The discovery of small-molecule inhibitors requires suitable binding pockets on protein surfaces. Proteins that lack this feature are considered undruggable and require innovative strategies for ...therapeutic targeting.
KRAS
is the most frequently activated oncogene in cancer, and the active state of mutant KRAS is such a recalcitrant target. We designed a natural product–inspired small molecule that remodels the surface of cyclophilin A (CYPA) to create a neomorphic interface with high affinity and selectivity for the active state of KRAS
G12C
(in which glycine-12 is mutated to cysteine). The resulting CYPA:drug:KRAS
G12C
tricomplex inactivated oncogenic signaling and led to tumor regressions in multiple human cancer models. This inhibitory strategy can be used to target additional KRAS mutants and other undruggable cancer drivers. Tricomplex inhibitors that selectively target active KRAS
G12C
or multiple RAS mutants are in clinical trials now (NCT05462717 and NCT05379985).
Editor’s summary
KRAS is one of the most common oncogenes, but unfortunately it is also commonly thought of as “undruggable” because it lacks a suitable binding pocket for small-molecule drug candidates. To get around this limitation, Schulze
et al
. built on observations from natural product–derived drugs to go after oncogenic KRAS indirectly (see the Perspective by Liu). The authors identified a naturally occurring compound that binds cyclophilin A, a type of cellular chaperone, and then modified this compound to also bind oncogenic mutant KRAS in a three-way complex. The authors used this approach to design multiple small molecules that effectively bound mutant KRAS in complex with cyclophilin A. These molecules were very effective at inhibiting the downstream pathways involved in cell proliferation and at suppressing tumor growth in multiple models. —Yevgeniya Nusinovich
Small molecules recruit cyclophilin A to the active state of mutant KRAS to disrupt oncogenic signaling and tumor growth.
RAS oncogenes (collectively NRAS, HRAS and especially KRAS) are among the most frequently mutated genes in cancer, with common driver mutations occurring at codons 12, 13 and 61
. Small molecule ...inhibitors of the KRAS(G12C) oncoprotein have demonstrated clinical efficacy in patients with multiple cancer types and have led to regulatory approvals for the treatment of non-small cell lung cancer
. Nevertheless, KRAS
mutations account for only around 15% of KRAS-mutated cancers
, and there are no approved KRAS inhibitors for the majority of patients with tumours containing other common KRAS mutations. Here we describe RMC-7977, a reversible, tri-complex RAS inhibitor with broad-spectrum activity for the active state of both mutant and wild-type KRAS, NRAS and HRAS variants (a RAS(ON) multi-selective inhibitor). Preclinically, RMC-7977 demonstrated potent activity against RAS-addicted tumours carrying various RAS genotypes, particularly against cancer models with KRAS codon 12 mutations (KRAS
). Treatment with RMC-7977 led to tumour regression and was well tolerated in diverse RAS-addicted preclinical cancer models. Additionally, RMC-7977 inhibited the growth of KRAS
cancer models that are resistant to KRAS(G12C) inhibitors owing to restoration of RAS pathway signalling. Thus, RAS(ON) multi-selective inhibitors can target multiple oncogenic and wild-type RAS isoforms and have the potential to treat a wide range of RAS-addicted cancers with high unmet clinical need. A related RAS(ON) multi-selective inhibitor, RMC-6236, is currently under clinical evaluation in patients with KRAS-mutant solid tumours (ClinicalTrials.gov identifier: NCT05379985).
