Additional Study Information: The purpose of this research study is to learn if sacituzumab govitecan (also called SG) can improve lifespan and delay the growth or spread of the disease in participants with endometrial cancer when compared to chemotherapy (doxorubicin or paclitaxel). Sacituzumab govitecan is a type of drug called an antibody-drug conjugate. An antibody-drug conjugate (ADC) is a cancer treatment that combines a monoclonal antibody (mAb) with a drug to deliver chemotherapy directly to cancer cells. Antibodies are proteins normally made by the immune system. The antibody part attaches to a certain type of protein called Trop-2, which is found in many cancers including endometrial cancer, to release the anti-cancer drug part to target and kill cancer cells. SG is not approved by the FDA. Doxorubicin and paclitaxel are each approved by the Food and Drug Administration (FDA) in the US for the treatment of several types of cancer. Doxorubicin and paclitaxel have not been formally approved by the FDA in the US for this use.