Metformin exhibits a synergistic effect with pyrotinib by inducing ferroptosis in HER2-positive cancers through the Keap1/Nrf2 pathway.

Human epidermal growth factor receptor 2 (HER2) overexpression plays a critical role in the progression of several cancers, driving the development of targeted therapies. However, drug resistance significantly limits the effectiveness of anti-HER2 treatments. Pyrotinib, an irreversible pan-ErbB tyrosine kinase inhibitor (TKI), and metformin, a first-line treatment for type II diabetes with anticancer properties, are potential candidates for combination therapy in HER2-positive cancers. Here we investigate the synergistic effects of pyrotinib and metformin on HER2-positive cancer cells. Our findings demonstrate that the combination of pyrotinib and metformin induces significant cell death in HER2-positive cell lines, including BT-474, SK-OV-3, and N87. Transcriptomic analysis reveals that HER2 is associated with the oxidative stress response and lipid metabolism. Mechanistically, the combination treatment primarily induces ferroptosis by reducing glutathione synthesis and impairing Fe2+ efflux, leading to excessive ROS accumulation. In vivo experiments using the SKOV-3 xenograft model show that the combination therapy significantly enhances antitumor efficacy compared to monotherapy, without causing noticeable toxicity. These results suggest that combining pyrotinib with metformin may provide an effective therapeutic strategy for HER2-positive cancers.