The objective of this work is to develop novel anti-cancer drugs that target, primarily, isoprenoid biosynthesis. The work builds on the discovery in several recent clinical trials that the bisphosphonate drug zoledronate has unexpected positive effects as an adjuvant (in combination therapy with aromatase inhibitors) in breast cancer, reducing the re-occurrence of disease (at any site) by 36%, in addition to increasing the survival of prostate cancer patients. Likely targets are direct tumor cell killing, inhibition of invasiveness and angiogenesis, and "phenotype switching" (34 T cell activation and conversion of tumor associated macrophages (TAMs) from a pro-tumor, M2, to an anti-tumor, M1, phenotype). In the work proposed here we will test the hypothesis that a new class of bisphosphonates called "lipophilic bisphosphonates" (LBPs) will be far more effective than zoledronate in tumor cell killing and in 34 T cell activation and that they will also switch macrophages from M2 -> M1, resulting in new leads for cancer chemotherapy and immunotherapy. We also propose to test the hypothesis that by using a combination of high-field solid-state NMR and calorimetry to develop molecular models for bone-ligand interactions, we can very effectively design other anti-cancer drugs that bind to bone, realizing the long sought after goal of "magic bullets" for bone diseases. In Aim 1, we will develop compounds that inhibit two prenyl synthase enzymes: farnesyl diphosphate synthase (FPPS) and geranylgeranyl diphosphate synthase (GGPPS), that are involved in protein (e.g. Ras, Rho, Rap1A) prenylation, of importance in cell signaling and cell survival pathways. In Aim 2, we will carry out cell-based and in vivo testing of the compounds made in Aim 1. In Aim 3, we will develop the concept of "bone-tags" or "magic bullets", compounds which enable the delivery of drugs to bone. If successful, we will thus develop completely new approaches to cancer chemotherapy and immunotherapy that, in the future, will have a major impact in the clinic.