Abstract only
591
Background: RAS proteins (such as KRAS, NRAS, HRAS) are small GTPases that drive cell proliferation and survival when bound to GTP. Mutant RAS proteins exist predominantly in the ...GTP-bound (RAS(ON)) state, leading to excessive downstream signaling via interaction with effectors such as RAF kinases. Oncogenic KRAS is required for the initiation, progression, and maintenance of pancreatic ductal adenocarcinoma (PDAC) (Hezel et al, 2006, Ying et al 2012). Although extinction of KRAS expression as well as pharmacological inhibition of RAS effectors clearly abrogate the growth of human PDAC models, clinical trials of drugs targeting key components of the RAS pathway have remained largely unsuccessful. Several factors contribute to these failures including redundancy in signaling surrogates downstream of KRAS and/or tumor complexity driven by co-occurring genomic alterations and intra-tumoral heterogeneity. Methods: RMC-6236 is a small molecule that binds to an intracellular chaperone protein, Cyclophilin A (CypA), resulting in an inhibitory binary complex that binds active, GTP-bound RAS to form a tri-complex and suppresses RAS signaling by disrupting interactions with effectors such as RAF kinases. Results: Here, we demonstrate that single agent RMC-6236, a first-in-class, orally bioavailable, RAS-selective tri-complex inhibitor of multiple RAS mutations and wild-type RAS (RASMULTI inhibitor) is highly efficacious in preclinical models of KRAS mutant PDAC (with marked activity in RAS-mutant colorectal cancer models described in Koltun et al, AACR 2021). RMC-6236 suppresses phosphorylation of ERK kinases, downstream effectors of RAS involved in cell proliferation, and induces growth suppression and apoptosis in multiple human cancer cell lines in vitro. Oral administration of RMC-6236 produces deep, durable, and dose-dependent suppression of tumor RAS pathway activation in vivo. An extended duration of tumor pharmacodynamic activity, relative to plasma exposure, is observed that likely reflects retention of RMC-6236 in tumor tissue due to high affinity binding to CypA. Daily dosing of RMC-6236 drives profound and durable tumor regressions in multiple cell line derived (CDX) and patient derived (PDX) xenograft models of KRAS mutant PDAC at doses that are well-tolerated. Conclusions: These results indicate that direct targeting of mutant and possibly wild-type RAS in PDAC, without inhibition of signaling nodes outside the canonical RAS pathway, has the potential to translate into clinical benefit for patients with pancreatic cancer harboring mutations in KRAS that may be superior to therapies aimed at upstream or downstream signaling elements within the RAS pathway. Our preclinical data strongly support the inclusion of PDAC patients in our planned clinical trial of RMC-6236 in patients with advanced solid tumors.
Abstract
The KRASG12C mutation is found in 11% of non-small cell lung cancers and 4% of colorectal cancers. Recently, a class of KRASG12C(OFF) inhibitors has shown promising activity in patients ...whose cancers bear KRASG12C. These data validate KRASG12C as an oncogenic driver, as well the mechanism of action of the KRASG12C(OFF) inhibitor class – sequestration of inactive, GDP-bound KRASG12C(OFF) proteins. Previous work has demonstrated this mechanism of action is vulnerable to adaptive tumor cell responses that activate KRASG12C by increasing upstream signaling and driving the cellular pool of KRASG12C towards the RAS(ON) state. These escape mechanisms, in which KRASG12C can be reactivated in the presence of a KRASG12C(OFF) inhibitor, highlight the potential for an inhibitor that directly targets and disables the KRASG12C(ON) form.
Using structure-based drug design, we have discovered RM-032, a potent covalent inhibitor of KRASG12C(ON) that forms a tri-complex between KRASG12C(ON) and cyclophilin A (CypA), a highly abundant immunophilin. The assembled tri-complex prevents KRASG12C(ON) from signaling via steric blockade of RAS effector binding. In cells, kinetic analyses demonstrate near-immediate disruption of RAS effector binding and extinction of KRASG12C(ON) signaling. RM-032 is dual selective for KRASG12C(ON) and NRASG12C(ON).
