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 on day of signing informed consent isdocumented.

• Histologically- or cytologically-documented, locally-advanced, or metastatic solidmalignancy or lymphoma that is incurable and has failed prior standard therapy, orfor which no standard therapy exists, or for which no standard therapy is consideredappropriate

• Any number of prior treatment regimens

• Tissue (or lymph node biopsy for rrcHL participants) available from an archivaltissue sample or, if appropriate, a newly obtained core or excisional biopsy of atumor lesion not previously irradiated

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

• 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 rrcHLparticipants)

• Participants with neuroblastoma with only metaiodobenzylguanidine (MIBG)-positiveevaluable disease may be enrolled

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

• Adequate organ function

• Female participants of childbearing potential should have a negative urine or serumpregnancy test within 72 hours before the first dose of study medication

• Female participant is not a woman of childbearing potential (WOCBP) or is a WOCBPwho is abstinent from heterosexual intercourse or using contraception during theintervention period and for at least 120 days after the last dose of studyintervention

• Contraceptive use by men should be consistent with local regulations regarding themethods of contraception for those participating in clinical studies.

• Demonstrate adequate organ function.

Exclusion Criteria:

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

• Diagnosis of immunodeficiency or receiving systemic steroid therapy or any otherform of immunosuppressive therapy within 7 days prior to the date ofallocation/randomization

• Prior systemic anti-cancer therapy including investigational agent within 2 weeksprior to study Day 1 or not recovered from adverse events due to a previouslyadministered agent

• Prior radiotherapy within 2 weeks of start of study treatment

• Known additional malignancy that is progressing or requires active treatment withthe exception of basal cell carcinoma of the skin, squamous cell carcinoma of theskin or carcinoma in situ (eg, breast carcinoma, cervical carcinoma in situ) withpotentially 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 corticosteroidreplacement therapy for adrenal or pituitary insufficiency) is acceptable

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

• Active infection requiring systemic therapy

• Pregnant or breastfeeding, or expecting to conceive or father children within theprojected duration of the trial through 120 days after the last dose of studymedication

• 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 orinhibitory 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 hematopoieticstem cell transplantation within the last 5 years. (Participants who have had anallogeneic hematopoietic transplant >5 years ago are eligible as long as there areno symptoms of Graft Versus Host Disease [GVHD].)

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

• Known psychiatric or substance abuse disorders that would interfere with therequirements of the study