KRASG12C inhibition produces a driver-limited state revealing collateral dependencies

Inhibitors targeting KRAS(G12C), a mutant form of the guanosine triphosphatase (GTPase) KRAS, are a promising new class of oncogene-specific therapeutics for the treatment of tumors driven by the mutant protein. These inhibitors react with the mutant cysteine residue by binding covalently to the switch-II pocket (S-IIP) that is present only in the inactive guanosine diphosphate (GDP)-bound form of KRAS(G12C), sparing the wild-type protein. We used a genome-scale CRISPR interference (CRISPRi) functional genomics platform to systematically identify genetic interactions with a KRAS(G12C) inhibitor in cellular models of KRAS(G12C) mutant lung and pancreatic cancer. Our data revealed genes that were selectively essential in this oncogenic driver-limited cell state, meaning that their loss enhanced cellular susceptibility to direct KRAS(G12C) inhibition. We termed such genes collateral dependencies (CDs) and identified two classes of combination therapies targeting these CDs that increased KRAS(G12C) target engagement or blocked residual survival pathways in cells and in vivo. From our findings, we propose a framework for assessing genetic dependencies induced by oncogene inhibition.