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Abstract Introduction: CD20xCD3 bispecific antibodies (BsAb) have been approved for use in relapsed/refractory (RR) large B-Cell lymphomas (LBCLs) with manageable toxicities. The main adverse events of clinical interest are cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). The risk factors for CRS and ICANS are not well understood. Knowledge of variables that contribute to increased risk may help clinicians identify and tailor management for high-risk patients (pts) and increase the comfort level for providers using these therapies in community practices. Methods: We performed a multicenter retrospective study at 21 US centers evaluating pts with RR LBCLs receiving commercially available epcoritamab (epco) or glofitamab (glofit) between 2023 and 2025. We obtained baseline characteristics, safety and efficacy outcomes. Univariate analysis was performed to identify associations between CRS, ICANS, and clinical variables of interest. Results: As of May 31, 2025, a total of 312 pts with RR LBCLs were treated with BsAb, Epco n=193 (62%), Glofit n= 119 (38%); median age 68; 63% male; 70% ECOG PS 0-1. Most common histologic type was diffuse large B-cell lymphoma, not otherwise specified (DLBCL, NOS) (n=239, 84%) followed by high-grade B-cell lymphoma (HGBL) (n=46, 16%). 179 pts (57%) were previously treated with chimeric antigen receptor T-cell (CAR-T) therapy, with 47% receiving CAR-T <6 months (mo) prior to BsAb. Among pts with prior CAR-T, CRS with CAR-T therapy of any grade occurred in 63%, with 26% ≥ grade 2. ICANS of any grade (G) occurred in 25% of pts (9.4% ≥ G3). Overall and complete response (ORR and CR) rates to BsAb were 51% and 29%, respectively. With a median follow up of 5 mo, median progression-free and overall survival (PFS and OS) were 2.3 and 7.3 mo, respectively. With BsAb treatment, CRS of any grade occurred in 117 (39%) patients: 24% G1, 8.7% G2, 4% G3, 1% G4 and 1% G5. The max grade CRS occurred most frequently after the third dose of epco (35%) and the first dose of glofit (23%). CRS was managed with additional steroids in 24% of pts and tocilizumab in 22%. 13% of pts experienced ICANS: 5.8% G1, 3.4% G2, 2% G3, 1% G4 and 0.3% G5. Factors that increased the risk for any grade CRS included: bulky disease ≥ 7.5 cm at time of BsAb treatment (OR 2.04, 95% CI 1.17 – 3.55, p = 0.012), elevated LDH (OR 2.56, 95% CI 1.45– 4.76, p = 0.002) and treatment with epco compared to glofit (OR 1.69, 95% CI 1.04- 2.77, p = 0.036). As G ≥2 CRS generally requires inpatient monitoring and management, we next compared the risk factors between pts with no CRS or G1 CRS and G ≥2 CRS. Factors associated with increased risk for high grade CRS included: bone marrow involvement by lymphoma (OR 3.47, 95% CI 0.97 – 11.3, p = 0.043), platelet count ≤ 75 (OR 2.46, 95% CI 1.21 – 4.87, p = 0.011), ≥ 2 extra nodal sites (OR 2.04, 95% CI 1.07 – 3.97, p = 0.032) and ≥G2 CRS with prior CAR-T (OR 3.35, 95% CI 1.13 – 9.97, p = 0.027). Factors that increased the risk for ICANS included: bulky disease (OR 2.67, 95% CI 1.28 – 5.49, p = 0.008), elevated Cr ≥ 1.5x ULN (OR 3.79, 95% CI 1.25 – 10.4, p = 0.012), elevated AST/ALT ≥ 3x ULN (OR 4.65, 95% CI 0.92 – 19.9, p = 0.042), low albumin (OR 2.85, 95% CI 1.49 - 5.5, p = 0.002), and co-occurrence of CRS with BsAb (OR 9.1, 95% CI 3.85- 25, p < 0.001). No other clinical variables including older age, histologic subtype, ECOG PS, B symptoms, IPI score, cell of origin or histologic subtype, baseline labs such as ALC, CRP, fibrinogen or D-dimer were significantly associated with CRS or ICANS risk. There was no difference in ORR or CR rates in patients who experienced CRS or ICANS. Conclusions: Our analysis of pts treated with commercial BsAb for LBCL shows an increased risk for CRS and ICANs based on clinical variables that are routinely obtained at baseline including tumor bulk, sites of disease, laboratory parameters, and history of prior CRS with CAR-T therapy. Differences in baseline populations receiving epco and glofit treatments in this real-world analysis have been previously reported (Brooks et al, Blood 2025) and the comparative risk for CRS between these treatments remains unclear. Future plans including multivariable analysis may allow for development of a predictive model to identify pts at high risk of CRS and ICANS with BsAb treatment, potentially leading to prospective clinical trials evaluating prophylactic interventions for high-risk pts.

