Key Inclusion Criteria:

          1. Have locally advanced (on TNM staging: T4b and any N, or any T and N2-3) or metastatic
             transitional cell carcinoma of the urothelium, including of the urinary bladder,
             urethra, ureter, and/or renal pelvis. The diagnosis must be histologically or
             cytologically confirmed.

          2. Have progression during or following platinum-containing chemotherapy or within 12
             months of neoadjuvant or adjuvant treatment with platinum-containing chemotherapy.

          3. Have available archival tumor or be willing to undergo diagnostic biopsy at screening.
             Sample must be of suitable quality and quantity to satisfy group assignment and
             biomarker endpoints.

          4. Have measurable disease according to Response Evaluation Criteria in Solid Tumors
             Version 1.1 (RECIST v1.1).

          5. Eastern Cooperative Oncology Group (ECOG) performance status (PS) ≤ 1.

        Key Exclusion Criteria:

          1. Participants with a history of idiopathic pulmonary fibrosis, organizing pneumonia,
             drug-induced pneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis on
             the Screening chest CT scan.

          2. Prior therapy with an anti-programmed cell death 1 (PD-1) or anti-PD-Ligand 1 agent,
             or with an agent directed to another co-inhibitory T-cell receptor or FGFR inhibitor.

          3. Patients with autoimmune disease or medical conditions that required systemic
             corticosteroids (> 10 mg/day prednisone or its equivalent) or other immunosuppressive
             medications or any other form of systemic immunosuppressive therapy within 7 days
             prior to the first dose of study treatment. Note: Replacement therapy (e.g.
             physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency,
             etc.) is not considered a form of systemic treatment.

          4. Primary central nervous system (CNS) malignancy or CNS metastases.

          5. History of clinically significant coagulation or platelet disorder in the past 12
             months.