This study is testing a new treatment called *zamtocabtagene autoleucel* (MB-CART2019.1) for people with a type of cancer called **diffuse large B cell lymphoma (DLBCL)**. DLBCL is a kind of cancer that affects the immune system. The study will also include people with other related cancers, such as B-cell lymphoma in the brain and mantle cell lymphoma. To join, participants must have tried at least two other treatments that didn’t work.

The study will use special cells, called **CAR-T cells**, made from the patient's own blood. These cells are changed in a lab to help them fight cancer better. Patients will take medicines to prepare their bodies before receiving the CAR-T cells through an IV.

• The study lasts up to 2 years, with more follow-up afterward.
• Participants will have multiple visits and treatments.
• They will be monitored for safety and how well the treatment works.

Eligibility includes having certain types of lymphoma and being in good enough health. Pregnant women or those with certain infections can't join. Participants need to have enough time after other treatments before starting this one.