The present invention provides novel compounds of Formula (I), and pharmaceutically acceptable salts, tautomers, stereoisomers, solvates, hydrates, polymorphs, and compositions thereof. Also provided are methods and kits involving the inventive compounds for treating proliferative diseases (e.g., cancers (e.g., breast cancer, prostate cancer, lung cancer, and ovarian cancer), benign neoplasms, angiogenesis, inflammatory diseases, and autoimmune diseases) in a subject. Treatment of a subject with a proliferative disease using a compound of the invention may enhance the anti-tumor immune response by inhibiting or eliminating the immune suppression mediated by immune suppressor myeloid cells (MDSCs), inducing apoptosis, and/or inhibit or down-regulate proteins (e.g., epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), estrogen receptor (ER), X-linked inhibitor of apoptosis protein (XIAP), and heat shock protein 90 (Hsp90)) in the subject.
