A Study Evaluating the Safety and Efficacy of Glofitamab + Gemcitabine + Oxaliplatin in U.S. Patients With Relapsed or Refractory Diffuse Large B-Cell Lymphoma

Inclusion Criteria: * Histologically confirmed DLBCL, not otherwise specified (NOS) * Relapsed (disease that has recurred following a response that lasted ≥ 6 months after completion of the last line of therapy) or refractory ( disease that did not respond to or that progressed \< 6 months after completion of the last line of therapy) disease * At least one prior line of systemic therapy * Participants who have failed only one prior line of therapy must not be a candidate for high-dose chemotherapy followed by autologous stem cell transplant (ASCT) * At least one bi-dimensionally measurable (\> 1.5 cm) nodal lesion, or one bi-dimensionally measurable (\> 1 cm) extranodal lesion, as measured on CT scan * Eastern Cooperative Oncology Group (ECOG) Performance Status of 0, 1, or 2 Exclusion Criteria: * Prior enrollment in Study GO41944 (STARGLO; NCT04408638) * Participant has failed only one prior line of therapy and is a candidate for stem cell transplantation * History of transformation of indolent disease to DLBCL * High-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements, and high-grade B-cell lymphoma NOS, as defined by 2016 WHO guidelines * Primary mediastinal B-cell lymphoma * History of severe allergic or anaphylactic reactions to humanized or murine monoclonal antibodies (or recombinant antibody-related fusion proteins) or known sensitivity or allergy to murine products * Prior treatment with glofitamab or other bispecific antibodies targeting both CD20 and CD3 * Prior treatment with gemcitabine or oxaliplatin * Peripheral neuropathy or paresthesia assessed to be Grade \>/= 2 according to NCI CTCAE v5.0 at enrollment * Treatment with radiotherapy, chemotherapy, immunotherapy, immunosuppressive therapy, or any investigational agent for the purposes of treating cancer within 2 weeks prior to first study treatment * Treatment with monoclonal antibodies for the purposes of treating cancer within 4 weeks prior to first study treatment * Primary or secondary CNS lymphoma at the time of recruitment or history of CNS lymphoma * Prior CNS involvement that has been definitively treated and confirmed via MRI or cerebrospinal fluid analysis to be in complete remission is permissible * Current or history of CNS disease, such as stroke, epilepsy, CNS vasculitis, or neurodegenerative disease * History of other primary malignancy, with exceptions defined by the protocol * Significant or extensive cardiovascular disease, or significant pulmonary disease * Known active bacterial, viral, fungal, mycobacterial, parasitic, or other infection (exclusing fungal infections of nail beds) at study enrollment or any major episode of infection within 4 weeks prior to the first study treatment * Documented severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection within 6 months of first study treatment, or positive SARS-CoV-2 test within 7 days prior to enrollment * Suspected or latent tuberculosis * Positive test results for hepatitis B (HBV) or hepatitis C (HCV) * Known or suspected chronic active Epstein-Barr viral infection * Known or suspected history of hemophagocytic lymphohistiocytosis (HLH) * Known history of progressive multifocal leukoencephalopathy * Prior solid organ transplantation * Prior allogenic stem cell transplant * Active autoimmune disease requiring treatment * Prior treatment with systemic immunosuppressive medications within 4 weeks prior to first dose of study treatment * Ongoing systemic corticosteroid use which, in the opinion of the investigator, puts the patient at increased risk of steroid-related iatrogenic adrenal insufficiency * Recent major surgery (within 4 weeks before the first study treatment) other than for diagnosis * Clinically significant history of cirrhotic liver disease