Clinical Acquired Resistance to KRASG12C Inhibition through a Novel KRAS Switch-II Pocket Mutation and Polyclonal Alterations Converging on RAS-MAPK Reactivation

Differential Response and Resistance to KRAS-Targeted Therapy

KRAS is the most frequently mutated oncogene. In epithelial malignancies such as lung, colorectal, and pancreatic tumors, KRAS is mutated in 25 to above 90% cases. KRAS was considered undruggable for over three decades until the recent development of covalent inhibitors targeting the KRAS G12C mutant. The recent approval of the KRAS G12C inhibitors sotorasib and adagrasib has ushered in a new era of KRAS-targeted therapy. Despite this success, a major challenge in KRAS-targeted therapy is intrinsic and acquired resistance to KRAS inhibitors. Clinical studies have shown that many patients with KRAS G12C cancers did not respond to sotorasib and adagrasib. Colorectal cancer, in particular, has a markedly lower response rate to KRAS G12C inhibitors compared to non-small cell lung cancer. Furthermore, the therapeutic response to KRAS G12C inhibition was short-lived, with quick emergence of acquired resistance. In this review, we summarize several major themes that have emerged from recent clinical and preclinical studies on the mechanisms of intrinsic and acquired resistance to KRAS-targeted therapy in colorectal, lung, and pancreatic cancers. We also discuss various combination strategies for targeting these mechanisms to overcome resistance to KRAS inhibitors.

Nondegradative Synthetic Molecular Glues Enter the Clinic

Molecular glues are small molecules that can induce or stabilize protein-protein interactions between proteins inside cells. Unlike classical small molecule drugs, molecular glues can target challenging disease-causing proteins lacking well-defined binding pockets. Nature has repeatedly used this mode of action, but identifying molecular glues for new target proteins has been a major challenge. Recently, manmade molecular glues, inspired by natural products, for KRas, entered clinical trials although KRas is a major cancer target long thought to be undruggable. Here, how these molecules are initially discovered and optimized to provide several advanced drug candidates for various KRas-dependent cancer types are outlined. The major insights obtained for this new class of drug modalities are further summarized. These results showcase how molecular glues that do not rely on protein degradation can provide clinical benefits for challenging drug targets.

Chaperone directed heterobifunctional molecules circumvent KRASG12C inhibitor resistance

While KRASG12C inhibitors have shown promising results in clinical activity, acquired resistance remains a significant barrier to durable responses. Combination therapies have been explored to improve the efficacy of KRASG12C inhibitors; however, their use is often restricted due to toxicity and limitations in clinically amendable dosing schedules. Transcriptomic profiling and functional assays on acquired resistant models to adagrasib identified an enrichment of HSP90 client proteins in resistant phenotypes, suggesting a therapeutic vulnerability. To address the finding, RNK07421, a novel heterobifunctional molecule, was developed to simultaneously target KRASG12C and HSP90-client oncoproteins. Structural and biochemical analyses demonstrated that RNK07421 disrupts KRASG12C interactions by inducing a non-natural interface with HSP90, thereby impairing oncogenic signaling. In vitro, RNK07421 effectively suppressed ERK reactivation and reduced viability in KRASG12C-mutant cell lines exhibiting either intrinsic or acquired resistance. In vivo, RNK07421 significantly reduced tumor burden in xenograft models, outperforming both monotherapies and combination therapies. These findings highlight dual KRASG12C and HSP90 inhibition as a promising strategy to overcome resistance in KRASG12C-driven cancers.

Evolution of computational techniques against various KRAS mutants in search for therapeutic drugs: a review article

KRAS was (Kirsten rat sarcoma viral oncogene homolog) revealed as an important target in current therapeutic cancer research because alteration of RAS (rat sarcoma viral oncogene homolog) protein has a critical role in malignant modification, tumor angiogenesis, and metastasis. For cancer treatment, designing competitive inhibitors for this attractive target was difficult. Nevertheless, computational investigations of the protein's dynamic behavior displayed the existence of temporary pockets that could be used to design allosteric inhibitors. The last decade witnessed intensive efforts to discover KRAS inhibitors. In 2021, the first KRAS G12C covalent inhibitor, AMG 510, received FDA (Food and drug administration) approval as an anticancer medication that paved the path for future treatment strategies against this target. Computer-aided drug designing discovery has long been used in drug development research targeting different KRAS mutants. In this review, the major breakthroughs in computational methods adapted to discover novel compounds for different mutations have been discussed. Undoubtedly, virtual screening and molecular dynamic (MD) simulation and molecular docking are the most considered approach, producing hits that can be employed in subsequent refinements. After comprehensive analysis, Afatinib and Quercetin were computationally identified as hits in different publications. Several authors conducted covalent docking studies with acryl amide warheads groups containing inhibitors. Future studies are needed to demonstrate their true potential. In-depth studies focusing on various allosteric pockets demonstrate that the switch I/II pocket is a suitable site for drug designing. In addition, machine learning and deep learning based approaches provide new insights for developing anti-KRAS drugs. We believe that this review provides extensive information to researchers globally and encourages further development in this particular area of research.

In Silico Identification of Putative Allosteric Pockets and Inhibitors for the KRASG13D-SOS1 Complex in Cancer Therapy

RAS mutations occur in about 30% of human cancers, leading to enhanced RAS signaling and tumor growth. KRAS is the most commonly mutated oncogene in human tumors, especially lung, pancreatic, and colorectal cancers. Direct targeting of KRAS is difficult due to its highly conserved sequence; but, its complex with the guanine nucleotide exchange factor Son of Sevenless (SOS) 1 promises an attractive target for inhibiting RAS-mediated signaling. Here, we first revealed putative allosteric binding sites of the SOS1, KRASG12C-SOS1 complex, and the ternary KRASG13D-SOS1 complex structures using two network-based models, the essential site scanning analysis and the residue interaction network model. The results enabled us to identify two new putative allosteric pockets for the ternary KRASG13D-SOS1 complex. These were then screened together with the known ligand binding site against the natural compounds in the InterBioScreen (IBS) database using the Glide software package developed by Schrödinger, Inc. The docking poses of seven hit compounds were assessed using 400 ns long molecular dynamics (MD) simulations with two independent replicas using Desmond, coupled with thermal MM-GBSA calculations for the estimation of the binding free energy values. The structural skeleton of the seven proposed compounds consists of different functional groups and heterocyclic rings that possess anti-cancer activity and exhibit persistent interactions with key residues in binding pockets throughout the MD simulations. STOCK1N-09823 was determined as the most promising hit that promoted the disruption of the interactions R73 (chain A)/N879 and R73 (chain A)/Y884, which are key for SOS1-mediated KRAS activation.

Research advancements in molecular glues derived from natural product scaffolds: Chemistry, targets, and molecular mechanisms

The mechanism of action of traditional Chinese medicine (TCM) remains unclear. Historically, research on TCM has mainly focused on exploring the mechanisms of active components acting on single targets. However, it is insufficient to explain the complex mechanisms by which these active components in TCM treat diseases. In recent years, the emergence of molecular glues (MGs) theory has provided new strategies to address this issue. MGs are small molecules that can promote interactions between proteins at their interface. The characteristic of MGs is to establish connections between diverse protein structures, thereby enabling a chemically-mediated proximity effect that triggers a wide spectrum of biological functions. Natural products are the result of billions of years of evolutionary processes in the natural environment. Thus, the extensive structural diversity of natural products renders them a rich source of MGs, including polyketides, terpenoids, steroids, lignans, organic acids, alkaloids and other classes. Currently, several well-known natural MGs, including the immunosuppressants cyclosporin A (CsA) and tacrolimus (FK506), as well as the anticancer agent taxol, have been incorporated into clinical practice. Meanwhile, the advancement of new technologies is propelling the discovery of novel MGs from natural products. Thus, we primarily summarize a growing variety of MGs from natural origins reported in recent years and categorize them based on the chemical structural types. Moreover, the main sources of TCM are natural products. The discovery of natural MGs promises to provide a new perspective for the elucidation of the molecular mechanism behind the efficiency of TCM. In summary, this review aims to provide insights from the perspective of natural products that could potentially influence TCM and modern drug development.

