This is an open-label, multicentre study too Evaluate the Safety and Pharmacokinetics of a Modified Tafasitamab IV Dosing Regimen Combined with Lenalidomide (LEN) in Patients with Relapsed or Refractory Diffuse Large B-Cell Lymphoma (R/R DLBCL) who have had at least one, but no more than three prior systemic regimens and who are not eligible for high dose chemotherapy (HDC) with autologous stem-cell transplantation (ASCT) at the time of study entry.