This study is testing a new treatment called MB-CART2019.1 for people with a type of blood cancer called diffuse large B-cell lymphoma (DLBCL). DLBCL is cancer that affects certain white blood cells. The treatment uses special T cells from the patient, modified to fight cancer. This process is called autologous T-cell therapy. Participants must have tried at least two other treatments that didn't work. The study will take about two years, during which doctors will monitor participants for cancer response and side effects.

• The study lasts for up to 2 years with regular follow-ups.
• Participants must have tried at least two previous cancer treatments.
• Participants will receive compensation for their time and effort.

Before joining, patients will be screened to ensure they qualify. They must be adults with a performance status of 0 or 1, meaning they can carry out daily activities with little assistance. Exclusions include active infections, pregnancy, and certain health conditions. The study will be conducted at multiple centers, with an initial safety phase before enrolling more participants. This study is important for finding new ways to treat people whose DLBCL has come back or hasn't responded to other treatments.