Two studies announced at this year's annual meeting of the American Association for Clinical Research are targeting unique molecular features that drive breast cancer.One study is testing the drug palbociclib, which targets an abnormality in the cancer cell cycle. The drug is being tested in hormone-positive breast cancer in combination with the aromatase inhibitor, Femara (letrozone). The combination significantly delays the time it takes for the cancer to continue growing. At the current time, it's not showing a survival advantage, but a phase 3 trial in progress may be the deciding factor for the drug's approval.Another study is looking at a drug called neratinib, specifically in HER2-positive breast cancers. It's part of the I-SPY2 study, which is testing multiple new therapies before surgery, as neoadjuvant therapy. The results show that neratinib can result in complete disappearance of the tumor. This may represent a new drug for patients with HER2-positive breast cancer, including patients who have progressed on other HER2-targeted therapies. Debu Tripathy is an oncologist and editor-in-chief of CURE. He is the co-leader of the Women's Cancer Program at Norris Comprehensive Cancer Center and Professor of Medicine at the Keck School of Medicine at the University of Southern California.