A Study of Pembrolizumab (MK-3475) in Pediatric Participants With an Advanced Solid Tumor or Lymphoma (MK-3475-051/KEYNOTE-051)

Inclusion Criteria:

- Between 6 months and <18 years of age (or between 3 years and <18 years of age for
rrcHL participants) on day of signing informed consent/assent (the first 3
participants dosed in Part 1 are to be ≥ 6 years of age)

- Histologically- or cytologically-documented, locally-advanced, or metastatic solid
malignancy or lymphoma that is incurable and has failed prior standard therapy, or for
which no standard therapy exists, or for which no standard therapy is considered
appropriate

- Any number of prior treatment regimens

- Tissue (or lymph node biopsy for rrcHL participants) available from an archival tissue
sample or, if appropriate, a newly obtained core or excisional biopsy of a tumor
lesion not previously irradiated

- Advanced melanoma or PD-L1-positive advanced, relapsed, or refractory solid tumor or
lymphoma

- Measurable disease based on RECIST 1.1 (Or based on IWG [Cheson, 2007] [i.e.,
measurement must be >15 mm in longest diameter or >10 mm in short axis] for rrcHL
participants)

- Participants with neuroblastoma with only metaiodobenzylguanidine (MIBG)-positive
evaluable disease may be enrolled

- Lansky Play Scale ≥50 for participants from 6 months up to and including 16 years of
age; or Karnofsky score ≥50 for participants >16 years of age

- Adequate organ function

- Female participants of childbearing potential should have a negative urine or serum
pregnancy test within 72 hours prior to receiving the first dose of study medication

- Female participants of childbearing potential must be willing to use 2 methods of
contraception or be surgically sterile, or abstain from heterosexual activity for the
course of the study through 120 days after the last dose of study medication

- Male participants of reproductive potential must agree to use an adequate method of
contraception starting with the first dose of study medication through 120 days after
the last dose of study medication

Exclusion Criteria:

- Currently participating and receiving study therapy in, or has participated in a study
of an investigational agent and received study therapy or used an investigational
device within 4 weeks of the date of allocation/randomization

- Diagnosis of immunodeficiency or receiving systemic steroid therapy or any other form
of immunosuppressive therapy within 7 days prior to the date of
allocation/randomization

- Prior systemic anti-cancer therapy including investigational agent within 2 weeks
prior to study Day 1 or not recovered from adverse events due to a previously
administered agent

- Prior radiotherapy within 2 weeks of start of study treatment

- Known additional malignancy that is progressing or requires active treatment with the
exception of basal cell carcinoma of the skin, squamous cell carcinoma of the skin or
carcinoma in situ (eg, breast carcinoma, cervical carcinoma in situ) with potentially
curative therapy, or in situ cervical cancer

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

- Tumor(s) involving the brain stem

- Severe hypersensitivity (≥ Grade 3) to pembrolizumab and/or any of its excipients

- Active autoimmune disease that has required systemic treatment in past 2 years;
replacement therapy (such as thyroxine, insulin, or physiologic corticosteroid
replacement therapy for adrenal or pituitary insufficiency) is acceptable

- Has a history of (non-infectious) pneumonitis that required steroids or current
pneumonitis.

- Active infection requiring systemic therapy

- Pregnant or breastfeeding, or expecting to conceive or father children within the
projected duration of the trial through 120 days after the last dose of study
medication

- Prior therapy with an anti-programmed cell death (PD)-1, anti-PD-ligand 1
(anti-PD-L1), anti-PD-L2 agent, or any agent directed to another stimulatory or
inhibitory T-cell receptor (eg, cytotoxic lymphocyte associated protein-4 [CTLA-4],
OX-40, CD137)

- Human immunodeficiency virus (HIV)

- Hepatitis B or C

- Known history of active tuberculosis (TB; Bacillus tuberculosis)

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

- Has undergone solid organ transplant at any time, or prior allogeneic hematopoietic
stem cell transplantation within the last 5 years. (Participants who have had an
allogeneic hematopoietic transplant >5 years ago are eligible as long as there are no
symptoms of Graft Versus Host Disease [GVHD].)

- History or current evidence of any condition, therapy, or laboratory abnormality, or
known severe hypersensitivity to any component or analog of the trial treatment, that
might confound the results of the trial, or interfere with the participant's
participation for the full duration of the study

- Known psychiatric or substance abuse disorders that would interfere with the
requirements of the study