This clinical trial is focused on studying a type of cancer called muscle-invasive urothelial carcinoma, which affects the bladder and other parts of the urinary system. The study is looking at patients who have a high risk of the cancer returning after they have had surgery to remove it. The trial will test a new treatment combination of two medications: V940 (also known as mRNA-4157) and pembrolizumab (also known as Keytruda). V940 is a type of treatment that uses a small piece of genetic material to help the body recognize and fight cancer cells. Pembrolizumab is a medication that helps the immune system attack cancer cells more effectively.

The purpose of the study is to compare the effectiveness of V940 plus pembrolizumab against a placebo plus pembrolizumab in preventing the cancer from coming back. Participants in the study will be randomly assigned to receive either the new treatment combination or the placebo combination. The study will be conducted in a way that neither the participants nor the researchers know who is receiving which treatment, to ensure unbiased results. The treatment will be given over a period of time, and participants will be monitored regularly to check for any changes in their health and to see how well the treatment is working.

Throughout the study, the main focus will be on measuring how long participants remain free from cancer, known as disease-free survival. Other aspects being monitored include overall survival, the time until cancer spreads to other parts of the body, and any side effects experienced by participants. The study aims to provide valuable information on whether the new treatment combination can offer better outcomes for patients with high-risk muscle-invasive urothelial carcinoma.