Vertical Pathway Inhibition Overcomes Adaptive Feedback Resistance to KRASG12C Inhibition

BRAF inhibition in BRAFV600 mutant cancers causes RTK-mediated reactivation of MAPK signaling through wild type RAS and RAF, particularly in colorectal cancer.

“BRAF inhibition in BRAFV600 mutant cancers leads to loss of negative feedback signals regulated by the MAPK pathway, leading to receptor tyrosine kinase (RTK)-mediated reactivation of MAPK signaling through wild type RAS and RAF, particularly in specific tumor types, such as colorectal cancer (9–12).”

• cites [9] Paraiso, 2010, Recovery of phospho-ERK activity allows melanoma cells to escape from BRAF inhibitor therapy, Br J Cancer sourcePartly supported

  The Abstract Results report rapid recovery of phospho-ERK signaling after BRAF inhibition in melanoma cells. The Discussion suggests that pathway blockade may relieve feedback inhibition and cites prior work on signaling shifting from BRAF to CRAF. It does not establish RTK-mediated reactivation through wild-type RAS and RAF or a particular effect in colorectal cancer; those mechanisms and the broader tumor-type claim go beyond this paper. (LLM, conf=0.88)

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• cites [10] Montero-Conde, 2013, Relief of feedback inhibition of HER3 transcription by RAF and MEK inhibitors attenuates their antitumor effects in BRAF-mutant thyroid carcinomas, Cancer Discov sourceSupported
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• cites [11] Corcoran, 2012, EGFR-mediated re-activation of MAPK signaling contributes to insensitivity of BRAF mutant colorectal cancers to RAF inhibition with vemurafenib, Cancer Discov sourcePartly supported

  The Results and Discussion (page unavailable) support EGFR-mediated reactivation of RAS, CRAF and MAPK signaling after vemurafenib treatment in BRAF-mutant colorectal cancer. The citing sentence also presents loss of MAPK-regulated negative feedback as the cause; the Discussion offers that mechanism as a possibility and says further study is needed to establish it. The paper does not explicitly establish that the RAS and RAF involved are wild type. (LLM, conf=0.87)

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• cites [12] Prahallad, 2012, Unresponsiveness of colon cancer to BRAF(V600E) inhibition through feedback activation of EGFR, Nature sourcePartly supported

  The ‘feedback activation of EGFR’ section reports that BRAF inhibition activates EGFR in BRAF-mutant colorectal cancer cells, and that adding an EGFR inhibitor produces more complete MEK and ERK inhibition. It describes feedback involving MEK, ERK and CDC25C, but does not establish that MAPK signaling is reactivated through wild-type RAS and RAF. (LLM, conf=0.86)

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KRASG12C inhibitors are selective for KRASG12C versus wild type KRAS or other RAS isoforms.

“These inhibitors undergo an irreversible reaction with the mutant cysteine present only in G12C mutant KRAS, making them highly selective for KRASG12C versus wild type KRAS or other RAS isoforms.”

• cites [3] Patricelli, 2016, Selective inhibition of oncogenic KRAS output with small molecules targeting the inactive state, Cancer Discov sourceNot checked — no full text of the source
• cites [4] Janes, 2018, Targeting KRAS mutant cancers with a covalent G12C-specific inhibitor, Cell sourceSupported
• cites [5] Fell, 2018, Discovery of tetrahydropyridopyrimidines as irreversible covalent inhibitors of KRAS-G12C with in vivo activity, ACS Med Chem Lett sourcePartly supported

  The passage labeled Abstract (page unavailable) reports that compound 13 was inactive in two wild-type KRAS cell lines and one KRAS-G12D cell line, supporting selectivity for KRAS-G12C over those comparators. It does not report testing against other RAS isoforms, so that part of the claim is not established by this paper. (LLM, conf=0.85)

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MEK inhibitor treatment in KRAS mutant cancers leads to adaptive feedback activation of RAS signaling, often through EGFR/HER family members or FGFR, limiting efficacy.

“in KRAS mutant cancers, MEK inhibitor treatment leads to adaptive feedback activation of RAS signaling, often through EGFR or other human epidermal growth factor receptor (HER) family members or FGFR, limiting efficacy (13,14).”

• cites [13] Manchado, 2016, A combinatorial strategy for treating KRAS-mutant lung cancer, Nature sourcePartly supported

  The “FGFR1 mediates adaptive drug resistance” section reports that trametinib increased FGFR1 signaling and RAS-GTP in KRAS-mutant lung cancer cells, supporting feedback activation that limits treatment efficacy. But the “FGFR1 inhibition enhances trametinib effects” section reports no increase in EGFR in the tested cells and only limited combinatorial activity for an EGFR/ERBB2 inhibitor. The paper therefore does not support the claim that EGFR or other HER family members are often the route of this response across KRAS-mutant cancers. Page numbers are not provided in our copy. (LLM, conf=0.86)

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• cites [14] Kitai, 2016, Epithelial-to-mesenchymal transition defines feedback activation of receptor tyrosine kinase signaling induced by MEK inhibition in KRAS-mutant lung cancer, Cancer Discov sourcePartly supported

  The Results and Discussion report that MEK inhibition triggers feedback activation of ERBB3 or FGFR1 signaling in different subsets of KRAS-mutant lung cancer, reactivating MAPK/ERK signaling and contributing to resistance. The claim extends this finding to KRAS-mutant cancers generally and names EGFR as a route; this paper’s EGFR feedback example concerns BRAF-inhibited colorectal cancer, not MEK-inhibited KRAS-mutant cancer. The paper primarily demonstrates reactivation of downstream MAPK/ERK signaling rather than RAS signaling itself. (LLM, conf=0.86)

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Early preclinical studies with KRASG12C inhibitors such as ARS-1620 suggested adaptive feedback as a potential resistance mechanism.

