Pembrolizumab and Tazemetostat to Overcome Immune Tolerance Following ASCT or CAR T-cell Therapy in Patients With Aggressive B-Cell Non-Hodgkin's Lymphoma

This study is testing a combination of two drugs — pembrolizumab (an immunotherapy) and tazemetostat (a targeted therapy) — for people with aggressive B-cell lymphoma who are receiving or planning to receive a stem cell transplant or CAR T-cell therapy. The goal is to see if these drugs can help the immune system work better after these intensive treatments. **You may be eligible if...** - You have been diagnosed with an aggressive form of B-cell non-Hodgkin lymphoma - You are planned for or currently undergoing a stem cell transplant (autologous) or CAR T-cell therapy - Your treatment used one of the approved CAR T-cell products (axicabtagene ciloleucel, tisagenlecleucel, or lisocabtagene maraleucel) - You are generally well enough to tolerate the study treatment **You may NOT be eligible if...** - You have active, uncontrolled autoimmune disease - You are on long-term steroid or immunosuppressive medication - You have serious liver, kidney, or heart problems - You have active infections (such as HIV, hepatitis B or C) - You have had prior treatment with tazemetostat or similar EZH2 inhibitors Talk to your doctor to see if this trial is right for you.