OUTLINE:~PART A: Patients receive mosunetuzumab subcutaneously (SC) over 30 seconds-2 minutes on days 1, 8, and 15 of cycle 1 and day 1 of subsequent cycles. Treatment repeats every 21 days for 8 cycles in the absence of disease progression or unacceptable toxicity.~PART B: Beginning cycle 9, patients who do not achieve a CR receive obinutuzumab intravenously (IV) on day 1 of cycle 9 and day 1 of subsequent cycles and polatuzumab vedotin IV on day 1. Treatment repeats every 21 day for 6 cycles in the absence of disease progression or unacceptable toxicity.~After completion of study treatment, patients are followed up for up to 5 years.
This phase II trial tests the effects of mosunetuzumab with or without polatuzumab vedotin and obinutuzumab for the treatment of patients with indolent B-cell non-Hodgkin lymphoma. Mosunetuzumab and obinutuzumab are monoclonal antibodies that may interfere with the ability of cancer cells to grow and spread. Polatuzumab vedotin is a monoclonal antibody, called polatuzumab, linked to a chemotherapy drug, called vedotin. Polatuzumab is a form of targeted therapy because it attaches to specific molecules (receptors) on the surface of cancer cells, known as CD79b receptors, and delivers vedotin to kill them. Giving mosunetuzumab with polatuzumab vedotin and obinutuzumab may work better in treating patients with untreated indolent B-cell non-Hodgkin lymphoma.