DIRAS3-derived cyclic peptides disrupt KRAS-RAF interaction and KRAS nanoclustering, suppressing KRAS-driven pancreatic and ovarian tumors.

Mutations in KRAS drive 88% of pancreatic ductal adenocarcinomas (PDAC) and up to 40% of low-grade serous ovarian cancers (LGSOC), making KRAS a long-standing therapeutic target. We previously showed that DIRAS3 binds RAS, forming heterodimers that disrupt RAS clustering and downstream MAPK signaling. Building on this, we developed conformationally constrained DIRAS3-derived peptides using two cyclization strategies and characterized them by NMR and biolayer interferometry. These cyclic peptides attenuate the interaction between KRAS and the BRAF RAS-binding domain, penetrate cells efficiently, and inhibit KRAS nanoclustering on the inner leaflet of the plasma membrane. Functionally, they reduce cell viability and suppress PDAC and LGSOC growth in cell culture and xenograft models. Our findings demonstrate that DIRAS3-based cyclic peptides represent a distinct strategy to directly inhibit oncogenic KRAS signaling and provide a promising framework for therapeutic development in KRAS-driven cancers.