A Study of Efficacy and Safety of Pembrolizumab Plus Enfortumab Vedotin (EV) +/- Investigational Agents in First-Line Metastatic Urothelial Carcinoma (mUC) (MK-3475-04B/KEYMAKER-U04)

The master study for this substudy is MK-3475-U04/KEYMAKER-U04. The master study will not be screening any participants and will not be registered. With Amendment 2, participants will discontinue treatment with coformulated vibostolimab/pembrolizumab (Arm B) and be transitioned to pembrolizumab only. Per protocol, no analysis of Part 2 primary or secondary outcome measures (including efficacy or safety) will occur since Part 2 of the study will no longer take place.