Mohamed, Hesham

Abstract Complete response (CR) is an important treatment goal in follicular lymphoma (FL). In relapsed or refractory (R/R) FL, CR rates decline, and disease progression accelerates with each treatment line, with particularly poor outcomes in patients with high‐risk features. Odronextamab, a CD20 × CD3 bispecific antibody, demonstrated deep, durable responses and generally manageable safety in R/R FL in the Phase 2 ELM‐2 study (NCT03888105); we present an exploratory analysis in patients who attained a CR. Patients received intravenous odronextamab with step‐up dosing in Cycle 1, 80 mg weekly in Cycles 2–4, then 160 mg once every 2 weeks until disease progression or other protocol‐defined reason for discontinuation. Patients with CR lasting ≥9 months switched to dosing once every 4 weeks. Overall, 73.4% (94/128) of patients attained CR, 93.6% (88/94) by first response assessment (~Week 12). Median time to CR was 2.7 months (range 2.3–7.9). Median duration of CR was 25.1 months (95% confidence interval [CI] 20.5–not evaluable [NE]) overall and 23.7 months (18.2–NE) in patients with high‐risk features. Overall, 79.5% (35/44) of patients who switched to Q4W dosing maintained CR at last assessment. Patients with low/undetectable CD20 expression by immunohistochemistry (<10% CD20 + cells) or RNA sequencing (messenger RNA < 500 transcripts per million) could achieve CR. Median progression‐free survival was 27.8 months (95% CI 23.0–NE) in patients with CR and not reached in those with undetectable circulating tumor DNA at Week 12. Treatment‐emergent adverse events (TEAEs) led to treatment discontinuation in 16.0% of patients with CR; the most common TEAE was cytokine release syndrome (56.4%). This generally manageable safety profile and the sustainability of CRs support odronextamab as a potential long‐term treatment for heavily pretreated R/R FL.

Abstract Introduction Odronextamab, a CD20×CD3 bispecific antibody, demonstrated compelling efficacy with a generally manageable safety profile in heavily pretreated patients (pts) with relapsed/refractory (R/R) follicular lymphoma (FL) in the Phase 2 ELM-2 study (NCT03888105; Kim TM, et al. Ann Oncol 2024). Pts in ELM-2 received odronextamab monotherapy until disease progression or unacceptable toxicity, with dosing frequency reduced to every 4 weeks (Q4W) in those with sustained complete response (CR) for at least 9 months. Here, we report longer term outcomes in the global FL population of ELM-2, including efficacy and safety in pts who switched to Q4W dosing. Methods Details of the ELM-2 study for the R/R FL cohort have been reported previously. Odronextamab monotherapy was administered intravenously, with step-up dosing in Cycle (C) 1 to help mitigate the risk of cytokine release syndrome (CRS), followed by 80 mg in C2–4, then 160 mg every 2 weeks (Q2W) maintenance. Pts with a CR for ≥9 months switched from 160 mg Q2W to Q4W. Pts with the opportunity for response assessment at 12 weeks were included in this analysis. Primary endpoint was objective response rate (ORR) per Lugano criteria by independent central review (ICR). Key secondary endpoints included CR rate, duration of response (DOR), and progression-free survival (PFS) by ICR, overall survival (OS), and safety. Results As of May 5, 2025 data cutoff, 128 pts with R/R FL Grade (Gr) 1–3a were evaluable for efficacy and safety analysis (overall global population). Median duration of odronextamab exposure was 42.9 weeks (range 0.4–264.0) and median follow-up was 34.1 months (95% CI 33.8–37.9). Eligible pts (n=48) switched to Q4W dosing, with median duration of follow-up from time of switching to Q4W dosing of 19.7 months (95% CI 16.2–31.9). Baseline characteristics were generally similar between the overall population and the subgroup of pts who switched to Q4W dosing. The ORR by ICR in the overall population was 80.5% and CR rate was 74.2%, with a median DOR of 26.0 months and median duration of CR of 32.2 months. In pts with sustained CR for ≥9 months who transitioned to Q4W maintenance, the median DOR from time of switching was 31.5 months. In the overall population, the median PFS was 24.1 months and median OS was not reached (estimated 24- and 36-month OS rates: 70.1% and 64.3%, respectively). In pts with CR, median PFS was 38.0 months and median OS was not reached (24- and 36-month OS rates: 80.1% and 75.2%). All 128 