A Clinical Study of Sacituzumab Tirumotecan (Sac-TMT, MK-2870) in People With Breast Cancer (MK-2870-032)

Researchers are looking for new ways to treat types of breast cancer that are both: * High-risk, which means the cancer may have a higher chance of getting worse or coming back after treatment * Early-stage, which means the cancer is in the breast or the lymph nodes around the breast The 2 types of breast cancer in this study are triple-negative breast cancer (TNBC) and hormone receptor (HR)-low positive/human epidermal growth factor receptor-2 (HER2) negative breast cancer. These cancers have zero or a low amount of a protein called HER2 and other proteins that attach to the hormones estrogen or progesterone. Sacituzumab tirumotecan (also known as sac-TMT or MK-2870), the study medicine, is a type of targeted therapy. A targeted therapy is a treatment that works to control how specific types of cancer cells grow and spread. The main goals of this study are to learn if people who receive sac-TMT, pembrolizumab, and chemotherapy: * Have fewer cancer cells found in the tumors and lymph nodes removed during surgery compared to those who receive only pembrolizumab and chemotherapy * Live longer without the cancer growing, spreading, or coming back compared to people who receive only pembrolizumab with chemotherapy

NCT Number	NCT06966700
Lead Sponsor	Merck Sharp & Dohme LLC
Conditions	Breast Neoplasms, Triple Negative Breast Neoplasms, HR Low-Positive/HER2-Negative Breast Neoplasms
Enrollment	2,400 participants
Start Date	2025-06-30
Primary Completion	2033-03-23 (estimated)
Study Completion	2034-12-29 (estimated)
Updated on ClinicalTrials.gov	2026-08-14