A Study to Evaluate the Safety and Efficacy of SCTB35 in Combination With Gemcitabine and Oxaliplatin in Patients With Relapsed or Refractory Diffuse Large B-Cell Lymphoma

Inclusion Criteria: * Age 18-80 years old * Histologically confirmed diffuse large B-cell lymphoma according to WHO 2022 criteria * Relapsed or refractory (R/R) disease following at least one prior systemic regimen that contained an anti-CD20 monoclonal antibody (mAb) in combination with chemotherapy * Participants who have failed after one prior line of therapy are not candidates for high-dose chemotherapy followed by autologous stem cell transplant (ASCT) * Presence of measurable or evaluable disease at baseline ECOG PS 0-2 * ECOG PS 0-2 * Adequate organ function and bone marrow function * Expected survival ≥ 3 months Exclusion Criteria: * Prior treatment with antibodies targeting both CD20 and CD3 * Contraindication to rituximab, gemcitabine or oxaliplatin, or prior treatment with an anti-CD20 antibody in combination with the GemOx regimen * Peripheral neuropathy assessed to be Grade \>1 according to National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) v6.0 at enrollment * Known central nervous system (CNS) involvement by lymphoma * Known any major episode of active infection requiring treatment with systemic antibiotics within 2 weeks * Treatment with chimeric antigen receptor T-cell (CAR-T) therapy within 100 days prior to first SCTB35 administration * Autologous HSCT within 100 days prior to first SCTB35 administration, or any prior allogeneic HSCT or solid organ transplantation * Major surgery within 4 weeks prior to first SCTB35 administration * Chemotherapy and other non-investigational antineoplastic agents (except CD20 mAbs) within 4 weeks or 5 half-lives (whichever is shorter) prior to first SCTB35 administration * Administration of a live, attenuated vaccine within 4 weeks before first study treatment administration or anticipation that such a live, attenuated vaccine will be required during the study