K-Ras and its inhibitors towards personalized cancer treatment: Pharmacological and structural perspectives

The discovery of genetic, genomic and clinical biomarkers have revolutionized the treatment option in the form of personalized medicine which allows to accurately predict a person's susceptibility/progression of disease, the patient's response to therapy, and maximize the therapeutic outcome in terms of low/no toxicity for a particular patient. Recently, the U.S. Food and Drug Administration has realized the contribution of pharmacogenomics in better healthcare and advocated the consideration of pharmacogenomic principles in making safer and more effective drug. Many anticancer drugs show reduced or no response in cancer patients with tumor specific gene mutations such as B-Raf and K-Ras. The high incidence of K-Ras mutation has been reported in pancreatic, colon, and lung carcinomas. The identification of K-Ras as a clinical biomarker and potential therapeutic target has attracted the scientific community to develop effective and precise anticancer drug. Inhibitors which block farnesylation of Ras have been developed or under clinical trial studies. Tipifarnib, approved by USFDA for the treatment of elderly acute leukemia is a Ras pathway inhibitor. Some peptidomimetics and bi-substrate inhibitors like FTI 276, FTI 277, B956, B1086, L731, L735, L739, L750, BMS-214662, L778123, and L778123 are under clinical trials. Recently mutant K-Ras has been considered as potential biomarker and target for precise cancer therapy. This review focuses primarily on the Ras/Raf/MEK/ERK signaling pathway including K-Ras mutation as therapeutic target, inhibitors and their structure activity relationships (SARs) for the design and development of anticancer agents.