For example, the ENCORE301 phase II study reported increased progression-free and overall survival in postmenopausal women with advanced HR+ and HER2− BC, not responsive to endocrine therapy, and treated with entinostat (HDAC inhibitor) plus exemestane (aromatase inhibitor) [190]; however, the E2112 phase III study did not confirm these results since no improvement in survival was documented [191]. Here, HDAC9 is linked to breast cancer.