Study of BEBT-209 in Combination With Fulvestrant Versus Placebo in Combination With Fulvestrant in Patients With HR+/HER2- Locally Advanced or Metastatic Breast Cancer Who Have Progressed After Prior Endocrine Therapy

This study tests BEBT-209 — a new targeted drug — combined with fulvestrant (a hormone-blocking therapy) compared to placebo plus fulvestrant in women with hormone receptor-positive, HER2-negative breast cancer that has spread or come back after prior hormone therapy. **You may be eligible if...** - You are a woman 18 or older with HR+/HER2- breast cancer that has spread or cannot be surgically cured - Your cancer progressed during or after prior hormone therapy - You have not received more than one prior chemotherapy regimen for metastatic disease - Your blood counts, liver, and kidney function are adequate - You have not previously been treated with fulvestrant, everolimus, or CDK4/6 inhibitors **You may NOT be eligible if...** - Your cancer has spread to the brain in an active and uncontrolled way - You have had a recent heart attack, stroke, or severe heart rhythm problem (within 6 months) - You have active HIV, hepatitis B or C - You cannot swallow pills or have conditions affecting gut absorption - You are pregnant, breastfeeding, or have poorly controlled diabetes or high blood pressure Talk to your doctor to see if this trial is right for you.