T-D showdown.

Trastuzumab emtansine (T-DM1) was once the go-to second line treatment for metastatic, HER2+ breast cancer. In the DESTINY-Breast03 trial, T-DM1 was matched head-to-head against trastuzumab deruxtecan (T-DXd) following progression on first-line treatment with trastuzumab and a taxane. So, what’s the difference between these drugs? Well, they’re both HER2 antibody-drug conjugates. T-DM1 is a conjugate of an anti-HER2 monoclonal antibody and the cytotoxic microtubule inhibitor DM1. T-DXd is a conjugate of an anti-HER2 monoclonal antibody and a cytotoxic topoisomerase I inhibitor. In DESTINY-Breast03, progression free survival at 12 months was more than doubled with T-DXd compared to T-DM1 (75.8% v 34.1%) resulting from a more than doubled overall response rate with T-DXd (79.7% v 34.2%). On the down side, T-DXd had a higher rate of adverse events including a 10.5% rate of interstitial lung disease or pneumonitis. | Cortes, N Engl J Med 2022