Clinical activity of MDM2 inhibitors among unselected diverse cancers has been limited17-19; however, occasional responses have been observed in individuals selected for wild-type TP53. 20,21 The low response rate with single-agent MDM2 inhibitors may be due to the lack of patient selection for MDM2 amplification or to co-altered genes (Data Supplement). This evidence concerns the gene TP53 and cancer.