Oliver Lai

Abstract 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 61 1 . 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).

Fluorescent live-cell microscopy enables the study of cellular dynamics by imaging specific molecules, their interactions, and biochemical states in living samples. It is vital for biological research and drug screening. However, live-cell imaging must balance temporal resolution with cell viability due to photo-toxicity, often necessitating lower temporal resolution to extend observation periods. This reduction complicates the tracking of cells and detection of cell division events, limiting the study of dynamic cellular processes. We present an integrated methodology combining contrastive learning and graph-based techniques to improve cell division detection and tracking in video microscopy with low temporal resolution. Our approach uses contrastive learning models to generate robust cell representations that enhance both division detection and tracking accuracy. Specifically, we develop a weakly-supervised contrastive learning strategy leveraging time-based augmentations to build temporal cell representations. In addition, we propose a novel graph optimization method to identify cell tracks using these representations alongside observed division events. Evaluation on an in-house dataset and public benchmarks demonstrates significant performance gains across both native and reduced temporal resolutions. The proposed methodology improves adaptability to various temporal resolutions, enabling more precise and efficient analysis of live-cell microscopy data. This advancement supports extended observation periods necessary for drug screening and biological studies by preserving cell viability and normal homeostasis. Our approach facilitates deeper insights into cellular mechanisms and has the potential to enhance therapeutic research workflows.

Abstract RAS family proteins regulate cell growth by transitioning between GTP-bound (ON) and GDP-bound (OFF) conformations. Transition to the OFF state is facilitated by endogenous GTPase activating proteins (GAPs). Oncogenic mutations in RAS - among the most prevalent genetic events in human cancer - perturb this regulatory cycle by disrupting GAP-mediated stimulation of GTP hydrolysis, leading to sustained RAS activation. The investigational RAS(ON) multi-selective inhibitor daraxonrasib has a dual mechanism of RAS(ON) inhibition: disrupting RAS(ON) effector binding and activating RAS(ON) GTPase activity. Daraxonrasib has demonstrated encouraging response rates and durable antitumor activity with acceptable tolerability in patients with RAS-addicted cancers. Additional strategies are needed to counter emergent drug resistance and further extend clinical benefit. The majority of acquired genomic resistance mechanisms to daraxonrasib converge on reactivation of RAS(ON) and, in particular, RAS gene amplification, highlighting a potential opportunity for RAS(ON) inhibitors less sensitive to such resistance mechanisms. We have leveraged our understanding of tri-complex RAS(ON) inhibitors to design a new class of inhibitors that mimic the catalytic activity of natural GAPs. These compounds bind non-covalently to cyclophilin A to form a binary complex that selectively engages RAS(ON) proteins, including mutant and wild-type variants. The primary mechanism of action of these catalytic RAS(ON) inhibitors is to markedly accelerate the GTPase activity of oncogenic RAS mutants and promote conversion of RAS(ON) to RAS(OFF). Importantly, a single CYPA:catalytic RAS(ON) binary complex can inactivate multiple RAS(ON) proteins. In G12-mutant cell lines the catalytic RAS(ON) inhibitors more efficiently reduced RAS-GTP levels and exhibited more potent inhibition of RAS(ON) signaling and cell proliferation compared to daraxonrasib. In vivo oral administration of the catalytic RAS(ON) inhibitor RM-055 preferentially suppressed RAS pathway activation in G12-mutant tumors relative to normal tissues. At well-tolerated doses RM-055 demonstrated robust antitumor activity represented by deep and particularly durable responses across a panel of G12-mutant xenograft and syngeneic models of PDAC, NSCLC, and CRC, including models refractory to daraxonrasib monotherapy. Furthermore, RM-055 overcame acquired resistance to RAS(ON) inhibition, driving deep and durable regressions in models with elevated oncogenic RAS signaling, such as those with RAS amplification. Collectively, these preclinical data support evaluation of the potential of this new class of mutant-targeted catalytic RAS(ON) inhibitors to sustain clinical antitumor activity in the setting of emergent resistance mechanisms that rely on enhanced RAS pathway flux. Citation Format: Kyle Seamon, Jingwei Yin, Ouma Onguka, Oliver Lai, Cristina Blaj, Lingyan Jiang, Jinyu Liu, Yue Huang, Abby Marquez, John Knox, Jim Cregg, Yongxian Zhuang, Yu Chi Yang, Urszula N. Wasko, Qiang Liu, Jennifer A. Roth, Matthew G. Rees, Melissa Ronan, Benjamin J. Maldonato, Muhammad Ali Al-Radhawi, Kartika Jayashankar, Zhican Wang, Mike Flagella, Elsa Quintana, Elena S. Koltun, Mallika Singh, Zhengping Wang, Adrian L. Gill, David Wilds, Jingjing Jiang, Jacqueline A. Smith, Matthew Holderfield. Discovery of a new class of mutant-targeted catalytic RAS(ON) inhibitors with retained antitumor activity in setting of emergent resistance due to elevated RAS flux [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 6782.