Abstract Introduction: Epcoritamab (epco) and glofitamab (glofit) are bispecific antibodies (BsAbs) approved for the treatment of patients (pts) with multiply relapsed or refractory (r/r) large B-cell lymphoma (LBCL). Though response rates are relatively high, most patients (pts) eventually experience progression of disease (POD). We sought to investigate the treatment patterns and clinical outcomes following POD post-BsAb for r/r LBCL Pts, as this has not previously been described. Methods: We performed a multicenter retrospective study including 21 US centers evaluating pts with r/r LBCL receiving commercially available epco or glofit between 2023 and 2025. Baseline characteristics and outcomes were extracted from medical records. Efficacy and survival outcomes were assessed by site investigators and included overall response rate (ORR), complete and partial response (CR, PR) rates, progression-free survival (PFS) and overall survival (OS), analyzed using the Kaplan Meier method. Results: As of May 15, 2025, a total of 312 pts with r/r LBCLs were treated with BsAb, of whom a total of 168 (53.8%) pts experienced POD [104 of 193 (53.8%) treated with prior epco and 64 of 119 (53.8%) treated with prior glofit]. Pts with POD had a median age at BsAb start of 67 years (interquartile range [IQR] 58-76), most were male (68.4%), and the most common histology was diffuse large B-cell lymphoma not otherwise specified (n=122 [71.8%]). Sixty-seven of 168 pts (39.9%) with POD after BsAb had experienced primary refractory disease defined as failure to achieve PR or CR to frontline therapy. A total of 102 (60.7%) pts with POD to BsAb had received chimeric antigen receptor (CAR) T-cell therapy prior to BsAbs, with 33.3% of these pts being refractory to CAR T and 30.4% progressing within 6 months of CAR T-cell infusion. The median time to progression following BsAb start was 48 days. Following POD, 70 pts received no further anti-lymphoma therapy. Among 98 pts receiving subsequent therapy, 85 initially received systemic therapy and 13 initially received local therapy with radiation (concurrently with systemic therapy in 8 pts). The most commonly-used next line of systemic therapies included: loncastuximab tesirine in 19 pts (ORR 16.7%, all PR); commercial CAR T in 11 pts (ORR 50% [CR 36.4%, PR 18.2%); tafasitamab with lenalidomide in 7 (no responses); and other chemotherapy in 46 pts (ORR 27.6% [CR 24.1%]). The median follow-up time from POD was 9.2 months among survivors (95% confidence interval [CI] 7.8-13.3). Among those who initiated subsequent-line therapy following BsAbs, the median progression-free survival (PFS2) was 1.9 months (95% CI 1.5-2.4) and median overall survival (OS) from initiation of subsequent-line therapy was 3.9 months (95% CI 2.4-5.5). The estimated 1-year OS following initiation of next therapy was 12%. Conclusions: We report the outcomes of largest cohort of pts with POD post-BsAbs in r/r LBCL. Progression events occurred early after initiation of single agent BsAbs, and almost half of pts who progressed did not receive subsequent therapy. For those who received standard subsequent-line therapy after POD, response rates and survival outcomes were poor. Pts with POD after BsAB should be strongly considered for clinical trials of novel therapeutics or combination therapies.