pts had treatment-emergent adverse events (TEAEs), with Gr ≥3 TEAEs reported in 112 pts (87.5%). Discontinuation due to TEAEs occurred in 29 pts (22.7%), and 5 pts died due to treatment-related TEAEs. With the 0.7/4/20 mg step-up regimen, CRS was reported in 55.0% (33/60; Gr 3 in 1 pt) of pts, with no new CRS events observed after switching to Q4W. Infections occurred in 81.3% (Gr ≥3, 46.1%) of pts, with COVID-19 (any Gr, 39.8%) the most frequent. After switching to Q4W dosing, the rate of any grade infection was 81.3% (Gr ≥3, 39.6%). Opportunistic infections (narrow SMQ defined) were reported in 18% (Gr ≥3, 8.6%) of pts in the overall population, with 22.9% (Gr ≥3, 8.3%) of pts having an opportunistic infection after switching to Q4W. Conclusions In the ELM-2 study with ~3-year follow-up in heavily pretreated pts with R/R FL, odronextamab continued to demonstrate deep and durable responses, as well as encouraging PFS and OS, particularly in the majority of pts who achieved CR. Responses remain durable in those who switched to Q4W dosing, lasting for a median additional 31.5 months from the time of switching, demonstrating the long-term, continued therapeutic benefit of odronextamab in pts with R/R FL. The safety profile remained generally manageable, with no new safety signals observed, and no evidence of increased infection risk in pts who switched to Q4W maintenance. Updated data will be presented.

7049 Background: Odronextamab, an investigational off-the-shelf CD20×CD3 bispecific antibody, demonstrated compelling efficacy and a generally manageable safety profile in heavily pretreated pts with R/R FL in the primary analysis of the Phase 2 ELM-2 study (NCT03888105; Kim TM, et al. Ann Oncol 2024). We present updated efficacy and safety data for odronextamab in pts with R/R FL from ELM-2 after >2 yrs follow-up. Methods: Odronextamab was administered intravenously until disease progression/unacceptable toxicity, with Cycle (C) 1 step-up dosing to help mitigate cytokine release syndrome (CRS) risk, as reported previously. Pts with a complete response (CR) for ≥9 months (mo) switched from maintenance dosing Q2W to Q4W. Primary endpoint: objective response rate (ORR) per Lugano criteria by independent central review (ICR); secondary endpoints: CR rate, duration of response (DOR), progression-free survival (PFS), overall survival (OS). Results: At the updated data cutoff (Aug 15, 2024), 157 pts with centrally confirmed R/R FL Grade (Gr) 1–3a were enrolled. Median no. of treatment cycles: 19.0 (range 0.1–117.3); 96.2% (n = 151) and 82.8% (n = 130) of pts completed C1 and C4, respectively. The global cohort comprised 128 pts evaluable for efficacy. At a median efficacy follow-up of 28.3 mo, ORR was 80.5% (n = 103) by ICR and CR rate was 74.2% (n = 95); 92.2% of responders achieved CR. Responses were durable (median DOR, 26.0 mo; median duration of CR, 32.2 mo). ORR was consistent across high-risk subgroups (Follicular Lymphoma International Prognostic Index score 3–5, 78.4%; progression of disease within 2 yrs of frontline therapy, 81.0%). Median PFS was 23.0 mo (estimated 36-mo PFS rate, 37.5%), and median OS was 54.2 mo (estimated 36-mo OS rate, 62.6%). Median PFS was longer in pts who were minimal residual disease (MRD) negative (42.4 mo) versus MRD positive (21.6 mo) at Week 12. Of 47/128 pts who switched to Q4W dosing, 32 remained in CR. The odronextamab long-term safety profile was consistent with the primary analysis. All 157 pts had TEAEs (Gr ≥3, 86.0%), and 15.3% discontinued treatment due to TEAEs (most common: COVID-19 infection, 2.5%). With 0.7/4/20 mg step-up dosing (n = 89), CRS events were mostly low grade (Gr 1, 46.1%; Gr 2, 13.5%; Gr 3, n = 1; Gr ≥4, n = 0), occurred mostly in C1, and resolved in a median of 8.4 hrs. Immune effector cell-associated neurotoxicity syndrome was reported in one pt (Gr 2). Infections were reported in 79.0% of pts (124/157; Gr ≥3, 42.0%). COVID-19-related infections were reported in 38.2% of pts (Gr 5, 5.7%). Conclusions: With longer follow-up, odronextamab demonstrated durable responses in heavily pretreated pts with R/R FL from ELM-2, with robust efficacy in those with high-risk features, and a generally manageable safety profile. Overall, these compelling results support odronextamab as a potential off-the-shelf treatment option for pts with R/R FL. Clinical trial information: NCT03888105 .

