Highlight
KRAS mutations, especially non-G12C subtypes, represent a significant challenge in NSCLC targeted therapy due to limited effective options.
MEK inhibitor trametinib induces adaptive resistance via feedback activation of multiple receptor tyrosine kinases (RTKs).
Pan-RTK inhibitor anlotinib effectively blocks this adaptive resistance when combined with trametinib in preclinical NSCLC models.
A clinical trial of 33 advanced non-G12C KRAS-mutant NSCLC patients demonstrated promising efficacy and manageable safety with this combination therapy.
Background
Non-small cell lung cancer (NSCLC) remains a leading cause of cancer-related mortality globally. Oncogenic mutations in the KRAS gene, particularly in codons such as G12 and Q61, drive tumorigenesis by constitutively activating downstream pathways like the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK) and phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) cascades. While targeted therapies against the KRASG12C variant have recently emerged, the majority of KRAS mutations (including G12D, G12V, G12S, Q61H) lack effective targeted treatments, constituting a significant unmet clinical need. MEK inhibitors, such as trametinib, have been explored but show limited clinical success due to adaptive resistance mechanisms, including feedback activation of receptor tyrosine kinases (RTKs) that reactivate downstream proliferative signaling. Understanding and overcoming these resistance pathways are pivotal for therapeutic advancement in KRAS-mutant NSCLC.
Study Design
This investigation encompassed both mechanistic preclinical studies and a phase I clinical trial. Preclinical experiments involved multiple KRAS-mutant NSCLC cell lines treated with the MEK inhibitor trametinib, alone or in combination with the pan-RTK inhibitor anlotinib. Cellular assays assessed proliferation, apoptosis, cell cycle status, migration, and invasion, while molecular analyses evaluated RTK activation and downstream signaling. In vivo xenograft models were utilized to verify therapeutic efficacy.
A phase I clinical trial (NCT04967079) enrolled 33 patients with advanced non-G12C KRAS-mutant NSCLC to evaluate the safety, tolerated dose, and preliminary efficacy of combined trametinib and anlotinib therapy. Phase Ia involved dose escalation to determine the recommended phase 2 dose (RP2D), while phase Ib served as an expansion cohort to assess the objective response rate (ORR), progression-free survival (PFS), overall survival (OS), disease control rate (DCR), and treatment-related adverse events.
Key Findings
Preclinical Mechanisms and Efficacy
Trametinib monotherapy inhibited short-term proliferation of KRAS-mutant NSCLC cells by targeting the MEK/ERK pathway but induced rapid adaptive resistance characterized by reactivation of ERK phosphorylation and increased AKT phosphorylation over prolonged exposure. Transcriptomic and proteomic analyses revealed feedback activation of multiple RTKs, including PDGFR, FGFR, c-KIT, EGFR, ERBB3, and VEGFR, which were implicated in resistance.
Anlotinib monotherapy demonstrated modest antitumor activity against KRAS-mutant NSCLC in retrospective clinical data and in vitro models, with a median PFS of approximately 4.2 months. However, the combination of trametinib with anlotinib effectively blocked the trametinib-induced RTK activation, sustained inhibition of ERK and AKT signaling, and enhanced antiproliferative effects across various KRAS mutation subtypes (G12C, G12D, G12V, G12S, Q61H). This synergy was supported by decreased expression of proliferation and cell cycle markers (CCND1, CCNE2, CDK2), increased apoptosis, and repression of the oncogene c-MYC. Enhanced tumor regression was observed in multiple xenograft models without significant toxicity.
Protein chip assays identified insulin-like growth factor binding protein 2 (IGFBP2) as a critical mediator of the combined therapy’s antitumor effect. Downregulation of IGFBP2 correlated with suppression of RTK signaling, while supplementation with exogenous IGFBP2 reversed these effects, implicating a MEK/RTK-IGFBP2-RTK signaling loop underpinning the synergy.
Clinical Safety and Efficacy
Phase Ia enrolled 13 patients, defining the RP2D as trametinib 2 mg plus anlotinib 8 mg daily. The cohort achieved an ORR of 69.2% (95% CI: 38.6–90.9), median PFS of 6.9 months, and DCR of 92%. Grade 3 or higher adverse events (AEs) occurred in 23%, primarily rash, diarrhea, and hypertension.
Phase Ib included 20 patients treated at RP2D, demonstrating an ORR of 65% (95% CI: 40.8–84.6), median PFS of 11.5 months, median OS of 15.5 months, and a DCR of 100%. The median duration of response was 9.3 months. Grade ≥3 AEs were reported in 35%, with manageable toxicities.
An integrated analysis of 33 patients from phases Ia and Ib showed sustained clinical benefit, with an ORR of approximately 66.7%, median PFS of 10.3 months, and median OS of 19.7 months. Subgroup analyses suggested favorable responses across various KRAS mutation subtypes and clinical characteristics.
The combination therapy’s toxicity profile was acceptable and manageable, with no grade 4 or 5 AEs observed, and no enhanced toxicity compared to monotherapy regimens. The study reported AEs consistent with those known for trametinib and anlotinib.
Expert Commentary
nThis study provides compelling preclinical and clinical evidence supporting the combined inhibition of MEK and RTKs as an effective therapeutic strategy in KRAS-mutant NSCLC beyond the G12C subtype. The mechanistic insights into adaptive resistance via multi-RTK activation and the critical involvement of IGFBP2 enhance the biological plausibility of this approach.
Previous clinical trials with MEK inhibitors alone or combined with chemotherapy failed to achieve substantive benefit, often due to compensatory RTK pathway activation. The pan-RTK inhibitory profile of anlotinib uniquely positions it to suppress this bypass mechanism, accounting for the improved efficacy observed here.
While the results are promising, the relatively small patient cohort and lack of a randomized control arm warrant cautious interpretation. Further phase II/III studies with larger, diverse populations are essential to validate clinical benefit and to optimize patient selection, dosing, and management of adverse events.
The potential for combining MEK/RTK inhibition with emerging KRAS-targeted agents, immunotherapeutics, or other pathway inhibitors represents an exciting avenue for future investigation.
Conclusion
The combination of the MEK inhibitor trametinib and the pan-RTK inhibitor anlotinib exhibits potent synergistic antitumor activity in KRAS-mutant NSCLC through sustained suppression of adaptive resistance pathways, mediated in part by the MEK/RTK-IGFBP2 axis. Clinical evaluation demonstrates encouraging efficacy and manageable toxicity in advanced non-G12C KRAS-mutant NSCLC patients. These findings warrant further large-scale clinical trials and offer a promising therapeutic option addressing a critical unmet need in lung cancer treatment.
References
nLu J, Hu M, Zhao Y, Chu T, Zhang W, Zhou Y, Cai X, Wu J, Hu L, Shi C, Xiong L, Gu A, Wang H, Zhang Y, Lou Y, Zhong R, Gao Z, Liu H, Zhou C, Wu Y, Zhu L, Zhong H, Ji H, Han B. Coinhibition of the MEK/RTK pathway has high therapeutic efficacy in KRAS-mutant non-small cell lung cancer. Signal Transduct Target Ther. 2025 Sep 12;10(1):299. doi: 10.1038/s41392-025-02382-w IF: 52.7 Q1 .