“early preclinical studies with KRASG12C inhibitors, such as ARS-1620, have suggested a potential role for adaptive feedback as a mechanism of resistance (7) (15).”

• cites [7] Lito, 2016, Allele-specific inhibitors inactivate mutant KRAS G12C by a trapping mechanism, Science sourcePartly supported

  The paper’s indexed text (section labeled Abstract; page unavailable) reports that feedback-related RTK activation attenuated the inhibitory effect of ARS853 and suggests ways resistance to this class of drugs might emerge. It studies ARS853, not the cited example ARS-1620, so it does not directly support the claim for that compound. (LLM, conf=0.86)

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• cites [15] Misale, 2019, KRAS G12C NSCLC models are sensitive to direct targeting of KRAS in combination with PI3K inhibition, Clin Cancer Res sourceNot checked — no full text of the source

Other RTKs can drive feedback in an EGFR-independent manner.

“However, preclinical and clinical data have demonstrated that other RTKs can drive feedback in an EGFR-independent manner”

• cites [34] Corcoran, 2018, Combined BRAF, EGFR, and MEK inhibition in patients with BRAFV600E-mutant colorectal cancer, Cancer Discov sourceSupported

HER family and FGFR signaling are key mediators of adaptive feedback to RAS-MAPK pathway inhibitors.

“This finding is consistent with prior studies identifying HER family and FGFR signaling as key mediators of adaptive feedback to RAS-MAPK pathway inhibitors (10–14,21,22) and recent functional genomic screens(40).”

• cites [10] Montero-Conde, 2013, Relief of feedback inhibition of HER3 transcription by RAF and MEK inhibitors attenuates their antitumor effects in BRAF-mutant thyroid carcinomas, Cancer Discov sourcePartly supported

  The Results and Discussion (page unavailable) identify HER2/HER3 signaling as a mediator of rebound signaling and reduced response to RAF or MEK inhibitors in BRAF-mutant thyroid cancer cells. Our copy does not identify FGFR signaling as a mediator; searches for “FGFR” and “fibroblast growth factor” found no supporting passage. The paper also emphasizes that the relevant reactivated receptors vary by cell type. (LLM, conf=0.90)

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• cites [11] Corcoran, 2012, EGFR-mediated re-activation of MAPK signaling contributes to insensitivity of BRAF mutant colorectal cancers to RAF inhibition with vemurafenib, Cancer Discov sourcePartly supported

  The Results (page not provided) identify EGFR, a HER-family receptor, as the predominant mediator of MAPK reactivation after RAF inhibition in BRAF-mutant colorectal cancer cells. The Discussion (page not provided) describes a possible feedback mechanism but says it remains unproven. Our copy does not establish FGFR signaling as a mediator, so it supports only the EGFR portion of the broader claim. (LLM, conf=0.88)

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• cites [12] Prahallad, 2012, Unresponsiveness of colon cancer to BRAF(V600E) inhibition through feedback activation of EGFR, Nature sourcePartly supported

  The “feedback activation of EGFR” section reports that BRAF or MEK inhibition activates EGFR, a HER-family receptor, in BRAF-mutant colorectal cancer cells. It does not establish FGFR signaling as a mediator, and its findings are narrower than a general claim about HER-family and FGFR responses to RAS–MAPK inhibitors. (LLM, conf=0.87)

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• cites [13] Manchado, 2016, A combinatorial strategy for treating KRAS-mutant lung cancer, Nature sourcePartly supported

  The Discussion identifies FGFR1 feedback activation as a prominent mechanism of resistance to the MEK inhibitor trametinib in KRAS-mutant lung cancer. The “FGFR1 inhibition enhances trametinib effects” section reports some combinatorial activity for an EGFR/ERBB2 inhibitor, but does not establish HER-family signaling as a key mediator in this setting. The claim also generalizes beyond the specific inhibitor and cancer contexts examined. (LLM, conf=0.87)

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• cites [14] Kitai, 2016, Epithelial-to-mesenchymal transition defines feedback activation of receptor tyrosine kinase signaling induced by MEK inhibition in KRAS-mutant lung cancer, Cancer Discov sourceSupported
• cites [21] Sun, 2014, Intrinsic resistance to MEK inhibition in KRAS mutant lung and colon cancer through transcriptional induction of ERBB3, Cell Rep sourcePartly supported

  The Discussion (page not provided) reports that MEK inhibition upregulates ERBB2 and ERBB3, forming active HER-family complexes that sustain downstream signaling. This supports the HER-family part of the claim in KRAS-mutant lung and colon cancer, but our copy does not identify FGFR signaling as a mediator of this feedback. (LLM, conf=0.86)

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• cites [22] Johnson, 2014, Molecular pathways: adaptive kinome reprogramming in response to targeted inhibition of the BRAF-MEK-ERK pathway in cancer, Clin Cancer Res sourcePartly supported

  Clinical-Translational Advances (page unavailable) describes receptor tyrosine kinase upregulation as an adaptive response to MEK inhibition, and Concluding Remarks gives a HER-family-targeting combination as an example. The copy does not identify FGFR signaling as a mediator of that feedback, so it supports only part of the attributed claim. (LLM, conf=0.86)

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• cites [40] Lou, 2019, KRAS(G12C) inhibition produces a driver-limited state revealing collateral dependencies, Sci Signal sourceSupported

Increased RTK activity may lead to increased cycling of KRASG12C to its active GTP-bound form that hinders the binding of most KRASG12C inhibitors, which bind specifically to the inactive GDP-bound form.

“First, as described by Lito et al, increased RTK activity may lead to increased cycling of KRASG12C to its active GTP-bound form that hinders the binding of most KRASG12C inhibitors, which bind specifically to the inactive GDP-bound form (7).”

