Inclusion Criteria:
1. Age ≥ 18 years, male or female;
2. Histologically confirmed diffuse large B-cell lymphoma (DLBCL);
3. Relapsed/refractory (R/R) disease；
4. At least one prior line of therapy containing rituximab;
5. Subjects must have at least one measurable lesion;
6. ECOG PS 0-2;
7. Life expectancy ≥ 3 months;
8. Adequate organ and bone marrow function, without severe hematopoietic abnormalities or cardiac, pulmonary, hepatic, renal, thyroid dysfunction, or immunodeficiencies;
9. Female subjects of childbearing potential (WOCBP) must have a negative serum pregnancy test within 7 days prior to the first dose of study drug; WOCBP subjects and male subjects with WOCBP partners must agree to practice effective contraceptive measures from the time of signing the informed consent form (ICF) until 6 months after the last dose of study drug;
10. Signed informed consent form (ICF), voluntarily agreeing to participate in this study.
Exclusion Criteria:
1. Patient is a candidate for hematopoietic stem cell transplantation.
2. Prior allogeneic hematopoietic stem cell transplantation.
3. Primary or secondary central nervous system (CNS) lymphoma or history of CNS lymphoma.
4. History of severe hypersensitivity or anaphylactic reaction to humanized or murine monoclonal antibodies.
5. Prior treatment with an EZH2 inhibitor, and/or an anti-CD20 and CD3 bispecific antibody, and/or GemOx (gemcitabine and oxaliplatin).
6. History of other malignancies within the past 2 years requiring systemic therapy.
7. Receipt of systemic anti-neoplastic therapy, including chemotherapy, immunotherapy, biologic therapy, etc., within 14 days prior to the start of study treatment.
8. Major surgery (excluding diagnostic procedures) within 28 days prior to the start of study treatment.
9. Presence of any active, known, or suspected autoimmune disease. (Subjects who are in a stable condition and do not require systemic immunosuppressive therapy are permitted to enroll.)
10. Use of immunosuppressive agents, including systemic corticosteroids, within 14 days prior to study drug administration (use of ≤10 mg/day prednisone or equivalent is permitted).
11. Any active infection requiring systemic anti-infective therapy within 14 days prior to the start of study treatment.
12. Presence of any uncontrolled comorbid conditions that may affect compliance with the study protocol, including major cardiovascular disease, bleeding disorders, etc.
13. Active hepatitis B virus (HBV) infection (HBV DNA positive) or hepatitis C virus (HCV) infection.
14. Known history of human immunodeficiency virus (HIV) positivity.
15. Inability to swallow oral medication, or any other factor affecting oral drug administration and absorption.
16. Known history of hypersensitivity to the study drug.
17. Pregnant or breastfeeding women.
18. Any other condition deemed inappropriate for inclusion by the investigator.
