BRAF/MEK inhibition in NSCLC: mechanisms of resistance and how to overcome it

Mechanisms of primary resistance to immune checkpoint inhibitors in NSCLC

Immune checkpoint inhibitors (ICIs) redefined the therapeutics of non-small cell lung cancer (NSCLC), leading to significant survival benefits and unprecedented durable responses. However, the majority of the patients develop resistance to ICIs, either primary or acquired. Establishing a definition of primary resistance to ICIs in different clinical scenarios is challenging and remains a work in progress due to the changing landscape of ICI-based regimens, mainly in the setting of early-stage NSCLC. The mechanisms of primary resistance to ICIs in patients with NSCLC include a plethora of pathways involving a cross-talk of the tumor cells, the tumor microenvironment and the host, leading to the development of an immunosuppressive phenotype. The optimal management of patients with NSCLC following primary resistance to ICIs represents a significant challenge in current thoracic oncology. Research in this field includes exploring other immunotherapeutic approaches, such as cancer vaccines, and investigating novel antibody-drug conjugates in patients with NSCLC.

Oncogenic Mutations and the Tumor Microenvironment: Drivers of Non-Small Cell Lung Cancer Progression

BACKGROUND/OBJECTIVES

Non-small cell lung cancer (NSCLC) is a major cause of cancer-related deaths globally. The study focuses on understanding the interplay between genetic mutations, cancer stem cells (CSCs), and the tumor microenvironment (TME) in driving NSCLC progression, resistance to therapies, and relapse.

METHODS

A systematic search was conducted in PubMed and Scopus databases to identify significant and valuable studies relevant to NSCLC, focusing on genetic mutations, CSCs, and the TME. Articles were selected based on their relevance, methodological severity, date of publication, and scientific soundness related to NSCLC biology and therapeutic strategies. This review synthesized findings from these sources to highlight key mechanisms and potential therapeutic interventions.

RESULTS

Mutations in critical genes in KRAS, EGFR, TP53, and other key genes interfere with stem cell regulation, promoting CSC-like behavior, resistance to therapy, and immune evasion. The tumor microenvironment (TME), including immune cells, fibroblasts, and extracellular matrix components, further supports tumor growth and reduction in treatment efficacy. Promising strategies, including CSC targeting, TME modulation, and the development of novel biomarkers, have shown potential in preclinical and clinical studies.

CONCLUSIONS

The association between genetic alterations, CSCs, the TME, and other cellular pathways-including cell metabolism and immune evasion-plays a crucial role in therapy resistance, highlighting the need for comprehensive treatment strategies. The combination of genomic profiling with TME-targeting therapies could lead to personalized treatment approaches, offering hope for better clinical outcomes and reduced mortality in NSCLC patients.

Canonical and noncanonical NOTCH signaling in the nongenetic resistance of cancer: distinct and concerted control

Therapeutic resistance in cancer is responsible for numerous cancer deaths in clinical practice. While target mutations are well recognized as the basis of genetic resistance to targeted therapy, nontarget mutation resistance (or nongenetic resistance) remains poorly characterized. Despite its complex and unintegrated mechanisms in the literature, nongenetic resistance is considered from our perspective to be a collective response of innate or acquired resistant subpopulations in heterogeneous tumors to therapy. These subpopulations, e.g., cancer stem-like cells, cancer cells with epithelial-to-mesenchymal transition, and drug-tolerant persisters, are protected by their resistance traits at cellular and molecular levels. This review summarizes recent advances in the research on resistant populations and their resistance traits. NOTCH signaling, as a central regulator of nongenetic resistance, is discussed with a special focus on its canonical maintenance of resistant cancer cells and noncanonical regulation of their resistance traits. This novel view of canonical and noncanonical NOTCH signaling pathways is translated into our proposal of reshaping therapeutic strategies targeting NOTCH signaling in resistant cancer cells. We hope that this review will lead researchers to study the canonical and noncanonical arms of NOTCH signaling as an integrated resistant mechanism, thus promoting the development of innovative therapeutic strategies.

