Inclusion Criteria

Inclusion criteria:

- Histologically-confirmed diagnosis of unresectable Stage III or metastatic melanoma
not amenable to local therapy (excluding uveal or ocular melanoma)

- At least one measurable lesion

- No prior systemic treatment (excluding adjuvant or neoadjuvant therapy) for melanoma
(first line) or one prior systemic treatment (excluding adjuvant or neoadjuvant
therapy) for melanoma (second line)

- Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1

- Archived tissue sample or new biopsy sample

- Female participants of childbearing potential and male participants must agree to use
effective contraception from Visit 1 to 120 days after the last dose of study drug;
male participants must agree to use an adequate method of contraception starting with
the first dose of study drug through 120 days after the last dose of study drug

Exclusion criteria:

- Prior treatment with ipilimumab or other anti-cytotoxic T-Lymphocyte Antigen 4
(CTLA-4) agent or any anti-programmed cell death (PD-1 or PD-L2) agent

- Chemotherapy, radioactive, or biological cancer therapy within four weeks prior to
the first dose of study drug, or not recovered from adverse events caused by cancer
therapeutics administered more than four weeks earlier

- Currently participating or has participated in a study of an investigational agent or
using an investigational device within 30 days of the first dose of study drug

- Expected to require any other form of systemic or localized antineoplastic therapy
while on study

- On any systemic steroid therapy within one week before the planned date for first
dose of randomized treatment or on any other form of immunosuppressive medication

- History of a malignancy (other than the disease under treatment in the study) within
5 years prior to first study drug administration, excluding adequately treated Stage
1 or Stage 2 basal/squamous cell carcinoma of the skin, carcinoma in situ of the
cervix or breast, or other in situ cancers.

- Known active central nervous system (CNS) metastases and/or carcinomatous meningitis;
participants with previously treated brain metastases are eligible

- Severe hypersensitivity reaction to treatment with another monoclonal antibody

- Active autoimmune disease or a documented history of autoimmune disease or syndrome
that requires systemic steroids or immunosuppressive agents

- Active infection requiring systemic therapy

- Known history of Human Immunodeficiency Virus (HIV)

- Known history of or positive for Hepatitis B or C

- Known psychiatric or substance abuse disorder

- Regular user (including recreational use) of illicit drugs or had a recent history
(within the last year) of substance abuse (including alcohol)

- Pregnant or breastfeeding, or expecting to conceive, or father children within the
projected duration of the study