Background: Follicular lymphoma (FL) is an incurable disease in which patients will relapse despite the effectiveness of first-line (1L) rituximab-based chemoimmunotherapy (CIT), indicating the need for alternative 1L treatments that can deepen and prolong response. Odronextamab, an off-the-shelf, CD20×CD3 bispecific antibody, showed compelling efficacy and generally manageable safety as a monotherapy at 3L+ for patients with relapsed/refractory (R/R) FL in the Phase 2 ELM-2 study (Villasboas, et al. ASH 2023). Objective and complete response (CR) rates were 80% and 73%, respectively, median duration of response was 22.6 months, median progression-free survival (PFS) was 20.7 months, and median overall survival was not reached. The rate of treatment-related adverse events leading to treatment discontinuation was 7.8%. The activity of odronextamab monotherapy in this heavily pretreated R/R FL population, including among patients with rituximab-refractory disease, provides a strong rationale for developing odronextamab as a chemotherapy-free option that can improve long-term outcomes in 1L. Methods: OLYMPIA-1 (NCT06091254) is a Phase 3, randomized, open-label, multicenter study of odronextamab versus investigator’s choice of CIT (R-CHOP, R-CVP, or R-bendamustine) in patients with previously untreated FL. The study consists of Part 1 (safety run-in), followed by Part 2 (randomization). In Part 1, patients will receive six 21-day cycles (induction) of intravenous odronextamab, administered in a step-up regimen during Cycle (C) 1 to mitigate the risk of cytokine release syndrome, followed by full dose starting from C2. Patients with CR or partial response at the end of induction will receive 12 doses of odronextamab maintenance given Q8W. In Part 2, patients will be randomized 1:1 to receive induction of six cycles of odronextamab followed by odronextamab maintenance, or CIT followed by rituximab maintenance. Key inclusion criteria: aged ≥18 years; CD20+ FL Grade 1–3a, stage II bulky or stage III/IV; measurable disease; and ECOG performance status 0–2. Patients with central nervous system lymphoma or histological Grade 3b are excluded. The Part 2 primary endpoint is CR at 30 months (CR30) as assessed by independent central review. Key secondary endpoints include PFS, event-free survival, investigator-assessed CR30, and patient-reported outcomes. Biomarkers (including minimal residual disease by ctDNA) will be evaluated as exploratory endpoints. This trial is currently recruiting and is expected to enroll ~12–32 patients in Part 1 and ~446 patients in Part 2 at ~200 global sites. Clinical trial information: NCT06091254.