Inhibitors of farnesyltransferase and geranylgeranyltransferase-I for antitumor therapy: Substrate-based design, conformational constraint and biological activity

The development of farnesyltransferase inhibitors, a novel approach to non-cytotoxic anticancer therapy, has been an active area of research over the past decade. Compounds that have advanced to clinical trials were evolved both from substrate-based design efforts and from compound library screening hits. This review focuses on the effort at Merck to evolve inhibitors from the protein substrate of farnesyltransferase, which resulted in the identification of a non-peptide inhibitor for clinical evaluation. X-ray crystal structures of farnesyltransferase complexed with early peptidomimetic as well as later non-peptide inhibitors have validated this design approach. NMR spectroscopic methods for studying enzyme-bound, inhibitor structure, in conjunction with the use of conformational constraints, were critical components of subsequent efforts to provide potent inhibitors with varying levels of farnesyltransferase and geranylgeranyltransferase-l inhibitory specificity. Several of these compounds were important tools for investigating the use of prenyltransferase inhibitors to target Ki-Ras-mediated tumor growth.