Trastuzumab emtansine in human epidermal growth factor receptor 2-positive breast cancer: A review

Purpose of Review: In this review, we aim to update the clinical data of trastuzumab-DM1 (T-DM1) in terms of safety and efficacy, and describe ongoing and future trials evaluating its potential role in the management of patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Recent Findings: Trastuzumab emtansine (T-DM1) is an antibody drug conjugate that optimizes delivery of chemotherapy with an anti-HER2 monoclonal antibody. As a conjugate, T-DM1's systemic side effects are significantly minimized due to its targeted delivery by trastuzumab to HER2-positive cells. Phase I and II studies show that the maximum tolerated dose, and thus the recommended dose for T-DM1, is 3.6 mg/kg given intravenously every 3 weeks. Single arm phase Ib/II, II and a randomized phase II first-line study of T-DM1 versus the combination of trastuzumab + docetaxel all showed improved tolerability, and at least equivalent efficacy, compared with our current standard of care. Two randomized phase III registration studies are now active, evaluating this agent in the refractory and first-line HER2-positive settings. Summary: T-DM1 has been shown to be a very promising agent for the targeted delivery of chemotherapy and anti-HER2 monoclonal antibody therapy for patients with metastatic, HER2-positive breast cancer. T-DM1 will likely play a role in the management of patients with advanced and early stage HER2-positive breast cancer, but this awaits further study.