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)

Inclusion Criteria: * Participants must have the capacity to participate/enroll in the study and to provide informed consent * Histologically confirmed muscle-invasive UC (also termed transitional cell carcinoma \[TCC\]) of the bladder or upper urinary tract * Tumor-node-metastasis (TNM ) classification (Union for International Cancer Control \[UICC\]/American Joint Committee on Cancer \[AJCC\] 7th edition) at pathological examination of surgical resection specimen of (y)pT3-4 or (y)pN+ and M0 * Surgical resection of MIUC of the bladder or upper tract * Participants who have received neoadjuvant chemotherapy (NAC), including antibody drug-conjugate, either alone or in combination with a checkpoint inhibitor (CPI), are eligible * Participants who have not received any prior NAC are also eligible, provided they meet one of the following criteria, which would make them ineligible to receive adjuvant cisplatin-based therapy: participant refusal, cisplatin ineligibility or investigator decision * Tumor tissue must be provided for biomarker analysis * Absence of residual disease and absence of metastasis, as confirmed by a negative baseline computed tomography (CT) or magnetic resonance imaging (MRI) scan of the pelvis, abdomen, and chest no more than 28 days prior to randomization * Full recovery from cystectomy or nephroureterectomy within 120 days following surgery * Eastern cooperative oncology group (ECOG) performance status of 0 or 1 * Negative human immunodeficiency virus (HIV) test at screening * Negative hepatitis B surface antigen (HbsAg) test at screening * Positive hepatitis B surface antibody (HBsAb), or a negative HBsAb at screening accompanied by either of the following: negative total hepatitis B core antibody (HBcAb) or positive total HBcAb test followed by quantitative hepatitis B virus (HBV) deoxyribonucleic acid (DNA) \< 500 international units/milliliter (IU/mL) * Negative hepatitis C virus (HCV) antibody test at screening, or a positive HCV antibody test followed by a negative HCV ribonucleic acid (RNA) test at screening Exclusion Criteria: * Partial cystectomy in the setting of bladder cancer primary tumor or partial nephroureterectomy in the setting of renal pelvis primary tumor * Any approved anti-cancer therapy, including chemotherapy, or hormonal therapy within 3 weeks prior to initiation of study treatment * Adjuvant chemotherapy, immunotherapy, or radiation therapy for UC following surgical resection * Prior active malignancies within 3 years prior to randomization * Treatment with a live, attenuated vaccine within 4 weeks prior to initiation of study treatment