The purpose of this study is to assess the safety and efficacy of avelumab in combination with other anti-tumor agents as a maintenance treatment in participants with bladder cancer.

Inclusion Criteria:

• Participants with histologically confirmed, unresectable locally advanced or metastatic urothelial carcinoma. Both transitional cell and mixed transitional/non- transitional cell histologies are allowed, but transitional cell carcinoma must be the predominant histology
• Participants has documented Stage IIIA/IIIB with N1-N3, or Stage IV disease (per American Joint Committee on Cancer/International Union for Cancer Control Tumor Node Metastasis system, 8th edition) at the start of first line chemotherapy.
• The last dose of first line chemotherapy must have been received no less than 4 weeks, and no more than 10 weeks, prior to randomization in the present study
• Estimated life expectancy of at least 3 months
• Participants without progressive disease as per RECIST v1.1 guidelines following completion of 4 to 6 cycles of 1L chemotherapy. Eligibility based on this criterion will be determined by Investigator review of pre chemotherapy and post chemotherapy radiological assessments (CT/MRI scans).
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0 or 1
• Adequate hematological, hepatic, and renal function as defined in the protocol
• Other protocol defined inclusion criteria could apply

Exclusion Criteria:

• Participants with prior immunotherapy with Interleukin-2 (IL-2), IL-15, interferon alfa (IFN-α), or an anti programmed death receptor-1 (PD-1), anti programmed death-ligand 1 (PD-L1), anti PD-L2, anti CD137, or cytotoxic T cell lymphocyte-4 (CTLA-4) antibody (including ipilimumab), anti TROP2, anti-T-cell-immuno-receptor with Ig and ITM domains (anti-TIGIT) any other antibody or drug specifically targeting T cell costimulation or immune checkpoint pathways, agents targeting Nectin-4, or any of the investigational drugs used in combination with avelumab.
• Participants with active infection 48 hours before randomization requiring systemic therapy
• Participants with known prior or suspected hypersensitivity to study drugs or any component in their formulations
• Participants with prior adjuvant or neoadjuvant systemic therapy within 12 months of randomization
• Participants with vaccination within 4 weeks of the first dose of study treatment and while on trial is prohibited except for administration of inactivated vaccines (for example, inactivated influenza vaccines) administered >= 2 weeks prior first dose of study treatment. All severe acute respiratory syndrome coronavirus (SARS-CoV-2) vaccines approved or authorized by local Health Authorities are allowed
• Other protocol defined exclusion criteria could apply

We are committed to enhancing public health through responsible sharing of clinical trial data. Following approval of a new product or a new indication for an approved product in both the US and European Union, the study sponsor and/or its affiliated companies will share study protocols, anonymized patient data and study level data, and redacted clinical study reports with qualified scientific and medical researchers, upon request, as necessary for conducting legitimate research. Further information on how to request data can be found on our website bit.ly/IPD21

Within six months after the approval of a new product or a new indication for an approved product in both the United States and the European Union

Qualified scientific and medical researchers can request the data. Such requests must be submitted in writing to the company's portal and will be internally reviewed regarding criteria for researchers' qualification and legitimacy of the research proposal.