Optimizing Osimertinib for NSCLC: Targeting Resistance and Exploring Combination Therapeutics

Non-small-cell lung cancer (NSCLC) is a leading cause of cancer-related deaths worldwide, with epidermal growth factor receptor (EGFR) mutations present in a substantial proportion of patients. Third-generation EGFR tyrosine kinase inhibitors (EGFR TKI), exemplified by osimertinib, have dramatically improved outcomes by effectively targeting the T790M mutation-a primary driver of acquired resistance to earlier-generation EGFR TKI. Despite these successes, resistance to third-generation EGFR TKIs inevitably emerges. Mechanisms include on-target mutations such as C797S, activation of alternative pathways like MET amplification, histologic transformations, and intricate tumor microenvironment (TME) alterations. These resistance pathways are compounded by challenges in tolerability, adverse events, and tumor heterogeneity. In light of these hurdles, this review examines the evolving landscape of combination therapies designed to enhance or prolong the effectiveness of third-generation EGFR TKIs. We explore key strategies that pair osimertinib with radiotherapy, anti-angiogenic agents, immune checkpoint inhibitors, and other molecularly targeted drugs, and we discuss the biological rationale, preclinical evidence, and clinical trial data supporting these approaches. Emphasis is placed on how these combinations may circumvent diverse resistance mechanisms, improve survival, and maintain a favorable safety profile. By integrating the latest findings, this review aims to guide clinicians and researchers toward more individualized and durable treatment options, ultimately enhancing both survival and quality of life for patients with EGFR-mutated NSCLC.

Navigating the complexity of BRAF mutations in non-small cell lung cancer: current insights and future prospects

There are many challenges that are faced in the treatment of Non-Small Cell Lung Cancer (NSCLC) due to the complexities associated with the tumor. Association of different types of mutations are one of the major complexities. Among these mutations, BRAF mutations are significantly gathering more attention due to their impact on disease progression and therapeutic response. This review provides an analysis of the current understanding of BRAF mutations in NSCLC, focusing on the molecular intricacies, clinical implications, and therapeutic advancements. The article explores the diverse spectrum of BRAF mutations, highlighting the prevalence of specific mutations such as V600E and non-V600E alterations. The review also highlights the intricate signalling pathways influenced by BRAF mutations, shedding light on their role in tumorigenesis and metastasis. Therapeutically, we critically evaluate the existing targeted therapies tailored for BRAF-mutant NSCLC, addressing their efficacy, limitations, and emerging resistance mechanisms. Furthermore, we outline ongoing clinical trials and promising investigational agents that hold potential for reshaping the treatment of NSCLC. This review provides comprehensive current information about the role of BRAF mutations in NSCLC. Understanding the molecular diversity, clinical implications, and therapeutic strategies associated with BRAF-mutant NSCLC is crucial for optimizing patient outcomes and steering the direction of future research in this evolving field.

MET alterations as resistance mechanisms of dabrafenib-trametinib in BRAF p.V600E mutated non-small cell lung cancer patient

The combination of BRAF and MEK inhibitors demonstrated significant clinical benefit in patients with BRAF-mutant non-small cell lung cancer (NSCLC). However, the molecular mechanisms of acquired resistance to BRAF and MEK inhibition in NSCLC are still unknown. Herein, we report a case of a 76-year-old man with a history of smoking who was diagnosed with BRAF V600E-mutant lung adenocarcinoma (PD-L1 > 50%) and subsequently candidate to first-line therapy with pembrolizumab. After 18 months since the start of immunotherapy, computed tomography scan showed disease progression and a second-line therapy with dabrafenib and trametinib was initiated. Seven months later, due to a suspect disease progression, a left supraclavicular lymphadenectomy was performed and next-generation sequencing analysis revealed the appearance of MET exon 14 skipping mutation, while fluorescence in situ hybridization analysis showed MET amplification. The patient is still on BRAF and MEK inhibitor treatment. Our case highlights the relevance of performing tumor tissue rebiopsy at the time of progression during treatment with BRAF/MEK inhibition with the aim of identifying putative mechanisms of resistance.

Pathways and targeting avenues of BRAF in non-small cell lung cancer

INTRODUCTION

BRAF is a serine-threonine kinase implicated in the regulation of MAPK signaling cascade. BRAF mutation-driven activation occurs in approximately 2-4% of treatment-naive non-small cell carcinomas (NSCLCs). BRAF upregulation is also often observed in tumors with acquired resistance to receptor tyrosine kinase inhibitors (TKIs).

AREAS COVERED

This review describes the spectrum of BRAF mutations and their functional roles, discusses treatment options available for BRAF p.V600 and non-V600 mutated NSCLCs, and identifies some gaps in the current knowledge.

