The purpose of this study is to assess the preliminary efficacy of TQB2825 in combination with chemotherapy in subjects with diffuse large B-cell lymphoma.

Inclusion Criteria:

• The subjects voluntarily participate in this study, sign the informed consent form, and have good compliance;
• Age ≥18 years (calculated from the date of informed consent);
• Eastern Cooperative Oncology Group (ECOG) score 0 ~ 2 points;
• Expected survival greater than 12 weeks;
• Histological or cytological diagnosis of diffuse large B-cell lymphoma in accordance with the World Health Organization (WHO) diagnostic criteria in 2022;
• Pathological diagnosis results containing CD20 positive expression and Myc rearrangement negative after anti-CD20 treatment must be provided;
• Subjects with relapsed or refractory diffuse large B-cell lymphoma who have received at least 1 line of systemic therapy;
• Not suitable for hematopoietic stem cell transplantation;
• According to the Lugano criteria in 2014, there is at least one measurable lesion, that is, the long diameter of lymph node lesions > 15 mm or extranodal lesions > 10 mm according to CT cross-sectional images; Positron emission tomography - computerized tomography (PET-CT) scan shows PET positive;
• Laboratory tests meet specific criteria;
• Adopt effective contraceptive measures;

Exclusion Criteria:

• Subjects who had or currently had other malignant tumors within 5 years prior to the first dose;

• Previous or current involvement or suspected involvement of the central nervous system by lymphoma;

• Failure to recover from adverse reactions to Common Terminology Criteria for Adverse Events version 5.0 (CTCAEv5.0) criteria ≤ grade 1 from previous treatment;

• History of previous anti-tumor treatment:

  1. previous use of other antibody drugs targeting CD3 and CD20 at the same time;
  2. received Chimeric Antigen Receptor T-Cell Immunotherapy (CAR-T) therapy, or other immune cell therapy, or autologous hematopoietic stem cell transplantation (auto-HSCT) within 3 months before the first dose;
  3. previous treatment with R-GemOx or GemOx;
  4. received chemotherapy, immunotherapy, monoclonal antibody therapy 4 times before the first dose, 2 times received radiotherapy or small molecule targeted drugs, or subjects who are still within 5 half-lives of the drug, the washout period is calculated from the end time of treatment;
  5. received treatment with Chinese patent medicines with clear anti-tumor indications in the package insert of National Medical Products Administration (NMPA)-approved drugs 2 times before the first dose;

• Subjects who have undergone major surgical treatment, significant traumatic injury, or expected major surgery during the study treatment period within 4 weeks prior to the first use of medication, or have long-term untreated wounds or fractures;

• Subjects who experience any bleeding or bleeding events ≥ Common Terminology Criteria Adverse Event (CTC AE) grade 3 within 4 weeks prior to the first administration;

• Hyperactive/venous thrombotic events within 6 months prior to first dose,Such as cerebrovascular accident (including transient ischemic attack), deep venous thrombosis and pulmonary embolism or any other history of severe thromboembolism;

• Clinically significant uncontrolled pleural effusion, ascites and more than moderate pericardial effusion requiring repeated drainage;

• Decompensated cirrhosis (Child-Pugh class B or C liver function) and active hepatitis;

• Pulmonary disease, including any of the following: 1) with or without current pneumonitis requiring corticosteroid therapy; 2) with or suspected chronic obstructive pulmonary disease (COPD), and forced expiratory volume in 1 second (FEV1) < 60% (predicted);

• Brain or mental disorders;

• Have major cardiovascular disease;

• Active or uncontrolled infection (≥ CTCAE grade 2 infection), including bacterial, fungal or viral infections including but not limited to active pneumonia, syphilis and tuberculosis.

• Unexplained fever > 38.5℃ during screening or before the first dose;

• Renal failure requiring hemodialysis or peritoneal dialysis, previous history of nephrotic syndrome;

• History of immunodeficiency, including HIV-positive or other acquired, congenital immunodeficiency diseases;

• Have or have had prior autoimmune disease requiring treatment.

• Prepare to undergo or have previously received organ transplantation, or have a significant host transplant response, or have previously received allogeneic hematopoietic stem cell transplantation; 19、Need to receive systemic immunosuppressive therapy;

• Known or suspected history of hemophagocytic syndrome (HLH);

• Known hypersensitivity to excipient components of the study drug.

• Subjects who participated in other anti-tumor clinical trials within 4 or 5 half-lives before the first dose.

• Any condition that, in the judgment of the investigator, would jeopardize the safety of the subject or prevent the subject from completing the study.