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Abstract Introduction: NAVD has become a standard-of-care for frontline (1L) treatment (tx) of advanced stage cHL, based on the results of the S1826 study. S1826 demonstrated a 1-year progression free survival (PFS) of 94% for NAVD compared to 86% for brentuximab vedotin-AVD, which remained durable at 2 years (Herrera et al, NEJM 2024). Adverse events (AEs) and efficacy have not been reported in patients (pts) treated with NAVD outside of a clinical trial. Hence, we sought to evaluate safety profile and efficacy outcomes of pts with cHL treated with 1L NAVD in a real-world setting (RWS). Methods: In this multicenter retrospective cohort study, we included pts ≥18 years with cHL treated with 1L standard of care NAVD between 2023 and 2025 at 20 US academic sites. The safety evaluable cohort received at least 1 cycle of NAVD and included pts who have not completed tx. The efficacy evaluable cohort had completed 6 cycles of tx including end of treatment (EOT) PET-CT and included pts who intended to complete tx but died or discontinued due to progressive disease or AEs. The primary endpoint was EOT overall response rate (ORR). Secondary endpoints included EOT complete response rate (CRR), PFS and overall survival (OS). PFS and OS were calculated from the start date of tx and analyzed using the Kaplan Meier method. Results: A total of 311 pts with cHL were treated with NAVD with 26% of pts with tx ongoing (n=83) and 73% with tx completed (n=228). Baseline demographics included 55% male pts, 60% with stage IV disease (stage IIB, n=4) and 84% with nodular sclerosis subtype. Median age was 37 years (range 18-88), 29% had bulky disease (>7.5 cm), 28% were EBV positive (n=74/268), 8% had history of an autoimmune disease, and 31% had an IPS 4-7. G-CSF was given in 64% of pts. All patients were safety evaluable. Tx was interrupted (any length) in 24%, reduced in 12%, and discontinued in 14%. The most common reason for dose reduction was neuropathy in 4%. Nivolumab was discontinued in 10% and all therapy in 3.7% due to toxicity. Any AE and any grade 3 or higher AE (>G3) were observed in 92% and 62%, respectively. Neutropenia of any grade occurred in 68% (48% >G3), infection in 25% (10% >G3), and neuropathy in 30% (2.8% >G3). Hospitalization for an AE occurred in 20% (4.5% febrile neutropenia). Among pts with complete data (n=305), any immune related AE (irAE) occurred in 78 pts (25.6%) with any >G3 irAE in 23 pts (7.5%). The most common irAEs included hypothyroidism (7.9%, all grade 1-2), hepatotoxicity (1.6% G1/G2, 3.3% >G3), inflammatory arthritis (3% G1/G2, 0.6% >G3), rash (2.6%, all grade 1-2), and colitis (1% G1/G2, 1% >G3). Other notable >G3 irAEs included adrenal insufficiency (n=2), AKI/ATN (n=1), myocarditis (n=1), diabetes (n=1) and pancreatitis (n=1). Of 84 irAE events, 47 (56%) have had complete resolution. Among all pts, 14.4% (n=45) required systemic steroids at any time (intravenous in 4.1%), 3.2% (n=10) require ongoing steroids/immunosuppression and 8.3% other therapy for an irAE (n=23 levothyroxine, n=1 hemodialysis, n=1 heart failure tx, n=1 insulin). Among all pts, 265 (85%) had an interim PET-CT after 2-4 cycles. The ORR and CRR at interim PET-CT were 97% and 78%, respectively. In the efficacy evaluable population (n=228), the EOT ORR and CRR were 96% and 90%. The median follow up was 10.2 mo (range 0.27-28.52). The 1-year PFS and OS estimates were 93.8% (95% CI: 90.8-98.4%) and 99.1% (95% CI: 97.9-100%), respectively. In multivariable analysis (MVA), only IPS score (OR 0.6, 95%CI: 0.59-0.60) was associated with lower CRR. In Cox univariable analysis, EBV+ status (HR=14.8, 95% CI: 3.2-69.2), IPS score (HR=1.5, 95% CI: 1.0-2.2), and ESR (HR=1.02, 95% CI: 1.00-1.04) were associated with worse PFS. Among the 11 pts with progression/relapse, 9 were primary refractory. 10 pts were started on second line (2L) therapy, and all pts are alive (1 pt pending 2L tx initiation). There were 2 deaths: one related to infectious complications and other unknown and both occurred after the first cycle of therapy. Conclusions: Pts treated with NAVD in a large RWS showed comparable response rates and 1-year survival outcomes to those in the pivotal S1826 trial. Most AEs were similar and grade 1-2, but close monitoring of irAEs is necessary given the potential long-term toxicity of checkpoint inhibitors and potential for ≥G3 irAEs (7.5%) in this young patient population. Our data supports the use of NAVD for 1L advanced stage cHL.

