The antibody-guided drug conjugate trastuzumab emtansine (T-DM1) as initial therapy prolonged progression-free survival (PFS) for patients with HER2-positive metastatic breast cancer compared with docetaxel plus trastuzumab, according to trial results reported at the European Multidisciplinary Cancer Conference.
The conjugate delivers trastuzumab directly to tumor cells by attaching the drug to DM1 using a stable linker. This limits the drug’s exposure to normal cells, thus producing fewer side effects than the drug delivers through traditional means.
The phase 2 trial randomized 137 patients who were chemotherapy-naïve to either T-DM1 or trastuzumab plus docetaxel chemotherapy. Median PFS was 14.2 months in the T-DM1 group compared with 9.2 months in the trastuzumab/docetaxel group. In the T-DM1 arm, only 7.2% of patients discontinued treatment because of side effects; 28.8% discontinued treatment in the trastuzumab/docetaxel arm.