A Trial of HRS-6209 in Combination With Fulvestrant, Letrozole, HRS-8080, or HRS-1358 in Breast Cancer Patients

This study is testing a new drug called HRS-6209, used in combination with other hormone-blocking medicines, for women with breast cancer that has spread or cannot be surgically removed. The cancer must be hormone receptor positive (meaning it is fueled by estrogen or progesterone). **You may be eligible if...** - You are a woman aged 18–75 - You have metastatic or locally advanced breast cancer that is ER-positive or PR-positive - You are postmenopausal, or if premenopausal, you are willing to take hormone-suppressing injections during the study - Your cancer has continued to grow during or after your last treatment - You have at least one measurable tumor outside the brain - Your heart, kidneys, liver, and blood counts are within acceptable ranges **You may NOT be eligible if...** - You have active brain metastases or fluid around your spine or brain - You have significant heart problems or abnormal heart rhythm (QT prolongation) - You have active autoimmune disease or HIV - You are pregnant, breastfeeding, or planning pregnancy - You have had another cancer in the past 5 years - You are taking certain medicines that affect drug metabolism (strong CYP3A4 inhibitors or inducers) Talk to your doctor to see if this trial is right for you.