Abstract Background: Systemic mastocytosis (SM) comprises a spectrum of subtypes characterized by neoplastic mast cell (MC) infiltration of tissues and release of MC mediators. Non-advanced SM (NonAdvSM), including indolent SM (ISM), smoldering SM (SSM), and bone marrow mastocytosis (BMM) subtypes, is the most prevalent form of SM. NonAdvSM can be associated with debilitating symptomology which can significantly impair quality of life. The gain-of-function somatic KIT c.2447 C>T (p.D816V) mutation is found in up to 95% of patients with SM. Bezuclastinib (CGT9486) is an oral, potent, and selective type 1 tyrosine kinase inhibitor with activity against KIT D816V. Results from Summit (NCT05186753) Part 1 informed the recommended phase 2 dose (100 mg QD bezuclastinib) for Part 2. We report topline results from the 24-week assessment of Summit Part 2. Methods: Summit is a multi-center, randomized, double-blind, placebo (PBO)-controlled Phase 2 trial of bezuclastinib in patients with NonAdvSM who had inadequate symptom control despite best supportive care (BSC) medications. The primary endpoint was 24-week mean change from baseline in Mastocytosis Symptom Severity Daily Diary (MS2D2) total symptom score (TSS) (range 0–110), which is a fit-for-purpose patient-reported outcome measure of NonAdvSM symptom severity. Key secondary endpoints included the proportion of patients with ≥50% reduction in serum tryptase, KIT p.D816V variant allele frequency (VAF), bone marrow (BM) MC burden, and MS2D2 TSS, ≥30% TSS reduction. Patients were randomized 2:1 to receive 100mg QD bezuclastinib + BSC or PBO + BSC. Results: As of May 22, 2025, 179 patients were enrolled in Part 2: 119 were randomized to receive bezuclastinib and 60 to placebo. Patients enrolled were representative of the NonAdvSM population with moderate to severe symptoms. Median age (range) was 51 (23-78) years; 65.9% female; mean (SD) baseline MS2D2 TSS 55.6 (19.8); 82% of patients had ISM, 11% had BMM, and 7% had smoldering SSM. At baseline, median (range) KIT p.D816V VAF in whole blood, BM MC burden, and serum tryptase was 0.25% (0-34%), 10% (1-75%), and 40 (6-692) ng/mL, respectively. Bezuclastinib demonstrated statistically significant superiority to placebo on all primary and key secondary endpoints. At Week 24, bezuclastinib led to significantly greater symptom improvement vs placebo (LS mean [95% CI] MS2D2 TSS change: –24.3 [–27.6 to –21.1] vs –15.4 [–19.6 to –11.2]; placebo-adjusted difference: –8.9 points; P=0.0002). A ≥50% reduction in serum tryptase was achieved in 87.4% of bezuclastinib-treated patients vs 0% on placebo (P<0.0001). Significantly more patients receiving bezuclastinib achieved ≥50% reductions in KIT D816V VAF, serum tryptase, BM MCs (P<0.0001), MS2D2 TSS (P=0.01), and ≥30% reduction in MS2D2 TSS (P=0.0004). Most treatment-emergent adverse events (TEAEs) were low grade (gr; 70% Gr 1) and reversible. The most common TEAEs (≥10%) in any treatment group and occurring in greater frequency in the bezuclastinib arm were hair color changes (69.5% vs 5.0%), altered taste (23.7% vs 0%), nausea (22.0% vs 13.3%), increased ALT/AST (22.0% vs 6.6%), headache (17.8% vs 11.7%), alopecia (11.9% vs 3.3%), and increased ALP (10.2% vs 3.3%). TEAEs (≥10%) that occurred more often in the placebo group were diarrhea (13% vs 18%), dizziness (10% vs 12%), fatigue (7% vs 12%), and arthralgia (6% vs 15%). ALT/AST elevations ≥Gr 3 were experienced by 5.9% of patients. The only hepatic adverse events (AEs) reported were transient lab abnormalities; none required hospitalization. Treatment-related AEs requiring dose reductions occurred in 11% of patients receiving bezuclastinib. All discontinuations (5.9%) due to treatment-related AEs were due to transaminase elevations; all fully resolved. Conclusions: At 24-weeks, bezuclastinib 100 mg QD demonstrated statistically and clinically significant improvements in symptom burden and biomarkers of disease vs placebo in patients with NonAdvSM. The treatment was generally well-tolerated and effective across a population that is representative of the real-world NonAdvSM population, including SSM. These results support the use of bezuclastinib to reduce SM burden and symptoms in pts with NonAdvSM, and a potentially disease-modifying impact.

