• Participants with relapsed or refractory diffuse and transformed large B-cell lymphoma (R/R DLBCL). DLBCL and cell of origin (GCB versus non-GCB) will be histologically determined by local pathology assessment for the purposes of study eligibility and stratification.

• Participants must have R/R disease following 2 or more lines of prior systemic therapy.

⁃ For participants with transformed DLBCL, at least the last systemic therapy used must have been for DLBCL

• Participants must be HSCT or CAR-T ineligible according to the investigator and must meet at least one of the following criteria:

‣ One or more co-morbidities, including cardiac, pulmonary, renal or hepatic dysfunction that in the opinion of the Investigator make the participant medically unfit to received HSCT or CAR-T therapy

⁃ Active disease following induction and salvage chemotherapy

⁃ Inadequate stem cell mobilization (for HSCT)

⁃ Relapse following prior HSCT or CAR-T

⁃ Unable to receive CAR-T therapy due to financial, geographic, insurance, or manufacturing issues

• Participants must have tumor tissue submitted to the central pathology lab. The tumor tissue submitted should be from the most recent biopsy that contains DLBCL.

• An Eastern Cooperative Oncology Group (ECOG) performance status score of 0 to 2

• Participants must have fluorodeoxyglucose (FDG)-avid disease by positron emission tomography (PET) and bidimensional measurable disease of at least 1.5 cm by computed tomography (CT), as assessed by the site radiologist within 28 days of Day 1.