Evaluate the Safety and Efficacy of Tafasitamab and Lenalidomide in Combination With Gemcitabine and Oxaliplatin Versus Rituximab in Combination With Gemcitabine and Oxaliplatin in Patients With Relapsed/Refractory Diffuse Large B-Cell Lymphoma

Prior treatment

• Prior exposure to anti-CD19 treatment, and (or) failed with gemcitabine plus platinum-based agent combination therapy.

Other illness

• Existing or prior history of other malignant tumor within 3 years, except for those who have received curative treatment.
• Current or history of central nervous system (CNS) lymphoma.
• History of allogeneic stem-cell transplantation.
• Clinically significant cardiovascular disease or nervous system disease.
• History of deep venous thrombosis/embolism, threatening thromboembolism or known thrombophilia or are at a high risk for a thromboembolic event in the opinion of the investigator and who are not willing/able to take venous thromboembolic event prophylaxis during the entire treatment period.
• Uncontrolled systemic infection requiring parenteral intravenous anti-infective therapy.
• Known human immunodeficiency virus (HIV), or serologic status reflecting active hepatitis B or C infection.

Lab values

• Current toxicity of ≥ Grade 2 from prior anti-cancer therapy (except for alopecia, neutrophil, hemoglobin and platelets).

Other

• Known high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements.
• Primary mediastinal B-cell lymphoma.

• 18 Years and older.
• One of the histologies of DLBCL confirmed by participated sites below with，not otherwise specified;T-cell/histiocyte-rich large B-cell lymphoma;Epstein-Barr virus (EBV) positive DLBCL (EBV-positive DLBCL); Composite lymphoma with a DLBCL component with a subsequent DLBCL relapse; Disease transformed from an earlier diagnosis of low-grade lymphoma into DLBCL with DLBCL treatment failure.
• Availability of tumor tissue biopsied post last line of therapy and prior to current study treatment for the patients enrolled in safety and tolerability stage.
• Relapsed/refractory (R/R) DLBCL, at least one (≥1) but no more than three (≤3) line of prior systemic therapies.
• Patients who have not received high dose therapy/stem cell transplantation (HDT/SCT) must be ineligible for HDT/SCT.
• At least one measurable site of disease per CT or magnetic resonance imaging (the longest axis of the lymph node lesion is \> 1.5 cm, and the longest diameter of the extra-nodal lesion is \> 1.0 cm).
• ECOG PS score of 0 to 2.
• Subject must have adequate organ functions, and the laboratory values comply with the protocol requirements.
• Life expectancy of ≥ 3 months.
• Informed consent before screening and can understand and comply with the requirements of the study.