Reversible Small Molecule Multivariant Ras Inhibitors Display Tunable Affinity for the Active and Inactive Forms of Ras

Activating mutations of Ras are one of the most prevalent drivers of cancer and are often associated with poor clinical outcomes. Despite FDA approval for two irreversible inhibitors that target the inactive state of KRasG12C, significant unmet clinical need still exists, and the susceptibility of non-G12C mutants to inactive-state inhibition remains unclear. Here we report the discovery of a novel series of reversible inhibitors that bind in an enlarged version of the switch I-II pocket with nanomolar affinities. Dependent on chemotype these can either preferentially bind to the inactive or active state or bind both with similar affinity. The active-state binders inhibit the Raf interaction for wild-type Ras, and a broad range of oncogenic KRas mutants with nanomolar potency. A subseries of these molecules displays cellular inhibition of Ras-Raf binding, as well as decreased phosphorylation of the downstream protein ERK, demonstrating that potent multivariant Ras inhibitors can be accessed from this novel pocket.

Discovery of Elironrasib (RMC-6291), a Potent and Orally Bioavailable, RAS(ON) G12C-Selective, Covalent Tricomplex Inhibitor for the Treatment of Patients with RAS G12C-Addicted Cancers

The discovery of elironrasib (RMC-6291) represents a significant breakthrough in targeting the previously deemed undruggable GTP-bound, active KRASG12C. To target the active state of RAS (RAS(ON)) directly, we have employed an innovative tri-complex inhibitor (TCI) modality involving formation of a complex with an inhibitor, the intracellular chaperone protein CypA, and the target protein KRASG12C in its GTP-bound form. The resulting tri-complex inhibits oncogenic signaling, inducing tumor regressions across various preclinical models of KRASG12C mutant human cancers. Here we report structure-guided medicinal chemistry efforts that led to the discovery of elironrasib, a potent, orally bioavailable, RAS(ON) G12C-selective, covalent, tri-complex inhibitor. The investigational agent elironrasib is currently undergoing phase 1 clinical trials (NCT05462717, NCT06128551, NCT06162221), with preliminary data indicating clinical activity in patients who had progressed on first-generation inactive state-selective KRASG12C inhibitors.

RASON promotes KRASG12C-driven tumor progression and immune evasion in non-small cell lung cancer

BACKGROUND

KRAS is the most frequently mutated oncogene in human cancers, with KRASG12C being a prevalent driver mutation in 12-13% non-small cell lung cancer (NSCLC) cases. Despite breakthroughs in KRASG12C inhibitors such as sotorasib (AMG-510) and adagrasib (MRTX-849), clinical resistance remains a challenging issue, highlighting the need for deeper understanding of the molecular mechanisms underlying KRASG12C-driven oncogenic signaling in NSCLC. Previously, we identified RASON as a novel regulator of KRASG12D/V signaling in pancreatic cancer. Herein, we aim to explore the role of RASON in KRASG12C-driven NSCLC and its therapeutic potential.

METHODS

Immunohistochemistry analysis of NSCLC patient cohorts was performed to demonstrate the correlation between RASON expression and NSCLC progression. Immunoblotting was performed to evaluate the effects of RASON on KRASG12C downstream signaling. In vitro and in vivo assays including cell proliferation, sphere formation, tumor implantation and genetic mouse models were performed to determine the oncogenic role of RASON. RNA-seq analysis was utilized to identify the key signaling pathway regulated by RASON. Immunofluorescence, immunoprecipitation, nuclear magnetic resonance and biochemistry assays were used to validate the interaction between KRASG12C and RASON. Phagocytosis assay and flow cytometry were conducted to explore the effects of RASON on the tumor immune microenvironment. Pharmacological inhibition in subcutaneous xenograft model was used to determine the therapeutical potential of RASON.

RESULTS

RASON is overexpressed in NSCLC with KRASG12C mutation and correlates with poor patient prognosis. Genetic knockout of RASON significantly reduced lung tumor burden in LSL-KRASG12D; Trp53R172H/+ mice. In KRASG12C-mutant lung cancer cell lines, RASON overexpression enhanced, while CRISPR-mediated knockout suppressed, both in vitro proliferation and in vivo tumor growth. Mechanistically, RASON directly binds KRASG12C, stabilizes it in the GTP-bound hyperactive state and promotes downstream signaling. RASON knockout significantly reduced CD47 expression, enhancing macrophage-mediated phagocytosis and anti-tumor immunity. Therapeutically, antisense oligonucleotides targeting RASON not only exhibited tumor-suppressive effects, but also synergized with the KRASG12C inhibitor AMG-510 to significantly enhance anti-tumor efficacy.

CONCLUSION

This study reveals RASON as a key oncogenic regulator of KRASG12C signaling, driving lung tumorigenesis and progression, and identifies RASON as a promising therapeutic target for KRASG12C mutant non-small cell lung cancer.

Oncogenic KRAS addiction states differentially influence MTH1 expression and 8-oxodGTPase activity in lung adenocarcinoma

The efficacy of strategies targeting oncogenic RAS, prevalent in lung adenocarcinoma (LUAD), is limited by rapid adaptive resistance mechanisms. These include loss of RAS addiction and hyperactivation of downstream signaling pathways, such as PI3K/AKT. We previously reported that oncogenic RAS-driven LUAD cells possess an enhanced reliance on MTH1, the mammalian 8-oxodGTPase, to prevent genomic incorporation of oxidized nucleotides, and that MTH1 depletion compromises tumorigenesis and oncogenic signaling. Here, we show that elevated MTH1 correlates with poor prognosis in LUAD and that its redox-protective 8-oxodGTPase activity is variably regulated in KRAS-addicted vs. non-addicted states. Multiple oncogenic KRAS mutants or overexpression of wildtype (wt) KRAS increased MTH1 expression. Conversely, KRAS depletion or its inhibition by AMG-510 (sotorasib) decreased MTH1 in KRASG12C-addicted LUAD cells. Separation-of-function MEK/ERK1/2-activating mutants recapitulated the elevated MTH1 expression induced by oncogenic RAS in wt KRAS LUAD cells. However, upon inhibition of the MEK/ERK1/2 pathway, compensatory AKT activation maintained MTH1 expression. Indeed, elevated AKT signaling maintained high MTH1 expression even when KRAS oncoprotein was low. We previously reported that cancer cells possess variable MTH1-specific and MTH1-independent 8-oxodGTPase activity levels. Whereas both ERK1/2 and AKT could regulate MTH1 protein levels in KRAS-addicted cells, only AKT signaling was associated with elevated MTH1-specific 8-oxodGTPase activity under KRAS-low or KRAS non-addicted states. Our studies suggest that despite loss of KRAS dependency, LUAD cells retain the requirement for high MTH1 8-oxodGTPase activity due to redox vulnerabilities associated with AKT signaling. Thus, MTH1 may serve as a novel orthogonal vulnerability in LUAD that has lost KRAS addiction.

SOS1 inhibitor BI-3406 shows in vivo antitumor activity akin to genetic ablation and synergizes with a KRASG12D inhibitor in KRAS LUAD

We evaluated the in vivo therapeutic efficacy and tolerability of BI-3406-mediated pharmacological inhibition of SOS1 in comparison to genetic ablation of this universal Ras-GEF in various KRAS-dependent experimental tumor settings. Contrary to the rapid lethality caused by SOS1 genetic ablation in SOS2KO mice, SOS1 pharmacological inhibition by its specific inhibitor BI-3406 did not significantly affect animal weight/viability nor cause noteworthy systemic toxicity. Allograft assays using different KRASmut cell lines showed that treatment with BI-3406 impaired RAS activation and RAS downstream signaling and decreased tumor burden and disease progression as a result of both tumor-intrinsic and -extrinsic therapeutic effects of the drug. Consistent with prior genetic evidence and the KRASmut allografts assays in immunocompromised mice, our analyses using an in vivo model of KRASG12D-driven lung adenocarcinoma (LUAD) in immunocompetent mice showed that single, systemic BI-3406 treatment impaired tumor growth and downmodulated protumorigenic components of the tumor microenvironment comparably to SOS1 genetic ablation or to treatment with the specific KRASG12D inhibitor MRTX1133. Furthermore, markedly stronger, synergistic antitumor effects were observed upon concomitant treatment with BI-3406 and MRTX1133 in the same in vivo LUAD mouse model. Our data confirm SOS1 as an actionable therapy target in RAS-dependent cancers and suggest that BI-3406 treatment may yield clinical benefit both as monotherapy or as a potential combination partner for multiple RAS-targeting strategies.