In vitro, RM-032 drives increased durability of inhibition of both RAS pathway signaling and cell proliferation in KRASG12C tumor cells compared with KRASG12C(OFF) inhibition. RM-032 displays attractive drug-like properties including cross-species oral bioavailability, and is predicted to achieve adequate exposures following oral dosing in humans. Oral administration of RM-032 produces deep and durable suppression of RAS pathway activity in KRASG12C tumor models and drives profound tumor regressions in vivo at well-tolerated doses. Across multiple tumor xenograft models, advanced KRASG12C(ON) inhibitors, including RM-032, appear to outperform KRASG12C(OFF) inhibitors.
RM-032 permits a broad array of combination opportunities for treating KRASG12C mutant cancer types where single agent KRASG12C(ON) inhibition may be insufficient, for example with agents targeting nodes both upstream (e.g., SHP2 and SOS1) and downstream (e.g., MEK and ERK) of RAS, as well as parallel pathways (e.g., mTORC1). RM-032 is a next generation mutant-selective inhibitor of KRASG12C(ON) that may overcome liabilities of first-generation KRASG12C(OFF) inhibitors and provide additional benefit to patients by directly targeting the active form of this important oncogenic driver mutation.
Citation Format: Robert J. Nichols, Jim Cregg, Christopher J. Schulze, Zhican Wang, Kevin Yang, Jingjing Jiang, Daniel M. Whalen, Rich Hansen, Lindsay S. Garrenton, Alun Bermingham, John E. Knox, Tiffany Choy, Denise Reyes, Mayra Rios, Kyle Seamon, Michael Longhi, Kang-Jye Chou, Shaoling Li, David P. Wildes, Mallika Singh, Elena S. Koltun, Adrian L. Gill, Jacqueline A. M. Smith. A next generation tri-complex KRASG12C(ON) inhibitor directly targets the active, GTP-bound state of mutant RAS and may overcome resistance to KRASG12C(OFF) inhibition abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1261.
Abstract
KRASG12V mutant cancers represent a significant unmet medical need with nearly 44,000 new diagnoses annually in the US. The KRASG12V mutation occurs frequently in multiple tumor histotypes; ...the incidence in NSCLC, CRC and pancreatic cancers is 6%, 10% and 26%, respectively.
RAS proteins are small GTPases that drive cell proliferation and survival when bound to GTP. Mutant RAS proteins exist predominantly in the GTP-bound (RAS(ON)) state, leading to excessive downstream signaling via interaction with effectors such as RAF. The intrinsic GTP hydrolysis rate of KRASG12V is significantly lower than that of either KRASG12C or KRASG12D. Therefore, targeting the KRASG12V(ON) state will be critical for maximal suppression of this oncogenic driver. No targeted, direct inhibitors of KRASG12V(ON) have been described to date. We have built a pipeline of small molecule inhibitors targeting multiple oncogenic RAS(ON) mutants. Here we describe the preclinical profile of KRASG12V(ON) inhibitors that promote a tri-complex between the inhibitor, the immunophilin cyclophilin A (CypA), and the active GTP-bound state of KRASG12V. In cancer cell lines bearing KRASG12V mutations, KRASG12V(ON) inhibitors trigger an immediate disruption of RAS-effector interactions, leading to attenuation of RAS pathway signaling, potent (sub-nM EC50) growth suppression, and apoptosis. KRASG12V(ON) inhibitors produce deep, durable, and dose-dependent suppression of tumor RAS pathway activation in vivo following oral administration. An extended duration of tumor pharmacodynamic activity, relative to plasma exposure, is observed that likely reflects retention of the inhibitors in tumor tissue due to high affinity binding to CypA. In human tumor xenograft models of KRASG12V mutant NSCLC, CRC and pancreatic cancers, oral administration of KRASG12V(ON) inhibitors is well-tolerated and drives profound and durable tumor regressions, with complete responses in some animals. KRASG12V(ON) inhibitors also downregulate immune checkpoint proteins PD-L1 and CD73 on KRASG12V mutant cancer cells, changes which can support enhanced anti-tumor immunity. The ability to target the GTP-bound form of mutant KRASG12V permits a broad array of combination opportunities in cancer types where single agent KRASG12V(ON) inhibition may be insufficient, for example with agents targeting pathway nodes both upstream (e.g. SHP2, SOS1) and downstream (e.g. MEK, ERK) of RAS, as well as parallel pathways (e.g. mTORC1). Tri-complex inhibitors that target KRASG12V(ON) are predicted to combat escape mechanisms in RAS-addicted cancer cells characterized by an increased pool of activated KRASG12V(ON). These inhibitors may lead to an attractive, targeted therapeutic option for the treatment of RAS-addicted cancers with a very high unmet medical need.
