Information HDM201 (Siremadlin) HDM201 (Siremadlin, NVP-HDM201) is a novel, highly potent and selective inhibitor of the p53-Mdm2 interaction with affinity constant for Mdm2 in the picomolar range and a selectivity ratio greater than 10000-fold vs Mdm4. Targets p53/MDM2 interaction In vitro HDM201 binds to the p53 binding-site of the Mdm2 protein, disrupting the interaction of the two proteins and leading to the activation of the p53 pathway. It induces robust p53-dependent cell cycle arrest and apoptosis in human p53 wild-type tumor cells. HDM201 exhibits highly selectivity across a panel of cancer cell lines. In vivo HDM201 displays desirable pharmacokinetic and pharmacodynamic profiles in animals together with excellent oral bioavailability. Application of the compound using various dosing schedules triggers rapid and sustained activation of p53-dependent pharmacodynamic biomarkers resulting in tumor regression in multiple xenografted models of p53 wild-type human cancers.