Advances in understanding tumor biology, particularly signaling pathways, have led to the
development and approval of many novel agents and have changed the landscape of
therapy for patients with metastatic breast cancer. This review highlights some of the recent
successes and failures in breast cancer drug development, including strategies to overcome
endocrine and human epidermal growth factor 2-neu (HER2) resistance, targeting triple-
negative breast cancers (which do not express the HER2, estrogen, and progesterone …