An inhibitor of the protein-protein interaction between MDM2 and p53 (IC50 = 5 nM in a p53-MDM2 HTRF binding assay); inhibits the proliferation of SJSA-1, RKO, and HCT116 cells (average IC50 = 20 nM); increases apoptosis in SJSA-1 cells in a concentration-dependent manner; reduces tumor growth and induces tumor regression in an SJSA-1 osteosarcoma mouse xenograft model at 1.56 and 6.25 mg/kg, respectively.