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The small GTPase KRAS is a key driver of carcinogenesis when mutated, and significant progress has been made in targeting KRAS G12C and other oncogenic variants. Building on our previous work demonstrating the potential of nucleotide-based inhibitors with an acrylamide warhead to target KRAS G13C , we designed and synthesized a library of nucleotide-based compounds with cyclic linkers to explore the effect of warhead orientation on reactivity toward Cys13. Using mass spectrometry, kinetic studies, and protein X-ray crystallography, we validated the binding and reactivity of these modulators. In addition, computational predictions of the conformational space of the linkers and warheads provided insights into their reactivity, which agreed well with the experimental data. These findings advance our understanding of the structure-reactivity relationship in these nucleotide-based KRAS inhibitors and will be the basis for further optimization.

Mutations within Ras proteins represent major drivers in human cancer. In this study, we report the structure-based design, synthesis, as well as biochemical and cellular evaluation of nucleotide-based covalent inhibitors for KRasG13C, an important oncogenic mutant of Ras that has not been successfully addressed in the past. Mass spectrometry experiments and kinetic studies reveal promising molecular properties of these covalent inhibitors, and X-ray crystallographic analysis has yielded the first reported crystal structures of KRasG13C covalently locked with these GDP analogues. Importantly, KRasG13C covalently modified with these inhibitors can no longer undergo SOS-catalysed nucleotide exchange. As a final proof-of-concept, we show that in contrast to KRasG13C, the covalently locked protein is unable to induce oncogenic signalling in cells, further highlighting the possibility of using nucleotide-based inhibitors with covalent warheads in KRasG13C-driven cancer.