This study is testing a drug called autogene cevumeran in combination with nivolumab, a cancer treatment drug known for treating bladder cancer. The purpose of this study is to compare the effects, good or bad, of autogene cevumeran plus nivolumab versus nivolumab on patients with Muscle Invasive Urothelial Carcinoma (MIUC.) In this study, you will get either autogene cevumeran plus nivolumab or saline plus nivolumab. Autogene Cevumeran is not approved by the Food and Drug Administration to treat muscle-invasive urothelial cancer. Are you Eligible? (Inclusion Criteria) 18 years or older - For...