Citation Format: Elena Koltun, Jim Cregg, Meghan A. Rice, Dan M. Whalen, Rebecca Freilich, Jingjing Jiang, Richard Hansen, Alun Bermingham, John E. Knox, Jay Dinglasan, Kyle Seamon, Cristina Blaj, Stephanie S. Chang, Yang Liu, Jun Huang, Kang-Jye Chou, Laura McDowell, Bianca J. Lee, David Wildes, Zhengping Wang, Mallika Singh, Adrian L. Gill, Jacqueline A. Smith. First-in-class, orally bioavailable KRASG12V(ON) tri-complex inhibitors, as single agents and in combinations, drive profound anti-tumor activity in preclinical models of KRASG12V mutant cancers abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1260.
Abstract Patients with advanced cancers harboring activating mutations in RAS, particularly those with non-small cell lung cancer, often develop brain metastases leading to increased morbidity and ...mortality. KRASG12V is the second most frequent RAS mutation in RAS-addicted cancers, including pancreatic cancer (34 %), colorectal cancer (21 %), and non-small cell lung cancer (19%). RMC-5127 is an orally bioavailable, mutant-selective tri-complex inhibitor of the GTP-bound (ON) form of RASG12V. RMC-5127 non-covalently binds to an abundant intracellular chaperone protein cyclophilin A (CypA), resulting in a binary complex that engages RASG12V(ON) to form a high-affinity tri-complex that sterically inhibits RAS binding to effectors. RMC-5127 drove deep suppression of RAS pathway activity, inhibited cell proliferation, and induced apoptosis in a panel of KRASG12V mutant human cancer cells in vitro but only caused submaximal inhibition in the panel of K/N/HRAS wildtype cancer cells, indicative of selectivity for KRASG12V over K/N/HRAS wildtype. Repeated oral dosing of RMC-5127 resulted in profound and durable anti-tumor activity in subcutaneous CDX and PDX models of KRASG12V mutant NSCLC, PDAC, and CRC in vivo. Dose-dependent exposure of RMC-5127 was observed in the whole brain of naïve mice, indicating the compound is brain penetrant. An intracranial xenograft model of KRASG12V tumors was established in immunodeficient mice to assess the CNS anti-tumor activity of RMC-5127. The intracranial tumor exposure of RMC-5127 was comparable with that observed in the whole brains of naïve mice and was sufficient to drive robust pharmacodynamic responses in the brain tumor. Moreover, RMC-5127 exhibited profound and durable anti-tumor activity in the intracranial model, with tumor regressions at well-tolerated doses. The anti-tumor activity of RMC-5127 in intracranial tumors was consistent with that in subcutaneous tumors at equivalent tumor exposures. In conclusion, these preclinical data demonstrate that RMC-5127 is a CNS-penetrant RASG12V(ON) inhibitor and support further study to determine the potential to benefit patients with advanced RASG12V-mutated cancers, including those that have developed or are at risk of developing brain metastases. Citation Format: Zhe Chen, Andre Eriksson, Bianca Lee, Jay Dinglasan, Nilufar Montazer, Jim Cregg, Anne Edwards, Kate Sanders, Jacqueline A. Smith, David Wildes, Mallika Singh, Zhican Wang, Jingjing Jiang. RMC-5127, a first-in-class, orally bioavailable mutant-selective RASG12V(ON) inhibitor is central nervous system (CNS)-penetrant and demonstrates anti-tumor activity in a preclinical intracranial xenograft model abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3340.
