Exploration of Dalpiciclib + Chidamide in HR+/HER2- Advanced Breast Cancer After Failure of CDK4/6 Inhibitor: a Phase Ⅰb Study

Dalpiciclib: 100 mg/d or 125 mg/d, po., qd, administered on an empty stomach (fasting should be ensured at least 1 hour before and 1 hour after administration). The drug will be administered in a 28-day cycle, with continuously administration in the first 3 weeks (D1-21), and discontinuation in the fourth week (D22-28).

Chidamide: 25 mg/BIW or 20 mg/BIW, po., q2w. The interval between doses should not be less than 3 days (e.g. Monday and Thursday, Tuesday and Friday, Wednesday and Saturday, etc.), administered 30 minutes after meals