Targeting ubiquitin-independent proteasome with small molecule increases susceptibility in pan-KRAS-mutant cancer models

Despite advances in the development of direct KRAS inhibitors, KRAS-mutant cancers continue to exhibit resistance to the currently available therapies. Here, we identified REGγ as a mutant KRAS-associated factor that enhanced REGγ transcription through the KRAS intermediate NRF2, suggesting that the REGγ-proteasome is a potential target for pan-KRAS inhibitor development. We elucidated a mechanism involving the KRAS/NRF2/REGγ regulatory axis, which links activated KRAS to the ATP- and ubiquitin-independent proteasome. We subsequently developed RLY01, a REGγ-proteasome inhibitor that effectively suppressed tumor growth in KRAS-mutant cancer models and lung cancer organoids. Notably, the combination of RLY01 and the KRASG12C inhibitor AMG510 exhibited enhanced antitumor efficacy in KRASG12C cancer cells. Collectively, our data support the hypothesis that KRAS mutations enhance the capacity of the REGγ-proteasome by increasing REGγ expression, highlighting the potential of ubiquitin-independent proteasome inhibition as a therapeutic approach for pan-KRAS-mutant cancers.

Advances in the treatment of KRASG12C mutant non-small cell lung cancer

Kirsten rat sarcoma (KRAS) is one of the most frequently mutated oncogenic drivers in metastatic non-small cell lung cancer (NSCLC). The development of selective, covalent KRAS G12C (KRASG12C) inhibitors represents a breakthrough in the treatment for KRASG12C mutant NSCLC, but the durability of response and efficacy of these inhibitors are limited by the rapid emergence of drug resistance and their ability to only bind KRASG12C in the guanosine diphosphate-bound form. Importantly, co-occurring gene alterations, including KEAP1, STK11, and CDKN2A, may affect prognosis and response to therapies, including immunotherapy and KRASG12C inhibitors. New therapeutic approaches are needed to both delay and overcome treatment resistance. Moreover, developing KRAS inhibitors with novel mechanisms of action and alternative allele specificities is necessary to overcome emerging on-target resistance mechanisms to KRASG12C inhibitors. A literature search was performed using PubMed, the Food and Drug Administration website, and Google search. The inclusive dates in the literature search were between 1982 and July 2024. In this article, the authors reviewed the disease prevalence, biology and therapeutic options, including specific KRASG12C inhibitors and new pan-KRAS therapeutic agents for KRASG12C mutant NSCLC. KRAS inhibitor resistance mechanisms, treatment strategies, and multi-targeted treatment approaches are also discussed.

Utilizing ctDNA to discover mechanisms of resistance to targeted therapies in patients with metastatic NSCLC: towards more informative trials

Advances in targeted therapies for patients with non-small-cell lung cancer have substantially improved the outcomes of those with actionable alterations in certain oncogenic driver genes. However, acquired resistance to these targeted therapies remains a major challenge. Understanding the mechanisms underlying acquired resistance will be crucial for the development of strategies that might either overcome this effect or delay the onset. Circulating tumour DNA, owing to the need for only minimally invasive sampling and a potential role as both a prognostic and predictive biomarker, is increasingly being used in both research and clinical practice. Several studies have explored the landscape of acquired resistance to targeted therapies using this approach. However, the methodologies of the published studies vary widely, and several major challenges remain in addressing the practical difficulties associated with these methods. These challenges currently limit the depth of research insight provided by the available data. In this Perspective, we review clinical reports describing the use of circulating tumour DNA to detect mechanisms of acquired resistance to targeted therapies, predominantly in patients with advanced-stage non-small-cell lung cancer, and highlight key unresolved questions with the aim of moving towards more-informative research studies.

Discovery of BBO-8520, a First-In-Class Direct and Covalent Dual Inhibitor of GTP-Bound (ON) and GDP-Bound (OFF) KRASG12C

Approved inhibitors of KRASG12C prevent oncogenic activation by sequestering the inactive, GDP-bound (OFF) form rather than directly binding and inhibiting the active, GTP-bound (ON) form. This approach provides no direct target coverage of the active protein. Expectedly, adaptive resistance to KRASG12C (OFF)-only inhibitors is observed in association with increased expression and activity of KRASG12C(ON). To provide optimal KRASG12C target coverage, we have developed BBO-8520, a first-in-class, direct dual inhibitor of KRASG12C(ON) and (OFF) forms. BBO-8520 binds in the Switch-II/Helix3 pocket, covalently modifies the target cysteine, and disables effector binding to KRASG12C(ON). BBO-8520 exhibits potent signaling inhibition in growth factor-activated states, in which current (OFF)-only inhibitors demonstrate little measurable activity. In vivo, BBO-8520 demonstrates rapid target engagement and inhibition of signaling, resulting in durable tumor regression in multiple models, including those resistant to KRASG12C(OFF)-only inhibitors. BBO-8520 is in phase 1 clinical trials in patients with KRASG12C non-small cell lung cancer. Significance: BBO-8520 is a first-in-class direct, small molecule covalent dual inhibitor that engages KRASG12C in the active (ON) and inactive (OFF) conformations. BBO-8520 represents a novel mechanism of action that allows for optimal target coverage and delays the emergence of adaptive resistance seen with (OFF)-only inhibitors in the clinic. See related commentary by Zhou and Westover, p. 455.

Recent advances in targeted degradation in the RAS pathway

RAS (rat sarcoma) is one of the most frequently mutated gene families in cancer, encoding proteins classified as small GTPases. Mutations in RAS proteins result in abnormal activation of the RAS signaling pathway, a key driver in the initiation and progression of various malignancies. Consequently, targeting RAS proteins and the RAS signaling pathway has become a critical strategy in anticancer therapy. While RAS was historically considered an "undruggable" target, recent breakthroughs have yielded inhibitors specifically targeting KRASG12C and KRASG12D mutations, which have shown clinical efficacy in patients. However, these inhibitors face limitations due to rapid acquired resistance and the toxic effects of combination therapies in clinical settings. Targeted protein degradation (TPD) strategies, such as PROTACs and molecular glues, provide a novel approach by selectively degrading RAS proteins, or their upstream and downstream regulatory factors, to block aberrant signaling pathways. These degraders offer a promising alternative to traditional inhibitors by potentially circumventing resistance and enhancing therapeutic precision. This review discusses recent advancements in RAS pathway degraders, with an emphasis on targeting RAS mutations as well as their upstream regulators and downstream effectors for potential cancer treatments.

Mechanisms of Resistance to KRAS Inhibitors: Cancer Cells' Strategic Use of Normal Cellular Mechanisms to Adapt

KRAS was long deemed undruggable until the discovery of the switch-II pocket facilitated the development of specific KRAS inhibitors. Despite their introduction into clinical practice, resistance mechanisms can limit their effectiveness. Initially, tumors rely on mutant KRAS, but as they progress, they may shift to alternative pathways, resulting in intrinsic resistance. This resistance can stem from mechanisms like epithelial-to-mesenchymal transition (EMT), YAP activation, or KEAP1 mutations. KRAS inhibition often triggers cellular rewiring to counteract therapeutic pressure. For instance, feedback reactivation of signaling pathways such as MAPK, mediated by receptor tyrosine kinases, supports tumor cell survival. Inhibiting KRAS disrupts protein homeostasis, but reactivation of MAPK or AKT can restore it, aiding tumor cell survival. KRAS inhibition also causes metabolic reprogramming and protein re-localization. The re-localization of E-cadherin and Scribble from the membrane to the cytosol causes YAP to translocate to the nucleus, where it drives MRAS transcription, leading to MAPK reactivation. Emerging evidence indicates that changes in cell identity, such as mucinous differentiation, shifts from alveolar type 2 to type 1 cells, or lineage switching from adenocarcinoma to squamous cell carcinoma, also contribute to resistance. In addition to these nongenetic mechanisms, secondary mutations in KRAS or alterations in upstream/downstream signaling proteins can cause acquired resistance. Secondary mutations in the switch-II pocket disrupt drug binding, and known oncogenic mutations affect drug efficacy. Overcoming these resistance mechanisms involves enhancing the efficacy of drugs targeting mutant KRAS, developing broad-spectrum inhibitors, combining therapies targeting multiple pathways, and integrating immune checkpoint inhibitors.

