Clinical Trial of TQB2825 Injection Combined 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.