RG7112 is a selective inhibitor of p53-MDM2 binding that frees p53 from negative control, activating the p53 pathway in cancer cells leading to cell cycle arrest and apoptosis. P53 is a potent tumor suppressor that activates the transcription of a subset of genes controlling cell-cycle progression and apoptosis. MDM2 is a negative regulator of p53 that binds the transactivation domain of p53 and inhibits its ability to activate transcription. MDM2 is also an E3 ubiquitin ligase that targets p53 for proteosomal degradation. MDM2 overexpression is one of the mechanisms by which the wild type p53 function is impaired.