Luminari, Stefano

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 The characteristics at diagnosis and clinical course of primary extranodal follicular lymphoma (EFL) have not been extensively described. The International Extranodal Lymphoma Study Group (IELSG) conducted an international retrospective survey aimed to describe the clinical features at diagnosis and the outcomes of FL cases with a clinically dominant extranodal component. The dataset included 605 pathologically reviewed cases from 19 different countries, and their outcomes were compared to those of nodal follicular lymphomas. The two most common presentation sites for EFL were the skin ( n = 334) and the gastrointestinal tract ( n = 72), with 22 cases having primary duodenal localization. These subsets exhibited unique features at diagnosis and significantly different overall survival (OS) patterns. After a median follow‐up of 5.5 years, primary cutaneous lymphomas showed a superior outcome [10‐year OS: 89% (95% CI, 83%–93%)], while primary gastrointestinal lymphomas had an intermediate outcome [10‐year OS: 79% (95% CI, 59%–90%)]. Among the gastrointestinal lymphomas, primary duodenal lymphomas tended toward the best outcome [10‐year OS: 95% (95% CI, 69%–99%)]. Other primary extranodal sites had inferior outcomes [10‐year OS: 59% (95% CI, 48%–68%)], similar to primary nodal lymphomas [10‐year OS: 57% (95% CI, 49%–64%)]. These findings support the identification of specific primary FL localizations as distinct entities with particular clinical and biological characteristics.

PURPOSE The combination of the Bruton tyrosine kinase inhibitor ibrutinib with bendamustine-rituximab for first-line treatment of mantle cell lymphoma (MCL) prolonged progression-free survival (PFS), but without improvement in overall survival (OS), likely because of toxicity. Acalabrutinib was shown to be efficacious and less toxic than ibrutinib in a head-to-head trial in chronic lymphocytic leukemia and therefore might lead to better outcomes in MCL. METHODS Patients 65 years and older with previously untreated MCL received acalabrutinib (100 mg twice daily) or placebo (until disease progression or unacceptable toxicity), plus six cycles of bendamustine (90 mg/m 2 once daily; days 1 and 2) and rituximab (375 mg/m 2 as a single dose; day 1) followed by rituximab maintenance in responding patients for 2 years. Crossover to acalabrutinib at disease progression was permitted. The primary end point was PFS per the independent review committee; overall response rate and OS were secondary end points. RESULTS In total, 598 patients were randomly assigned, with 299 in each arm. At a median follow-up of 49.8 months using the reverse Kaplan-Meier method, the median PFS was 66.4 months in the acalabrutinib arm and 49.6 months in the placebo arm (hazard ratio [HR], 0.73 [95% CI, 0.57 to 0.94]; P = .0160). Benefit was seen across all subgroups, including those with high-risk features. Overall response/complete response rates were 91.0%/66.6% and 88.0%/53.5% in the acalabrutinib and placebo arms, respectively. OS was not significantly different (HR, 0.86 [95% CI, 0.65 to 1.13]; P = .27). Grade 3 or greater adverse events were reported in 88.9% and 88.2% in the acalabrutinib and placebo arms, respectively. CONCLUSION The combination of acalabrutinib with bendamustine-rituximab significantly improved PFS. Clinical benefit of acalabrutinib with bendamustine-rituximab was achieved with manageable toxicity.

