Abstract
The human epidermal growth factor receptor-2 (HER2)-targeted therapies have improved
clinical outcomes for patients at any stage of HER2-positive breast cancer (BC). Trastuzumab,
a monoclonal antibody that targets the HER2 receptor on BC cells, showed improved
survival in metastatic BC (MBC). However, resistance to therapy arises in the majority
of patients with advanced disease. Antibody–drug conjugate (ADC) is a relatively new
development to deliver cytotoxic drugs specifically to cancer cells. Trastuzumab emtansine
(T-DM1) is a HER2-targeted ADC, composed of trastuzumab, a stable thioether linker,
and the potent cytotoxic agent, emtansine (DM1, derivative of maytansine). T-DM1 has
been approved for use in patients with MBC who have failed prior therapy with trastuzumab
and a taxane. Dose finding Phase I study established the maximum tolerated dose at
3.6 mg/kg every 3 weeks. Phase I and II studies of T-DM1 have shown clinical activity
and a favorable safety profile in HER2-positive MBC patients. The Phase III randomized
EMILIA and TR3RESA trials demonstrated that T-DM1 significantly improves progression-free
and overall survival in pretreated HER2-positive MBC patients. Nausea and fatigue
are most commonly reported adverse drug reactions with T-DM1 and cardiac toxicity
comparable with standard of care therapies. The drug is well tolerated in most patients,
with a predictable pharmacokinetic profile and minimal systemic exposure to free cytotoxic
DM1. T-DM1 has emerged as an effective therapeutic option for the management of patients
with HER2-positive MBC.
Keywords
Drug conjugate - human epidermal growth factor receptor-2 - metastatic breast cancer
- Trastuzumab emtansine