• cites [7] Lito, 2016, Allele-specific inhibitors inactivate mutant KRAS G12C by a trapping mechanism, Science sourcePartly supported

  In the supplied copy (section labeled Abstract; no page given), Lito et al. report that RTK-mediated nucleotide exchange affects inhibition and that increased exchange lowers the GDP-bound KRASG12C available for ARS853 binding. This supports the proposed mechanism for ARS853, but the paper does not establish that most KRASG12C inhibitors bind specifically to the GDP-bound form. (LLM, conf=0.88)

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SHP2 dephosphorylates and activates multiple nodes of RAS signaling downstream of RTKs, enhancing signaling through the RAS-RAF-MEK-ERK cascade.

“SHP2 acts to dephosphorylate and activate multiple nodes of RAS signaling downstream of RTKs, enhancing signaling through the RAS-RAF-MEK-ERK cascade (25–28).”

• cites [25] Nichols, 2018, RAS nucleotide cycling underlies the SHP2 phosphatase dependence of mutant BRAF-, NF1- and RAS-driven cancers, Nat Cell Biol sourcePartly supported

  The Introduction describes SHP2 as a phosphatase and scaffold downstream of RTKs that promotes RAS activation. The Results and Discussion link SHP2 to RAS-GTP loading and downstream RAS/MAPK signaling through adaptor-protein interactions and membrane recruitment. They do not establish that SHP2 dephosphorylates and activates multiple RAS-signaling nodes, so that specific mechanism is unsupported. (LLM, conf=0.86)

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• cites [26] Frankson, 2017, Therapeutic targeting of oncogenic tyrosine phosphatases, Cancer Res sourcePartly supported

  In “SHP2 Is a Bona Fide Oncoprotein” (page not available), the paper says SHP2 is required for full Ras/ERK1/2 activation and describes several sites whose dephosphorylation can promote that signaling, including Ras itself. But it presents the mechanisms involving several sites as current models and says they remain under investigation; the claim states them as established and specifies RAF and MEK, which the cited passage does not discuss. (LLM, conf=0.84)

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• cites [27] Mainardi, 2018, SHP2 is required for growth of KRAS-mutant non-small-cell lung cancer in vivo, Nat Med sourcePartly supported

  The main text (lines 35–37 and 58–60; page not provided) describes SHP2 as linking RTK signaling to the RAS-RAF-MEK-ERK pathway and says increased RTK signaling activates that pathway through SHP2. It does not say that SHP2 dephosphorylates and activates multiple nodes of RAS signaling; that specific mechanism is unsupported by the cited passages. (LLM, conf=0.85)

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• cites [28] Ruess, 2018, Mutant KRAS-driven cancers depend on PTPN11/SHP2 phosphatase, Nat Med sourcePartly supported

  The introduction (lines 37–40, 63–64; page not specified) describes SHP2 as a phosphatase involved in signaling downstream of receptors and says it promotes RAS–RAF–MEK–ERK signaling. The results (lines 168–175; page not specified) show that SHP2 phosphatase activity is required to restore MAPK signaling after MEK inhibition. Our copy does not identify multiple RAS-signaling nodes that SHP2 dephosphorylates and activates. (LLM, conf=0.86)

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In BRAFV600 colorectal cancer, targeting EGFR in combination with BRAF inhibition has led to an improvement in clinical efficacy.

“Indeed, in BRAFV600 colorectal cancer, targeting EGFR—the RTK thought to be the primary driver of feedback reactivation from preclinical studies—in combination with BRAF inhibition, has led to an improvement in clinical efficacy (34–39).”

• cites [34] Corcoran, 2018, Combined BRAF, EGFR, and MEK inhibition in patients with BRAFV600E-mutant colorectal cancer, Cancer Discov sourceSupported
• cites [35] van Geel, 2017, A phase Ib dose-escalation study of encorafenib and cetuximab with or without alpelisib in metastatic BRAF-mutant colorectal cancer, Cancer Discov sourceSupported
• cites [36] Yaeger, 2015, Pilot trial of combined BRAF and EGFR inhibition in BRAF-mutant metastatic colorectal cancer patients, Clin Cancer Res sourcePartly supported

  The Discussion reports enhanced activity for combined BRAF and EGFR inhibition compared with historical data for vemurafenib alone. But the study was small and had no vemurafenib-only control arm, so it does not establish the clinical improvement as firmly as the citing sentence implies. (LLM, conf=0.83)

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• cites [37] Kopetz, 2017, Randomized trial of irinotecan and cetuximab with or without vemurafenib in BRAF-mutant metastatic colorectal cancer (SWOG S1406), J Clin Oncol sourceNot checked — no full text of the source
• cites [38] Cutsem, 2019, Binimetinib, encorafenib, and cetuximab triplet therapy for patients with BRAF V600E–mutant metastatic colorectal cancer: safety lead-in results from the phase III BEACON Colorectal Cancer Study, J Clin Oncol sourceSupported
• cites [39] Hyman, 2015, Vemurafenib in multiple nonmelanoma cancers with BRAF V600 mutations, N Engl J Med sourcePartly supported

  The Results > Efficacy section reports one response with vemurafenib plus cetuximab in BRAF V600–mutated colorectal cancer, versus none with vemurafenib alone. It does not establish an overall improvement in clinical efficacy: median progression-free and overall survival were shorter in the combination cohort, and the Discussion describes its clinical activity as modest. Page numbers were not available in our copy. (LLM, conf=0.85)

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SHP2 perhaps plays a more important role in KRASG12C-driven tumor growth in vivo.

“supporting previous findings that SHP2 perhaps plays a more important role in KRASG12C-driven tumor growth in vivo (27,28).”

