This study is testing how well a drug called Rina-S works for endometrial cancer (EC), which is cancer in the lining of the uterus. It compares Rina-S to standard treatments like paclitaxel or doxorubicin. In this study, patients have a 50% chance of getting Rina-S and a 50% chance of getting one of the standard treatments. The study will last about 3 years, but each person will get treatment for about 4 to 6 months.

All participants will receive real treatment, not a placebo (a fake treatment). You will need to visit the study site for this research.

• Study lasts up to 3 years, with treatment for about 4 to 6 months.
• Requires visits to the research site; no placebo is used.
• Participants will be randomly assigned to either Rina-S or standard treatment.