Chidamide/Everolimus for PIK3CA Wild-type/Mutant HR+/HER2- Advanced Breast Cancer

This study is testing a combination of two drugs — chidamide (a type of targeted cancer drug) and everolimus (an immune-modulating drug) — for women with hormone receptor-positive, HER2-negative advanced breast cancer whose cancer progressed after treatment with CDK4/6 inhibitors. The study has two groups based on whether patients have a specific genetic mutation (PIK3CA). **You may be eligible if:** - You are a woman aged 18–75 with hormone receptor-positive, HER2-negative advanced or metastatic breast cancer - Your cancer progressed after CDK4/6 inhibitor therapy - You have received no more than 2 prior lines of chemotherapy - You have at least one measurable tumor on imaging - Your general health allows treatment (ECOG score 0–2) **You may NOT be eligible if:** - You have received prior treatment with drugs similar to chidamide or everolimus - You have uncontrolled infections, severe organ dysfunction, or active autoimmune disease - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.