• cites [27] Mainardi, 2018, SHP2 is required for growth of KRAS-mutant non-small-cell lung cancer in vivo, Nat Med sourceSupported
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• cites [28] Ruess, 2018, Mutant KRAS-driven cancers depend on PTPN11/SHP2 phosphatase, Nat Med sourcePartly supported

  The tumor-maintenance results (lines 140–153) report slower in vivo tumor growth after SHP2 loss in KRASG12D models and in xenografts bearing KRASG12D or KRASG12V. The paper supports a role for SHP2 in mutant-KRAS tumor growth, but the passages do not establish that its role is greater in KRASG12C-driven tumors. (LLM, conf=0.85)

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KRASG12C inhibitors lock mutant KRAS in an inactive GDP-bound state.

“The inhibitors function by locking KRASG12C in an inactive GDP bound state, exploiting the unique property of KRASG12C to cycle between the GDP- and GTP-bound states (6,7).”

• cites [6] Ostrem, 2016, Direct small-molecule inhibitors of KRAS: from structural insights to mechanism-based design, Nat Rev Drug Discov sourceNot checked — no full text of the source
• cites [7] Lito, 2016, Allele-specific inhibitors inactivate mutant KRAS G12C by a trapping mechanism, Science sourceSupported

The combination of BRAF and EGFR only suppresses signaling in a subset of patients.

“and that the combination of BRAF and EGFR only suppresses signaling in a subset of patients (34).”

• cites [34] Corcoran, 2018, Combined BRAF, EGFR, and MEK inhibition in patients with BRAFV600E-mutant colorectal cancer, Cancer Discov sourceSupported

RTK-driven feedback reactivation of RAS-MAPK signaling has been identified as a key driver of resistance in BRAFV600E cancers treated with BRAF inhibitors (colorectal cancer in particular) and in KRAS-mutant cancers treated with MEK inhibitors.

“For example, RTK-driven feedback reactivation of RAS-MAPK signaling has been identified as a key driver of resistance in BRAFV600E cancers treated with BRAF inhibitors (colorectal cancer in particular) and in KRAS-mutant cancers treated with MEK inhibitors (11,12,32).”

• cites [11] Corcoran, 2012, EGFR-mediated re-activation of MAPK signaling contributes to insensitivity of BRAF mutant colorectal cancers to RAF inhibition with vemurafenib, Cancer Discov sourcePartly supported

  The Results and Discussion (page not provided) identify EGFR-driven RAS–MAPK reactivation as a mechanism of reduced sensitivity to vemurafenib in BRAF-mutant colorectal cancer. Our copy does not support the separate claim about RTK-driven resistance to MEK inhibitors in KRAS-mutant cancers. (LLM, conf=0.88)

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• cites [12] Prahallad, 2012, Unresponsiveness of colon cancer to BRAF(V600E) inhibition through feedback activation of EGFR, Nature sourcePartly supported

  Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

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• cites [32] Sun, 2014, Reversible and adaptive resistance to BRAF(V600E) inhibition in melanoma, Nature sourcePartly supported

  The main text (p. 5) says that feedback activation of EGFR causes resistance to BRAF inhibition in BRAF-mutant colon cancer, supporting the colorectal-cancer part of the claim. The paper studies BRAF-mutant melanoma as well, but the passages found do not establish the claimed mechanism in KRAS-mutant cancers treated with MEK inhibitors. (LLM, conf=0.85)

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Adaptive feedback resistance has been a key limitation in prior clinical efforts to target the RAS-MAPK pathway.

“However, adaptive feedback resistance has been a key limitation in prior clinical efforts to target the RAS-MAPK pathway.”

• cites [11] Corcoran, 2012, EGFR-mediated re-activation of MAPK signaling contributes to insensitivity of BRAF mutant colorectal cancers to RAF inhibition with vemurafenib, Cancer Discov sourcePartly supported

  The Discussion (page unavailable) links the poor response of BRAF-mutant colorectal cancers to vemurafenib with EGFR-mediated reactivation of MAPK signaling, supporting feedback resistance as a limitation in that setting. The paper does not establish that it was a key limitation across prior clinical efforts to target the RAS–MAPK pathway more broadly; its mechanistic evidence comes from cell and xenograft studies. (LLM, conf=0.84)

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• cites [12] Prahallad, 2012, Unresponsiveness of colon cancer to BRAF(V600E) inhibition through feedback activation of EGFR, Nature sourcePartly supported

  The 'feedback activation of EGFR' section links feedback after BRAF inhibition to the poor clinical response of BRAF V600E-mutant colon cancer to vemurafenib monotherapy (page not provided). That supports a specific example of feedback resistance, but not the broader claim that it has been a key limitation across prior clinical efforts to target the RAS-MAPK pathway. (LLM, conf=0.85)

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• cites [32] Sun, 2014, Reversible and adaptive resistance to BRAF(V600E) inhibition in melanoma, Nature sourcePartly supported

  The main text (p. 4) says BRAF and MEK inhibitors produced strong initial responses in patients with BRAF-mutant melanoma, but resistance developed rapidly. It also discusses feedback activation of EGFR in BRAF-mutant colorectal cancer (p. 5). These passages support resistance as a limitation for specific pathway-targeting treatments, but do not establish that adaptive feedback resistance was a key limitation across prior clinical efforts to target the RAS–MAPK pathway generally. (LLM, conf=0.82)

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SHP2 inhibition alone was shown to have anti-tumor effects in vitro and in vivo.

“Indeed, SHP2 inhibition alone was shown to have anti-tumor effects in vitro and in vivo (25).”

