INCLUSION CRITERIA:

          1. Age ≥18 years

          2. Histologically confirmed diagnosis, according to the World Health Organization (WHO,
             2008) classification, of: DLBCL NOS, THRLBCL, EBV-positive DLBCL, composite lymphoma
             with a DLBCL component with a DLBCL relapse subsequent to DLBCL treatment, disease
             transformed from an earlier diagnosis of low grade lymphoma (i.e. an indolent
             pathology such as follicular lymphoma, marginal zone lymphoma) into DLBCL with a DLBCL
             relapse subsequent to DLBCL treatment.

          3. Fresh tumour tissue for central pathology review must be provided as an adjunct to
             participation in this study. Should it not be possible to obtain a fresh tumour tissue
             sample, archival paraffin embedded tumour tissue acquired ≤3 years prior to screening
             for this protocol must be available for this purpose.

          4. Patients must have:

               1. relapsed or refractory DLBCL

               2. at least one bidimensionally measurable disease site. The lesion must have a
                  greatest transverse diameter of ≥1.5 cm and greatest perpendicular diameter of
                  ≥1.0 cm at baseline. The lesion must be positive on PET scan

               3. received at least one, but no more than three previous systemic therapy lines for
                  the treatment of DLBCL. At least one previous therapy line must have included a
                  CD20-targeted.

               4. ECOG 0 to 2

          5. Patients after failure of ASCT or patients considered in the opinion of the
             investigator currently not eligible for HDC with subsequent ASCT.

          6. Patients must meet the following laboratory criteria at Screening:

               1. ANC ≥1.5 × 109/L (unless secondary to bone marrow involvement by DLBCL)

               2. PLTs ≥90 × 109/L (unless secondary to bone marrow involvement by DLBCL) and
                  absence of active bleeding

               3. total serum bilirubin ≤2.5 × ULN unless secondary to Gilbert's syndrome (or
                  pattern consistent with Gilbert's) or documented liver involvement by lymphoma.
                  Patients with Gilbert's syndrome or documented liver involvement by lymphoma may
                  be included if their total bilirubin is ≤5 x ULN

               4. ALT, AST and AP ≤3 × ULN or <5 × ULN in cases of documented liver involvement by
                  lymphoma

               5. serum creatinine ≤2.0 x ULN or creatinine clearance must be ≥40 mL/min calculated
                  using a standard Cockcroft-Gault formula (Cockroft & Gault, 1976)

          7. For a female of childbearing potential (FCBP), a negative pregnancy test must be
             confirmed before enrolment. An FCBP must commit to take highly effective contraceptive
             precautions without interruption during the study and for 3, 6 or 12 months after the
             last dose of Tafasitamab, BEN or RTX respectively, whichever is later. An FCBP must
             refrain from breastfeeding and donating blood or oocytes during the course of the
             study and for 3, 6 or 12 months after the last dose of Tafasitamab, BEN or RTX
             respectively, whichever is later. Restrictions concerning blood donations apply as
             well to females who are not of childbearing potential.

          8. Males must use an effective barrier method of contraception without interruption
             during the study and for 3, 6 or 12 months after the last dose of Tafasitamab, BEN or
             RTX respectively, whichever is later, if the patient is sexually active with an FCBP.
             Males must refrain from donating blood or sperm during study participation and for 3,
             6 or 12 months after the last dose of Tafasitamab, BEN or RTX respectively, whichever
             is later.

          9. In the opinion of the investigator, the patients must:

               1. be able to comply with all study-related procedures, medication use, and
                  evaluations

               2. be able to understand and give informed consent

               3. not be considered to be potentially unreliable and/or not cooperative.

        EXCLUSION CRITERIA:

          1. Patients who have: any other histological type of lymphoma including, e.g., primary
             mediastinal (thymic) large B-cell lymphoma (PMBL) or Burkitt's lymphoma, primary
             refractory DLBCL, patients with known "double/triple hit" DLBCL genetics, CNS lymphoma
             involvement in present or past medical history

          2. Patients who had a major surgery less than 30 days prior to Day 1 dosing

          3. Patients who have, within 14 days prior to Day 1 dosing:

               1. not discontinued CD20-targeted therapy, chemotherapy, radiotherapy,
                  investigational anticancer therapy or other lymphoma-specific therapy

               2. received live vaccines

               3. required parenteral antimicrobial therapy for active, intercurrent systemic
                  infections

          4. Patients who:

               1. in the opinion of the investigator, have not recovered sufficiently from the
                  adverse toxic effects of prior therapies, major surgeries or significant
                  traumatic injuries

               2. were previously treated with CD19-targeted therapy or BEN

               3. have a history of previous severe allergic reactions to compounds of similar
                  biological or chemical composition to Tafasitamab, RTX, murine proteins or BEN,
                  or the excipients contained in the study drug formulations

               4. have undergone ASCT within a period of ≤3 months prior to signing the informed
                  consent form. Patients who have a more distant history of ASCT must exhibit full
                  haematological recovery before enrolment into the study.

               5. have undergone previous allogeneic stem cell transplantation

               6. concurrently use other anticancer or experimental treatments

          5. Prior history of malignancies other than DLBCL, unless the patient has been free of
             the disease for ≥3 years prior to Screening. Exceptions to the ≥3-year time limit
             include history of the following:

               1. basal cell carcinoma of the skin

               2. squamous cell carcinoma of the skin

               3. carcinoma in situ of the cervix, breast and bladder

             f) incidental histological finding of prostate cancer (Tumour/Node/Metastasis [TNM]
             stage of T1a or T1b)

          6. Patients with:

               1. positive hepatitis B and/or C serology

               2. known seropositivity for or history of active viral infection with HIV

               3. evidence of active, severe uncontrolled systemic infections or sepsis

               4. a history or evidence of severely immunocompromised state

               5. a history or evidence of severe hepatic impairment (total serum bilirubin > 3
                  mg/dL), jaundice unless secondary to Gilbert's syndrome or documented liver
                  involvement by lymphoma

               6. a history or evidence of clinically significant cardiovascular, cerebrovascular,
                  CNS and/or other disease that, in the investigator's opinion, would preclude
                  participation in the study or compromise the patient's ability to give informed
                  consent