In recent years, there has been a significant improvement in the understanding of molecular events and critical pathways involved in
breast cancer. This has led to the identification of novel targets and development of anticancer
therapies referred to as targeted
therapy. Targeted
therapy has high specificity for the molecules involved in key molecular events that are responsible for
cancer phenotype such as cell growth, survival, migration, invasion,
metastasis, apoptosis, cell-cycle progression, and angiogenesis. Targeted agents that have been approved for
breast cancer include
trastuzumab and
lapatinib, directed against
human epidermal growth factor receptor 2 (HER2) and
bevacizumab, directed against
vascular endothelial growth factor (
VEGF). Several other targeted agents currently under evaluation in preclinical and clinical trials include inhibitors of
epidermal growth factor receptor (EGFR), dual EGFR and HER2 inhibitors,
VEGF/VEGFR inhibitors, and agents that interfere with crucial signaling pathways such as PI3K/AKT/mTOR and RAS/
MEK/ERK; agents against other
tyrosine kinases such as Src,
insulin-like growth factor (IGF)/IGF-receptor (IGFR); agents that promote apoptosis such as
Poly ADP ribose polymerase inhibitors; agents that target invasion and
metastasis such as
matrix metalloproteinases inhibitors and others. In this review, we highlight the most promising targeted agents and their combination with mainstream chemotherapeutic drugs in clinical trials.