• cites [25] Nichols, 2018, RAS nucleotide cycling underlies the SHP2 phosphatase dependence of mutant BRAF-, NF1- and RAS-driven cancers, Nat Cell Biol sourceSupported

SHP2 inhibition was also demonstrated to have single-agent efficacy in preclinical KRASG12C models by reducing cycling to the active GTP-bound state.

“Furthermore, SHP2 inhibition was also demonstrated to have single-agent efficacy in preclinical KRASG12C models by reducing cycling to the active GTP-bound state, offering an additional advantage as a potential combination partner (25).”

• cites [25] Nichols, 2018, RAS nucleotide cycling underlies the SHP2 phosphatase dependence of mutant BRAF-, NF1- and RAS-driven cancers, Nat Cell Biol sourceSupported

Combination therapies to suppress adaptive feedback proved key to optimizing the frequency and durability of response in each tumor type.

“Still, in all cases, combination therapies to suppress adaptive feedback proved key to optimizing the frequency and durability of response in each tumor type (34,50,51).”

• cites [34] Corcoran, 2018, Combined BRAF, EGFR, and MEK inhibition in patients with BRAFV600E-mutant colorectal cancer, Cancer Discov sourcePartly supported

  The Abstract and Discussion report that targeting adaptive feedback improved response rates in BRAF V600E–mutant colorectal cancer. But the Discussion says response duration remained poor and further optimization was needed. This study therefore does not establish that the combination optimized durability, or outcomes in every tumor type. (LLM, conf=0.87)

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• cites [50] Planchard, 2016, Dabrafenib plus trametinib in patients with previously treated BRAF(V600E)-mutant metastatic non-small cell lung cancer: an open-label, multicentre phase 2 trial, Lancet Oncol sourcePartly supported

  The Results and Discussion report frequent, durable responses to dabrafenib plus trametinib in previously treated BRAF V600E–mutant NSCLC, with higher response and progression-free survival than an indirect comparison with dabrafenib alone. But the Discussion says whether the proposed resistance mechanisms occur in these NSCLC patients is unknown. This trial therefore does not establish that suppressing adaptive feedback was the reason combination therapy improved responses, or that this was proved across tumor types. No page number is available in our copy. (LLM, conf=0.87)

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• cites [51] Molina-Arcas, 2019, Development of combination therapies to maximize the impact of KRAS-G12C inhibitors in lung cancer, Sci Transl Med sourcePartly supported

  The Results (page unavailable) report that adding IGF1R and mTOR inhibitors to a KRAS-G12C inhibitor produced durable regression in lung-cancer xenografts where inhibitor treatment alone led to progression. The Discussion (page unavailable) describes suppressing compensatory feedback, but cautions that resistance may still evolve. These preclinical lung-cancer findings do not establish that combination therapy proved key to response frequency and durability in every tumor type. (LLM, conf=0.88)

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Active GTP-bound wild type RAS isoforms NRAS and HRAS increase by 48 hours after ARS-1620 in most cell lines, in a dose-dependent manner.

“in most cell lines, increases in the levels of the active GTP-bound forms of the wild type RAS isoforms (NRAS-GTP, HRAS-GTP) were noted by 48 hours in a dose dependent manner”

No clear rebound in KRAS-GTP levels occurs between 4 and 48 hours of ARS-1620 treatment at any inhibitor concentration.

“no clear rebound in KRAS-GTP levels was noted between 4 and 48 h of treatment at any inhibitor concentration”

SHP2 inhibition suppresses adaptive resistance to KRASG12C inhibition across all cell lines tested.

“SHP2 inhibition was effective in suppressing adaptive resistance to KRASG12C inhibition across all cell lines.”

• AssumptionRests on an assumption: The KRASG12C-mutant cell lines and xenograft models used are representative of KRASG12C-mutant human cancers, so findings generalize to patients.

In each KRASG12C cell line, combining a specific RTK inhibitor with ARS-1620 decreases cell viability more than ARS-1620 alone.

“in each cell line, inhibition of a specific RTK in combination with ARS-1620 led to a marked decrease in cell viability relative to ARS-1620 alone.”

ARS-1620 suppresses KRAS-GTP levels dose-dependently in all cell lines.

“ARS-1620 effectively suppressed KRAS-GTP levels as measured by a RAF-RAS binding domain (RBD) pulldown assay in all cell lines in a dose-dependent manner”

On average, phospho-ERK levels rebound to about 75% of baseline by 72 hours after KRASG12C inhibition.

“RAS-MAPK pathway activity, as assessed by phospho-ERK levels, rebounded on average to ~75% of baseline levels by just 72 hours.”

Co-inhibition of SHP2 abrogates feedback reactivation more universally than targeting single RTKs.

“co-inhibition of SHP2, which mediates signaling from multiple RTKs to RAS, abrogated feedback reactivation more universally”

• Also stated in: § INTRODUCTION · plain

  “co-targeting of SHP2 (17,18), a key phosphatase that mediates signaling from multiple RTKs to RAS, is able to abrogate feedback reactivation of RAS signaling following KRASG12C inhibition across all models”

• AssumptionRests on an assumption: The KRASG12C-mutant cell lines and xenograft models used are representative of KRASG12C-mutant human cancers, so findings generalize to patients.

Across all models, highest concentrations of ARS-1620 produce on average a 4- to 5-fold increase in NRAS-GTP and HRAS-GTP by 48 hours.

“on average we observed a 4 to 5-fold increase in NRAS-GTP and HRAS-GTP levels by 48 hours following treatment with the highest concentrations of ARS-1620 across all models.”

High basal levels of several phosphorylated RTKs, including phospho-EGFR, are present in most cell lines.

“We observed high basal levels of several phosphorylated RTKs, including phospho-EGFR in most cell lines.”

The reduction in KRAS-GTP and RAS-GTP levels translated to further suppression of the MAPK pathway downstream of RAS by 48 hours.

