KEYMAKER-U04 Substudy 04D: A Clinical Study of New Treatments Given With Enfortumab Vedotin and Pembrolizumab in People With Urothelial Cancer (MK-3475-04D/KEYMAKER-U04)

Inclusion Criteria: The main inclusion criteria include but are not limited to the following: * Has histologically documented urothelial carcinoma (UC) that is locally advanced and unresectable or metastatic * Must provide a newly obtained or archival tumor tissue sample (core or excisional biopsy) * Must not have received prior systemic therapy for locally advanced or metastatic UC * If infected with Human Immunodeficiency Virus (HIV), has well controlled HIV on antiretroviral therapy * If positive for hepatitis B surface antigen, has received hepatitis B virus (HBV) antiviral therapy for at least 4 weeks and has undetectable HBV viral load before randomization * If participant has a history of hepatitis C virus (HCV), has undetectable HCV viral load before randomization Exclusion Criteria: The main exclusion criteria include but are not limited to the following: * Has history of documented severe dry eye syndrome, severe Meibomian gland disease and/or blepharitis, or corneal disease that prevents/delays corneal healing * Has active keratitis or corneal ulcerations * Has active inflammatory bowel disease requiring immunosuppressive medication, or previous history of inflammatory bowel disease (eg, Crohn's disease, ulcerative colitis, or chronic diarrhea) * Has uncontrolled, significant cardiovascular disease or cerebrovascular disease within the 6 months preceding study intervention * Has a history of uncontrolled diabetes * Has pleural effusion, ascites, and/or pericardial effusion that are symptomatic or require repeated drainage * Has active autoimmune disease that has required systemic treatment in the past 2 years * Has known additional malignancy that is progressing or has required active treatment within the past 2 years * Has known active central nervous system metastases and/or carcinomatous meningitis * Has a history of (noninfectious) pneumonitis/interstitial lung disease that required steroids, or has current pneumonitis/interstitial lung disease * Has an active infection requiring systemic therapy * If infected with HIV, has a history of Kaposi's sarcoma and/or Multicentric Castleman's Disease * Has concurrent active HBV and HCV infection * Has a history of stem cell/solid organ transplant