Background: Positron emission tomography (PET) scan is the imaging modality of choice for initial staging and response assessment of follicular lymphoma (FL). Quantitative parameters such as standardized uptake value (SUV) have been investigated as putative prognosticators in FL, with high baseline SUVmax predicting aggressive disease. To date, there is no data to guide treatment choices in patients (pts) with high SUVmax but with no documented evidence of histologic transformation (HT). Specifically, it remains unclear whether anthracycline-containing regimens, such as R-CHOP, are more beneficial than R-Bendamustine (BR) in these pts. Therefore, we aimed to compare the efficacy of frontline R-CHOP and BR in newly diagnosed FL pts based on the SUVmax at baseline PET (bPET). Patients and Methods: Pts with newly diagnosed, biopsy-proven FL1-2 and FL3A who had a bPET scan and who received either first-line R-CHOP or BR within 6 months of diagnosis between 2002 and 2022 were evaluated. Analysis was restricted to pts with age &lt; 70 years to reduce confounding of age with treatment selection. Cohorts included were the FOLL12 (n=562, Luminari et al JCO 2022) and the R-chemotherapy arm of the RELEVANCE (n=216, Morschhauser et al NEJM 2018) clinical trials, the prospectively enrolled Molecular Epidemiology Resource (MER) and the Lymphoma Epidemiology of Outcomes (LEO) cohorts (n=288) and a retrospective cohort from 13 Australian centers (n=219). Choice of chemotherapy regimen was per treating physician. Maintenance was per protocol (FOLL12/RELEVANCE) or per treating physician (MER/LEO/Australia). Event-free survival (EFS) and overall survival (OS) were defined as time from treatment initiation to progression, relapse, retreatment or death; both were censored at 72 months due to varying follow-up across cohorts. SUVmax was grouped by tertile within each cohort to account for potential differences in SUVmax distributions and patient populations across cohorts. Kaplan Meier curves and multivariable Cox models cohort-stratified and adjusted for clinical factors (FLIPI, ECOG PS, age, grade 3A) were used to evaluate outcomes. Results: The median age at diagnosis was 57 years (IQR 49-64). 651 (51%) pts were treated with R-CHOP and 634 (49%) with BR. Within the study cohorts, there was a prevalence of cases receiving BR compared to R-CHOP in the Australian (90% vs 10%) and MER/LEO (68% vs 32%) cohorts, while the opposite was observed in the RELEVANCE (16% vs 84%) and FOLL12 (37% vs 63; p&lt;0.001) trials. Pts receiving R-CHOP were slightly younger (median 56 vs 58 years, p=0.005), more frequently had grade 3A (17% vs 7%, p&lt;0.001), elevated LDH (27% vs 22%, p=0.029), bulky disease &gt; 7 cm (44% vs 37%, p=0.019), lower ECOG PS (PS &gt;1 7% vs 13%, p&lt;0.001), and higher rate of high risk FLIPI (37% vs 30%, p=0.005). Baseline SUVmax was slightly lower in R-CHOP (median 10.7, IQR 7.9-14.9) vs BR (median 11.0, IQR 8.2-14.2) treated pts (p=0.0045). At a median follow-up of 56 months (range, 1-72 months), 415 pts (32%) had an event and 103 (8%) died. Higher SUVmax was not associated with EFS (middle tertile HR=0.96, 95% CI 0.76-1.22; upper tertile HR=0.86, 95% CI 0.68-1.09; p=0.45) or OS (middle tertile HR=1.28, 95% CI 0.80-2.05; upper tertile HR=0.97, 95% CI 0.59-1.59; p=0.44) in multivariable models stratified on cohort and adjusted for treatment and clinical factors. We then compared outcomes by treatment within tertiles of SUVmax. In multivariable models, R-CHOP had modestly inferior EFS to BR in low (HR=1.27, 95% CI 0.84-1.93) and middle tertiles (HR=1.49, 95% CI 0.99-2.25), and modestly superior OS to BR in low (HR=0.59, 95% CI 0.23-1.47) and middle (HR=0.79, 95% CI 0.37-1.71) tertiles. Both EFS (HR=1.06, 95% CI 0.71-1.58) and OS (HR=1.02, 95% CI 0.45-2.30) for R-CHOP were similar to BR in the highest tertile. No comparisons identified a statistically significant benefit for either therapy in multivariable models when evaluating SUVmax tertile subsets. Conclusions: In this large multicenter study of newly diagnosed FL pts with bPET who received frontline immunochemotherapy, higher baseline SUVmax was not associated with inferior outcomes after adjusting for treatment and clinical factors. Within the caveats of retrospective studies and confounding of treatment selection, these data provide no clear insights for SUVmax-based therapy selection in first-line follicular lymphoma pts treated with immunochemotherapy.

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 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.

