A Study to Evaluate the Efficacy and Safety of Autogene Cevumeran With Nivolumab Versus Nivolumab Alone in Participants With High-risk Muscle-invasive Urothelial Carcinoma (MIUC)

The original purpose of this study was to evaluate the efficacy of adjuvant treatment with autogene cevumeran plus nivolumab compared with nivolumab in participants with high risk MIUC. In this study participants will be enrolled in a safety run-in phase to receive autogene cevumeran + nivolumab. This phase will be conducted to monitor and ensure the safety of study participants. After all participants in the safety run-in have been enrolled to receive autogene cevumeran + nivolumab, further participants will be randomized in either autogene cevumeran + nivolumab or the nivolumab monotherapy arm. Following the Sponsor's decision to phase out the study, as of Protocol Version 5, the primary purpose of the study is to ensure treatment continuity and safety for the participants who continue to participate in the study and receive study treatment.