A Study to Evaluate D-0502 in Subjects With ER+ Her2- Locally Advanced or Metastatic Breast Cancer

This study tests a new oral drug called D-0502 in women with estrogen receptor-positive (ER+), HER2-negative breast cancer that has spread or cannot be removed by surgery. D-0502 is a type of selective estrogen receptor degrader (SERD) — it works by blocking and breaking down the estrogen receptor that fuels the cancer's growth. **You may be eligible if...** - You have ER-positive, HER2-negative breast cancer that has come back or spread - Your cancer progressed during or after hormone therapy (either adjuvant or after 1–2 lines of systemic treatment) - You have at least one measurable tumor on imaging, or bone lesions that can be evaluated - Your estimated survival is at least 12 weeks **You may NOT be eligible if...** - You have unstable or growing brain metastases (brain spread) - You have already received more than 2 prior chemotherapy regimens for metastatic disease - Your doctor considers you unsuitable for hormone therapy due to serious fluid buildup around the lungs, heart, or abdomen Talk to your doctor to see if this trial is right for you.