An orally available MDM2 (murine double minute 2) antagonist with potential antineoplastic activity. Upon oral administration, MDM2 inhibitor DS-3032b binds to, and prevents the binding of MDM2 protein to the transcriptional activation domain of the tumor suppressor protein p53. By preventing this MDM2-p53 interaction, the proteosome-mediated enzymatic degradation of p53 is inhibited and the transcriptional activity of p53 is restored. This results in the restoration of p53 signaling and leads to the p53-mediated induction of tumor cell apoptosis. MDM2, a zinc finger protein and a negative regulator of the p53 pathway, is overexpressed in cancer cells; it has been implicated in cancer cell proliferation and survival.