• 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.