De novo design of Ras isoform selective binders.

The four major isoforms encoded by RAS proto-oncogenes are differentially associated with cancer, but there are few isoform-specific binding reagents becasue the sequence differences are confined to their disordered C termini. To overcome this limitation, we use deep learning-based methods to design Ras isoform-specific binders (RIBs) for all major Ras isoforms de novo by targeting the Ras C terminus. The RIBs bind to their target Ras isoforms both in vitro and in cells with remarkable specificity, disrupting their membrane localization and inhibiting Ras activity. The RIBs enable dissection of the distinct roles of Ras isoforms during Ras(G12C) inhibitor resistance, demonstrating their utility in understanding Ras biology and disease and suggesting potential therapeutic applications.