organization of K-Ras is controlled by the prenylbinding protein PDEδ, which enhances Ras diffusion in the cytosol. Inhibition of the Ras–PDEδ interaction by small molecules impairs Ras localization and signaling. Here we describe in detail the identification and structure guided development of Ras–PDEδ inhibitors targeting the farnesyl binding pocket of PDEδ with nanomolar affinity. We report kinetic