A Pilot Study of the Combination of Entinostat With Capecitabine in High Risk Breast Cancer After Neo-adjuvant Therapy

In order to identify the maximum dose that should be used in future participants, the first participants will start at a low dose of both drugs. If the participants on this dose level tolerate the treatment well without too many side effects, the next participants will receive a higher dose of one of the medications, and if those participants also tolerate the treatment well, then the drugs will continue to be increased with the next participants until a maximum dose that participants tolerate well is reached. Participants in both groups will receive entinostat on days 1, 8, and 15 of each 21-day cycle and capecitabine on days 1-14 of each cycle. MBC participants may receive this treatment as long as they do not have disease progression or side effects that require them to stop study treatment while participants with high-risk BC after neo-adjuvant therapy will receive up to 8 cycles of study treatment as long as they do not have disease progression or side effects that require them to stop study treatment. While participants are on study treatment, they will have regular physical exams and labs. After participants finish study treatment, they should be followed by their primary oncologist at least once a year. Study staff will also be in contact by phone at least once a year for 10 years.