A Study to Evaluate the Safety, Tolerability, Drug Levels, and Preliminary Efficacy of Relatlimab Plus Nivolumab in Pediatric and Young Adults With Hodgkin and Non-Hodgkin Lymphoma

Inclusion Criteria:

• Participants with pathologically confirmed high-risk R/R cHL, after non-response toor failure of 1or more lines of standard therapy.

• Participants with pathologically confirmed R/R NHL after non-response to or failureof 1or more lines of standard therapy, including, but not limited to, R/R primarymediastinal B-cell lymphoma, diffuse large B-cell lymphoma (DLBCL), mediastinal grayzone lymphoma (MGZL), anaplastic large cell lymphoma (ALCL), or peripheral T-celllymphoma (PTCL).

• Participants with pathologically confirmed R/R NHL after non-response to or failureof 2 or more lines of standard therapy, including Burkitt lymphoma (blast count <25%malignant Burkitt cells and/or per the investigator's clinical assessment of riskstatus), lymphoblastic lymphoma (blast count < 25% of marrow nucleated cells and/orper the investigator's clinical assessment of risk status), NK/T-cell lymphoma (nasal and non-nasal NK/T-cell lymphoma subtypes, but not aggressive NK/T-cellleukemia/lymphoma subtype).

• The participant's current disease state must be R/R to standard therapy.

• Participants must have measurable PET positive disease in both cHL and NHL cohorts.

Exclusion Criteria:

• Primary CNS lymphoma of the brain or spinal cord, and secondary CNS lymphoma (ie,from systemic non-Hodgkin lymphoma) involving the brain, spinal cord, or withleptomeningeal seeding.

• Prior treatment with an anti-cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA-4) antibody, or any other antibody or drug specifically targeting T-cellco-stimulation or checkpoint pathways, with the exception of anti-PD(L)-1 targetedtherapies.

• Prior treatment with lymphocyte activation gene-3 (LAG-3)-targeted agents.

• Participants with clinically significant systemic illnesses unrelated to the canceras judged by the investigators, which would compromise the participant's ability totolerate the study treatment.

• Participants with autoimmune disease.

• Prior allogeneic bone marrow transplantation.

Other protocol-defined inclusion/exclusion criteria apply