Tazemetostat and Mosunetuzumab in Untreated Follicular Lymphoma

Inclusion Criteria: Ability to comply with the study protocol Willing to use highly effective contraception, if of childbearing potential Diagnosed with follicular lymphoma (FL; Grades 1-3a) Received no prior systemic lymphoma therapy (local radiotherapy is not considered systemic therapy) Exclusion Criteria: Inability to take oral medication OR have malabsorption syndrome or any other uncontrolled gastrointestinal condition (eg, nausea, diarrhea, vomiting) that might impair the bioavailability of tazemetostat Grade 3b FL History of transformation of indolent disease to diffuse large B cell lymphoma Any prior history of myeloid malignancies, including myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML) or myeloproliferative neoplasm (MPN) Any prior history of T cell lymphoblastic lymphoma (T-LBL)/ T cell lymphoblastic leukemia (T-ALL) Active or history of central nervous system lymphoma or leptomeningeal infiltration Prior standard or investigational systemic anti cancer therapy for lymphoma. Patients who have received prior XRT will not be excluded History of solid organ transplantation History of severe allergic or anaphylactic reaction to humanized, chimeric or murine monoclonal antibodies (MAbs) Known or suspected chronic active Epstein-Barr virus (EBV) infection Known or suspected history of hemophagocytic lymphohistiocytosis (HLH) Clinically significant history of liver disease, including viral or other hepatitis, or cirrhosis Active Hepatitis B or Hepatitis C infection HIV positive with CD4 count <200 and not currently taking antiretroviral therapy History of progressive multifocal leukoencephalopathy (PML) Active autoimmune disease requiring treatment History of autoimmune disease, including, but not limited to: myocarditis, pneumonitis, myasthenia gravis, myositis, autoimmune hepatitis, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, vascular thrombosis associated with antiphospholipid syndrome, Wegener's granulomatosis, Sjögren's syndrome, Guillain-Barré syndrome, multiple sclerosis, vasculitis, or glomerulonephritis Prior allogeneic stem cell transplant (SCT) Significant cardiovascular disease (e.g., New York Heart Association Class III or IV cardiac disease, myocardial infarction within the previous 6 months, unstable arrhythmia, or unstable angina) or significant pulmonary disease (such as obstructive pulmonary disease or history of bronchospasm) Major surgery other than for diagnosis within 28 days prior to Day 1 of Cycle 1 Day 1 or anticipation of a major surgical procedure during the course of the study Active central nervous system disease or underlying neurologic disease such as stroke or intracranial hemorrhage within 3 months prior to enrollment, history of seizure disorder, or history of neurogenerative disease History of pneumonitis or interstitial lung disease Pregnant or breastfeeding or intending to become pregnant during the study