This study is about testing a new treatment called **LYL314** for a disease called **aggressive large B-cell lymphoma**. Lymphoma is a type of cancer that affects cells in the immune system called lymphocytes. The study is split into two parts, **Phase 1** and **Phase 2**. Phase 1 will involve up to 150 participants to find a safe dose of LYL314. Phase 2 will focus on how well LYL314 works, especially in participants from one group.

The treatment involves one dose of LYL314, given through an **IV (intravenous)** after preparing the body with two chemotherapy medicines. Participants will be closely watched for about 2 years and then checked yearly for up to 15 years to see how they are doing.

• The study includes 5 different groups of people, based on their past treatments and disease stage.
• Participants need to be 18 or older and must have had previous treatments for lymphoma.
• Some people cannot join, like those with certain other health problems or who recently had other cancer treatments.