FGTI-2734 Inhibits ERK Reactivation to Overcome Sotorasib Resistance in KRAS G12C Lung Cancer

INTRODUCTION

KRAS G12C targeted therapies, such as sotorasib, represent a major breakthrough, but overall response rates and progression-free survival for patients with KRAS G12C lung cancer are modest due to the emergence of resistance mechanisms involving adaptive reactivation of ERK, which requires wild-type HRAS and NRAS membrane localization.

METHODS AND RESULTS

Here, we demonstrate that the dual farnesyltransferase and geranylgeranyltransferase-1 inhibitor FGTI-2734 inhibits wild-type RAS membrane localization and sotorasib-induced ERK feedback reactivation, and overcomes sotorasib adaptive resistance. The combination of FGTI-2734 and sotorasib is synergistic at inhibiting the viability and inducing apoptosis of KRAS G12C lung cancer cells, including those highly resistant to sotorasib. FGTI-2734 enhances sotorasib's anti-tumor activity in vivo leading to significant tumor regression of a patient-derived xenograft (PDX) from a patient with KRAS G12C lung cancer and several xenografts from highly sotorasib-resistant KRAS G12C human lung cancer cells. Importantly, treatment of mice with FGTI-2734 inhibited sotorasib-induced ERK reactivation in KRAS G12C PDX, and treatment of mice with the combination of FGTI-2734 and sotorasib was also significantly more effective at suppressing in vivo the levels of P-ERK in sotorasib-resistant human KRAS G12C lung cancer xenografts and the NSCLC PDX.

CONCLUSION

Our findings provide a foundation for overcoming sotorasib resistance and potentially improving the treatment outcomes of KRAS G12C lung cancer.

Cholangiocarcinoma Targeted Therapies: Mechanisms of Action and Resistance

Cholangiocarcinoma is an aggressive bile duct malignancy with heterogeneous genomic features. Although most patients receive standard-of-care chemotherapy/immunotherapy, genomic changes that can be targeted with established or emerging therapeutics are common. Accordingly, precision medicine strategies are transforming the next-line treatment for patient subsets. Hotspot IDH1 mutations and activating fibroblast growth factor receptor 2 fusions occur frequently, and small-molecule inhibitors against these alterations are US Food and Drug Administration approved. Translational and basic science studies have elucidated the mechanisms of response and resistance in cholangiocarcinoma, providing insights into these targets that extend to other cancers. Additional US Food and Drug Administration-approved and National Comprehensive Cancer Network guideline-recommended treatments for recurrent genomic changes include BRAF inhibition (BRAF-V600E) and trastumazab deruxtecan (human epidermal growth factor receptor 2 amplification). Furthermore, ongoing clinical trials show promising results with KRAS inhibition (KRAS-codon 12 mutations), PRTM5 inhibition, alone or with methylthioadenosine inhibition (5-methylthioadenosine phosphorylase deletion), and murine double minute 2 inhibition (murine double minute 2 amplification). Despite these advances, the rate, depth, and duration of response to each treatment need improvement. Moreover, many patients do not have currently targetable genotypes. This review examines the clinical efficacy and mechanisms of resistance associated with these treatments, as well as insights into the molecular and biological effects of pathway activation and inhibition, based on study of patient samples and preclinical models. It also explores strategies to overcome resistance and possible precision medicine approaches for additional patient subsets.

Intratumor heterogeneity in KRAS signaling shapes treatment resistance

KRAS mutations are linked to some of the deadliest forms of cancer. Pharmacological studies suggest that co-targeting KRAS with feedback/bypass pathways could lead to enhanced anti-tumor activity. The underlying premise is that cancers display a deep-rooted hypersensitivity to KRAS inactivation. Here, we investigate the role of intratumor heterogeneity in pancreatic ductal adenocarcinoma, focusing on oncogenic KRAS addiction and treatment resistance. Integrated analysis of single-cell and bulk RNA sequencing data reveals that most tumors display a mixture of cells with vastly different degrees of KRAS dependency. We identify distinct cell populations that vary in their gene expression patterns pertaining to the predicted level of KRAS signaling activity, cell growth, and differentiation commitment within each tumor. Selective targeting of mutant KRAS suppresses the growth of tumor cells with high RAS/mitogen-activated protein kinase (MAPK) activity while sparing pre-existing subsets with low RAS signaling activity, necessitating alternative treatments. Combination immunotherapy leads to durable tumor regression in preclinical models.

Innovative design and potential applications of covalent strategy in drug discovery

Covalent inhibitors provide persistent inhibition while maintaining excellent selectivity and efficacy by creating stable covalent connections with specific amino acids in target proteins. This technique enables the precise inhibition of previously undruggable targets, lowering the frequency of administration and potentially bypassing drug resistance. Because of these advantages, covalent inhibitors have tremendous potential in treating cancer, inflammation, and infectious illnesses, making them extremely important in modern pharmacological research. Covalent inhibitors targeting EGFR, BTK, and KRAS (G12X), which overcome drug resistance and off-target, non-"medicinal" difficulties, as well as covalent inhibitors targeting SARS-CoV-2 Mpro, have paved the way for the development of new antiviral medicines. Furthermore, the use of covalent methods in drug discovery procedures, such as covalent PROTACs, covalent molecular gels, covalent probes, CoLDR, and Dual-targeted covalent inhibitors, preserves these tactics' inherent features while incorporating the advantages of covalent inhibitors. This synthesis opens up new therapeutic opportunities. This review comprehensively examines the use of covalent techniques in drug discovery, emphasizing their transformational potential for future drug development.

Genomic landscape of clinically acquired resistance alterations in patients treated with KRASG12C inhibitors

BACKGROUND

Mutant-selective inhibitors of KRASG12C (KRASG12Ci) have demonstrated efficacy in KRASG12C cancers. However, resistance invariably develops, resulting in short-lived responses. We aimed to define the genomic landscape of acquired resistance to KRASG12Ci and to elucidate whether novel classes of KRAS inhibitors can overcome these resistance mechanisms.

METHODS

To assess clinical frequencies of acquired resistance alterations, we evaluated genomic sequencing data from postprogression cell-free DNA samples in patients treated with KRASG12Ci at two United States cancer centers, alongside data from six previously published studies. Cell viability assays using engineered cell models were employed to functionally validate candidate resistance drivers and to evaluate novel classes of KRAS inhibitors.

RESULTS

A total of 143 patients were analyzed. Most patients had non-small-cell lung cancer (NSCLC, n = 68) or colorectal cancer (CRC, n = 58) and were treated with single-agent KRASG12Ci (n = 109) or combined with anti-EGFR antibodies (n = 30). RAS/MAPK alterations emerged in 46% of patients (n = 66), with 39% developing one or more new KRAS alterations (n = 56) and 23% (n = 33) showing multiple concurrent alterations. The genomic landscape of acquired alterations included KRAS-activating mutations (25% of patients), KRAS amplifications (22%), RAF/MAPK mutations/fusions (21%), KRAS switch-II pocket mutations (14%), and NRAS/HRAS mutations (8%). Notably, the proportion of patients with one or more acquired RAS/MAPK alteration was significantly higher in CRC compared with NSCLC (69% versus 26%, P < 0.001). Functional studies confirmed most alterations as resistance drivers. Sotorasib, adagrasib, and divarasib demonstrated distinct activity against KRAS switch-II pocket mutations, yet all were responsive to the RAS(ON) G12C-selective tri-complex inhibitor RM-018. The KRAS-selective inhibitor Pan KRAS-IN-1 effectively targeted KRAS-activating mutations, and the RAS(ON) multiselective tri-complex inhibitor RMC-7797 demonstrated high potency across all RAS alterations.

CONCLUSIONS

Acquired RAS/MAPK alterations are recurrent drivers of resistance to KRASG12Ci detected in CRC and, less frequently, in NSCLC. Preclinical data suggest that novel (K)RAS inhibitors may overcome many of these resistance alterations.

