RG7388 exhibits improved in vitro and in vivo potency against tumor cell lines and xenografts, improved CYP inhibition profile, and 2.5- to 20-fold lower projected human efficacious dose. Preclinical studies have indicated that tumors expressing wild-type p53 may respond to this novel therapeutic strategy that releases p53 from MDM2 inhibition, and tumors with wild-type p53 and MDM2 over-expression or amplification are likely to be the most sensitive. Results from preclinical safety and toxicology studies support further exploration of this compound in cancer patients. In view of the existing unmet medical need in advanced cancers expressing the above molecular signature, RG7388 is believed to be a promising agent that may offer a new therapeutic option.