Abstract
The KRASG12V mutation is the second most common oncogenic RAS mutation and is frequently observed in pancreatic, lung, and colorectal cancers. Developing a selective inhibitor of KRASG12V ...presents significant drug discovery challenges. The intrinsic GTP hydrolysis rate of KRASG12V is about 12-fold lower than that of KRASG12C, further biasing the cellular KRASG12V pool to the active, GTP-bound (“RAS(ON)”) state and emphasizing the importance of targeting the KRASG12V(ON) state for maximal suppression of this oncogenic driver. Additionally, achieving selectivity over wild-type RAS with small molecules is difficult because the valine residue introduced by KRASG12V is neither amenable to covalent inhibition nor to formation of polar, non-covalent interactions. We have previously applied our tri-complex inhibitor platform, which uses chemical re-remodeling of the cellular chaperone cyclophilin A (CypA) in order to bind to undruggable surfaces, to design mutant-selective inhibitors targeting KRASG12C, KRASG13C, KRASG12D, and KRASQ61H, in addition to the RASMULTI inhibitor RMC-6236. Here, we describe RM-048, a potent, selective, and oral tri-complex inhibitor of KRASG12V(ON). RM-048 binds to CypA with high affinity to form a binary complex. Binding to CypA creates a neomorphic interface that forms a selective, high-affinity, non-covalent interaction with KRASG12V(ON). The resulting tri-complex sterically blocks effector binding to KRASG12V(ON), thereby inhibiting downstream signaling. RM-048 potently suppressed ERK phosphorylation and proliferation in KRASG12V mutant cancer cells. In preclinical species, RM-048 showed good bioavailability, dose-proportional exposure, and low clearance, allowing for oral dosing. In human xenograft tumors harboring KRASG12V mutations, a single dose of RM-048 induced dose-dependent, deep, and durable suppression of RAS pathway signaling in vivo. Repeated daily oral administration of RM-048 was well tolerated and demonstrated profound anti-tumor activity, driving tumor regressions across a panel of KRASG12V xenograft models, including NSCLC, PDAC, and CRC models. RM-048 complements the mutant-selective tri-complex KRAS(ON) inhibitors RMC-6291 (KRASG12C) and RMC-9805 (KRASG12D) by potentially providing a mutant-selective inhibitor option for patients with tumors harboring one of the most frequent RAS mutations. Preclinical combination studies with RAS companion inhibitors, including the RASMULTI inhibitor RMC-6236, are ongoing.
Citation Format: Bianca J Lee, Jim Cregg, Anne Edwards, Jerry Chen, Andre Eriksson, Emily Tonogai, Aidan Tomlinson, Kyle Seamon, Mariela Moreno Ayala, Nataliya Tovbis Shifrin, Nilufar Montazer, Kate Sanders, Jun Huang, Kang-Jye Chou, Benjamin Madej, Yang Liu, Zhican Wang, Zhengping Wang, John Knox, Elena Koltun, Jingjing Jiang, Adrian Gill, Jacqueline A.M. Smith. Selective inhibition of the active state of KRASG12V with the non-covalent, tri-complex inhibitor RM-048 abstract. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B137.
