Liposomal doxorubicin

The purpose of this study is to compare sacituzumab tirumotecan as a single agent, and in combination with pembrolizumab, versus Treatment of Physician's Choice (TPC) in participants with hormone receptor positive/human epidermal growth factor receptor-2 negative (HR+/HER2-) unresectable locally advanced, or metastatic, breast cancer. The primary hypotheses are that sacituzumab tirumotecan as a single agent and sacituzumab tirumotecan plus pembrolizumab are superior to TPC with respect to progression-free survival (PFS) per Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1) by blinded independent central review (BICR) in all participants.

Researchers are looking for other ways to treat breast cancer (BC) that is hormone receptor-positive and human epidermal growth factor receptor 2-negative (HR+/HER2-) and either unresectable locally advanced or metastatic. * HR positive (HR+) means the cancer cells have proteins that attach to estrogen or progesterone (hormones) which help the cancer to grow and spread * HER2 negative (HER2-) means the cancer cells have a low amount of a protein called HER2 * Unresectable locally advanced means the cancer cannot be completely removed by surgery and has spread into nearby tissue or muscles * Metastatic means the cancer has spread to other parts of the body Treatment for this type of breast cancer usually includes endocrine therapy (ET) and sometimes a second treatment. The main goal of this study is to learn if people who receive patritumab deruxtecan (also known as HER3-DXd and MK-1022) live longer overall or without the cancer growing/spreading, compared to people who receive chemotherapy or a different drug called trastuzumab deruxtecan.