This clinical trial is focused on studying a type of skin cancer called Melanoma. The study is investigating a new treatment combination for patients who have had their melanoma surgically removed but are at high risk of the cancer returning. The treatment being tested includes a new investigational drug called V940 (mRNA-4157) and an existing medication known as Pembrolizumab, which is also referred to by its brand name, KEYTRUDA. Pembrolizumab is a type of medication that helps the immune system fight cancer cells. The study will compare the effects of V940 plus Pembrolizumab against a placebo plus Pembrolizumab to see which is more effective in preventing the cancer from coming back.

The purpose of this study is to determine if the combination of V940 and Pembrolizumab can improve the time patients remain free from cancer recurrence, known as Recurrence-Free Survival (RFS). Participants in the study will receive either the combination of V940 and Pembrolizumab or a placebo and Pembrolizumab. The study is designed to be “double-blind,” meaning neither the participants nor the researchers will know who is receiving the actual treatment or the placebo, to ensure unbiased results.

Throughout the study, participants will receive regular treatments and check-ups to monitor their health and the status of their melanoma. The study will also track other important outcomes, such as the time until the cancer spreads to distant parts of the body, known as Distant Metastasis Free Survival (DMFS), overall survival rates, and any side effects experienced by participants. The study aims to provide valuable information on the effectiveness and safety of the new treatment combination for melanoma patients.