A large meta-analysis! suggests trastuzumab emtansine confers much lower rates of left ventricular ejection fraction decline (<1%) than any other trastuzumab regimen (i.e., conjugated to deruxtecan or in combo with chemo) which all carry risks of 4-6%, presumably because there’s a lesser cytoxic-drug/HER2-drug ratio and the cytotoxic drug is uniquely not membrane-permeable (i.e., once internalized into HER2-expressing tumor cells, it stays there). | Seth, JAMA Netw Open 2025