EXPERT OPINION

Administration of combined BRAF/MEK inhibitors usually produces significant, although often a short-term, benefit to NSCLC patients with BRAF V600 (class 1) mutations. There are no established treatments for BRAF class 2 (L597, K601, G464, G469A/V/R/S, fusions, etc.) and class 3 (D594, G596, G466, etc.) mutants, which account for up to two-thirds of BRAF-driven NSCLCs. Many important issues related to the use of immune therapy for the management of BRAF-mutated NSCLC deserve further investigation. The rare occurrence of BRAF mutations in NSCLC is compensated by high overall incidence of lung cancer disease; therefore, clinical studies on BRAF-associated NSCLC are feasible.

Enhancing Lung Cancer Care in Portugal: Bridging Gaps for Improved Patient Outcomes

Lung cancer has the highest incidence and cancer-related mortality worldwide. In Portugal, it ranks as the fourth most common cancer, with nearly 6000 new cases being diagnosed every year. Lung cancer is the main cause of cancer-related death among males and the third cause of cancer-related death in females. Despite the globally accepted guidelines and recommendations for what would be the ideal path for a lung cancer patient, several challenges occur in real clinical management across the world. The recommendations emphasize the importance of adequate screening of high-risk individuals, a precise tumour biopsy, and an accurate final diagnosis to confirm the neoplastic nature of the nodule. A detailed histological classification of the lung tumour type and a comprehensive molecular characterization are of utmost importance for the selection of an efficacious and patient-directed therapeutic approach. However, in the context of the Portuguese clinical organization and the national healthcare system, there are still several gaps in the ideal pathway for a lung cancer patient, involving aspects ranging from the absence of a national lung cancer screening programme through difficulties in histological diagnosis and molecular characterization to challenges in therapeutic approaches. In this manuscript, we address the most relevant weaknesses, presenting several proposals for potential solutions to improve the management of lung cancer patients, helping to decisively improve their overall survival and quality of life.

Emerging Therapies in Kirsten Rat Sarcoma Virus (+) Non-Small-Cell Lung Cancer

Kirsten rat sarcoma virus (KRAS) is the most frequently found oncogene in human cancers, including non-small-cell lung cancer (NSCLC). For many years, KRAS was considered "undruggable" due to its structure and difficult targeting. However, the discovery of the switch II region in the KRAS-G12C-mutated protein has changed the therapeutic landscape with the design and development of novel direct KRAS-G12C inhibitors. Sotorasib and adagrasib are FDA-approved targeted agents for pre-treated patients with KRAS-G12C-mutated NSCLC. Despite promising results, the efficacy of these novel inhibitors is limited by mechanisms of resistance. Ongoing studies are evaluating combination strategies for overcoming resistance. In this review, we summarize the biology of the KRAS protein and the characteristics of KRAS mutations. We then present current and emerging therapeutic approaches for targeting KRAS mutation subtypes intending to provide individualized treatment for lung cancer harboring this challenging driver mutation.

Resistance to BRAF inhibition explored through single circulating tumour cell molecular profiling in BRAF-mutant non-small-cell lung cancer

BACKGROUND

Resistance mechanisms to combination therapy with dabrafenib plus trametinib remain poorly understood in patients with BRAFV600E-mutant advanced non-small-cell lung cancer (NSCLC). We examined resistance to BRAF inhibition by single CTC sequencing in BRAFV600E-mutant NSCLC.

METHODS

CTCs and cfDNA were examined in seven BRAFV600E-mutant NSCLC patients at failure to treatment. Matched tumour tissue was available for four patients. Single CTCs were isolated by fluorescence-activated cell sorting following enrichment and immunofluorescence (Hoechst 33342/CD45/pan-cytokeratins) and sequenced for mutation and copy number-alteration (CNA) analyses.

RESULTS

BRAFV600E was found in 4/4 tumour biopsies and 5/7 cfDNA samples. CTC mutations were mostly found in MAPK-independent pathways and only 1/26 CTCs were BRAFV600E mutated. CTC profiles encompassed the majority of matched tumour biopsy CNAs but 72.5% to 84.5% of CTC CNAs were exclusive to CTCs. Extensive diversity, involving MAPK, MAPK-related, cell cycle, DNA repair and immune response pathways, was observed in CTCs and missed by analyses on tumour biopsies and cfDNA. Driver alterations in clinically relevant genes were recurrent in CTCs.

