Researchers are looking for new ways to treat people with proficient mismatch repair (pMMR) endometrial cancer (EC) that is advanced or recurrent. * EC is a type of cancer that starts in the tissues inside the uterus (womb) * pMMR indicates that certain normal proteins are present in the cancer cells * Advanced means the cancer has spread locally or to other parts of the body (metastatic) and cannot be removed with surgery * Recurrent means the cancer came back after surgery Sacituzumab tirumotecan (also known as sac-TMT) and pembrolizumab are the study medicines. Sac-TMT is an antibody drug conjugate (ADC). An ADC attaches to specific targets on cancer cells and delivers treatment to destroy those cells. The goal of this study is to learn if people who receive sac-TMT with pembrolizumab live longer and without the cancer getting worse compared to people who receive pembrolizumab alone.