Abstract Patients with relapsed/refractory diffuse large B-cell lymphoma progressing after chimeric antigen receptor T-cell (CAR-T) therapy have dismal outcomes. The prespecified post–CAR-T expansion cohort of the ELM-1 study investigated the efficacy and safety of odronextamab, a CD20×CD3 bispecific antibody, in patients with disease progression after CAR-Ts. Sixty patients received IV odronextamab weekly for 4 cycles followed by maintenance until progression. The primary end point was objective response rate (ORR) by independent central review. The median number of prior lines of therapy was 3 (range, 2-9), 71.7% were refractory to CAR-Ts, and 48.3% relapsed within 90 days of CAR-T therapy. After a median follow-up of 16.2 months, ORR and complete response (CR) rate were 48.3% and 31.7%, respectively. Responses were similar across prior CAR-T products and time to relapse on CAR-T therapy. Median duration of response was 14.8 months and median duration of CR was not reached. Median progression-free survival and overall survival were 4.8 and 10.2 months, respectively. The most common treatment-emergent adverse event was cytokine release syndrome (48.3%; no grade ≥3 events). No cases of immune effector cell–associated neurotoxicity syndrome were reported. Grade ≥3 infections occurred in 12 patients (20.0%), 2 of which were COVID-19. Odronextamab monotherapy demonstrated encouraging efficacy and generally manageable safety, supporting its potential as an off-the-shelf option for patients after CAR-T therapy. This trial was registered at www.clinicaltrials.gov as #NCT02290951.

Introduction Patients (pts) with relapsed/refractory (R/R) follicular lymphoma (FL) experience progressively worse outcomes with each successive line of therapy; complete response (CR) rates are 44% with third-line (3L), 27% with 4L, and 22% with 5L+ therapies (Ghione P et al. Haematologica 2023). CR duration is particularly important considering the rapid disease progression observed with 3L+ therapies in pts with FL, with especially poor outcomes in those with high-risk features (Liu J et al. Front Oncol 2023; Philips T et al. ASH 2023). In ELM-2 (NCT03888105), odronextamab (an investigational CD20×CD3 bispecific antibody) demonstrated deep and durable responses and generally manageable safety in pts with R/R FL who had received ≥2 prior lines of systemic therapy. Median progression-free survival (PFS) and overall survival (OS) in pts with CR were 28 months (95% CI 23.0-not evaluable [NE]) and not reached (95% CI 40.4-NE), respectively. Grade ≥3 treatment-emergent adverse events (TEAEs) occurred in 86% of pts (Taszner M et al. EHA 2024). For the current analysis, we present details on the efficacy and safety of 3L+ odronextamab treatment in pts with R/R FL who attained CR in ELM-2, including those with high-risk features. Methods ELM-2 is an ongoing, open-label, multicenter, Phase 2 trial of odronextamab in pts with R/R B-cell non-Hodgkin lymphoma, including a cohort with FL Grade 1-3a. Intravenous odronextamab was administered in step-up doses with steroid prophylaxis during Cycle (C) 1, followed by 80 mg on Days 1, 8, and 15 of C2-4. After C4, dosing continued at 160 mg once every 2 weeks (Q2W); pts switched to Q4W dosing if they had a durable CR for ≥9 months. The primary endpoint was objective response rate (ORR) according to Lugano classification, by independent central review (ICR). Secondary endpoints included CR rate, PFS, OS, duration of response, and safety. Results Primary results in pts evaluable for efficacy and safety (N=128) using the Oct 20, 2023, data cutoff have been reported. Median duration of efficacy follow-up was 20.1 months (95% CI 17.3-27.8). The ORR was 80.5% (103/128 pts; 95% CI 72.5-86.9), and CR rate was 73.4% (94/128; 95% CI 64.9-80.9). Median duration of CR (DOCR) was 25.1 months (95% CI 20.5-NE), and median time to CR was 2.7 months (range 2.3-7.9). Baseline characteristics of pts with CR (n=94) were