CONCLUSIONS

Resistance was not driven by BRAFV600E-mutant CTCs. Extensive tumour genomic heterogeneity was found in CTCs compared to tumour biopsies and cfDNA at failure to BRAF inhibition, in BRAFV600E-mutant NSCLC, including relevant alterations that may represent potential treatment opportunities.

Nanomedicine Combats Drug Resistance in Lung Cancer

Lung cancer is the second most prevalent cancer and the leading cause of cancer-related death worldwide. Surgery, chemotherapy, molecular targeted therapy, immunotherapy, and radiotherapy are currently available as treatment methods. However, drug resistance is a significant factor in the failure of lung cancer treatments. Novel therapeutics have been exploited to address complicated resistance mechanisms of lung cancer and the advancement of nanomedicine is extremely promising in terms of overcoming drug resistance. Nanomedicine equipped with multifunctional and tunable physiochemical properties in alignment with tumor genetic profiles can achieve precise, safe, and effective treatment while minimizing or eradicating drug resistance in cancer. Here, this work reviews the discovered resistance mechanisms for lung cancer chemotherapy, molecular targeted therapy, immunotherapy, and radiotherapy, and outlines novel strategies for the development of nanomedicine against drug resistance. This work focuses on engineering design, customized delivery, current challenges, and clinical translation of nanomedicine in the application of resistant lung cancer.

Cutaneous adverse reactions resulting from targeted cancer therapies: histopathologic and clinical findings

Targeted cancer treatments-designed to interfere with specific molecular signals responsible for tumor survival and progression-have shown benefit over conventional chemotherapies but may lead to diverse cutaneous adverse effects. This review highlights clinically significant dermatologic toxicities and their associated histopathologic findings, resulting from various targeted cancer drugs. Case reports and series, clinical trials, reviews, and meta-analyses are included for analysis and summarized herein. Cutaneous side effects resulting from targeted cancer therapies were reported with incidences as high as 90% for certain medications, and reactions are often predictable based on mechanism(s) of action of a given drug. Common and important reaction patterns included: acneiform eruptions, neutrophilic dermatoses, hand-foot skin reaction, secondary cutaneous malignancies, and alopecia. Clinical and histopathologic recognition of these toxicities remains impactful for patient care.

Real-World Experience in Treatment of Patients with Non-Small-Cell Lung Cancer with BRAF or cMET Exon 14 Skipping Mutations

BRAF and cMET exon 14 skipping are rare mutations of NSCLC. The treatment sequence in these cases for the first and second line is not clear. An international registry was created for patients with advanced NSCLC harboring BRAF or cMET exon 14 skipping mutations, diagnosed from January 2017 to June 2022. Clinicopathological and molecular data and treatment patterns were recorded. Data on 58 patients, from eight centers across five countries, were included in the final analysis. We found that 40 patients had the cMET exon 14 skipping mutation and 18 had the BRAF V600E mutation. In total, 53 and 28 patients received first- and second-line treatments, respectively, among which 52.8% received targeted therapy (TT) in the first line and 53.5% in the second line. The overall response rate (ORR) and disease control rate (DCR) for first-line treatment with TT vs. other treatment such as immune checkpoint inhibitors ± chemotherapy (IO ± CT) were 55.6% vs. 21.7% (p = 0.0084) and 66.7% vs. 39.1% (p = 0.04), respectively. The type of treatment in first-line TT vs. other affected time to treatment discontinuation (TTD) was 11.6 m vs. 4.6 m (p= 0.006). The overall survival for the whole group was 15.4 m and was not statistically affected by the type of treatment (19.2 m vs. 13.5 m; p = 0.83).

Phase II, Open-Label Study of Encorafenib Plus Binimetinib in Patients With BRAFV600-Mutant Metastatic Non-Small-Cell Lung Cancer

PURPOSE

The combination of encorafenib (BRAF inhibitor) plus binimetinib (MEK inhibitor) has demonstrated clinical efficacy with an acceptable safety profile in patients with BRAFV600E/K-mutant metastatic melanoma. We evaluated the efficacy and safety of encorafenib plus binimetinib in patients with BRAFV600E-mutant metastatic non-small-cell lung cancer (NSCLC).

METHODS

In this ongoing, open-label, single-arm, phase II study, patients with BRAFV600E-mutant metastatic NSCLC received oral encorafenib 450 mg once daily plus binimetinib 45 mg twice daily in 28-day cycles. The primary end point was confirmed objective response rate (ORR) by independent radiology review (IRR). Secondary end points included duration of response (DOR), disease control rate (DCR), progression-free survival (PFS), overall survival, time to response, and safety.

