The modified engineering structure further improved the function of ADCs.5 DESTINY-Breast03 study showed T-Dxd significantly prolonged the median progression-free survival (PFS) compared with T-DM1 for patients after progression on trastuzumab.6 Under this circumstance, T-Dxd has become a new standard treatment for HER2-positive breast cancer failed to trastuzumab.7-9. The gene discussed is ERBB2; the disease is breast carcinoma.