Pembro Plus CAR T-cell Therapy in R/R in PMBCL

This study is testing whether adding the immunotherapy drug pembrolizumab (also known as Keytruda) to CAR T-cell therapy (a type of personalized immune cell treatment) improves outcomes in people with certain types of aggressive B-cell lymphomas that have returned or stopped responding to treatment. **You may be eligible if...** - You have a confirmed diagnosis of PMBCL (primary mediastinal B-cell lymphoma), EBV+ DLBCL, or THRLBCL - You are eligible to receive standard CAR T-cell therapy - Your cancer progressed after at least two prior treatment regimens, or you relapsed within 12 months of first-line therapy, or you are not a candidate for stem cell transplant - You are in good health with a heart ejection fraction of at least 50% (ECOG 0–1) **You may NOT be eligible if...** - You have active HIV, hepatitis B or C - You have an active uncontrolled infection (fungal, bacterial, or viral) - You are being treated for another active cancer - You are pregnant or breastfeeding - You have significant heart, lung, or other major organ problems Talk to your doctor to see if this trial is right for you.