Azacitidine and Entinostat in Treating Patients With Advanced Breast Cancer

PRIMARY OBJECTIVES: I. To evaluate objective response rate by Response Evaluation Criteria In Solid Tumors (RECIST) criteria of the combination of azacitidine (5-AZA) and entinostat in women with advanced breast cancer; triple-negative and hormone-refractory. SECONDARY OBJECTIVES: I. To determine the safety and tolerability of the combination of 5-AZA and entinostat in women with advanced breast cancer. II. To determine progression-free survival, overall survival, and clinical benefit rate of the combination of 5-AZA and entinostat. TERTIARY OBJECTIVES: I. To collect safety and toxicity data as well as the feasibility and response rate where hormonal therapy is added to the combination under investigation at the time of progressive disease. (Exploratory) II. To determine the pharmacokinetic profile of 5-AZA (full profile) and entinostat (trough concentrations) in patients with advanced breast cancer. (Exploratory) III. To assess serum cytidine deaminase pharmacogenetics and phenotypic activity as a potential biomarker of response to 5-AZA. (Exploratory) IV. To evaluate baseline and change in candidate gene re-expression (e.g., estrogen receptor \[ER\] alpha, retinoic acid receptor \[RAR\] beta) in malignant tissue obtained from selected patients through fine-needle aspiration (FNA) and core biopsy, prior to and following combination therapy. (Exploratory) V. To evaluate baseline and change in gene methylation silencing in circulating deoxyribonucleic acid (DNA) obtained prior to and following combination therapy. (Exploratory) VI. To evaluate baseline and change in gene methylation in malignant tissue obtained through FNA and core biopsy. (Exploratory) OUTLINE: This is a multicenter study. Patients receive azacitidine subcutaneously (SC) on days 1-5 and 8-10, and entinostat orally (PO) on days 3 and 10. Courses repeat every 28 days in the absence of disease progression or unacceptable toxicity. Patients with progressive disease may continue azacitidine and entinostat in combination with hormonal therapy, at treating physician discretion, or undergo event monitoring. After completion of study therapy, patients are followed up every 3-6 months for up to 3 years.