“The reduction in KRAS-GTP and RAS-GTP levels translated to further suppression of the MAPK pathway downstream of RAS by 48 hours.”

A non-significant trend toward enhanced efficacy relative to ARS-1620 alone was seen with a specific RTK combination in each model.

“while neither reached statistical significance, a clear trend toward enhanced efficacy relative to ARS-1620 alone was observed with a specific RTK combination in each model”

Strong induction of RAS activity was observed with the MEK and ERK inhibitor combinations.

“though strong induction of RAS activity was observed with these combinations”

The SHP2 inhibitor SHP099 led to incomplete suppression of KRAS-GTP levels as a single agent.

“we found that the SHP2 inhibitor SHP099 led to incomplete suppression of KRAS-GTP levels as a single agent (Fig. 3A).”

SHP2 inhibition enhanced suppression of active RAS when combined with ARS-1620 across both models.

“we found that SHP2 inhibition could enhance suppression of active RAS in combination with ARS-1620 across both models”

Combined KRASG12C and SHP2 inhibition led to a statistically significant reduction in cell number relative to either agent alone in all KRASG12C models.

“combined KRASG12C and SHP2 inhibition led to a statistically significant reduction in cell number relative to either agent alone in all KRASG12C models”

Modest and incomplete suppression of ERK-dependent transcripts, such as DUSP6, was observed after 4 days of treatment with either ARS-1620 or SHP099 alone.

“we observed modest and incomplete suppression of ERK-dependent transcripts, such as DUSP6 after 4 days of treatment with either ARS-1620 or SHP099 alone (Figs. 4E,F and Supplementary Fig. S9).”

RTK-driven induction of wild type RAS (NRAS or HRAS) activity following KRASG12C inhibitor treatment can reactivate signaling in a KRASG12C-independent manner.

“Second, in this study we see clear evidence of RTK-driven induction of wild type RAS (NRAS or HRAS) activity following KRASG12C inhibitor treatment, which can reactivate signaling in a KRASG12C-independent manner.”

A reduction in phospho-AKT was noted in some cell lines (SW1463, MIA PaCa-2, NCIH23, NCIH358) and unaffected or increased levels in other cell lines.

“with a reduction noted in some cell lines (SW1463, MIA PaCa-2, NCIH23, NCIH358) and unaffected or increased levels noted in other cell lines”

The MIA PaCa-2 model is more dependent on FGFR signaling.

“and MIA PaCa-2 more dependent on FGFR signaling”

Combined treatment with ARS-1620 and SHP099 maintained a greater decrease after 4 days of treatment compared to each inhibitor alone.

“However, combined treatment with ARS-1620 and SHP099 maintained a greater decrease after 4 days of treatment compared to each inhibitor alone.”

Combined KRASG12C and SHP2 inhibition had no effect in the KRASG12D Ls174T model.

“while having no effect in the KRASG12D Ls174T model (Fig. 3D, Supplementary Fig. S7, S8).”

SHP099 abrogated the adaptive increase in activated NRAS-GTP levels by 48 hours induced by ARS-1620 in some models.

“and abrogated the adaptive increase in activated NRAS-GTP levels by 48 hours induced by ARS-1620 in some models”

Some models (NCIH358, Calu-1) demonstrated marked suppression of viability with ARS-1620 alone.

“While some models (NCIH358, Calu-1) demonstrated marked suppression of viability with ARS-1620 alone”

The pattern of RTK-dependence is highly variable between KRASG12C mutant cancers.

“and that the pattern of RTK-dependence is highly variable between KRASG12C mutant cancers.”

Strong feedback reactivation of MAPK signaling downstream of RAS occurs after KRASG12C inhibition.

“strong feedback reactivation of MAPK signaling downstream of RAS is observed following KRASG12C inhibition”

The combination of ARS-1620 and SHP099 showed a statistically significant increase in anti-tumor efficacy compared to each agent alone.

“the combination of ARS-1620 and SHP099 showed a statistically significant increase in anti-tumor efficacy compared to each agent alone”

Multiple receptor tyrosine kinases can contribute to adaptive feedback resistance against KRASG12C inhibition.

“multiple RTKs can contribute to adaptive feedback resistance to KRASG12C inhibition”

The predominant RTK dependency differed between SW837 and MIA PaCa-2 models.

“the predominant RTK dependency of each model differed”

A reduction in tumor growth relative to vehicle control was observed in both SW837 and MIA PaCa-2 xenograft models with single agent ARS-1620 or SHP099.

“While a reduction in tumor growth relative to vehicle control was observed in both SW837 and MIA PaCa-2 xenograft models with single agent ARS-1620 or SHP099”

SHP099 reduced NRAS-GTP levels in several cell lines.

“SHP099 also reduced NRAS-GTP levels in several cell lines”

Feedback reactivation is driven by multiple RTKs.

“We observe that feedback reactivation is driven by multiple RTKs”

The pattern of RTK-dependence is highly heterogeneous across KRASG12C models.

“and that the pattern of RTK-dependence is highly heterogeneous across KRASG12C models.”

Combining KRASG12C inhibition with MEK and ERK inhibitors showed potential cooperativity across the panel of KRASG12C models.

“we also assessed potential combinations of KRASG12C inhibition with MEK and ERK inhibitors, which also displayed potential cooperativity across the panel of KRASG12C models”

Concurrent ARS-1620 and SHP099 treatment led to more complete suppression of both KRAS-GTP and total RAS-GTP levels compared to either agent alone at 48 hours in all cell lines.

“in all cell lines, concurrent ARS-1620 and SHP099 treatment led to more complete suppression of both KRAS-GTP and total RAS-GTP levels when compared to either agent alone at 48 hours (Fig. 3A).”