similar to those of the overall population, and median duration of treatment exposure was 13.8 months (range 1.8-45.0). In total, 88 pts (93.6%) had CR at the first response assessment (~Week 12) and 6 (6.4%) reached CR later, including 3 pts who had stable disease initially. Twenty-eight pts (29.8%) were still receiving treatment at data cutoff, and 66 (70.2%) had discontinued treatment. Of those who discontinued, 42 still had CR at the last response assessment. Primary reasons for treatment discontinuation were disease progression (n=17), TEAEs (n=16 [including 6 pts with COVID-19]), physician decision (n=12), withdrawal by subject (n=11), and death (n=8). All 8 deaths resulted from TEAEs, including COVID-19 in 5 pts. Eighty-five pts (90.4%) with CR had high-risk features (POD24, 48.9%; FLIPI score 3-5, 55.3%; refractory to last treatment, 70.2%); median DOCR and median time to CR in these pts were similar to those in all pts (23.7 months [95% CI 18.2-NE] and 2.7 months [range 2.3-7.9], respectively). At the time of the current analysis, 44 pts with CR by ICR (46.8%) had switched to Q4W dosing, with a median duration of exposure of 17.7 months (range 13.1-45.0). Among these pts, 22 had discontinued treatment at data cutoff due to adverse events (n=7 [including 1 with COVID-19]), physician decision (n=6), death (n=3), withdrawal by subject (n=3), progressive disease (n=2), and an “other” reason (n=1). Conclusions Pts with R/R FL and CR to 3L+ odronextamab treatment in ELM-2 had a median DOCR of 25.1 months that was prolonged beyond the median duration of treatment exposure (13.8 months). Almost half (46.8%) of pts proceeded to monthly odronextamab administration, with a median duration of treatment exposure of 17.7 months. These data show the sustainability of CR in pts with FL treated with 3L+ odronextamab, including in those with high-risk features. The safety profile of odronextamab was generally manageable in the overall population, including in pts with CR, despite their prolonged drug exposure. These findings support the potential of odronextamab as a treatment for R/R FL.

Introduction CD19-directed CAR T-cell therapies are an important option for the management of relapsed/refractory (R/R) DLBCL. Studies suggest that ~50% of pts receiving CAR T-cell therapies will relapse within 6 months, with an estimated overall survival (OS) of only 5 months. Additionally, 25-35% of pts do not receive subsequent treatment, indicating a high unmet need. CD19 loss is a potential mechanism of resistance to CAR T-cell therapies; thus, treatments that target alternate B-cell antigens are an attractive option. Here, we report for the first time the primary analysis of the ELM-1 expansion cohort investigating the efficacy and safety of odronextamab, a CD20×CD3 bispecific antibody, in pts with R/R DLBCL progressing after CAR T-cell therapy (NCT02290951). Methods Pts aged ≥18 with DLBCL and disease progression after CAR T-cell therapy received intravenous odronextamab weekly in 21-day (D) cycles during Cycles (C) 1-4, with steroid prophylaxis and step-up dosing in C1 (described previously), followed by 160 mg on D 1, 8, and 15 of C2-4. After C4, odronextamab maintenance treatment continued at 320 mg Q2W until disease progression or unacceptable toxicity. Pts with complete response (CR) for ≥9 months transitioned to Q4W dosing. All pts received infection prophylaxis. The primary analysis was conducted when all pts had completed ≥9 months of follow-up. Primary endpoint was objective response rate (ORR), as assessed by independent central review (ICR) according to the Lugano classification. Key secondary endpoints included duration of response (DOR), progression-free survival (PFS), and OS. Exploratory endpoints included immune biomarker assessment. Results As of January 22, 2024, 60 pts were treated and evaluable for efficacy and safety, with median follow-up of 16.2 months. Prior CAR T-cell therapies were axi-cel (50%), tisa-cel (12%), liso-cel (10%), and not specified (28%). Median time since prior CAR T-cell therapy was 6.5 months (range 1.2-46.2). Median age was 63 years (range 27-82; aged ≥75 years: 10%), and 65% were male. Pts had received a median of 3 prior lines of therapies (range 2-9); 77% of pts were refractory to their last therapy, 77% were double refractory, and 72% were refractory to prior CAR T-cell therapy. 