Safety and Efficacy Study of Pembrolizumab (MK-3475) in Chinese Participants With Locally Advanced or Metastatic Melanoma (MK-3475-151/KEYNOTE-151)

Inclusion Criteria:

* Is of the Chinese descent, was born in China, and has a Chinese home address.
* Has histologically confirmed diagnosis of locally advanced (unresectable Stage III) or metastatic (Stage IV) melanoma not amenable to local therapy.
* Participant may not have a diagnosis of uveal or ocular melanoma.
* Overall proportion of participants with mucosa melanoma will be no more than 22%.
* Has failed the first line chemotherapy (excluding adjuvant or neoadjuvant therapy) or targeted therapy for melanoma.
* Has at least one measurable lesion as defined by RECIST 1.1 on imaging studies (computed tomography \[CT\] or magnetic resonance imaging \[MRI\]).
* Has a performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG) Performance Scale.
* Has an anticipated life expectancy of at least 3 months.
* Demonstrates adequate organ function.
* Has provided tissue for anti-programmed cell death ligand-1 (PD-L1) expression evaluation from an archival tissue sample or newly obtained core or excisional biopsy of a tumor lesion not previously irradiated.
* Has documented BRAF mutation status or is willing to provide a tumor tissue for BRAF genotyping.
* Females may be enrolled in the study if they are:
* Of non-childbearing potential which is defined as:

  * Is ≥45 years of age and has not had menses for greater than 2 years.
  * Is amenorrheic for \<2 years without a hysterectomy and oophorectomy and has a follicle stimulating hormone (FSH) value in the postmenopausal range upon screening evaluation, and/or,
  * Is status post hysterectomy, oophorectomy or tubal ligation.
* Female and male participants of childbearing potential must be willing to use an adequate method of contraception for the course of the study through 120 days after the last dose of study treatment. Note: Abstinence is acceptable if this is the usual lifestyle and preferred contraception for the participant.

Exclusion Criteria:

* Has received prior therapy with an anti-programmed cell death 1 (anti-PD-1), anti-PD-L1, anti-PD-L2 agents.
* Is currently participating and receiving study therapy or has participated in a study of an investigational agent and received study therapy or used an investigation device within 4 weeks of the first dose of study drug.
* Has had a prior anti-cancer monoclonal antibody (mAb) within 4 weeks prior to the first dose of study drug or who has not recovered (i.e., ≤ Grade 1 or baseline) from AEs due to agents administered more than 4 weeks earlier.
* Has had chemotherapy, targeted small molecule therapy, radiotherapy within 2 weeks prior to the first dose of study drug, or who has not recovered (i.e., ≤ Grade 1 or baseline) from AEs due to a previously administered agent.
* Has a known history of another (including unknown primary) malignancy within 5 years prior to first dose of study drug. (Exceptions include adequately treated Stage 1 or Stage 2 basal/squamous cell carcinoma of the skin, superficial bladder cancer, or cancer in situ which has undergone potentially curative therapy.)
* Is expected to require any other form of systemic or localized antineoplastic therapy while in study.
* Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis.
* Has active autoimmune disease that has required systemic treatment in past 2 years (i.e., with use of disease modifying agents, corticosteroids or immunosuppressive drugs).
* Is receiving systemic steroid therapy or any other form of immunosuppressive therapy within 1 week prior to the first dose of study drug.
* Has an active infection requiring intravenous systemic therapy.
* Has received a live vaccine within 4 weeks prior to the first dose of study drug.
* Has a known hypersensitivity to the components of the study drug or another mAb.
* Has a history of (non-infectious) pneumonitis that required steroids or current pneumonitis.
* Is known to be Human Immunodeficiency Virus (HIV) positive.
* Has known active Hepatitis B or C.
* Has known psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the study.
* Is pregnant or breastfeeding, or expecting to conceive or father children within the projected duration of the study, starting with the screening visit (Visit 1) through 120 days after the last dose of study treatment.