Background The class of CD20×CD3 bispecific antibodies (BsAbs) has emerged as an important anti-lymphoma modality for patients (pts) with R/R B-cell non-Hodgkin lymphoma. Odronextamab, a novel, off-the-shelf, CD20×CD3 BsAb, has previously demonstrated compelling efficacy in both R/R diffuse large B-cell lymphoma and R/R FL. In pts with R/R FL, odronextamab monotherapy achieved 75% complete response (CR) rates and encouraging durability of responses, and showed generally manageable safety, in the Phase 2 ELM-2 study (NCT03888105; Kim TM, et al. ASH. 2022). Here, we report the results of a second, pre-specified interim analysis of ELM-2. Methods Intravenous odronextamab was administered weekly in 21-day cycles during Cycles (C) 1-4. Optimization of the step-up regimen to further mitigate cytokine release syndrome (CRS) was reported previously (Kim TM, et al. ASH. 2022). Odronextamab was administered with steroid prophylaxis and step-up doses of 0.7/4/20 mg during C1, followed by 80 mg on Days 1, 8, and 15 of C2-4. After C4, odronextamab maintenance treatment continued at 160 mg every 2 weeks until disease progression or unacceptable toxicity. Pts who achieved a durable CR for ≥9 months transitioned to dosing every 4 weeks. A pre-specified interim analysis was performed when 80 pts had completed ≥12 months follow-up. The primary endpoint was objective response rate (ORR), assessed by independent central review (ICR) according to the Lugano classification. Key secondary endpoints included CR rate, duration of response (DoR), progression-free survival (PFS), overall survival (OS), and changes in scores of patient-reported outcomes. Minimal residual disease (MRD) was included as an exploratory endpoint. Results At data cut off (Jan 31, 2023), the global study was fully enrolled and included 140 safety-evaluable pts with FL; 128 pts were efficacy-evaluable and 85 pts had ≥12 months follow-up. The median duration of study follow-up for efficacy was 26.6 months. In the safety-evaluable FL population, median age was 60.5 years (range 22-84), 53% were male, and pts had received a median of 3 (range 2-13) prior lines of therapy. 73% of pts were refractory to their last therapy, 41% were double refractory, and 74% were refractory to an anti-CD20 antibody. 50% of pts had progression of disease within 2 years (POD24) and 29% had a prior autologous hematopoietic stem cell transplant. ORR and CR rate by ICR were 80% (102/128) and 72% (92/128), respectively, and were consistent across pts with high-risk features. Responses were durable, with both median DoR and duration of CR of 21.7 months; the probability of maintaining CR for 24 months was 48%. Median PFS was 20.7 months (95% CI: 16.7-26.5) and median OS was not reached; the probability of survival at 3 years was 63%. Patient-reported overall quality of life (QoL) scores were maintained during the course of treatment. MRD status at 12 weeks was highly predictive of PFS. Safety was generally consistent with previous reports, and no new treatment-related Grade (Gr) 5 events were recorded since the first interim analysis. The most common treatment-emergent AEs (&gt;30% all grades) were CRS (55%), anemia (34%), neutropenia (34%), and pyrexia (33%). With the optimized 0.7/4/20 mg step-up regimen (n=72), 98% of CRS events were Gr 1/2, and only one pt had Gr 3 CRS. All CRS events resolved with supportive measures; 13 pts received tocilizumab for CRS management with the optimized regimen. Only one low-grade ICANS event was reported with the optimized regimen. Gr ≥3 infections occurred in 50 (36%) pts (Gr 5, n=14 [10%]); COVID-19 infections were reported in 46 (35%) pts (Gr 5, n=8 [6%]). Conclusions The results of this pre-specified analysis of the Phase 2 ELM-2 study continue to demonstrate deep and durable responses with odronextamab in heavily pretreated, refractory pts with R/R FL. 90% of responders were complete responders, with a 48% probability of maintaining CR for 2 years. High CR rates appear to translate to favorable, long-term survival outcomes in the setting of incurable disease. The incidence of AEs was consistent with earlier reports, with no new treatment-related Gr 5 events. Importantly, continued treatment with odronextamab had no detrimental effects on overall QoL. These data underscore the promise of odronextamab as a potentially effective agent for the management of R/R FL. Updated data will be presented.