RAS oncogenes (collectively NRAS, HRAS and especially KRAS) are among the most frequently mutated genes in cancer, with common driver mutations occurring at codons 12, 13 and 61¹. Small molecule inhibitors of the KRAS(G12C) oncoprotein have demonstrated clinical efficacy in patients with multiple cancer types and have led to regulatory approvals for the treatment of non-small cell lung cancer^2,3. Nevertheless, KRAS^G12C mutations account for only around 15% of KRAS-mutated cancers^4,5, and there are no approved KRAS inhibitors for the majority of patients with tumours containing other common KRAS mutations. Here we describe RMC-7977, a reversible, tri-complex RAS inhibitor with broad-spectrum activity for the active state of both mutant and wild-type KRAS, NRAS and HRAS variants (a RAS(ON) multi-selective inhibitor). Preclinically, RMC-7977 demonstrated potent activity against RAS-addicted tumours carrying various RAS genotypes, particularly against cancer models with KRAS codon 12 mutations (KRAS^G12X). Treatment with RMC-7977 led to tumour regression and was well tolerated in diverse RAS-addicted preclinical cancer models. Additionally, RMC-7977 inhibited the growth of KRAS^G12C cancer models that are resistant to KRAS(G12C) inhibitors owing to restoration of RAS pathway signalling. Thus, RAS(ON) multi-selective inhibitors can target multiple oncogenic and wild-type RAS isoforms and have the potential to treat a wide range of RAS-addicted cancers with high unmet clinical need. A related RAS(ON) multi-selective inhibitor, RMC-6236, is currently under clinical evaluation in patients with KRAS-mutant solid tumours (ClinicalTrials.gov identifier: NCT05379985).

Generation of genetically engineered mouse models (GEMMs) for chromosomal translocations in the endogenous loci by a knockin strategy is lengthy and costly. The CRISPR/Cas9 system provides an innovative and flexible approach for genome engineering of genomic loci in vitro and in vivo. Here, we report the use of the CRISPR/Cas9 system for engineering a specific chromosomal translocation in adult mice in vivo. We designed CRISPR/Cas9 lentiviral vectors to induce cleavage of the murine endogenous Eml4 and Alk loci in order to generate the Eml4-Alk gene rearrangement recurrently found in non-small-cell lung cancers (NSCLCs). Intratracheal or intrapulmonary inoculation of lentiviruses induced Eml4-Alk gene rearrangement in lung cells in vivo. Genomic and mRNA sequencing confirmed the genome editing and the production of the Eml4-Alk fusion transcript. All mice developed Eml4-Alk-rearranged lung tumors 2 months after the inoculation, demonstrating that the CRISPR/Cas9 system is a feasible and simple method for the generation of chromosomal rearrangements in vivo.

Purpose: BRAF mutations are divided into functional classes distinguished by signaling mechanism and kinase activity: V600-mutant kinase-activating monomers (class I), kinase-activating dimers (class II), and kinase-inactivating heterodimers (class III). The relationship between functional class and disease characteristics in BRAF-mutant non–small cell lung cancer (NSCLC) has not been fully explored. Experimental Design: We performed a retrospective analysis of BRAF-mutant NSCLCs treated at 2 institutions from 2005 to 2017 to determine clinicopathologic characteristics, progression-free survival (PFS) on chemotherapy, and overall survival (OS). Results: We identified 236 patients with BRAF-mutant NSCLC (n = 107 class I, n = 75 class II, and n = 54 class III). Patients with class II or III mutations were more likely to have brain metastases (P ≤ 0.01) and RAS coalterations (P ≤ 0.001) than class I. Compared with class I, PFS on chemotherapy was shorter for class II (P = 0.069) and class III (P = 0.034). OS was shorter for class II and III (class I, 40.1 months; class II, 13.9 months; and class III, 15.6 months; I vs. II, P < 0.001; I vs. III, P = 0.023); however, this difference was driven by fewer extrathoracic metastases and higher use of targeted therapies in class I patients. When patients treated with targeted therapy and those with thoracic-only metastases were excluded, there was no difference in OS across the 3 classes. Conclusions: BRAF-mutant NSCLC is a heterogeneous disease that encompasses 3 distinct functional classes. Classes II and III have more aggressive clinical features leading to less favorable outcomes. The distinct biological characteristics of class II and III tumors suggest that class-specific therapies may be necessary to effectively target these molecular subsets.