Abstract Background: For LS-DLBCL, clinical trials (FLYER, LYSA/GOELAMS 02-03, LYSA LNH09-1B, S1001) have shown that 4 cycles of rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (RCHOP4) without radiation (RT) leads to durable remissions in >90% of cases. However, only patients (pts) with non-bulky disease and/or international prognostic index (IPI) of 0 and complete metabolic response (CMR) on interim positron emission tomography (PET) scan, if performed, were eligible for RCHOP4 alone in these studies. Outcomes in trial-ineligible LS-DLBCL and the appropriate real-world candidates for RCHOP4 are still undefined. Methods: We conducted a multicenter retrospective study of adult pts with stage I/II DLBCL of any tumor bulk, IPI and with or without B-symptoms diagnosed after 2011 and treated with RCHOP4 +/- 2 cycles R from 21 U.S. centers. Pts with PMBCL, PTLD or receiving non-standard dose RCHOP for cycle (C) 1 or planned consolidative RT were excluded. The primary endpoint was PFS from C1 by Kaplan-Meier method, not counting indolent lymphoma relapse. Event free survival (EFS) was time to next therapy without progression (including unplanned RT for non-CR), progression or death. A competing risks analysis of non-relapse mortality (NRM) vs. DLBCL progression was performed. Results: The characteristics of the 428 pts were: median age 60 (18-88), 60% male, 11% Hispanic and 4% non-Hispanic Black, 62% stage I, 15% elevated LDH, 3% ECOG PS>1, 5% tumor bulk >7cm, 9% had B-symptoms and median Charlson Comorbidity Index (CCI) was 4 (2-12). IPI was 0, 1 and 2-3 in 42%, 46% and 12% and stage-modified IPI (smIPI) was 0, 1, 2 and 3-4 in 25%, 48%, 21% and 6% of pts. 66% had nodal (59% head/neck, 11% pelvic, 9% multiple above diaphragm, 7% abdominal) and 46% extranodal sites (37% head/neck, 20% gastric/intestinal, 9% spleen, 8% skin/soft tissue); 6% had transformed/concurrent FL/MZL or grade 3B FL, 33% (138/408) were non-GCB cell of origin (COO), 25% (90/357) double expressor (DEL) and 0.5% (2/379) double-hit. 13% had completely resected disease, 97% staging PET and 47% bone marrow biopsy. Median diagnosis to treatment interval was 30 days (IQR 20-43), 6% had dose reductions after C1, 77% had an interim PET (iPET) after C2 (33%) or C3 (67%), 15% received 2 additional cycles R and 4% CNS prophylaxis. CMR rates by iPET were 83% after C2 and 94% after C3, and 95% by end-of-treatment PET. iPET PMR was more likely if smIPI>2 or bulky disease. Median follow-up time was 2.7 years. There were 32 progression events: 14 occurred at the primary site and 17 at distant sites (1 unknown), and 12 occurred after 2 years. Another 11 pts received unplanned RT after RCHOP4 for non-CR. There were 24 deaths, 12 without prior progression. Cause of death was DLBCL in 7 and non-DLBCL in 17 cases (6 infection, 2 ILD, 2 heart failure, 2 second cancer, 1 seizure, 4 unknown). EFS, PFS and OS rates were 88%, 90% and 96% at 3 years. By univariable Cox regression, Black race, elevated LDH, smIPI>2, DEL, increasing CCI, multiple subdiaphragmatic nodal sites and iPET PMR were associated with worse PFS. Non-significant variables of note included COO, extranodal sites, complete resection, missing bone marrow biopsy, missing iPET and additional cycles R. By multivariable analysis (including age>60, stage, ECOG PS>1, elevated LDH, bulky disease, CCI, B-symptoms and DEL), ECOG PS>1 (HR 3.95 p=0.050), CCI (HR 1.29 p=0.003) and DEL (HR 2.02 p=0.069) were associated with worse PFS. Cumulative incidence of DLBCL progression and NRM were 8% and 2% at 3 years. Competing risk analysis by univariable models found that age>60, ECOG PS>1, smIPI>2, elevated LDH, CCI and bulky disease were associated with NRM, while DEL and B-symptoms were associated with DLBCL progression.Conclusion: Presented is the largest retrospective cohort of LS-DLBCL treated uniformly with RCHOP4 to date. Despite modest follow-up time and lack of an “intention-to-treat“ population, this study shows that abbreviated RCHOP4 leads to excellent outcomes in the real-world, albeit with continuous risk of late relapse. smIPI risk factors were associated with worse PFS, though this may in part be driven by risk of non-lymphoma death. As pts with advanced age, poor performance status or comorbidities may benefit from reduced treatment exposure, RCHOP4 should still be considered for these and other “trial-ineligible” pts, particularly if other high-risk features (iPET PMR, DEL or B-symptoms) are absent.

