This is a multicenter, randomized, open-label, phase 3 clinical study to evaluate the efficacy of SHR-A1912 combined with R-GemOx in relapsed refractory diffuse large B-cell lymphoma.

Inclusion Criteria:

1. Histologically confirmed diffuse large B-cell lymphoma (DLBCL).
2. Have received ≥1 line of systemic antitumor therapy.
3. At least one bi-dimensionally measurable lesion.
4. Expected survival of at least 3 months.
5. Age ≥18 years old and under 80 years old.
6. The patients voluntarily participated in the study, signed informed consent, had good compliance and were willing to cooperate with follow-up.

Exclusion Criteria:

1. Central nervous system lymphoma involvement.
2. Primary mediastinal (thymus) large B-cell lymphoma.
3. Patients who have only one prior line therapy and are candidates for stem cell transplantation.
4. A history of immunodeficiency.
5. A history of severe cardiovascular disease.
6. A history of other malignancies within 5 years prior to administration of the first dose.