This study is looking at two drugs, rituximab and mosunetuzumab, to treat people with a type of cancer called follicular lymphoma that has a low tumor burden (small amount of tumor). Follicular lymphoma is a cancer of the white blood cells. Rituximab is a medication that helps the body’s immune system attack cancer cells. Mosunetuzumab is a new drug that may stop cancer cells from growing. We are not sure which drug works better yet. The study will last several years, and patients will be checked regularly for up to 10 years. In one group, patients receive rituximab through a vein (IV) and under the skin (SC) every 56 days for up to 5 cycles. In the other group, patients receive mosunetuzumab under the skin every 21 days for up to 8 cycles.

• The study involves regular visits and tests over a long period.
• Patients will be checked every 6 months for 5 years and then yearly up to 10 years.
• Participants must not have had prior treatment for follicular lymphoma.