Abstract Introduction: Epcoritamab (epco) and glofitamab (glofit) are bispecific antibodies (BsAbs) approved for the treatment of patients (pts) with relapsed or refractory (r/r) large B-cell lymphomas (LBCLs). Their use is associated with relatively high response rates, with some patients experiencing prolonged remission. It is unclear whether continuous treatment beyond 12 months for pts in remission is beneficial, as continued immunosuppression may result in additional toxicity. We sought to report the outcomes of pts with prolonged remission and survival following BsAb administration. Methods: We performed a multicenter retrospective study including 21 US centers evaluating pts with r/r LBCLs receiving commercially available epco or glofit between 2023 and 2025. Baseline characteristics and outcomes were extracted from medical records. Efficacy and survival outcomes were assessed by site investigators and included overall response rate (ORR), complete and partial response (CR, PR) rates. Pts who responded to BsAbs and had ≥365 days of follow-up from initiation of BsAb treatment were included in the analysis. Results: As of May 15, 2025, a total of 312 pts with r/r LBCLs were treated with BsAbs (epco n=193, glofit n=119) with a median age of 66 years (interquartile range [IQR] 59-73) at BsAb start. Most were male (64.5%), had advanced stage disease (77.4%) and had ECOG performance status of ≤1 (93.3%) at BsAb start. Of 207 pts who had initiated treatment with BsAb ≥12 months prior to data cutoff, we identified 31 pts (15.0%) who had a response to BsAbs (19 epco, 12 glofit) and were alive without progression at 12-months post-BsAb initiation and included them in this landmark analysis. Of the cohort of 19 pts treated with epco, 6 discontinued due to reasons other than disease progression including CAR-T cell therapy (n=2), secondary malignancy (n=2), allogeneic transplant (n=1), or other reasons (n=1). Thirteen of 19 pts received ≥12 months of epco treatment, and, with a median follow-up of 16 months from the start of BsAb, 12 of 13 pts continued receiving epco beyond 12 months with one pt discontinuing after 12 months (observed for an additional 41 days prior to censoring). Of the cohort of 12 pts treated with glofit, 8 pts were observed after completing all planned therapy and 4 patients underwent allogeneic transplant. Among all 31 BsAb-treated patients alive and in remission at 12 months, at the time of data cutoff, 5 pts (12.9%) had progressed (2 previously treated with epco and 3 with glofit). Three of the 4 pts who underwent allogeneic transplant after prior glofit treatment experienced disease relapse. A total of 24 pts (77.4%) were alive at the time of last follow-up, with the causes of death being disease progression (n=1), secondary malignancy (n=1), infection (n=1), and unknown cause (n=4). Conclusions: In this large cohort of r/r LBCL pts treated with BsAbs monotherapy in the standard of care setting, a relatively small proportion of pts (15%) achieve the 12 month PFS landmark. In the absence of robust evidence for what constitutes best practice, different strategies are employed, including continuation of BsAb, observation as well as consolidation with allogeneic transplant or CAR T-cell therapy. Additional follow-up will be reported to help guide clinical decision making regarding the optimal management strategy for this high risk pt population.

