Mosunetuzumab and Zeprumetostat in Treating Patients With Follicular Lymphoma

This is a prospective, open-label, multicenter, multi-cohort phase 2 study evaluating Mosunetuzumab combined with Zeprumetostat (SHR2554) in follicular lymphoma (FL). The study is conducted in two stages: Stage 1: Safety Run-in Phase Initially, 6 participants in Cohort 1 will be enrolled to evaluate dose-limiting toxicities (DLTs) during Cycle 1 (28 days). If the safety is acceptable, the study will proceed to Stage 2. Stage 2: Expansion Phase Enrollment will expand to three independent cohorts: Cohort 1: Previously untreated high-risk FL (FLIPI 3-5). Cohort 2: Previously untreated low-tumor-burden FL. Cohort 3: Relapsed or refractory FL.