Cis-imidazoline analog that inhibits the interaction between p53 and its negative regulator MDM2 (IC50 = 0.09 μM). It induces the expression of p53-regulated genes and exhibits potent antiproliferative activity in cells with functional p53, but not in cells with mutated p53. Nutlin-3 also inhibits the growth of human tumor xenografts in nude mice by 90% at a dose of 200 mg/kg.