The treatment landscape of B-cell lymphomas has significantly evolved in recent years with approval of novel targeted therapies. CD3 × CD20 bispecific antibodies and CD19-directed monoclonal antibodies and antibody–drug conjugates have demonstrated efficacy in relapsed/refractory follicular lymphoma (FL). Bruton tyrosine kinase (BTK) inhibitor–based regimens are emerging as effective treatment options for patients with TP53-mutated classical mantle cell lymphoma (MCL). Results from ongoing clinical trials suggest that the addition of CD3 × CD20 bispecific antibodies to chemoimmunotherapy improves outcomes in patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL). These NCCN Guideline Insights highlight significant updates to the NCCN Guidelines for B-Cell Lymphomas for the treatment of FL, MCL, and DLBCL.

Abstract Epcoritamab and glofitamab are CD20-directed bispecific antibodies (BsAbs) approved in the United States for relapsed or refractory (R/R) diffuse large B-cell lymphoma (DLBCL). Limited data exist for patients treated outside of trials. Patients with R/R DLBCL receiving commercial epcoritamab or glofitamab between 1 January 2023 and 15 October 2024 were collected from 21 United States institutions. Among 245 patients, 156 received epcoritamab and 89 received glofitamab, 113 were refractory to front-line therapy, 40 had MYC and BCL2 and/or BCL6 rearrangements, 147 received prior chimeric antigen receptor T-cell therapy, and 174 patients would have been ineligible for registrational trials. The overall response rate (ORR) for epcoritamab and glofitamab was 51% (23% complete response, [CR]) and 53% (30% CR), respectively. Median progression-free survival (PFS) was 2.6 months (95% confidence interval [CI], 2.0-3.8 months), and median overall survival (OS) was 7.8 months (95% CI, 6.2-11.0 months). The 6-month PFS was 36% (95% CI, 30-44) and the 6-month OS was 60% (95% CI, 54-67). Both trial ineligibility and undetectable CD20 pre-BsAbs portended shorter PFS and OS. Of 17 individuals with paired biopsies, 15 (88.2%) lost CD20 expression after BsAbs with a median time to progression of 3.7 months. This analysis including patients with R/R DLBCL shows the ORR to CD3/CD20 BsAbs was comparable to pivotal trials, although PFS and OS were lower. Baseline undetectable levels of CD20 were associated with poor outcomes. These results demonstrate the activity of BsAbs in R/R DLBCL, and underscore the importance of target antigen expression.

Introduction: Bispecific antibodies (BsAbs) epcoritamab (Epco) and glofitamab (Glofit) are approved in the US for the treatment of patients (pts) with relapsed or refractory (r/r) large B-cell lymphomas (LBCLs) based upon high response rates and manageable toxicity profiles reported in pivotal trials. However, data on outcomes for pts treated with BsAbs outside of clinical trials are limited. As such, we sought to investigate the safety and efficacy of Epco and Glofit for the treatment of pts with r/r LBCLs in real-world settings. Methods: We performed a retrospective study including 19 US centers evaluating pts with r/r LBCLs receiving commercially available Epco or Glofit between 2023 and 2024. Baseline characteristics and outcomes were extracted from medical records. Efficacy outcomes included overall response rate (ORR), complete and partial response (CR, PR) rates, progression-free survival (PFS) and overall survival (OS), analyzed using the Kaplan Meier method. Key safety outcomes included cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). Results: As of May 31, 2024, a total of 209 pts with r/r LBCLs were treated with Epco (n=139) or Glofit (n=70). Median age at BsAb start was 67 years (interquartile range [IQR] 58-76). Most were male (62.2%), and the most common histology was diffuse large B-cell lymphoma (n=155 [74.2%]). Of pts with molecular testing (n=168), 34 (20.2%) had double/triple hit lymphoma. Most (78.9%) had Ann Arbor stage III-IV disease and 91% had an ECOG performance status of ≤1. Median number of lines of treatment before BsAb was 3 (range 1-12). Of pts with known response assessment following front-line therapy, 54 (32.1%) had primary refractory disease, defined as failure to achieve PR or CR to front-line therapy. Most pts (n=126 [60.3%]) received prior chimeric antigen receptor (CAR) T-cell