RO8994 is a highly potent and selective series of spiroindolinone small-molecule MDM2 inhibitor, with IC50 of 5 nM (HTRF binding assays) and 20 nM (MTT proliferation assays).IC50 value: 5 nM (in HTRF binding assays), 20 nM (in MTT proliferation assays)Target: MDM2in vitro: RO8994 represents a new generation of p53-MDM2 antagonists with marked improvement in pharmacological properties for potential clinical development. RO8994 induces dose-dependent up-regulation of p53 target genes and apoptosis in wild-type p53 cancer cells, consistent with its non-genotoxic mechanism of p53 activation.in vivo: RO8994 displays remarkable tumor growth inhibition in the wild-type p53, MDM2-amplified SJSA-1 osteosarcoma tumor xenograft model - exhibiting significant (>60%) tumor growth inhibition at the low dose of 1.56 mg/kg, tumor stasis at 3.125 mg/kg and regression at 6.25 mg/kg.