This study is looking at a new treatment for certain types of breast cancer that cannot be surgically removed or have spread to other parts of the body. The study will test a medicine called *sacituzumab tirumotecan*, alone and with another medicine called *pembrolizumab*, against other treatments chosen by doctors. Sacituzumab tirumotecan is a medicine that targets cancer cells, while pembrolizumab helps the immune system fight cancer. The study aims to see if these medicines can stop cancer from growing longer than current treatments.

Participants need to have specific types of breast cancer that are hormone receptor-positive (HR+) and human epidermal growth factor receptor 2 negative (HER2-). They should have tried certain hormone treatments before and should be healthy enough to undergo chemotherapy.

• The study will last for several months with regular visits.
• Participants will receive either the study treatment or a treatment chosen by their doctor.
• Potential side effects include those typical of cancer treatments, such as tiredness or infection risks.