48% of pts relapsed within 90 D of CAR T-cell therapy, and 67% relapsed within 180 D. Of the 20 pts with available tumor biopsies at baseline, 10 were CD19(-) and only 2 were CD20(-). 92% of pts completed C1 and 52% completed ≥4 C of treatment. The median duration of treatment was 12 weeks (range 0.7-154.1). The ORR and CR rate by ICR were 48% and 32%, respectively, and were consistent across pts with high-risk features and across prior CAR T products. ORR in pts relapsing in ≤90 D was 21% (6/29) and in pts relapsing in ≤180 D was 33% (13/40). ORR was observed even in pts with low CD20. Median DOR was 14.8 months (95% CI 2.8-not estimable [NE]) and median duration of CR was not reached (NR) (95% CI 3.3-NE); the probability of maintaining CR for 24 months was 68%. Median PFS was 4.8 months (95% CI 2.6-5.4) and median OS was 10.2 months (95% CI 4.6-15.8). Median PFS and OS in complete responders was NR. T-cell counts increased at Week 14 and demonstrated a functional phenotype (CD69 expression and TEMRA count), which was confirmed by ex vivo stimulation. T-cell expansion was observed regardless of CAR T product or time from CAR T administration. The most common TEAE was CRS (any grade [G]: 48%; G1: 25%; G2: 23%; G≥3: 0%). G≥3 TEAEs occurred in 77% of pts (most common: neutropenia 17%, anemia 13%, and neutrophil and white blood cell count decrease 10% each). Five pts (8%) permanently discontinued odronextamab due to AEs (COVID-19, pneumonia, encephalopathy, epilepsy, and gait disturbance [n=1 each]). There was one treatment-related death (COVID-19 pneumonia). No cases of ICANS were reported. G≥3 infections occurred in 12 pts (20%); 2 were due to COVID-19. No cases of tumor flare or TLS were reported. Conclusions ELM-1 is the only study to prospectively evaluate efficacy and safety of a CD20×CD3 bispecific antibody in pts with R/R DLBCL progressing after CAR T-cell therapy. Odronextamab monotherapy was associated with encouraging efficacy and generally manageable safety in a setting with limited treatment options and historically dismal outcomes. Efficacy was observed even in pts relapsing in ≤90 D, supporting the potential of odronextamab as an accessible, off-the-shelf option in the post-CAR T setting.

Introduction In ELM-2 (NCT03888105), a Phase 2, open-label, multicohort study, odronextamab monotherapy demonstrated encouraging clinical efficacy, generally manageable safety, and maintenance of patient-reported outcomes in R/R FL (Chong et al. AACR 2024; Tessoulin et al. ASH 2023). In the absence of head-to-head clinical trials comparing CD20×CD3 bispecific antibodies in R/R FL, two unanchored MAICs were conducted to evaluate the efficacy of odronextamab versus mosunetuzumab and epcoritamab in patients with R/R FL in the third-line or later (3L+) setting. Methods Patient-level data from the ELM-2 R/R FL cohort receiving odronextamab (N=128; data cutoff: October 2023) were compared with published data from similar cohorts in the GO29781 trial of mosunetuzumab (N=90; Budde et al. Lancet Oncol 2022) and EPCORE NHL-1 trial of epcoritamab (N=128; Linton et al. Lancet Haematol 2024). To adjust for baseline differences in the trial populations, a priori-identified prognostic variables (progression of disease within 2 years, primary refractory, refractory to last line of therapy [LOT], number of prior LOTs, serum lactate dehydrogenase level, Eastern Cooperative Oncology Group performance status, Follicular Lymphoma International Prognostic Index, age at start of LOT, and Ann Arbor disease stage) were included