therapy and 21 (10.0%) received prior autologous hematopoietic progenitor cell transplant. CD20 expression was assessed in 106 biopsies (50.7%) prior to BsAb and was positive in 90 (84.9%). A total of 172 pts were response-evaluable. The best ORR was 50.6%, with CR in 41 (23.8%), PR in 46 (26.7%), stable disease in 10 (5.8%), and progressive disease in 75 (43.6%). The ORR and CR rates were 49% and 23% for Epco, and 53% and 25% for Glofit, respectively. With a median follow-up of 5 months, the median PFS was 2.7 months (95% CI 2.0, 3.9) and median OS was 7.2 months (95% CI 6.1, not reached [NR]). The estimated PFS and OS at six months were 35% (95% CI 29%-43%) and 59% (95% CI 52%-67%), respectively. For pts who relapsed after CAR T-cell therapy, the median PFS and OS were 2.5 (95% CI 1.8, 4.7) and 7.8 (95% CI 6.2, NR) months, respectively. Pts without detectable CD20 expression via immunohistochemistry or flow cytometry prior to BsAb therapy had significantly inferior outcomes (PFS 1.1 vs 3.4 months, P < 0.001 and OS 1.3 vs 13 months, P < 0.001) compared to pts with detectable CD20. CRS of any grade occurred in 82 pts (39.2%), corresponding to 51.1% and 28.6% of pts treated with Epco and Glofit, respectively. Grade ≥3 CRS occurred in 9 (4.3%), all of whom received Epco. CRS was treated with tocilizumab in 43 pts (53.1%). ICANS occurred in 24 (11.5%) pts; any grade ICANS occurred in 13.7% and 7.1% of pts treated with Epco and Glofit, respectively. Grade ≥3 ICANS occurred in 6 pts (2.9%), 5 of which received Epco (3.6%). Of those experiencing ICANS, 66.0% were treated with corticosteroids. Two pts had deaths attributed to ICANS and one to CRS. A total of 122 (58.4%) pts discontinued therapy after a median of 3 cycles (range 0-48), 91 (74.6%) due to disease progression and 31 (25.4%) due to adverse events (15 due to infection, 3 due to ICANS, 2 due to CRS, and 11 for other reasons). Conclusions: In this heavily pretreated group with adverse disease features and high rate of CAR T exposure, the response rates, PFS, and OS following BsAb therapy were lower compared to pivotal trials. Poor outcomes were observed for those without detectable CD20. Rates of ICANS and grade ≥3 CRS were higher than reported in pivotal trials, as was the rate of discontinuation of therapy due to adverse events. Future efforts to improve outcomes may include intensified dose escalation protocols to more rapidly achieve disease control, combination therapies, and characterization of clinicopathologic factors that predict response to BsAb to identify subgroups of pts who can derive maximal benefit from these agents.

Abstract Little is known about the central nervous system (CNS) risk in high-grade B-cell lymphoma, not otherwise specified (HGBL NOS). Hence, we sought to describe the rates of baseline CNS involvement, risk of CNS recurrence after primary therapy, and management strategies in HGBL NOS. In this multicenter retrospective study, we included 160 adults with newly diagnosed HGBL NOS treated between 2016 and 2021 at 20 US institutions. Eleven patients (7%) had baseline CNS involvement at diagnosis (leptomeningeal = 6, parenchymal = 4, and both = 1). Baseline CNS involvement was significantly associated only with MYC rearrangement (OR = 3.5) and testicular (in men) or female pelvic (in women) involvement (OR = 8.1). There was no significant difference in survival outcomes between patients with HGBL NOS with (median PFS = 4 years) or without (median PFS = 2.4 years) baseline CNS involvement (P = 0.45). The cumulative incidence of CNS recurrence at 3 years was 11%. Patients with baseline CNS involvement were at the highest risk (48.5% vs 8% for those without baseline CNS involvement) and were excluded from the risk factors analysis for CNS recurrence. The risk for CNS recurrence was significantly associated with blood or bone marrow involvement, CD5 expression, non–germinal center B-cell subtype, and “dual-expresser lymphoma” phenotype, however, high CNS IPI was not. The prognosis of relapsed HGBL NOS was poor, regardless of whether recurrence was systemic or limited to the CNS, and with currently available salvage strategies, including autologous transplantation and chimeric antigen receptor T-cell modalities, almost all patients with CNS recurrence ultimately succumbed to their disease.

