(±)-Nutlin-3 blocks the interaction of p53 with its negative regulator Mdm2 (IC50 = 90 nM), inducing the expression of p53-regulated genes and blocking the growth of tumor xenografts in vivo. CAY10682 is a pyrrolo[3,4c]pyrazole derivative that inhibits the p53-Mdm2 interaction as potently as (±)-nutlin-3 (Ki = 83 nM) and also dose-dependently reduces activation of the NF-κB pathway. It specifically prevents phosphorylation of IκBα by the kinases IKKα, IKKβ, and IKK (IC50s = 80.5, 78.2, and 57.1 μM, respectively). CAY10682 blocks the growth of cancer cells in vitro (IC50s = 2-6 μM) and inhibits the growth of A549 cell xenografts in mice without significantly reducing body weight.