Avelumab and M1774 in ARID1A-mutated Endometrial Cancer

This study is testing a combination of two drugs — avelumab (an immunotherapy that helps the immune system attack cancer) and M1774 (a drug that blocks a DNA repair pathway in cancer cells) — in people with endometrial cancer (cancer of the uterine lining) that carries a specific gene change called an ARID1A mutation. These mutations may make cancer cells more vulnerable to this drug combination. **You may be eligible if...** - You have endometrial cancer confirmed to have an ARID1A loss-of-function mutation (tested by a certified lab using next-generation DNA sequencing) - Your cancer is measurable on imaging scans (at least one lesion visible per RECIST 1.1 criteria) - Your disease has come back or progressed after at least one prior treatment **You may NOT be eligible if...** - Your tumor does not have an ARID1A loss-of-function mutation - You have active autoimmune diseases that require systemic treatment - You have serious heart problems or uncontrolled infections - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.