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Background: Polatuzumab vedotin (Pola) is an antibody drug conjugate targeting CD79b that incorporates the microtubule disrupting monomethyl auristatin E payload. Pola was approved in 2023 for the upfront treatment of diffuse large B cell lymphoma (DLBCL) in combination with rituximab, cyclophosphamide, doxorubicin, and prednisone (polaRCHP) based on the POLARIX trial. However, the activity of pola appears to vary based on DLBCL cell of origin (COO) subtype, with greater efficacy in activated B cell (ABC) DLBCL compared to germinal center B cell (GCB) DLBCL (Russler-Germain Blood 2023). When outcomes in POLARIX are stratified by COO, polaRCHP demonstrated progression free survival (PFS) and overall survival (OS) benefits over RCHOP in patients with ABC but not GCB subtype DLBCL (PFS HR 0.34 ABC vs 1.03 GCB, OS HR 0.27 ABC vs 1.64 GCB; Morschhauser ASH 2023 and FDA data). Most prospective studies of pola used gene expression to assess COO, which is not readily clinically available. This study aims to examine if COO subtype by Hans algorithm (based on CD10, BCL6, and MUM1 expression by immunohistochemistry) is predictive of pola responses and outcomes in patients with large B cell lymphoma (LBCL). Methods: We conducted a retrospective, multicenter observational study of adults with LBCL who received pola (monotherapy or in combination) from 2015-2024 with Hans algorithm COO data and response assessment available. Patients were stratified by receipt of pola in the frontline vs relapsed/refractory (R/R) setting. The primary endpoint was overall response rate (ORR) to pola-based treatment in GCB vs non-GCB subtypes. Secondary endpoints included complete response rate (CRR), PFS, and OS. For time to event endpoints, patients responding to pola who received CAR T or stem cell transplantation prior to progression were censored at time of cellular therapy. Demographics were summarized by descriptive statistics. Comparative and survival analyses used Chi squared/Fischer exact tests and Kaplan Meier analysis. Data cutoff was July 1, 2024. Results: 718 patients were included. Median follow-up was 15 months (interquartile range [IQR] 8-32). Median age at LBCL diagnosis was 66 years (IQR 56-74); 62% were men; 69 (10%) had double hit lymphoma (DHL); 129 (18%) had underlying low grade lymphoma. Pola was used in the frontline setting in 293 (41%) patients, of whom 139 (47%) had GCB vs 154 (53%) non-GCB COO. Of the 426 patients receiving pola for R/R LBCL (including one patient receiving pola retreatment), 224 (53%) had GCB vs 202 (47%) non-GCB COO. Among patients receiving pola-based regimens in the R/R setting (GCB vs non-GCB: pola monotherapy = 7% vs 4%, pola + R = 26% vs 26%, pola + BR = 55% vs 61%, pola + other = 12% vs 9%; p = 0.44), the ORR in GCB vs non-GCB LBCL was 36% vs 61% (p < 0.001), while CRR in GCB vs non-GCB was 17% vs 36% (p < 0.001). COO remained a significant component of logistic multivariate regression models of ORR (p < 0.001) and CRR (p < 0.001) when incorporating IPI at original LBCL diagnosis, histology, DHL status, and refractory status to frontline therapy. Despite this, no significant PFS or OS differences by COO were seen, potentially due to approximately 1/4 patients being censored due to receiving subsequent cellular therapy (e.g. CAR T) prior to progression. In patients receiving frontline pola-based regimens (of which 275 [94%] included an anthracycline), ORR and CRR were similar in GCB vs non-GCB (ORR 89% vs 88% p > 0.5; CRR 76% vs 77% p > 0.5). While PFS and OS were similar between COO groups in the frontline cohort, follow-up and cohort size were limited. Conclusion: Based on this real-world evidence, COO classification by Hans algorithm is a strong predictor of the activity of pola-containing therapy in R/R LBCL, with significantly higher ORR and CRR in patients with non-GCB compared to GCB COO LBCL. This aligns with the cumulative existing evidence. ORR and CRR to pola-containing therapy in the frontline setting did not differ significantly by COO subtype, but longer follow-up of larger cohorts is needed to clarify the predictive role of COO by Hans algorithm in this setting, especially considering the PFS advantage with polaRCHP in POLARIX was not associated with significant differences in ORR or CRR. Overall, clinicians should consider factoring COO subtype into treatment decisions regarding pola-containing regimens, and studies of pola-based therapies should stratify patients and report outcomes by COO subtype.

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.