Abstract
The KRASG12C mutation occurs in 11 - 14% of non-small cell lung cancers, ~4% of colorectal cancers, and ~2% of pancreatic cancers in the U.S., and drives these cancers by shifting the ...cellular equilibrium of KRAS towards the GTP-bound, active state, KRASG12C(ON). The resulting increased levels of KRASG12C(ON) in turn increase signaling output to initiate and support the oncogenic state. RMC-6291 is a potent, orally bioavailable inhibitor of KRASG12C(ON) that forms a tri-complex within tumor cells along with KRASG12C(ON) and cyclophilin A (CypA), driving a near-immediate disruption of RAS effector binding and extinction of KRASG12C(ON) signaling. RMC-6291 treatment produces deep and durable suppression of RAS pathway activity in KRASG12C tumor models and drives profound tumor regressions in vivo. In a mouse clinical trial with a representative panel of xenograft models of KRASG12C NSCLC, RMC-6291 outperformed adagrasib, displaying a potential ‘best-in-class’ profile with an increased number of responses, greater depth of tumor regressions and improved durability of responses. Thus, RMC-6291 is a clinical stage inhibitor of KRASG12C(ON) that potentially overcomes limitations of first-generation KRASG12C(OFF) inhibitors.
Citation Format: Jim Cregg, R J. Nichols, Y C. Yang, C J. Schulze, Z Wang, R Dua, J Jiang, N Nasholm, J E. Knox, K Seamon, M Longhi, A Tomlinson, K Chou, S Li, D P. Wildes, M Singh, E S. Koltun, A L. Gill, J A. Smith. Discovery of RMC-6291, a tri-complex KRASG12C(ON) inhibitor abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr ND07.
Abstract
The clinical activity of KRASG12C(OFF) inhibitors has validated KRASG12C as an oncogenic driver in human cancers and demonstrated the power of targeting cysteine mutations with covalent ...inhibitors. A second oncogenic RAS cysteine mutation, KRASG13C, is found predominantly in non-small cell lung cancer (NSCLC), with > 2,700 new cases reported in the USA in 2020 but relatively little is known about the biochemical and cellular properties of KRASG13C. KRASG12C-selective inhibitors are not active against KRASG13C and currently there are no direct, targeted inhibitors available for patients with KRASG13C-driven cancers. We report the development of a potent, selective, orally bioavailable tri-complex inhibitor of KRASG13C. Using chemical and genetic approaches, we describe unique properties of KRASG13C and their influence on oncogenic signaling and the co-mutational landscape of KRASG13C mutant tumors. These insights provide the basis for targeting KRASG13C NSCLC in the clinic and shape future combination strategies.
RM-041 is a potent and selective covalent inhibitor of KRASG13C(ON) with attractive drug-like properties. RM-041 forms a tri-complex between KRASG13C(ON) and cyclophilin A (CypA), a highly abundant intracellular chaperone protein. The assembled non-covalent tri-complex rapidly prevents KRASG13C(ON) signaling via steric blockade of RAS effector binding, and covalent engagement with Cys-13 converts the inactive assembly into an irreversibly inhibited complex. In cells, RM-041 covalently modifies KRASG13C(ON), drives deep suppression of RAS pathway signaling, and inhibits cell proliferation in KRASG13C mutant cancer cell lines. In KRASG13C xenograft tumor models, oral administration of RM-041 produces deep and durable suppression of RAS pathway activity and induces tumor regressions in vivo at well-tolerated doses.
Compared to KRASG12C, KRASG13C exhibits a higher rate of spontaneous nucleotide exchange, reducing its dependence on GEF reloading and sensitivity to upstream inhibitors (e.g., SHP2 and SOS1) and underscoring the need for direct KRASG13C inhibition. In addition, KRASG13C is uniquely sensitive to select GAPs, including NF1. In line with this observation, an analysis of the co-mutational landscape of KRASG13C patient tumor samples revealed a high prevalence of NF1LOF mutation, likely resulting in enhanced wild-type RAS signaling. Our preclinical combination data support a therapeutic strategy of mutant selective KRASG13C inhibition with RM-041 and co-targeting an upstream node, such as SHP2, to attenuate cooperative wild-type RAS signaling. In summary, RM-041 is a first-in-class, mutant-selective, oral, tricomplex inhibitor of KRASG13C(ON) with the potential to address an unmet need in patients with KRASG13C mutant cancer, supporting the advancement of RM-041 towards clinical evaluation.