KRAS inhibitors in drug resistance and potential for combination therapy

Kirsten Rat Sarcoma (KRAS) is a potent target for cancer therapy because it acts as a signaling hub, engaging in various signaling pathways and regulating a number of cellular functions like cell differentiation, proliferation, and survival. Recently, an emergency approval from the US-FDA has been issued for KRASG12C inhibitors (sotorasib and adagrasib) for metastatic lung cancer treatment. However, clinical studies on covalent KRASG12C inhibitors have rapidly confronted resistance in patients. Many methods are being assessed to overcome this resistance, along with various combinatorial clinical studies that are in process. Moreover, because KRASG12D and KRASG12V are more common than KRASG12C, focus must be placed on the therapeutic strategies for this type of patient, along with sustained efforts in research on these targets. In the present review, we try to focus on various strategies to overcome rapid resistance through the use of combinational treatments to improve the activity of KRASG12C inhibitors.

KRAS inhibitors: resistance drivers and combinatorial strategies

In 1982, the RAS genes HRAS and KRAS were discovered as the first human cancer genes, with KRAS later identified as one of the most frequently mutated oncogenes. Yet, it took nearly 40 years to develop clinically effective inhibitors for RAS-mutant cancers. The discovery in 2013 by Shokat and colleagues of a druggable pocket in KRAS paved the way to FDA approval of the first covalently binding KRASG12C inhibitors, sotorasib and adagrasib, in 2021 and 2022, respectively. However, rather than marking the end of a successful assault on the Mount Everest of cancer research, this landmark only revealed new challenges in RAS drug discovery. In this review, we highlight the progress on defining resistance mechanisms and developing combination treatment strategies to improve patient responses to KRAS therapies.

KRASG 12C-inhibitor-based combination therapies for pancreatic cancer: insights from drug screening

Pancreatic ductal adenocarcinoma (PDAC) has limited treatment options, emphasizing the urgent need for effective therapies. The predominant driver in PDAC is mutated KRAS proto-oncogene, KRA, present in 90% of patients. The emergence of direct KRAS inhibitors presents a promising avenue for treatment, particularly those targeting the KRASG12C mutated allele, which show encouraging results in clinical trials. However, the development of resistance necessitates exploring potent combination therapies. Our objective was to identify effective KRASG12C-inhibitor combination therapies through unbiased drug screening. Results revealed synergistic effects with son of sevenless homolog 1 (SOS1) inhibitors, tyrosine-protein phosphatase non-receptor type 11 (PTPN11)/Src homology region 2 domain-containing phosphatase-2 (SHP2) inhibitors, and broad-spectrum multi-kinase inhibitors. Validation in a novel and unique KRASG12C-mutated patient-derived organoid model confirmed the described hits from the screening experiment. Our findings propose strategies to enhance KRASG12C-inhibitor efficacy, guiding clinical trial design and molecular tumor boards.

AGER-dependent macropinocytosis drives resistance to KRAS-G12D-targeted therapy in advanced pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) driven by the KRAS-G12D mutation presents a formidable health challenge because of limited treatment options. MRTX1133 is a highly selective and first-in-class KRAS-G12D inhibitor under clinical development. Here, we report that the advanced glycosylation end product-specific receptor (AGER) plays a key role in mediating MRTX1133 resistance in PDAC cells. The up-regulation of AGER within cancer cells instigates macropinocytosis, facilitating the internalization of serum albumin and subsequent amino acid generation. These amino acids are then used to synthesize the antioxidant glutathione, leading to resistance to MRTX1133 treatment due to the inhibition of apoptosis. The underlying molecular mechanism involves AGER's interaction with diaphanous-related formin 1 (DIAPH1), a formin protein responsible for driving Rac family small GTPase 1 (RAC1)-dependent macropinosome formation. The effectiveness and safety of combining MRTX1133 with pharmacological inhibitors of the AGER-DIAPH1 complex (using RAGE299) or macropinocytosis (using EIPA) were confirmed in patient-derived xenografts, orthotopic models, and genetically engineered mouse PDAC models. This combination therapy also induces high-mobility group box 1 (HMGB1) release, resulting in a subsequent antitumor CD8+ T cell response in immunocompetent mice. Collectively, the study findings underscore the potential to enhance the efficacy of KRAS-G12D blockade therapy by targeting AGER-dependent macropinocytosis.

KRAS Loss of Heterozygosity Promotes MAPK-Dependent Pancreatic Ductal Adenocarcinoma Initiation and Induces Therapeutic Sensitivity to MEK Inhibition

Pancreatic cancer is characterized by the prevalence of oncogenic mutations in KRAS. Previous studies have reported that altered KRAS gene dosage drives progression and metastasis in pancreatic cancer. Whereas the role of oncogenic KRAS mutations is well characterized, the relevance of the partnering wild-type (WT) KRAS allele in pancreatic cancer is less well understood and controversial. Using in vivo mouse modeling of pancreatic cancer, we demonstrated that WT KRAS restrains the oncogenic impact of mutant KRAS and dramatically impacts both KRAS-mediated tumorigenesis and therapeutic response. Mechanistically, deletion of WT Kras increased oncogenic KRAS signaling through the downstream MAPK effector pathway, driving pancreatic intraepithelial neoplasia initiation. In addition, in the KPC mouse model, a more aggressive model of pancreatic cancer, lack of WT KRAS led to accelerated initiation but delayed tumor progression. These tumors had altered stroma and an enrichment of immunogenic gene signatures. Importantly, loss of WT Kras sensitized Kras mutant tumors to MEK1/2 inhibition though tumors eventually became resistant and then rapidly progressed. This study demonstrates the repressive role of WT KRAS during pancreatic tumorigenesis and highlights the critical impact of the presence of WT KRAS in both tumor progression and therapeutic response in pancreatic cancer. Significance: KRAS allelic status impacts pancreatic cancer progression and has the potential to guide effective treatment in a substantial subset of patients.

Novel potent SOS1 inhibitors containing a tricyclic quinazoline scaffold: A joint view of experiments and simulations

Small molecules that possess the ability to regulate the interactions between Son of Sevenless 1 (SOS1) and Kristen rat sarcoma (KRAS) offer immense potential in the realm of cancer therapy. In this study, we present a novel series of SOS1 inhibitors featuring a tricyclic quinazoline scaffold. Notably, we have identified compound 8d, which demonstrates the highest potency with an IC50 value of 5.1 nM for disrupting the KRAS:SOS1 interaction. Compound 8d exhibits a promising pharmacokinetic profile and achieves a remarkable 70.5 % inhibition of tumor growth in pancreas tumor xenograft models. Furthermore, molecular dynamic simulations have unveiled that the tricyclic quinazoline derivatives exhibit extensive interaction with Tyr884, a crucial residue for the recognition between SOS1 and KRAS. Our findings provide fresh insights into the design of future SOS1 inhibitors, paving the way for innovative therapeutic strategies.

Targeting KRAS: from metabolic regulation to cancer treatment

The Kirsten rat sarcoma viral oncogene homolog (KRAS) protein plays a key pathogenic role in oncogenesis, cancer progression, and metastasis. Numerous studies have explored the role of metabolic alterations in KRAS-driven cancers, providing a scientific rationale for targeting metabolism in cancer treatment. The development of KRAS-specific inhibitors has also garnered considerable attention, partly due to the challenge of acquired treatment resistance. Here, we review the metabolic reprogramming of glucose, glutamine, and lipids regulated by oncogenic KRAS, with an emphasis on recent insights into the relationship between changes in metabolic mechanisms driven by KRAS mutant and related advances in targeted therapy. We also focus on advances in KRAS inhibitor discovery and related treatment strategies in colorectal, pancreatic, and non-small cell lung cancer, including current clinical trials. Therefore, this review provides an overview of the current understanding of metabolic mechanisms associated with KRAS mutation and related therapeutic strategies, aiming to facilitate the understanding of current challenges in KRAS-driven cancer and to support the investigation of therapeutic strategies.

HSF1 at the crossroads of chemoresistance: from current insights to future horizons in cell death mechanisms

Heat Shock Factor 1 (HSF1) is a major transcriptional factor regulating the heat shock response and has become a potential target for overcoming cancer chemoresistance. This review comprehensively examines HSF1's role in chemoresistance and its potential as a therapeutic target in cancer. We explore the complex, intricate mechanism that regulates the activation of HSF1, HSF1's function in promoting resistance to chemotherapy, and the strategies used to manipulate HSF1 for therapeutic benefit. In addition, we discuss emerging research implicating HSF1's roles in autophagy, apoptosis, DNA damage repair, drug efflux, and thus chemoresistance. This article highlights the significance of HSF1 in cancer chemoresistance and its potential as a target for enhancing cancer treatment efficacy.