in the base-case MAICs. Two additional variables (double refractory and prior autologous stem cell transplant), reported in ELM-2 and the comparator studies, were included in a sensitivity analysis. The MAICs reported here were focused on response outcomes as assessed by independent central review, which were reported across trials. Relative treatment effects before and after matching were presented as odds ratios (ORs), along with 95% confidence intervals (CIs). Results The effective sample size for odronextamab was 102.0 after matching with mosunetuzumab and 90.6 after matching with epcoritamab in the base-case MAICs. All key prognostic variables were balanced between ELM-2 and both comparator trials in each analysis. Before and after matching, odronextamab demonstrated comparable objective response rates (ORRs) and significantly higher complete response (CR) rates versus mosunetuzumab (before matching: ORR 80.5% vs 80.0%, OR 1.03 [95% CI 0.52-2.03], p=0.93; CR rate 73.4% vs 60.0%, OR 1.84 [95% CI 1.04-3.28], p=0.04; after matching: ORR 83.5% vs 80.0%, OR 1.27 [95% CI 0.61-2.65], p=0.53; CR rate 75.7% vs 60.0%, OR 2.08 [95% CI 1.12-3.86], p=0.02). Odronextamab demonstrated numerically higher CR rates versus epcoritamab before and after matching (before matching: CR rate 73.4% vs 62.5%, OR 1.66 [95% CI 0.98-2.82], p=0.06; after matching: CR rate 69.4% vs 62.5%, OR 1.36 [95% CI 0.77-2.41], p=0.29). The ORRs of odronextamab and epcoritamab were comparable before matching (ORR 80.5% vs 82.0%, OR 0.90 [95% CI 0.48-1.69], p=0.75) and after matching (ORR 78.1% vs 82.0%, OR 0.78 [95% CI 0.40-1.53], p=0.47). Consistent results were observed in the sensitivity analyses. Conclusions In the absence of head-to-head clinical trials comparing bispecific antibodies in the setting of 3L+ FL, MAICs demonstrate that odronextamab was associated with higher CR rates compared with mosunetuzumab and epcoritamab. Since achieving a CR in the R/R FL setting is an important treatment goal, our results highlight the potential of odronextamab as an effective treatment option in R/R FL.

e19057 Background: In ELM-2 (NCT03888105), a Ph 2, single arm, open label trial, odronextamab demonstrated robust efficacy, generally manageable safety, and overall maintenance of patient-reported outcomes (PROs) in R/R FL pts (Villasboas et al. ASH 2023). In FL, pts with disease progression within 2 yrs of frontline chemoimmunotherapy (POD24) are hard to treat with poor clinical outcomes, representing an unmet need. We report PROs by POD24 status in pts with Grade 1–3a R/R FL from ELM-2. Methods: Pts received IV odronextamab in 21-day cycles (C): 80 mg QW in C1–4, with C1 dose step up to mitigate cytokine release syndrome, then 160 mg Q2W (Q4W if complete response ≥9 mo) until progression. PROs were collected at baseline (BL), Wks 2–4, 10, then Q8W in Yr 1, and Q12W in Yr 2. Post-hoc POD24 subgroup analyses were performed on six EORTC QLQ-C30 scales, the EQ-5D-3L VAS, and FACT-Lym LymS. Estimated mean change from BL (CFB) was analyzed using mixed models for repeated measures (MMRM) through Wk 42 (≥10 pts at last assessment). Published meaningful CFB thresholds were used to define deterioration/improvement in responder analyses. Results: By Jan 31, 2023, 140 pts with R/R FL had received odronextamab. Pts with POD24 (n=70) were younger than pts without POD24 (n=70; median age 57.5 vs 62.0 y), had fewer prior Tx lines (median 2 vs 3), and a higher proportion double refractory to anti-CD20 Ab + alkylator (53% vs 29%). Objective response rate was similar in evaluable pts with (n=63; 79%) and without (n=65; 80%) POD24. PRO questionnaire completion ranged from 52–95% through Wk 42 across groups. Descriptive analyses suggest BL PRO scores were similar by POD24 status, showing good HRQoL/functioning and low symptom burden, and were generally maintained through Wk 42 with minimal between-group differences (overlapping 95% CIs for LS mean CFB [Table]). In both groups, more pts reported PRO maintenance or improvement vs deterioration across visits, except for fatigue at Wk 10 in pts without POD24. Conclusions: In pts with heavily pretreated R/R FL, odronextamab Tx maintained HRQoL, functioning, and symptoms irrespective of POD24 status. Clinical trial information: NCT03888105 . [Table: see text]

