This study systematically elucidates multiple resistance mechanisms to trastuzumab deruxtecan (T-DXd) in HER2-mutant non-small cell lung cancer (NSCLC), revealing the molecular basis for retained sensitivity to HER2 tyrosine kinase inhibitors (TKIs) after resistance develops, thereby providing direct evidence for clinical sequential treatment strategies.
Literature Overview
The article titled “Loss of payload sensitivity and other mechanisms of resistance to T-DXd in HER2-mutant NSCLC: implications for subsequent responsiveness to HER2 TKIs,” published in the Journal of Thoracic Oncology: Official Publication of the International Association for the Study of Lung Cancer, systematically investigates the mechanisms of acquired resistance to the antibody–drug conjugate (ADC) trastuzumab deruxtecan (T-DXd) in patients with HER2-mutant non–small cell lung cancer (NSCLC), and evaluates the sensitivity of these resistant tumors to subsequent HER2 tyrosine kinase inhibitor (TKI) therapies. By integrating preclinical models, high-throughput mutational screening, and patient sample analyses, the study reveals that resistance is not due to loss of HER2 expression, but rather driven by multiple targetable mechanisms.Background Knowledge
Approximately 3% of non–small cell lung cancers harbor activating ERBB2/HER2 mutations, primarily exon 20 insertions, which are associated with adenocarcinoma histology and poor prognosis. Although T-DXd has demonstrated a 49% objective response rate in platinum-resistant patients, nearly all eventually progress, and subsequent treatment options remain limited. Currently, HER2–targeted therapy faces multiple challenges: on one hand, HER2 exon 20 insertions cause steric hindrance in the kinase domain, limiting binding of conventional TKIs; on the other, the mechanisms of ADC resistance are poorly understood, and it remains unclear whether resistance to ADCs confers cross-resistance to TKIs. Furthermore, reliable biomarkers to guide subsequent treatment selection are lacking. This study focuses on systematically dissecting the molecular mechanisms of T-DXd resistance and clarifying their impact on sensitivity to HER2 TKIs, providing a theoretical foundation for overcoming resistance and optimizing treatment sequencing.
Research Methods and Experiments
The authors first established T-DXd–resistant cell lines using Ba/F3 cells and human NSCLC cell lines (H1781, H2170) by long-term exposure to increasing concentrations of T-DXd. Subsequently, they employed the LentiMutate high-throughput scanning mutagenesis platform to introduce random mutations in the HER2 gene in HCC827 cells and screened for mutants conferring resistance to trastuzumab-based ADCs. Patient-derived xenograft (PDX) models were also developed to assess molecular and phenotypic changes during resistance in vivo. At the clinical level, circulating tumor DNA (ctDNA) and tissue samples from patients before and after T-DXd treatment were analyzed to validate the clinical relevance of resistance mechanisms. Key experiments included drug sensitivity assays, Western blotting, flow cytometry for antibody binding, RNA-seq, and GSEA analysis, which collectively demonstrated the relationship between resistance mechanisms and TKI sensitivity.Key Conclusions and Perspectives
Research Significance and Prospects
This study challenges the traditional notion that “ADC resistance equates to target loss,” establishing that HER2 remains a valid therapeutic target after resistance develops, thus providing strong evidence for the use of HER2 TKIs following T-DXd progression. From a drug development perspective, sequential or combination strategies targeting distinct resistance mechanisms—such as MRP1 inhibitors combined with T-DXd—should be prioritized. For clinical monitoring, molecular profiling after T-DXd progression is recommended to assess SLFN11, ABCC1, and HER2 mutation status to guide subsequent therapy. In terms of disease modeling, this work sets a paradigm for developing PDX and cell models that more accurately reflect clinical resistance processes, facilitating accelerated evaluation of novel therapeutics.
Conclusion
This study profoundly reveals heterogeneous resistance mechanisms to T-DXd in HER2-mutant NSCLC, including payload insensitivity, efflux pump activation, and mutations in the antibody-binding site, none of which lead to inactivation of the HER2 signaling pathway. Instead, resistant tumors retain sensitivity to HER2 TKIs, supporting a sequential therapeutic strategy of using TKIs after T-DXd progression. These findings reshape clinical understanding of targeted therapy after ADC resistance and underscore the importance of longitudinal molecular monitoring. From bench to bedside, this study lays the foundation for optimizing treatment pathways in HER2-mutant lung cancer, suggesting that personalized, mechanism-driven sequential therapy may prolong patient survival. Future efforts should further explore combination strategies to overcome EMT- or MRP1-mediated resistance and validate the predictive value of biomarkers in larger cohorts to advance precision medicine.
