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

This is a two-part study of pembrolizumab (MK-3475) in pediatric participants who have any of the following types of cancer: advanced melanoma (6 months to <18 years of age), advanced, relapsed or refractory programmed death-ligand 1 (PD-L1)-positive malignant solid tumor or other lymphoma (6 months to <18 years of age), relapsed or refractory classical Hodgkin lymphoma (rrcHL) (3 years to <18 years of age), or advanced relapsed or refractory microsatellite-instability-high (MSI-H) solid tumors (6 months to <18 years of age), or advanced relapsed or refractory tumor-mutational burden-high =10 mutation/Mb (TMB-H) solid tumors (6 months to <18 years of age), or with adjuvant treatment of resected high-risk Stage IIB, IIC, III, or IV melanoma in children 12 years to <18 years of age Part 1 will find the maximum tolerated dose (MTD)/maximum administered dose (MAD), confirm the dose, and find the recommended Phase 2 dose (RP2D) for pembrolizumab therapy. Part 2 will further evaluate the safety and efficacy at the pediatric RP2D. The primary hypothesis of this study is that intravenous (IV) administration of pembrolizumab to children with either advanced melanoma; a PD-L1 positive advanced, relapsed or refractory solid tumor or other lymphoma; advanced, relapsed or refractory MSI-H solid tumor; or rrcHL, will result in an Objective Response Rate (ORR) greater than 10% for at least one of these types of cancer. The 10% assessment does not apply to the MSI-H and TMB-H cohorts. With Amendment 8, enrollment of participants with solid tumors and of participants aged 6 months to <12 years with melanoma were closed. Enrollment of participants aged =12 years to =18 years with melanoma continues. Enrollment of participants with MSI-H and TMB-H solid tumors also continues.