Genetics and biology of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) poses a grim prognosis for patients. Recent multidisciplinary research efforts have provided critical insights into its genetics and tumor biology, creating the foundation for rational development of targeted and immune therapies. Here, we review the PDAC genomic landscape and the role of specific oncogenic events in tumor initiation and progression, as well as their contributions to shaping its tumor biology. We further summarize and synthesize breakthroughs in single-cell and metabolic profiling technologies that have illuminated the complex cellular composition and heterotypic interactions of the PDAC tumor microenvironment, with an emphasis on metabolic cross-talk across cancer and stromal cells that sustains anabolic growth and suppresses tumor immunity. These conceptual advances have generated novel immunotherapy regimens, particularly cancer vaccines, which are now in clinical testing. We also highlight the advent of KRAS targeted therapy, a milestone advance that has transformed treatment paradigms and offers a platform for combined immunotherapy and targeted strategies. This review provides a perspective summarizing current scientific and therapeutic challenges as well as practice-changing opportunities for the PDAC field at this major inflection point.

"Undruggable KRAS": druggable after all

The three RAS genes (HRAS, KRAS, and NRAS) comprise the most frequently mutated oncogene family in cancer. KRAS is the predominant isoform mutated in cancer and is most prevalently mutated in major causes of cancer deaths including lung, colorectal, and pancreatic cancers. Despite extensive academic and industry efforts to target KRAS, it would take nearly four decades before approval of the first clinically effective KRAS inhibitors for the treatment of KRAS mutant lung cancer. We revisit past anti-KRAS strategies and painful lessons learned and then focus on the rapidly evolving landscape of direct RAS inhibitors, resistance mechanisms, and potential combination treatments.

SOS1 Inhibition Enhances the Efficacy of KRASG12C Inhibitors and Delays Resistance in Lung Adenocarcinoma

The clinical effectiveness of KRASG12C inhibitors (G12Ci) is limited both by intrinsic and acquired resistance, necessitating the development of combination approaches. Here, we identified targeting proximal receptor tyrosine kinase signaling using the SOS1 inhibitor (SOS1i) BI-3406 as a strategy to improve responses to G12Ci treatment. SOS1i enhanced the efficacy of G12Ci and limited rebound receptor tyrosine kinase/ERK signaling to overcome intrinsic/adaptive resistance, but this effect was modulated by SOS2 protein levels. G12Ci drug-tolerant persister (DTP) cells showed up to a 3-fold enrichment of tumor-initiating cells (TIC), suggestive of a sanctuary population of G12Ci-resistant cells. SOS1i resensitized DTPs to G12Ci and inhibited G12C-induced TIC enrichment. Co-mutation of the tumor suppressor KEAP1 limited the clinical effectiveness of G12Ci, and KEAP1 and STK11 deletion increased TIC frequency and accelerated the development of acquired resistance to G12Ci, consistent with clinical G12Ci resistance seen with these co-mutations. Treatment with SOS1i both delayed acquired G12Ci resistance and limited the total number of resistant colonies regardless of KEAP1 and STK11 mutational status. Together, these data suggest that targeting SOS1 could be an effective strategy to both enhance G12Ci efficacy and prevent G12Ci resistance regardless of co-mutations. Significance: The SOS1 inhibitor BI-3406 both inhibits intrinsic/adaptive resistance and targets drug tolerant persister cells to limit the development of acquired resistance to clinical KRASG12C inhibitors in lung adenocarcinoma cells.

Advances and Challenges in RAS Signaling Targeted Therapy in Leukemia

RAS mutations are prevalent in leukemia, including mutations at G12, G13, T58, Q61, K117, and A146. These mutations are often crucial for tumor initiation, maintenance, and recurrence. Although much is known about RAS function in the last 40 years, a substantial knowledge gap remains in understanding the mutation-specific biological activities of RAS in cancer and the approaches needed to target specific RAS mutants effectively. The recent approval of KRASG12C inhibitors, adagrasib and sotorasib, has validated KRAS as a direct therapeutic target and demonstrated the feasibility of selectively targeting specific RAS mutants. Nevertheless, KRASG12C remains the only RAS mutant successfully targeted with FDA-approved inhibitors for cancer treatment in patients, limiting its applicability for other oncogenic RAS mutants, such as G12D, in leukemia. Despite these challenges, new approaches have generated optimism about targeting specific RAS mutations in an allele-dependent manner for cancer therapy, supported by compelling biochemical and structural evidence, which inspires further exploration of RAS allele-specific vulnerabilities. This review will discuss the recent advances and challenges in the development of therapies targeting RAS signaling, highlight emerging therapeutic strategies, and emphasize the importance of allele-specific approaches for leukemia treatment.

A New Dawn for Targeted Cancer Therapy: Small Molecule Covalent Binding Inhibitor Targeting K-Ras (G12C)

K-Ras is a frequently mutated oncogene in human malignancies, and the development of inhibitors targeting various oncogenic K-Ras mutant proteins is a major challenge in targeted cancer therapy, especially K-Ras(G12C) is the most common mutant, which occurs in pancreatic ductal adenocarcinoma (PDAC), non-small cell lung cancer (NSCLC), colorectal cancer (CRC) and other highly prevalent malignancies. In recent years, significant progress has been made in developing small molecule covalent inhibitors targeting K-Ras(G12C), thanks to the production of nucleophilic cysteine by the G12C mutant, breaking the "spell" that K-Ras protein cannot be used as a drug target. With the successful launch of sotorasib and adagrasib, the development of small molecule inhibitors targeting various K-Ras mutants has continued to gain momentum. In recent years, with the popularization of highly sensitive surface plasmon resonance (SPR) technology, fragment-based drug design strategies have shown great potential in the development of small molecule inhibitors targeting K-Ras(G12C), but with the increasing number of clinically reported acquired drug resistance, addressing inhibitor resistance has gradually become the focus of this field, indirectly indicating that such small molecule inhibitors still the potential for the development of these small molecule inhibitors are also indirectly indicated. This paper traces the development of small molecule covalent inhibitors targeting K-Ras(G12C), highlighting and analyzing the structural evolution and optimization process of each series of inhibitors and the previous inhibitor design methods and strategies, as well as their common problems and general solutions, in order to provide inspiration and help to the subsequent researchers.

Breakthrough in RAS targeting with pan-RAS(ON) inhibitors RMC-7977 and RMC-6236

The multi-selective tri-complex RAS(ON) inhibitors RMC-7977 and RMC-6236 signal new avenues for RAS targeting. This systematic review aims to comprehensively present the available preclinical and early clinical data on these agents. We screened Medline, Scopus, the ESMO and ASCO conference sites and ClinicalTrials.gov for related studies and found four published preclinical studies and one clinical trial. In these reports, RMC-7977 and RMC-6236 effectively drove tumor suppression, especially in non-small cell lung cancer and pancreatic ductal adenocarcinoma, and minimal effects in healthy tissue were observed. MYC amplification was reported to be a main contributor to the development of resistance. Six trials are currently ongoing, including one randomized trial, and promising results are expected from combination with other agents, such as immune-checkpoint blockers.

WEE1 confers resistance to KRASG12C inhibitors in non-small cell lung cancer

KRASG12C inhibitors sotorasib and adagrasib have been approved for the treatment of KRASG12C-mutant non-small cell lung cancer (NSCLC). However, the efficacy of single-agent treatments is limited, presumably due to multiple resistance mechanisms. To overcome these therapeutic limitations, combination strategies that potentiate the antitumor efficacy of KRASG12C inhibitors must be developed. Through unbiased high-throughput screening of 1395 kinase inhibitors, we identified adavosertib, a WEE1 inhibitor, as a promising combination partner of sotorasib. The combination of sotorasib and adavosertib exhibited synergistic antiproliferative activities both in vitro and in vivo, irrespective of TP53, STK11, and KEAP1 co-mutation profiles. WEE1 inhibition potentiated MCL-1-mediated apoptosis in sotorasib-treated cancer cells. Mechanistically, the combination downregulated MCL-1 protein levels by attenuating de novo translation and enhancing its degradation. WEE1 overexpression conferred resistance against sotorasib via MCL-1 upregulation. Moreover, cells that acquired sotorasib resistance profoundly upregulated both WEE1 and MCL-1 proteins, highlighting WEE1 as a crucial driver of sotorasib resistance. Importantly, WEE1 inhibition re-sensitized resistant cells to sotorasib treatment. The current findings demonstrate that combined inhibition of KRASG12C and WEE1 not only exhibits synergistic antitumor efficacy but also overcomes resistance to KRASG12C inhibitors, thus representing a novel therapeutic strategy for KRASG12C-mutant NSCLC.