RESULTS

At data cutoff, 98 patients (59 treatment-naïve and 39 previously treated) with BRAFV600E-mutant metastatic NSCLC received encorafenib plus binimetinib. Median duration of treatment was 9.2 months with encorafenib and 8.4 months with binimetinib. ORR by IRR was 75% (95% CI, 62 to 85) in treatment-naïve and 46% (95% CI, 30 to 63) in previously treated patients; median DOR was not estimable (NE; 95% CI, 23.1 to NE) and 16.7 months (95% CI, 7.4 to NE), respectively. DCR after 24 weeks was 64% in treatment-naïve and 41% in previously treated patients. Median PFS was NE (95% CI, 15.7 to NE) in treatment-naïve and 9.3 months (95% CI, 6.2 to NE) in previously treated patients. The most frequent treatment-related adverse events (TRAEs) were nausea (50%), diarrhea (43%), and fatigue (32%). TRAEs led to dose reductions in 24 (24%) and permanent discontinuation of encorafenib plus binimetinib in 15 (15%) patients. One grade 5 TRAE of intracranial hemorrhage was reported. Interactive visualization of the data presented in this article is available at the PHAROS dashboard (https://clinical-trials.dimensions.ai/pharos/).

CONCLUSION

For patients with treatment-naïve and previously treated BRAFV600E-mutant metastatic NSCLC, encorafenib plus binimetinib showed a meaningful clinical benefit with a safety profile consistent with that observed in the approved indication in melanoma.

Osimertinib Resistance: Molecular Mechanisms and Emerging Treatment Options

The development of tyrosine kinase inhibitors (TKIs) targeting the mutant epidermal growth factor receptor (EGFR) protein initiated the success story of targeted therapies in non-small-cell lung cancer (NSCLC). Osimertinib, a third-generation EGFR-TKI, is currently indicated as first-line therapy in patients with NSCLC with sensitizing EGFR mutations, as second-line therapy in patients who present the resistance-associated mutation T790M after treatment with previous EGFR-TKIs, and as adjuvant therapy for patients with early stage resected NSCLC, harboring EGFR mutations. Despite durable responses in patients with advanced NSCLC, resistance to osimertinib, similar to other targeted therapies, inevitably develops. Understanding the mechanisms of resistance, including both EGFR-dependent and -independent molecular pathways, as well as their therapeutic potential, represents an unmet need in thoracic oncology. Interestingly, differential resistance mechanisms develop when osimertinib is administered in a first-line versus second-line setting, indicating the importance of selection pressure and clonal evolution of tumor cells. Standard therapeutic approaches after progression to osimertinib include other targeted therapies, when a targetable genetic alteration is detected, and cytotoxic chemotherapy with or without antiangiogenic and immunotherapeutic agents. Deciphering the when and how to use immunotherapeutic agents in EGFR-positive NSCLC is a current challenge in clinical lung cancer research. Emerging treatment options after progression to osimertinib involve combinations of different therapeutic approaches and novel EGFR-TKI inhibitors. Research should also be focused on the standardization of liquid biopsies in order to facilitate the monitoring of molecular alterations after progression to osimertinib.

Non-Small Cell Lung Cancer Targeted Therapy: Drugs and Mechanisms of Drug Resistance

The advent of precision medicine has brought light to the treatment of non-small cell lung cancer (NSCLC), expanding the options for patients with advanced NSCLC by targeting therapy through genetic and epigenetic cues. Tumor driver genes in NSCLC patients have been uncovered one by one, including epidermal growth factor receptor (EGFR), mesenchymal lymphoma kinase (ALK), and receptor tyrosine kinase ROS proto-oncogene 1 (ROS1) mutants. Antibodies and inhibitors that target the critical gene-mediated signaling pathways that regulate tumor growth and development are anticipated to increase patient survival and quality of life. Targeted drugs continue to emerge, with as many as two dozen approved by the FDA, and chemotherapy and targeted therapy have significantly improved patient prognosis. However, resistance due to cancer drivers' genetic alterations has given rise to significant challenges in treating patients with metastatic NSCLC. Here, we summarized the main targeted therapeutic sites of NSCLC drugs and discussed their resistance mechanisms, aiming to provide new ideas for follow-up research and clues for the improvement of targeted drugs.