Recent Advances in the Development and Clinical Use of HER2 Inhibitors in Non-Small Cell Lung Cancer

Alterations in the human epidermal growth factor receptor 2 (HER2) gene are well-recognized oncogenic drivers and therapeutic targets in non-small cell lung cancer (NSCLC). The first anti-HER2 inhibitor, trastuzumab-deruxtecan, was approved for previously treated advanced NSCLC with HER2 mutations, which accounts for 2–4% of NSCLC. The first anti-HER2 antibody, trastuzumab, was approved for HER2-positive metastatic breast cancer in 1998, and a combination therapy comprising trastuzumab, pertuzumab, and docetaxel demonstrated efficacy in the first-line setting. Some EGFR-tyrosine kinase inhibitors (TKIs) have been evaluated as pan-HER TKIs but have shown limited benefits in HER2-altered NSCLC. However, HER2-specific TKIs, such as zongertinib and BAY2927088, have demonstrated encouraging results. Zongertinib was the first HER2-specific TKI to be approved by the FDA in 2025 for previously treated ERBB2-mutated advanced NSCLC. In this narrative review, we have summarized the latest research on the biology of HER2 signaling, HER2 alterations, HER2-targeting therapies, and challenges of treating HER2-overexpressing or -mutated NSCLC. Despite different targets of HER2 mutations in NSCLC and HER2 amplification/overexpression in breast cancer, the development of HER2-targeting agents has been more advanced in breast cancer than in NSCLC. Therefore, pivotal clinical studies in breast cancer may help in identifying more effective therapies for NSCLC.