Conventionally, MDM2 inhibitors have primarily been evaluated as a method for the activation of p53 in wild-type p53 cancer cells; however, MDM4 inhibitors have recently been attracting increasing attention, and one of them is CEP-1347, the inhibitory effects of which on MDM4 protein expression were demonstrated in our recent study [22,23,24]. The gene discussed is MDM2; the disease is cancer.