Case Report: A patient with the rare third-generation TKI-resistant mutation EGFR L718Q who responded to afatinib plus cetuximab combination therapy

Strategies Beyond 3rd EGFR-TKI Acquired Resistance: Opportunities and Challenges

The seminal identification of epidermal growth factor receptor (EGFR) mutations as pivotal oncogenic drivers in non-small cell lung cancer (NSCLC) has catalyzed the evolution of biomarker-guided therapeutic paradigms for advanced disease. Currently, third-generation EGFR tyrosine kinase inhibitors (EGFR-TKI) have revolutionized first-line treatment for advanced EGFR-mutated NSCLC, yet acquired resistance remains an inevitable and formidable clinical challenge. This review systematically summarizes molecular mechanisms underlying treatment resistance, with a focus on clinical challenges associated with central nervous system (CNS) metastases. Therapeutic resistance mechanisms are categorized into EGFR-dependent (on-target) pathways, typified by acquired kinase domain mutations (e.g., C797S), and EGFR-independent (off-target) pathways, involving compensatory activation of parallel signaling effectors (e.g., MET amplification, HER2 activation) or phenotypic transformation. We further evaluated contemporary diagnostic modalities for identifying resistance drivers and appraised emerging therapeutic strategies, including fourth-generation EGFR-TKI, various combination therapies, and antibody-drug conjugates (ADCs), and so forth, with emphasis on ongoing clinical trials that may transform the existing treatment paradigm. By synthesizing preclinical and clinical insights, this review aims to advance mechanistic understanding and propose therapeutic strategies to overcome acquired resistance to third-generation EGFR-TKI in first-line treatment.

A rare epidermal growth factor receptor T790M/cis-C797S/L718Q compound mutation in a lung adenocarcinoma patient who did not derive any benefit from combination therapy with afatinib and bevacizumab

The most common mutations in epidermal growth factor receptor (EGFR) are exon 19 deletions and exon 21 L858R mutations, both of which respond effectively to EGFR tyrosine kinase inhibitors. However, the efficacy of EGFR tyrosine kinase inhibitors against rare EGFR mutations remains controversial. Many patients eventually develop resistance to EGFR tyrosine kinase inhibitors. Here, we encountered the case of a 62-year-old male with lung adenocarcinoma and a history of hypertension, who harbored a rare EGFR L858R/T790M/cis-C797S/L718Q compound mutation and showed resistance to osimertinib. The patient showed a partial response to treatment with a combination of afatinib and bevacizumab lasting 2 months. Although this case did not demonstrate a clear benefit from dual therapy with afatinib and bevacizumab, it provides a valuable therapeutic reference for patients with rare compound EGFR mutations and offers insights for future studies.

Acquired multiple EGFR mutations‑mediated resistance to a third‑generation tyrosine kinase inhibitor in a patient with lung adenocarcinoma who responded to afatinib: A case report and literature review

For patients with advanced non-small cell lung cancer (NSCLC) that have epidermal growth factor receptor (EGFR) mutations, EGFR tyrosine kinase inhibitors (TKIs) are the standard treatment and have significant clinical benefits. Third-generation TKIs, such as osimertinib, almonertinib and furmonertinib, are effective for the treatment of NSCLC that is EGFR-sensitizing mutation-positive and T790M-positive. Despite the efficacy of third-generation TKIs, patients inevitably develop resistance and the resistance mechanisms are heterogeneous. Second-generation inhibitors, such as afatinib, may be crucial in treating diseases that have developed resistance to first- or third-generation inhibitors. However, the clinical effect of afatinib in patients with acquired multiple EGFR mutations is not well defined. To the best of our knowledge, the present report describes the first case of a patient with lung adenocarcinoma who had multiple co-existing EGFR resistance mutations, including EGFR L718Q, EGFR C797S, EGFR C797G, EGFR L792H, EGFR V802F and EGFR V689L. These mutations conferred resistance to almonertinib, whilst maintaining sensitivity to afatinib.

Inhaled delivery of cetuximab-conjugated immunoliposomes loaded with afatinib: A promising strategy for enhanced non-small cell lung cancer treatment

Afatinib (AT), an FDA-approved aniline-quinazoline derivative, is a first-line treatment for metastatic non-small cell lung cancer (NSCLC). Combining it with cetuximab (CX), a chimeric human-murine derivative immunoglobulin-G1 monoclonal antibody (mAb) targeting the extracellular domain of epidermal growth factor receptor (EGFR), has shown significant improvements in median progression-free survival. Previously, we developed cetuximab-conjugated immunoliposomes loaded with afatinib (AT-MLP) and demonstrated their efficacy against NSCLC cells (A549 and H1975). In this study, we aimed to explore the potential of pulmonary delivery to mitigate adverse effects associated with oral administration and intravenous injection. We formulated AT-MLP dry powders (AT-MLP-DPI) via freeze drying using tert-butanol and mannitol as cryoprotectants in the hydration medium. The physicochemical and aerodynamic properties of dry powders were well analyzed firstly. In vitro cellular uptake and cytotoxicity study revealed concentration- and time-dependent cellular uptake behavior and antitumor efficacy of AT-MLP-DPI, while Transwell assay demonstrated the superior inhibitory effects on NSCLC cell invasion and migration. Furthermore, in vivo pharmacokinetic study showed that pulmonary delivery of AT-MLP-DPI significantly increased bioavailability, prolonged blood circulation time, and exhibited higher lung concentrations compared to alternative administration routes and formulations. The in vivo antitumor efficacy study carried on tumor-bearing nude mice indicated that inhaled AT-MLP-DPI effectively suppressed lung tumor growth.