People can join this study if they are 18 years old or older and have endometrial cancer that is advanced, has spread, or has come back after treatment. The cancer must be confirmed by lab testing and must meet specific types and features, including certain gene changes that doctors can test for. If the cancer can be measured on scans, it must be large enough for doctors to track during the study. People may have had some treatments before, such as chemotherapy, radiation, or hormone therapy, but there must be enough time since those treatments ended. They cannot have had certain newer immune or targeted treatments before. Participants must be healthy enough to take part in the study and able to do most daily activities. They cannot be pregnant or breastfeeding. Patients with treated brain disease may be able to join if it is stable.