A trial led by City of Hope, one of the largest cancer research and treatment organizations in the nation, contributed to the U.S. Food and Drug Administration's approval of mosunetuzumab (commercial name: Lunsumio) to treat people with relapsed or difficult-to-treat follicular lymphoma (FL) after receiving two or more standard therapies. FL is the most common indolent form of non-Hodgkin lymphoma (NHL) and is often characterized by periods of remission and relapse and poor long-term prognosis.