This clinical trial is focused on studying a type of cancer known as Relapsed/Refractory Aggressive Mature B-cell Neoplasms, which includes specific subtypes like Burkitt’s lymphoma, Burkitt-like lymphoma, and Diffuse Large B-cell Lymphoma (DLBCL). These are aggressive forms of cancer that affect a type of white blood cell called B-cells. The study is testing a new treatment called Epcoritamab (GEN3013), which is a type of medicine known as a bispecific antibody. This medicine is given as a solution for injection under the skin.

The purpose of the study is to evaluate the safety and how the body processes Epcoritamab in children and young adults who have these types of B-cell cancers and have not responded to previous treatments. Participants in the study will receive the medication and be monitored for any side effects and how well the treatment is tolerated. The study will also look at how the medicine moves through and affects the body.

Throughout the study, researchers will observe participants for any serious side effects, such as Cytokine Release Syndrome (CRS), which is a reaction that can occur when the immune system is activated, and Immune Cell-Associated Neurotoxicity Syndrome (ICANS), which affects the nervous system. The study will also track how long participants live without the cancer getting worse, their overall survival, and the possibility of needing further treatments like stem cell transplants or CAR-T cell therapy. The study aims to provide valuable information about the potential benefits and risks of using Epcoritamab for treating these aggressive cancers in young patients.