Multiple RTKs appear to be involved in feedback reactivation following KRASG12C inhibition.

“Similarly, we note that multiple RTKs appear to be involved in feedback reactivation following KRASG12C inhibition”

The effects of combined KRASG12C and SHP2 inhibition on cell viability were more pronounced in long-term viability assays.

“Interestingly, the effects of combined KRASG12C and SHP2 inhibition on cell viability were more pronounced in long-term viability assays.”

Consistent evidence of rapid feedback reactivation of RAS pathway signaling in KRASG12C cancer models following treatment with KRASG12C inhibitors was found.

“we find consistent evidence of rapid feedback reactivation of RAS pathway signaling in KRASG12C cancer models following treatment with KRASG12C inhibitors.”

The efficacy of SHP099 monotherapy in vivo was more striking than seen in our in vitro experiments.

“The efficacy of SHP099 monotherapy in vivo was more striking than seen in our in vitro experiments”

The combination led to tumor regressions in the majority of tumors in each model.

“and led to tumor regressions in the majority of tumors in each model (Figs. 4A, B; Supplemental Fig. S9).”

ARS-1620 showed modest efficacy as a single agent in both SW837 and MIA PaCa-2 xenograft models.

“ARS-1620 demonstrated modest efficacy as a single agent in both the SW837 and MIA PaCa-2 xenograft models”

The SW837 model is more dependent on HER signaling.

“with the SW837 model more dependent on HER signaling”

Adaptive feedback reactivation under KRASG12C inhibition showed variable RTK dependence across models for maintaining KRAS-GTP and total RAS-GTP levels.

“we found that adaptive feedback reactivation in the setting of KRASG12C inhibition exhibited a similarly variable RTK dependence in each model for maintaining both KRAS-GTP and total RAS-GTP levels”

The effects of KRASG12C or SHP2 inhibition on PI3K/AKT signaling, as measured by phospho-AKT, were highly variable across cell lines.

“the effects of KRASG12C or SHP2 inhibition on PI3K/AKT signaling, as measured by phospho-AKT, was highly variable across cell lines”

Some RTK inhibitors-in particular the pan-HER inhibitor afatinib and the FGFR inhibitor BGJ398-are effective in combination with KRASG12C inhibitors in many models.

“our data do indicate that some RTK inhibitors—in particular the pan-HER inhibitor afatinib and the FGFR inhibitor BGJ398—are effective in combination with KRASG12C inhibitors in many models”

Some models showed the greatest sensitivity to KRASG12C inhibition in combination with a specific RTK inhibitor.

“Although some models showed the greatest sensitivity to KRASG12C inhibition in combination with a specific RTK inhibitor”

SHP2 inhibition could consistently block the adaptive increase in wild type RAS (HRAS, NRAS) activation observed after KRASG12C inhibition in many models.

“Moreover, we observed that SHP2 inhibition could consistently block the adaptive increase in wild type RAS (HRAS, NRAS) activation observed after KRASG12C inhibition in many models (Fig. 3A).”

RTK combinations showed differential effects across in vivo models.

“and RTK combinations showed differential effects across in vivo models (Fig. 2C)”

SHP2 may be a common node through which multiple RTKs' feedback reactivation of RAS signaling can be inhibited.

“the RTK associated phosphatase SHP2 may represent a common node through which to inhibit feedback reactivation of RAS signaling by multiple RTKs”

Adaptive feedback reactivation after KRASG12C inhibition corresponds with increased wild-type RAS activity, particularly NRAS and HRAS.

“these data suggest that adaptive feedback reactivation of pathway signaling following KRASG12C inhibition corresponds with a rebound in RAS activity, in particular an increase in wild-type RAS activity”

Early clinical data with AMG510 showed an initial overall response rate of 24% (13/55) in patients with KRASG12C mutant cancers.

“Early clinical data with the KRASG12C inhibitor AMG510 was recently reported, showing an initial overall response rate of 24% (13/55) in patients with KRASG12C mutant cancers”

• cites [16] Govindan, 2019, 446PDPhase I study of AMG 510, a novel molecule targeting KRAS G12C mutant solid tumours, Ann Oncol sourceNot checked — no full text of the source

Vertical inhibition strategies may enhance clinical efficacy of KRASG12C inhibitors.

“highlight the potential importance of vertical inhibition strategies to enhance the clinical efficacy of KRASG12C inhibitors.”

• AssumptionRests on an assumption: Effects on cell viability in vitro and xenograft tumor growth in vivo predict clinical efficacy of KRASG12C inhibitor combinations.

Feedback reactivation of wild type RAS is a key mechanism of adaptive resistance to KRASG12C inhibitors.

“These data identify feedback reactivation of wild type RAS as a key mechanism of adaptive resistance to KRASG12C inhibitors”

• AssumptionRests on an assumption: The KRASG12C-mutant cell lines and xenograft models used are representative of KRASG12C-mutant human cancers, so findings generalize to patients.

Adaptive feedback reactivation of RAS-MAPK pathway signaling is a major mode of therapeutic resistance to RAS-RAF-MEK pathway inhibition.

“previous efforts to target the RAS-RAF-MEK pathway have been hindered by adaptive feedback reactivation of pathway signaling as a major mode of therapeutic resistance.”

Multiple RTKs can contribute to adaptive feedback resistance to KRASG12C inhibition.

“These results support that multiple RTKs can contribute to adaptive feedback resistance to KRASG12C inhibition”

• AssumptionRests on an assumption: The KRASG12C-mutant cell lines and xenograft models used are representative of KRASG12C-mutant human cancers, so findings generalize to patients.

Blocking adaptive feedback signals may be necessary to enhance efficacy of KRASG12C inhibitors.

