Comparing Rituximab and Mosunetuzumab Drug Treatments for People With Low Tumor Burden Follicular Lymphoma

This phase III trial compares the effectiveness of rituximab to mosunetuzumab in treating patients with follicular lymphoma with a low tumor burden. Rituximab is a monoclonal antibody. It binds to a protein called CD20, which is found on B cells (a type of white blood cell) and some types of cancer cells. This may help the immune system kill cancer cells. Mosunetuzumab is a monoclonal antibody that may interfere with the ability of cancer cells to grow and spread. It is not yet known if giving rituximab or mosunetuzumab works better in treating patients with follicular lymphoma with a low tumor burden.

PRIMARY OBJECTIVES: I. To compare the 3-year milestone progression free survival (PFS) probabilities in participants with previously untreated, low tumor burden follicular lymphoma randomized to the rituximab arm versus the mosunetuzumab arm. II. To compare progression free survival (PFS) in participants with previously untreated, low tumor burden follicular lymphoma randomized to the rituximab arm versus the mosunetuzumab arm. SECONDARY OBJECTIVES: I. To compare overall survival (OS) between participants randomized to rituximab versus mosunetuzumab. II. To compare overall response rates at the Week 40 assessment between participants randomized to rituximab versus mosunetuzumab. III. To compare event free survival (EFS) between participants randomized to rituximab versus mosunetuzumab. IV. To compare the frequency and severity of toxicities between participants randomized to rituximab versus mosunetuzumab. V. To compare the restricted chance of longer PFS (2-6 years) between participants randomized to rituximab versus mosunetuzumab. BANKING OBJECTIVE: I. To bank specimens for future correlative studies. OUTLINE: Patients are randomized to 1 of 2 arms. ARM I: Patients receive rituximab intravenously (IV) on day 1 of cycle 1 and receive rituximab and hyaluronidase subcutaneously (SC) on days 8, 15 and 22 of cycle 1 and SC on day 1 of subsequent cycles. Cycles repeat every 56 days for up to 5 cycles in the absence of disease progression or unacceptable toxicity. Patients undergo computed tomography (CT) scan and/or positron emission tomography (PET)/CT and blood sample collection on study and during follow up. ARM II: Patients receive mosunetuzumab SC on days 1, 8 and 15 of cycle 1 and on day 1 of subsequent cycles. Cycles repeat every 21 days for up to 8 cycles in the absence of disease progression or unacceptable toxicity. Patients undergo CT scan and/or PET/CT and blood sample collection on study and during follow up. After completion of study treatment, patients are followed up every 6 months for 5 years and then yearly for a total of 10 years.