A Study of the Safety and Efficacy of Various Combinations of Avelumab as Therapy in Locally Advanced or Metastatic Urothelial Carcinoma (JAVELIN Bladder Medley)

Inclusion Criteria:

1. 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
2. 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.
3. 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
4. Estimated life expectancy of at least 3 months
5. 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).
6. Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0 or 1
7. Adequate hematological, hepatic, and renal function as defined in the protocol

Other protocol defined inclusion criteria could apply

Exclusion Criteria:

1. 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.
2. Participants with active infection 48 hours before randomization requiring systemic therapy
3. Participants with known prior or suspected hypersensitivity to study drugs or any component in their formulations
4. Participants with prior adjuvant or neoadjuvant systemic therapy within 12 months of randomization
5. 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