This phase I trial is combining a new intravenous drug (RO7082859) with an immunotherapy (Rituximab or Obinutuzumab) and chemotherapy (CHOP) treatment in patients with newly diagnosed Diffuse Large B-Cell Lymphoma (DLBCL)A Phase 1B Study Evaluating RO7082859 in Combination With Rituximab (R) or Obinutuzumab (G) Plus Cyclophosphamide, Doxorubicin, Vincristine, and Prednisone (CHOP) in Participants With Relapsed Refractory Follicular Lymphoma (R/R FL) or in Participants With Untreated Diffuse Large B-Cell Lymphoma

Exclusion

• Inability to comply with protocol mandated hospitalization and restrictions
• Participants with known active infection, or reactivation of a latent infection, whether bacterial, viral (including, but not limited to Epstein Barr virus (EBV), cytomegalovirus (CMV), HBV, HCV, and HIV), fungal, mycobacterial, or other pathogens (excluding fungal infections of nail beds) or any major episode of infection requiring hospitalization or treatment with IV antibiotics (for IV antibiotics, this pertains to completion of last course of antibiotic treatment) within 4 weeks of dosing
• Prior treatment with systemic immunotherapeutic agents, including, but not limited to, radioimmuno-conjugates, antibody-drug conjugates, immune/cytokines, and monoclonal antibodies (e.g., anti-CTLA4, anti-PD1, and anti-PDL1) within 4 weeks or five half-lives of the drug, whichever is shorter, before G- or R-CHOP or Pola-R-CHP infusion on Cycle 1/Day 1
• Current Grade > 1 peripheral neuropathy by clinical examination or demyelinating form of Charcot-Marie-Tooth disease (only for participants treated in the polatuzumab vedotin arm)
• History of treatment-emergent immune-related AEs associated with prior immunotherapeutic agents, as follows: Grade >/=3 AEs, with the exception of Grade 3 endocrinopathy managed with replacement therapy; Grade 1-2 AEs that did not resolve to baseline after treatment completion
• Contraindication to any of the individual components of the immunochemotherapy
• Treatment with standard radiotherapy, any chemotherapeutic agent, or treatment with any other investigational anti-cancer agent within 4 weeks prior to study treatment at Cycle 1/Day 1 infusion
• Prior solid organ transplantation
• Prior allogeneic stem cell transplantation
• Autologous stem cell transplantation within 100 days prior to Cycle 1/Day 1
• Prior treatment with CAR T-cell therapy within 30 days prior to study treatment at Cycle 1 Day 1
• History of autoimmune disease
• History of severe allergic or anaphylactic reactions to humanized or murine monoclonal antibody therapy (or recombinant antibody-related fusion proteins)
• A history of confirmed progressive multifocal leukoencephalopathy
• Current or past history of central nervous system (CNS) lymphoma
• Ongoing corticosteroid use > 30 mg/day of prednisone or equivalent. Participants who received corticosteroid treatment with </=30 mg/day of prednisone or equivalent must be documented to be on a stable dose of at least 4 weeks' duration prior to Cycle 1/Day 1. Participants may have received a brief (<7 days) course of systemic steroids (</=100 mg prednisone equivalent per day) prior to initiation of study therapy for control of lymphoma-related symptoms
• Current or past history of CNS disease, such as stroke, epilepsy, CNS vasculitis, or neurodegenerative disease
• Evidence of significant, uncontrolled concomitant diseases that could affect compliance with the protocol or interpretation of results, including diabetes mellitus, history of relevant pulmonary disorders (bronchospasm, obstructive pulmonary disease), and known autoimmune diseases
• Major surgery or significant traumatic injury < 28 days prior to the study treatment infusion at Cycle 1/Day 1 (excluding biopsies) or anticipation of the need for major surgery during study treatment
• Participants with another invasive malignancy that could affect compliance with the protocol or interpretation of results
• Significant or extensive cardiovascular disease
• Left ventricular ejection fraction < 50%
• Administration of a live, attenuated vaccine within 4 weeks before study treatment infusion on Cycle 1 Day 1 or anticipation that such a live, attenuated vaccine will be required during the study
• History of illicit drug or alcohol abuse within 12 months prior to screening, in the Investigator's judgment
• Any other diseases, metabolic dysfunction, physical examination finding (including mental status), or clinical laboratory finding giving reasonable suspicion of a disease or condition that would contraindicate the use of an investigational drug
• Participants with latent or active tuberculosis