7012 Background: DLBCL with expression of MYC and BCL2 (double expressor lymphoma, DEL), has an adverse prognosis. Venetoclax, an inhibitor of BCL2, was previously studied in combination with R-CHOP. A051701 is a phase II/III randomized trial of chemoimmunotherapy +/- venetoclax in DEL and double hit lymphoma cohorts. Here we report initial phase II results from the DEL cohort. Methods: Patients (pts) age ≥ 18 years (y) with untreated DEL were randomized 1:1 to R-CHOP (Arm 1) or R-CHOP-venetoclax (Arm 2). DEL was defined as MYC expression ≥40% and BCL2 expression ≥50%, without double hit cytogenetics. Enrollment was based on local pathology results that were centrally confirmed. Venetoclax 800 mg was given orally days 4-8 of cycle 1 and days 1-5 of subsequent cycles for up to 6 cycles. All cycles were supported by GCSF or peg-GCSF. The primary endpoint was progression-free survival (PFS) with 84% power to detect a HR of 0.518 corresponding to 2y PFS rate of 65% in Arm 1 and 80% in Arm 2 (1-sided α=0.20). Results: 119 DEL pts were enrolled: 60 Arm 1; 59 Arm 2. Analyses were performed for the modified intent-to-treat population, defined as eligible pts with confirmed DEL histology (n=113; 56 Arm 1, 57 Arm 2). Median age was 64 y (range 22-85); baseline demographic factors were well balanced except for advanced stage (more common in Arm 1; (77% vs 60%, p=0.051). Most pts were non-germinal center B cell-like by immunohistochemistry (Arm 1 72%, Arm 2 58%), high-intermediate/high risk IPI (Arm 1 54%, Arm 2 51%) and ECOG performance status 0-1 (Arm 1 95%, Arm 2 86%). BCL2 rearrangements were detected in 25% and 33% of pts on Arm 1 and Arm 2, respectively. Most pts completed therapy per protocol (84% Arm 1, 75% Arm 2). Median follow up is 27 months (m). No difference in PFS was observed with 12-m PFS estimates of 77% in Arm 1, 76% in Arm 2 [HR = 0.98 (95% CI: 0.48 – 2.01), p=0.95]. The end of treatment (EOT) overall and complete response rates among patients with an EOT assessment were 87.5% and 70% in Arm 1, and 90% and 82% in Arm 2. Overall survival (OS) was not statistically significantly different with 12-mo OS estimates of 94% in Arm 1 and 79% in Arm 2 [HR = 1.27 (95% CI: 0.57 – 2.79), p=0.56]. Grade ≥3 adverse events (AEs) occurred more frequently in Arm 2 (42% vs 76%). The most commonly increased grade ≥3 AEs included neutropenia (20% vs 47%), anemia (4% vs 25.5%), thrombocytopenia (5.5% vs 24%), febrile neutropenia (7% vs 16%) and fatigue (0% vs 11%). No grade 5 AEs on treatment were reported on Arm 1, and 3 were reported on Arm 2 (lung infection and sudden death NOS, both possibly related; respiratory failure, unlikely related). Conclusions: Adding venetoclax to R-CHOP in DEL pts did not improve PFS and resulted in increased toxicity. The study did not meet its primary endpoint in phase II, and so did not proceed to phase III. Clinical trial information: NCT03984448 .