“these data suggest that blocking adaptive feedback signals driving pathway may be necessary to enhance the efficacy of KRASG12C inhibitors.”

• AssumptionRests on an assumption: The KRASG12C-mutant cell lines and xenograft models used are representative of KRASG12C-mutant human cancers, so findings generalize to patients.
• AssumptionRests on an assumption: Effects on cell viability in vitro and xenograft tumor growth in vivo predict clinical efficacy of KRASG12C inhibitor combinations.

Multiple RTKs may contribute to adaptive feedback after KRASG12C inhibition.

“suggesting that multiple RTKs may play a role in adaptive feedback to KRASG12C inhibition.”

GTP-bound state-selective KRASG12C inhibitors are unlikely to be effective against RTK-driven activation of wild type RAS.

“this mechanism of action is unlikely to be effective against the second mechanism of adaptive feedback (RTK-driven activation of wild type RAS) (33).”

• cites [33] Young, 2013, Oncogenic and wild-type Ras play divergent roles in the regulation of mitogen-activated protein kinase signaling, Cancer Discov sourceNot checked — no full text of the source

SHP2 is a key phosphatase that mediates signaling from multiple RTKs to RAS.

“co-targeting of SHP2 (17,18), a key phosphatase that mediates signaling from multiple RTKs to RAS”

• cites [17] Agazie, 2003, Molecular mechanism for a role of SHP2 in epidermal growth factor receptor signaling, Mol Cell Biol sourceNot checked — no full text of the source
• cites [18] Dance, 2008, The molecular functions of Shp2 in the Ras/Mitogen-activated protein kinase (ERK1/2) pathway, Cell Signal sourceNot checked — no full text of the source

KRASG12C may be uniquely dependent on some level of basal upstream activation from RTKs to maintain activity.

“Because KRASG12C actively cycles between its GDP-bound inactive state and its GTP-bound active state, KRASG12C may be uniquely dependent on some level of basal upstream activation from RTKs to maintain activity.”

• AssumptionRests on an assumption: KRASG12C cycles between a GDP-bound inactive state and a GTP-bound active state.

Vertical inhibition strategies can suppress adaptive feedback resistance to KRASG12C inhibition.

“these data support the potential for vertical inhibition strategies to suppress adaptive feedback resistance to KRASG12C inhibition”

SHP2 is a common downstream node through which signaling from multiple RTKs can be inhibited.

“supporting the potential for SHP2 as a common downstream node through which to inhibit signaling from multiple RTKs”

Co-inhibition of individual RTKs may not be broadly effective across KRASG12C cancers.

“but also suggest that co-inhibition of individual RTKs may not be broadly effective across KRASG12C cancers”

SHP2 inhibitors could be a promising combination partner for KRASG12C inhibitors.

“While our data suggest that SHP2 inhibitors could be a promising combination partner for KRASG12C inhibitors”

SHP2 inhibition can mitigate the induction of wild type RAS activity that drives adaptive feedback reactivation of RAS and MAPK pathway signaling in response to KRASG12C inhibition.

“Thus, our results suggest that SHP2 inhibition can mitigate the induction of wild type RAS activity that drives adaptive feedback reactivation of RAS and MAPK pathway signaling in response to KRASG12C inhibition.”

Prior experience predicts that adaptive resistance may pose a key obstacle for KRASG12C inhibitors.

“Thus, this prior experience predicts that adaptive resistance may pose a key obstacle for KRASG12C inhibitors, as well”

Vertical pathway inhibition strategies can overcome adaptive resistance to KRASG12C inhibition.

“Together, these data support the potential of vertical pathway inhibition strategies to overcome adaptive resistance to KRASG12C inhibition.”

Combining RTK or SHP2 inhibitors with KRASG12C inhibition could be a more effective therapeutic strategy to overcome resistance and improve efficacy in KRAS G12C-mutant tumors.

“combined inhibition of RTKs or SHP2 and KRASG12C could represent a more effective therapeutic strategy to overcome resistance and improve efficacy in KRAS G12C-mutant tumors”

Interrupting the adaptive feedback loop following KRASG12C inhibition may be critical to overcoming adaptive resistance.

“our data suggest that interrupting the adaptive feedback loop following KRASG12C inhibition may be critical to overcoming adaptive resistance.”

RTK-driven feedback may contribute to RAS reactivation through two mechanisms.

“RTK-driven feedback may contribute to RAS reactivation through two mechanisms.”

Inhibiting SHP2 has the potential to block the ability of multiple RTKs to activate RAS.

“Thus, inhibition of SHP2 has the potential to block the ability of multiple RTKs to activate RAS.”

Adaptive feedback is likely to play a key role in resistance to KRASG12C inhibitors.

“Taken together, our data suggest that adaptive feedback is likely to play a key role in resistance to KRASG12C inhibitors”

Co-targeting a single RTK is unlikely to be universally effective.

“suggesting that co-targeting a single RTK is unlikely to be universally effective.”

The pattern of tumor type-specific difference in response is highly consistent with prior examples of adaptive resistance.

“Interestingly, this pattern of tumor type-specific difference in response is highly consistent with prior examples of adaptive resistance.”

Combined KRASG12C and SHP2 inhibition supports its potential as a more universal approach.

“supporting its potential as a more universal approach.”

Targeting SHP2 provides the potential opportunity to intercept a common signaling node linking multiple RTKs to RAS signaling.

“Conversely, targeting SHP2 provides the potential opportunity to intercept a common signaling node linking multiple RTKs to RAS signaling.”

Therapeutic combinations will be key to overcoming adaptive resistance and enhancing clinical benefit of KRASG12C inhibitors.

“Similarly, our data suggest that therapeutic combinations will be key to overcoming adaptive resistance and enhancing clinical benefit of KRASG12C inhibitors.”