 pathway engagement and activation of apoptosis. Overall, this study identifies cyclopenta[b]indoles as a new chemical scaffold for dual MDM2/MDM4 inhibition providing a basis for further biochemical and cellular optimization.