Sequence-defined phosphoestamers for selective inhibition of the KRASG12D/RAF1 interaction

RAS proteins are the most frequently mutated in cancer, yet they have proved extremely difficult to target in drug discovery, largely because interfering with the interaction of RAS with its downstream effectors comes up against the challenge of protein-protein interactions (PPIs). Sequence-defined synthetic oligomers could combine the precision and customisability of synthetic molecules with the size required to address entire PPI surfaces. We have adapted the phosphoramidite chemistry of oligonucleotide synthesis to produce a library of nearly one million non-nucleosidic oligophosphoester sequences (phosphoestamers) composed of units taken from synthetic supramolecular chemistry, and used a fluorescent-activated bead sorting (FABS) process to select those that inhibit the interaction between KRASG12D (the most prevalent, and undrugged, RAS mutant) and RAF, a downstream effector of RAS that drives cell proliferation. Hits were identified using tandem mass spectrometry, and orthogonal validation showed effective inhibition of KRASG12D with IC50 values as low as 25 nM, and excellent selectivity over the wild type form. These findings have the potential to lead to new drugs that target mutant RAS-driven cancers, and provide proof-of-principle for the phosphoestamer chemical platform against PPIs in general - opening up new possibilities in neurodegenerative disease, viral infection, and many more conditions.

Adagrasib in KRYSTAL-12 has Not Broken the KRAS G12C Enigma Code of the Unspoken 6-Month PFS Barrier in NSCLC

Mutations in KRAS G12C are among the more common oncogenic driver mutations in non-small cell lung cancer (NSCLC). In December 2022, the US Food and Drug Administration (FDA) granted accelerated approval to adagrasib, a small molecule covalent inhibitor of KRAS G12C, for the treatment of patients with locally advanced or metastatic KRAS G12C mutant NSCLC who received at least one prior systemic therapy based on promising results from phase 1 and 2 trials wherein adagrasib demonstrated a median PFS of 6.5 months. Results from the phase 3 KRYSTAL-12 trial were recently presented, showing benefit with adagrasib compared to docetaxel, with participants in the adagrasib group demonstrating a PFS of 5.5 months compared to 3.8 months in the docetaxel group. However, these results fall short of the 6-month PFS benchmark that had seemed achievable from what had been seen in phase 1 and 2 trials, mirroring similarly disappointing results from the CodeBreaK 200 trial wherein sotorasib, the first-in-class KRAS G12C inhibitor, also failed to meet the 6-month benchmark also thought to be possible when examining earlier trials. These results raise the question of adagrasib's true value in the second-line treatment setting and compel us to explore more potent novel therapies, combination therapies, and more as we seek to break the 6-month PFS barrier in the treatment of KRAS G12C mutant NSCLC.

SRC kinase drives multidrug resistance induced by KRAS-G12C inhibition

Direct targeting of the KRAS-G12C-mutant protein using covalent inhibitors (G12Ci) acts on human non-small cell lung cancer (NSCLC). However, drug resistance is an emerging concern in this approach. Here, we show that MRTX849, a covalent inhibitor targeting the KRAS-G12C mutation, leads to the reactivation of the mitogen-activated protein kinase signaling pathway in MRTX849-resistant NSCLC and pancreatic ductal adenocarcinoma. A genome-wide CRISPR screen revealed that the adenosine triphosphate binding cassette transporter ABCC1 mediates MRTX849 resistance. Functional studies demonstrated that the transcription factor JUN drives ABCC1 expression, resulting in multidrug resistance. An unbiased drug screen identified the tyrosine kinase inhibitor dasatinib that potentiates MRTX849 efficacy by inhibiting SRC-dependent JUN activation, avoiding multidrug resistance and tumor suppression in vitro as well as in suitable preclinical mouse models and patient-derived organoids. SRC inhibitors (DGY-06-116, dasatinib, and bosutinib) also exhibit synergistic effects with MRTX849 in eliminating various tumor cell lines carrying KRAS-G12C mutations. Thus, SRC inhibitors amplify the therapeutic utility of G12Ci.

Opposing lineage specifiers induce a pro-tumor hybrid-identity state in lung adenocarcinoma

The ability of cancer cells to alter their identity, known as lineage plasticity, is crucial for tumor progression and therapy resistance. In lung adenocarcinoma (LUAD), tumor progression is characterized by a gradual loss of lineage fidelity and the emergence of non-pulmonary identity programs. This can lead to hybrid-identity (hybrid-ID) states in which developmentally incompatible identity programs are co-activated within individual cells. However, the molecular mechanisms underlying these identity shifts remain incompletely understood. Here, we identify the gastrointestinal (GI) transcriptional regulator HNF4α as a critical driver of tumor growth and proliferation in KRAS-driven LUAD. In LUAD cells that express the lung lineage specifier NKX2-1, HNF4α can induce a GI/liver-like state by directly binding and activating its canonical targets. HNF4α also forms an aberrant protein complex with NKX2-1, which disrupts NKX2-1 localization and dampens pulmonary identity within hybrid-ID LUAD. Sustained signaling through the RAS/MEK pathway is critical for maintaining the hybrid-ID state. Moreover, RAS/MEK inhibition augments NKX2-1 chromatin binding at pulmonary-specific genes and induces resistance-associated pulmonary signatures. Finally, we demonstrate that HNF4α depletion enhances sensitivity to pharmacologic KRAS G12D inhibition. Collectively, our data show that co-expression of opposing lineage specifiers leads to a hybrid identity state that can drive tumor progression and dictate response to targeted therapy in LUAD.

Reactivation of MAPK-SOX2 pathway confers ferroptosis sensitivity in KRASG12C inhibitor resistant tumors

The clinical success of KRASG12C inhibitors (G12Ci) including AMG510 and MRTX849 is limited by the eventual development of acquired resistance. A novel and effective treatment to revert or target this resistance is urgent. To this end, we established G12Ci (AMG510 and MRTX849) resistant KRASG12C mutant cancer cell lines and screened with an FDA-approved drug library. We found the ferroptosis inducers including sorafenib and lapatinib stood out with an obvious growth inhibition in the G12Ci resistant cells. Mechanistically, the G12Ci resistant cells exhibited reactivation of MAPK signaling, which repressed SOX2-mediated expression of cystine transporter SLC7A11 and iron exporter SLC40A1. Consequently, the low intracellular GSH level but high iron content engendered hypersensitivity of these resistant tumors to ferroptosis inducers. Ectopic overexpression of SOX2 or SLC7A11 and SLC40A1 conferred resistance to ferroptosis in the G12Ci resistant cells. Ferroptosis induced by sulfasalazine (SAS) achieved obvious inhibition on the tumor growth of xenografts derived from AMG510-resistant KRASG12C-mutant cells. Collectively, our results suggest a novel therapeutic strategy to treat patients bearing G12Ci resistant cancers with ferroptosis inducers.

High throughput application of the NanoBiT Biochemical Assay for the discovery of selective inhibitors of the interaction of PI3K-p110α with KRAS

The NanoBiT Biochemical Assay (NBBA) was designed as a biochemical format of the NanoBiT cellular assay, aiming to screen weak protein-protein interactions (PPIs) in mammalian cell lysates. Here we present a High Throughput Screening (HTS) application of the NBBA to screen small molecule and fragment libraries to identify compounds that block the interaction of KRAS-G12D with phosphatidylinositol 3-kinase (PI3K) p110α. This interaction promotes PI3K activity, resulting in the promotion of cell growth, proliferation and survival, and is required for tumour initiation and growth in mouse lung cancer models, whilst having little effect on the health of normal adult mice, establishing the significance of the p110α/KRAS interaction as an oncology drug target. Despite the weak binding affinity of the p110α/KRAS interaction (KD = 3 μM), the NBBA proved to be robust and displayed excellent Z'-factor statistics during the HTS primary screening of 726,000 compounds, which led to the identification of 8,000 active compounds. A concentration response screen comparing KRAS/p110α with two closely related PI3K isoforms, p110δ and p110γ, identified selective p110α-specific compounds and enabled derivation of an IC50 for these hits. We identified around 30 compounds showing greater than 20-fold selectivity towards p110α versus p110δ and p110γ with IC50 < 2 μM. By using Differential Scanning Fluorimetry (DSF) we confirmed several compounds that bind directly to purified p110α. The most potent hits will be followed up by co-crystallization with p110α to aid further elucidation of the nature of the interaction and extended optimisation of these compounds.