Citation Format: Christopher J. Schulze, Jim Cregg, Kyle J. Seamon, Yu Chi Yang, Zhican Wang, Lindsay S. Garrenton, Alun Bermingham, John E. Knox, Aidan Tomlinson, Kang-Jye Chou, Shaoling Li, David P. Wildes, Mallika Singh, Elena S. Koltun, Adrian L. Gill, Robert J. Nichols, Jacqueline A. Smith. A first-in-class tri-complex KRASG13C(ON) inhibitor validates therapeutic targeting of KRASG13Cand drives tumor regressions in preclinical models abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3598.
Abstract
Mutant RAS is common in pancreatic carcinoma (PDAC), non-small cell lung cancer (NSCLC) and colorectal cancer (CRC) and exists predominantly in the GTP-bound (RAS(ON)) state, leading to ...excessive downstream oncogenic signaling. KRASG12C(OFF) inhibitors have provided clinical proof of concept for targeting mutant KRAS. Preclinical data suggests inhibition of RAS(ON) may be a superior therapeutic strategy. In addition, KRASG12 mutations such as KRASG12D and KRASG12V remain unserved.RMC-6236 is a first-in-class, potent, oral tri-complex RASMULTI(ON) small molecule inhibitor designed to treat cancers driven by a variety of RAS mutations. RMC-6236 non-covalently binds to an abundant intracellular chaperone protein, cyclophilin A (CypA), resulting in a binary complex that engages RAS(ON) to form a high-affinity, RAS-selective tri-complex that sterically inhibits RAS binding to effectors. Exposure to RMC-6236 suppressed ERK phosphorylation and cell growth, and induced apoptosis in multiple human RAS-addicted cancer cell lines in vitro.RMC-6236 induced dose-dependent, deep, and durable suppression of RAS pathway activation up to 48 hours in preclinical xenograft models in vivo. Prolonged exposure in tumors was observed relative to blood and various healthy tissues, likely mediated by high affinity binding of RMC-6236 to tumor CypA.RMC-6236 at tolerable doses induced profound and durable tumor regressions in multiple cell line-derived (CDX) and patient-derived (PDX) RASMUT xenograft models, including NSCLC, CRC and PDAC. Anti-tumor activity was particularly notable in KRAS position 12 (G12X) mutant tumors, particularly KRASG12D, KRASG12V, and KRASG12R, with significant tumor regressions observed. Tumor growth inhibition was durable even in tumors that did not regress. Intermittent scheduling of RMC-6236 was active and permitted a higher dose intensity than daily dosing.RMC-6236 promoted anti-tumor immunity in vivo and was additive with anti-PD1 antibodies, driving durable complete responses and immunologic memory in a KRAS mutant CRC model. Furthermore, RMC-6236 treatment reversed oncogenic RAS-driven immune evasion mechanisms in a checkpoint blockade refractory KRAS mutant model, significantly transforming the tumor microenvironment in favor of anti-tumor immunity.These preclinical results support the inclusion of NSCLC, PDAC, and CRC patients in our planned clinical trial of RMC-6236 in patients with KRASG12X advanced solid tumors.
Citation Format: Elena S. Koltun, Meghan A. Rice, W. Clay Gustafson, David Wilds, Jingjing Jiang, Bianca J. Lee, Zhengping Wang, Stephanie Chang, Mike Flagella, Yunming Mu, Nuntana Dinglasan, Nicole Nasholm, James W. Evans, Yingyun Wang, Kyle Seamon, Yang Liu, Cristina Blaj, John Knox, Rebecca Freilich, Elsa Quintana, Jim Cregg, Alun Bermingham, Adrian L. Gill, Jacqueline Am Smith, Mallika Singh. Direct targeting of KRASG12X mutant cancers with RMC-6236, a first-in-class, RAS-selective, orally bioavailable, tri-complex RASMULTI(ON) inhibitor abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3597.
