Targeting Kras -mutant cancer with a mutation-specific inhibitor.

The RAS genes, which include H, N, and KRAS, comprise the most frequently mutated family of oncogenes in cancer. Mutations in KRAS - such as the G12C mutation - are found in most pancreatic, half of colorectal and a third of lung cancer cases and is thus responsible for a substantial proportion of cancer deaths. Consequently, KRAS has been the subject of exhaustive drug-targeting efforts over the past 3-4 decades. These efforts have included targeting the KRAS protein itself but also its posttranslational modifications, membrane localization, protein-protein interactions and downstream signalling pathways. Most of these strategies have failed and no KRAS-specific drugs have yet been approved. However, for one specific mutation, KRAS , there is light on the horizon. MRTX849 was recently identified as a potent, selective and covalent KRAS inhibitor that possesses favourable drug-like properties. MRTX849 selectively modifies the mutant cysteine residue in GDP-bound KRAS and inhibits GTP-loading and downstream KRAS-dependent signalling. The drug inhibits the in vivo growth of multiple KRAS -mutant cell line xenografts, causes tumour regression in patient-derived xenograft models and shows striking responses in combination with other agents. It has also produced objective responses in patients with mutant-specific lung and colorectal cancer. In this review, we discuss the history of RAS drug-targeting efforts, the discovery of MRTX849, and how this drug provides an exciting and long-awaited opportunity to selectively target mutant KRAS in patients.