KRAS is one of the most commonly mutated proteins in cancer, and efforts to directly inhibit its function have been continuing for decades. The most successful of these has been the development of covalent allele-specific inhibitors that trap KRAS G12C in its inactive conformation and suppress tumour growth in patients^{1,2,3,4,5,6,7}. Whether inactive-state selective inhibition can be used to therapeutically target non-G12C KRAS mutants remains under investigation. Here we report the discovery and characterization of a non-covalent inhibitor that binds preferentially and with high affinity to the inactive state of KRAS while sparing NRAS and HRAS. Although limited to only a few amino acids, the evolutionary divergence in the GTPase domain of RAS isoforms was sufficient to impart orthosteric and allosteric constraints for KRAS selectivity. The inhibitor blocked nucleotide exchange to prevent the activation of wild-type KRAS and a broad range of KRAS mutants, including G12A/C/D/F/V/S, G13C/D, V14I, L19F, Q22K, D33E, Q61H, K117N and A146V/T. Inhibition of downstream signalling and proliferation was restricted to cancer cells harbouring mutant KRAS, and drug treatment suppressed KRAS mutant tumour growth in mice, without having a detrimental effect on animal weight. Our study suggests that most KRAS oncoproteins cycle between an active state and an inactive state in cancer cells and are dependent on nucleotide exchange for activation. Pan-KRAS inhibitors, such as the one described here, have broad therapeutic implications and merit clinical investigation in patients with KRAS-driven cancers.

KRAS 是癌症中最常见的突变蛋白之一，直接抑制其功能的努力已经持续了数十年。其中最成功的是共价等位基因特异性抑制剂的开发，该抑制剂将 KRAS G12C 捕获在其非活性构象中并抑制患者的肿瘤生长^{1,2,3,4,5,6,7}。非活性状态选择性抑制是否可用于治疗靶向非 G12C KRAS 突变体仍在研究中。在这里，我们报告了一种非共价抑制剂的发现和表征，该抑制剂优先并以高亲和力与 KRAS 的非活性状态结合，同时不影响 NRAS 和 HRAS。尽管仅限于少数氨基酸，但 RAS 亚型 GTPase 结构域的进化差异足以赋予 KRAS 选择性正构和变构约束。该抑制剂阻断核苷酸交换，以防止野生型 KRAS 和多种 KRAS 突变体的激活，包括 G12A/C/D/F/V/S、G13C/D、V14I、L19F、Q22K、D33E、Q61H、K117N和A146V/T。下游信号传导和增殖的抑制仅限于携带突变 KRAS 的癌细胞，药物治疗可抑制小鼠 KRAS 突变肿瘤的生长，且不会对动物体重产生不利影响。我们的研究表明，大多数 KRAS 癌蛋白在癌细胞中在活性状态和非活性状态之间循环，并且依赖于核苷酸交换来激活。泛 KRAS 抑制剂（例如本文所述的抑制剂）具有广泛的治疗意义，值得对 KRAS 驱动的癌症患者进行临床研究。