A Substudy of Investigational Agents in Programmed Cell Death-1/Ligand 1 (PD-1/L1) Refractory Locally Advanced or Metastatic Urothelial Carcinoma (mUC) (MK-3475-04A)

Prior treatment

• Known additional nonurothelial malignancy that is progressing or has required active treatment within 3 years prior to study randomization/allocation.
• Received prior systemic anticancer therapy including investigational agents within 4 weeks before randomization/allocation.
• Received a live or live-attenuated vaccine within 30 days before the first dose of study intervention. Administration of killed vaccines are allowed.

Other illness

• Active infection requiring systemic therapy.
• Known history of human immunodeficiency virus (HIV).
• Known history of hepatitis B or known hepatitis C virus infection.

• The main inclusion and exclusion criteria include but are not limited to the following:
• Histologically or cytologically confirmed diagnosis of locally advanced/unresectable or mUC of the renal pelvis, ureter (upper urinary tract), bladder, or urethra.
• Arm A: PD-1/L1 refractory locally advanced or mUC as evidenced by: EITHER disease progression while on treatment or after treatment with an anti-PD-1/L1 monoclonal antibody (mAb) for locally advanced/unresectable or mUC administered either as monotherapy, or in combination with other checkpoint inhibitors or other therapies OR disease recurrence while on treatment or after treatment with an anti-PD-1/L1 mAb for muscle-invasive urothelial carcinoma (MIUC) administered as monotherapy.
• Arm A: Participants must provide an archival tumor tissue sample or newly obtained core or excisional biopsy of a tumor lesion demonstrating UC, not previously irradiated, and adequate for biomarker evaluation.
• Arm B: PD-1/L1 refractory locally advanced or mUC as evidenced by: EITHER disease progression after treatment with an anti-PD-1/L1 mAb for locally advanced/unresectable or mUC administered either as monotherapy, or in combination with other checkpoint inhibitors or other therapies; OR disease recurrence after treatment with an anti-PD-1/L1 mAb for MIUC administered as monotherapy or in combination with other checkpoint therapies \>12 months after last dose of treatment with an anti-PD-1/L1 mAb.
• Arm B: Participants must provide an archival tumor tissue sample or newly obtained core or excisional biopsy of a tumor lesion from a metastatic site or from a primary tumor that has become locally advanced and not previously irradiated.