Study of Pembrolizumab (MK-3475) in Participants With Advanced Urothelial Cancer (MK-3475-052/KEYNOTE-52)

Participants receiving pembrolizumab who attain a complete response (CR) may consider
stopping trial treatment if they meet criteria for holding therapy. Participants who stop
trial treatment after receiving 24 months of trial treatment for reasons other than
progressive disease (PD) or intolerability, or participants who attain a CR and stop trial
treatment may be eligible for up to one year of retreatment upon experiencing PD.

Inclusion Criteria:

- Histologically- or cytologically-confirmed diagnosis of advanced/unresectable
(inoperable) or metastatic urothelial cancer of the renal pelvis, ureter, bladder, or
urethra (transitional cell and mixed transitional/non-transitional cell histologies)

- Ineligible for cisplatin therapy

- No prior systemic chemotherapy for metastatic disease (adjuvant or neoadjuvant
platinum-based chemotherapy with recurrence >12 months since completion of therapy is
allowed)

- Available tissue from a newly obtained core or excisional biopsy of a tumor lesion
not previously irradiated

- Measureable disease

- Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1 or 2

- Adequate organ function

- Female participants of childbearing potential have a negative urine or serum
pregnancy test; surgically sterile, or willing to use 2 acceptable methods of birth
control, or abstain from heterosexual activity for the course of the study through
120 days after the last dose of study treatment

- Male participants must be willing to use an adequate method of contraception starting
with the first dose of study medication through 120 days after the last dose of study
treatment

Exclusion Criteria:

- Disease that is suitable for local therapy administered with curative intent

- Currently participating or has participated in a study of an investigational agent
and received study therapy or used an investigational device within 4 weeks prior to
the first dose of study treatment

- Prior anti-cancer monoclonal antibody (mAb) for direct anti-neoplastic treatment
within 4 weeks prior to study Day 1 or who has not recovered from adverse events due
to agents administered more than 4 weeks earlier

- Prior chemotherapy, targeted small molecule therapy, or radiation therapy within 2
weeks prior to study Day 1 or not recovered from AEs due to a previously administered
agent

- Known additional malignancy that is progressing or requires active treatment
excepting basal cell carcinoma of the skin, squamous cell carcinoma of the skin that
has undergone potentially curative therapy, or in situ cancer

- Known active central nervous system (CNS) metastases and/or carcinomatous meningitis

- Active autoimmune disease that has required systemic treatment in past 2 years

- Evidence of interstitial lung disease or active non-infectious pneumonitis

- Active infection requiring systemic therapy

- Pregnant or breastfeeding, or expecting to conceive or father children within the
projected duration of the trial, starting with the screening visit through 120 days
after the last dose of study treatment

- Prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent, or with an agent
directed to another co-inhibitory T-cell receptor

- Known human immunodeficiency virus (HIV)

- Known active Hepatitis B or C

- Received a live virus vaccine within 30 days of planned start of study treatment