Abstract Background: R/R FL is an incurable disease and outcomes worsen with successive relapses. A high unmet need remains for therapies that improve tumor control and extend survival after relapse. Odronextamab, an off-the-shelf CD20×CD3 bispecific antibody, demonstrated compelling efficacy, generally manageable safety, and maintenance of pt-reported overall quality of life scores from baseline in an interim analysis of the ELM-2 study (NCT03888105) in heavily pretreated pts with R/R FL (Villasboas et al. ASH 2023). Here, for the first time, we present the primary analysis of R/R FL in ELM-2. Methods: IV odronextamab was administered in 21-day cycles (C) until disease progression/unacceptable toxicity. Steroid prophylaxis and step-up dosing (0.7/4/20 mg) were used in C1 to mitigate the risk of cytokine release syndrome (CRS), followed by 80 mg on Days (D) 1, 8, and 15 of C2-4. Maintenance dosing continued at 160 mg Q2W, or Q4W if complete response (CR) was durable for 9 months (mo). Primary endpoint was objective response rate (ORR) per Lugano criteria by independent central review (ICR). Secondary endpoints included CR rate, duration of response (DOR), progression-free survival (PFS), and overall survival (OS). Primary analysis was performed when 128 pts had ≥52 weeks’ follow-up. Results: At data cutoff (Oct 20, 2023), 128 pts with FL Grade (Gr) 1-3a were evaluable for efficacy and safety: median age 61 yrs (range 22-84); FLIPI risk score 3-5 57.8%; POD24 49.2%; median 3 prior lines of therapy (2-13); 71.9% refractory to last treatment (Tx); 74.2% refractory to an anti-CD20 antibody. The median no. of Tx cycles was 19.4 (0.1-95.9); 95.3% and 85.2% of pts completed C1 and C4, respectively.Median efficacy follow-up was 20.1 mo; ORR was 80.5% and CR rate was 73.4% confirmed by ICR. Responses were durable (median DOR 22.6 mo; median DOCR 25.1 mo). Median PFS was 20.7 mo and 24-mo PFS was 46.1%. Median OS was not reached and 24-mo OS was 70.1%.The odronextamab safety profile was generally manageable and consistent with previous reports. Tx-emergent adverse events (AEs) occurred in all pts (Gr ≥3 85.9%); 15.6% had AEs leading to Tx discontinuation. With 0.7/4/20 mg step up (n=60), CRS events were mostly low grade (Gr 1 45.0%; Gr 2 10.0%; Gr 3 in 1 pt), occurred mostly in C1, and resolved in a median of 2 days; ICANS was reported in 1 pt (Gr 2). Infection rates were consistent with heavily pretreated, immunosuppressed pts (Leonard et al. JCO 2019; Hayne et al. BBMT 2020), occurring in 79.7% (102/128) of pts (Gr 4/5 14.0%; COVID-19 36.7% [Gr 5 6.3%]).Conclusion: Odronextamab demonstrated deep and durable responses in heavily pretreated pts with R/R FL; 91% of responders achieved CR, correlating with favorable PFS and OS at 24 mo. Odronextamab had a generally manageable safety profile and a low incidence of Gr 3 CRS/ICANS. Odronextamab could offer an important off-the-shelf Tx option for pts with heavily pretreated R/R FL. Citation Format: Geoffrey Chong, Michal Taszner, Silvana Novelli, Seok-Goo Cho, Jose C. Villasboas, Ana Jiménez Ubieto, Benoît Tessoulin, Michelle Poon, David Tucker, Jan Walewski, Yuqin Song, Emmanuel Bachy, Stephanie Guidez, Aranzazu Alonso, Deepa Jagadeesh, Stefano Luminari, Laura Magnano Mayer, Elżbieta Iskierka-Jażdżewska, Monica Tani, Jingxian Cai, Amulya Uppala, Saleem Shariff, Jurriaan Brouwer-Visser, Aafia Chaudhry, Hesham Mohamed, Srikanth Ambati, Tae Min Kim. Primary analysis of the Phase 2 ELM-2 study: Odronextamab in patients (pts) with relapsed/refractory follicular lymphoma (R/R FL) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT243.