M1C is a druggable target for NSCLC KRAS G12C mutant tumors resistant to KRAS inhibitors.

Treatment of NSCLC KRAS G12C mutant tumors with the allele-selective sotorasib and adagrasib inhibitors is invariably associated with acquired resistance. The MUC1-encoded oncogenic M1C protein is necessary for self-renewal of NSCLC KRAS mutant cells. We report that treatment of NSCLC KRAS G12C cells with sotorasib induces M1C expression by a STAT1-dependent pathway. In turn, M1C drives the sotorasib resistant phenotype by NF-κB-mediated induction of the epithelial-mesenchymal transition (EMT) and a mucinous gene program. Targeting M1C→NF-κB signaling (i) suppresses EMT and mucin genes, and (ii) reverses sotorasib resistance. Of translational relevance, treatment with a M1C antibody-drug conjugate (ADC) is effective against two sotorasib-resistant NSCLC KRAS G12C cell lines and two patient-derived tumor xenograft models. Analysis of patients with NSCLC KRAS G12C tumors treated with sotorasib/adagrasib and overexpressing MUC1 associates with decreases in overall survival. These findings identify M1C as a key effector of sotorasib resistance and as a target for treatment of patients with refractory NSCLC KRAS G12C mutant tumors.