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

Number of Participants With Dose-Limiting Toxicities (DLTs) - Part A

Hepatic DLT * ALT or AST \> 8 × ULN * ALT or AST \> 5 and ≤ 8 × ULN, that fails to return to ≤ Grade 1 within 2 weeks despite medical intervention. * TB \> 5 × ULN. * ALT or AST \> 3 × ULN and concurrent total bilirubin \> 2 × ULN. Non-Hematologic DLT * ≥ Grade 2 episcleritis, uveitis, iritis or any other immune-related eye pain or reduction in visual acuity that requires systemic treatment. * ≥ Grade 3 non-hepatic or non-hematologic toxicity with the exceptions noted below. Hematologic DLT * Grade 4 anemia not explained by underlying disease. * Grade 3 febrile neutropenia lasting \> 48 hours, or Grade 4 febrile neutropenia * Grade 4 neutropenia that does not resolve to Grade 3 or less within 5 days of initiation of granulocyte colony stimulating factor. * Grade 3 thrombocytopenia associated with clinically significant bleeding. * Grade 3 hemolysis

Time frame: 1 cycle, defined as 28 days

Complete Metabolic Response (CMR) Rate - Part B

The CMR rate is defined as the percentage of all response-evaluable participants who achieve the best response of CMR using Lugano 2014 criteria. No participants enrolled in Part B.

Time frame: From first dose until the first documented response

Number of Participants With Adverse Events (AEs) - Part A

An adverse event (AE) is defined as any new untoward medical occurrence or worsening of a pre-existing medical condition in a clinical investigation participant administered study treatment that does not necessarily have a causal relationship with this treatment.

Time frame: From first dose to 135 days post last dose (Up to approximately 11 months)

Number of Participants Who Died - Part A

Number of participants who died due to any cause

Time frame: from first dose to 135 days post last dose (Up to approximately 11 months)

Number of Participants With Serious Adverse Events (SAEs) - Part A

Serious Adverse Event (SAE) is defined as any untoward medical occurrence that, at any dose results in death, is life-threatening, and requires inpatient hospitalization or causes prolongation of existing hospitalization.