Inclusion Criteria:  Provide signed written informed consent, which includes compliance with the requirements and restrictions listed in the consent form. Male or female, 18-70 years old (at the time consent is obtained) Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. Histologically confirmed diagnosis of DLBCL in a subject who has been pretreated with at least 2 lines of systematic treatment (regimens containing anthracyclines and anti-CD20 immunotherapy must be included); Subjects whose most recent therapy was CAR-T cell therapy were also eligible.  Exclusion Criteria:  Patients previously exposed to any anti-LAG-3 treatment.  History of ≥Grade 3 CRS, neurotoxicity, or hemophagocytic lymphohistiocytosis) during previous CAR-T cell therapy. Impaired cardiac function or clinically significant cardiac disease. Active, known or suspected autoimmune disease or a documented history of autoimmune disease within two years prior to screening with a few exceptions as per protocol.