Steroidal saponins: Natural compounds with the potential to reverse tumor drug resistance (Review)

Steroidal saponins are a type of natural product that have been widely used in Chinese herbal medicine, with a variety of pharmacological activities, such as antitumor, anti-inflammatory and anti-bacterial effects. Cancer has become a growing global health problem, and drug therapy is currently the most important clinical antitumor treatment. However, drug resistance is a major obstacle to the effectiveness of chemotherapy, resulting in >90% of deaths of patients with cancer receiving conventional chemotherapy. It has been found that steroidal saponins may exert an effect on the reversal of drug resistance in tumor cells by regulating apoptosis, autophagy, epithelial-mesenchymal transition and drug efflux through multiple related signaling pathways. The present study reviews the role and mechanism of steroidal saponins in the treatment of tumor drug resistance, aiming to provide a scientific basis and research ideas for the future development and clinical application of natural steroidal saponins.

Dual inhibition of HERs and PD-1 counteract resistance in KRASG12C-mutant head and neck cancer

BACKGROUND

Basket clinical trials targeting the KRASG12C-mutation in solid tumors have shown initial promise, including in orphan KRASG12C head and neck cancer (HNC). However, development of resistance to KRASG12C-mutant-specific inhibitors (KRASG12Ci) remains a major obstacle. Here, we investigated the intrinsic (tumor-cell autonomus) and tumor-microenvironment (TME) mechanisms of resistance to the KRASG12Ci-MRTX849 and AMG510 in a unique syngenic murine KRASG12C-mutated HNC cell line.

METHODS

Western-blotting was used for protein abundance and activation, overexpression, and ligand activation studies to verify the intrinsic mechanism of resistance to KRASG12Ci in KRASG12C-mutated HNC cell line, 4NQO-L. In vitro KRASG12C-acquired-resistant cells were developed from 4NQO-L (4NQO-L-AcR). MRTX849/lapatinib combination efficacy, and CD8+ T-cells depletion, were assessed in C57BL/6 J mice and supplementation of anti-PD-1 (αPD-1) to MRTX849/lapatinib was also performed in 4NQO-L- KRASG12Ci-senisitve and 4NQO-L-AcR tumors. Immunohistochemistry (IHC) and Immunoflourescence (IF) analyses were performed to profile the TME and programmed death-ligand 1 (PD-L1) expression in tumors.

RESULTS

Activation and upregulation of EGFR and HER2/3 (pan-HERs) are the intrinsic mechanism of resistance to KRASG12Ci in 4NQO-L cells, and blocking pan-HERs signaling with lapatinib enhanced MRTX849 efficacy in vitro by inhibiting the MAPK and AKT/mTOR pathways. 4NQO-L-AcR upregulated the expression of pan-HERs, and lapatinib treatment re-sensitized 4NQO-L-AcR to MRTX849. In mice, MRTX849 showed a slight anti-tumor effect, but in combination with lapatinib a significant tumor growth delay was observed, but all tumors progressed over time. Histopathology analysis of the TME revealed infiltration of CD8+ T-cells after treatment combination, and these CD8+ T-cells play a key role in MRTX849/lapatinib efficacy. MRTX849/lapatinib treatment upregulated PD-L1 overexpression in both stromal and tumor cells, which presumably suppressed CD8+ T-cells and enabled immune escape and tumor progression. Supplementation of αPD-1 prolonged the progression-free survival of 4NQO-L-bearing mice treated with MRTX849/lapatinib. MRTX849/lapatinib treatment delayed tumor growth of 4NQO-L-AcR in mice; however, the percentages of CD8+ T-cells in 4NQO-L-AcR were low, and supplementation of MRTX849/lapatinib with αPD-1 did not improve the outcome.

CONCLUSIONS

Our study highlights the critical need for blocking both intrinsic and extrinsic mechanisms of resistance for the prolonged response and shows that such treatment is ineffective in KRASG12Ci-AcR tumors.

The Potential Treatment Options and Combination Strategies of KRAS-Mutated Lung Cancer

In non-small cell lung cancer (NSCLC), Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations are found in up to 30% of all cases, with the most prevalent mutations occurring in codons 12 and 13. The development of KRAS-targeted drugs like sotorasib and adagrasib has generated significant excitement in the clinical arena, offering new therapeutic options. Their potential for combination with other treatments broadens the scope for clinical exploration. Acquired resistance to KRAS exon 2 p.G12C inhibitors is a significant challenge, with several reported mechanisms. In this scenario, combination therapy strategies that include targeting Src Homology Region 2 Domain-Containing Phosphatase-2 (SHP2), Son of Sevenless Homolog 1 (SOS1), or downstream effectors of KRAS exon 2 p.G12C are showing promise in overcoming such resistance. However, the efficacy of immune checkpoint inhibitors in this context still requires comprehensive evaluation. The response to anti-Programmed Cell Death Protein 1/Programmed Cell Death Protein 1 Ligand (anti-PD-1/PD-L1) drugs in NSCLC may be significantly influenced by co-occurring mutations, underscoring the need for a personalized approach to treatment based on the specific genetic profile of each tumor.

Stromal Reprogramming Optimizes KRAS-Specific Chemotherapy Inducing Antitumor Immunity in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is a clinically challenging cancer and is often characterized with rich stroma and mutated KRAS, which determines the tumor microenvironment (TME) and therapy response. Turning immunologically "cold" PDAC into "hot" is an unmet need to improve the therapeutic outcome. Herein, we propose a programmable strategy by sequential delivery of pirfenidone (PFD) and nanoengineered KRAS specific inhibitor (AMG510) and gemcitabine (GEM) liposomes. PFD could achieve precise reduction of the extracellular matrix (ECM) by reprogramming pancreatic stellate cells (PSCs). Subsequently, targeting the KRAS-directed oncogenic signaling pathway effectively inhibited tumor proliferation and migration, which sensitized a chemotherapeutic drug and promoted immunogenic cell death (ICD). In preclinical mouse models of PDAC, PFD mediated stromal modulation enhanced the deep penetration of nanoparticles and improved their subsequent performance in tumor growth inhibition. The molecular mechanisms elucidated that the stroma intervention and KRAS signal pathway regulation reshaped the immunosuppression of PDAC and optimized cytotoxic T-cell-mediated antitumor immunity with sustained antitumor memory. Overall, our study provides a practical strategy with clinical translational promise for immunologically cold tumor PDAC treatment.

A Classical Epithelial State Drives Acute Resistance to KRAS Inhibition in Pancreatic Cancer

Intratumoral heterogeneity in pancreatic ductal adenocarcinoma (PDAC) is characterized by a balance between basal and classical epithelial cancer cell states, with basal dominance associating with chemoresistance and a dismal prognosis. Targeting oncogenic KRAS, the primary driver of pancreatic cancer, shows early promise in clinical trials, but efficacy is limited by acquired resistance. Using genetically engineered mouse models and patient-derived xenografts, we find that basal PDAC cells are highly sensitive to KRAS inhibitors. Employing fluorescent and bioluminescent reporter systems, we longitudinally track cell-state dynamics in vivo and reveal a rapid, KRAS inhibitor-induced enrichment of the classical state. Lineage tracing uncovers that these enriched classical PDAC cells are a reservoir for disease relapse. Genetic or chemotherapy-mediated ablation of the classical cell state is synergistic with KRAS inhibition, providing a preclinical proof of concept for this therapeutic strategy. Our findings motivate combining classical state-directed therapies with KRAS inhibitors to deepen responses and counteract resistance in pancreatic cancer. Significance: KRAS inhibitors hold promise in pancreatic cancer, but responses are limited by acquired resistance. We find that a classical epithelial cancer cell state is acutely resistant to KRAS inhibition and serves as a reservoir for disease relapse. Targeting the classical state alongside KRAS inhibition deepens responses, revealing a potent therapeutic strategy. See related commentary by Marasco and Misale, p. 2018.