Exploration of Dalpiciclib Plus HDACi in HR+/HER2- Advanced Breast Cancer After Failure of CDK4/6 Inhibitor

100 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).

25 mg/BIW, po. 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

5mg/QW，po.