Abstract Background Chimeric antigen receptor T-cell (CAR-T) and bispecific antibody (BsAb) therapies are both effective for patients with relapsed/refractory (R/R) follicular lymphoma (FL), but differ in treatment schedules and associated “time toxicity,” or contact days spent physically interacting with the healthcare system. While contact days can be estimated from clinical trials, real-world data provides a more nuanced depiction of treatment-related time burden, which may guide treatment decision-making. The comparative time toxicity of CAR-T vs BsAb in R/R FL is not defined. Methods We conducted a multicenter retrospective study of adults with R/R grade 1-3A FL who received standard-of-care CAR-T (axi-cel, tisa-cel, liso-cel) or BsAb (mosunetuzumab, epcoritamab) in the third-line or later setting before Jan 1, 2025. Time toxicity was defined as outpatient or inpatient days with physical health care system contact, counting multiple visits on the same day as only one day. All days after treatment initiation were counted, regardless of disease progression, therapy completion, or relation to FL therapy. Median contact days over 1-year time horizon were compared, stratified by CAR-T vs BsAb, prior lines of therapy (LOT, 2 vs 3+), and time intervals (0-1, 1-3, 3-6, 6-9, and 9-12 months). Progression-free survival (PFS) and overall survival (OS) were calculated from day of CAR-T infusion or day 1, cycle 1 for BsAb. Cox regression and propensity matching (by age, ECOG, refractory to prior LOT, POD24) were used to assess predictors and survival associations with contact days. Results Among 209 patients from 15 U.S. academic centers, median age was 64, 37% were female, 61% received CAR-T (80% axi-cel, 7% liso-cel, 13% tisa-cel) and 39% BsAb (93% mosun, 7% epcor). Most had Grade 1-2 FL (72%), advanced stage (84%), and extranodal disease (51%). Median prior LOT was 3 (range 2-15), 41% were refractory to prior LOT, and 52% had POD24. Median number of BsAb doses was 10 (range 1-36). Patients receiving BsAb were significantly older (p<.01) and had higher CIRS comorbidity scores (p<.02) in both 2 and 3+ prior LOT cohorts, and had higher ECOG scores (p=.01) and were less likely to be refractory to prior LOT (p=.029) in 3+ LOT cohort. There were no differences in POD24 rates between CAR-T and BsAb. Median PFS for the entire cohort was 3.6 yrs; median OS was not reached. In the 2 prior LOT cohort (N=75), 60% received CAR-T and 40% BsAb. With median follow-up of 1.5 years, median PFS was not reached for CAR-T and 1.6 yrs for BsAb (p<.0001). In the 3+ prior LOT cohort (N=134), 62% received CAR-T and 38% BsAb. With median follow-up of 2 yrs, median PFS was 3.6 yrs for CAR-T and 1.6 yrs for BsAb (p=.0044). In propensity matched analysis, PFS was shorter for BsAb in both 2 LOT (HR 9.0, 95% CI 1.14-71.04, p=.037) and 3+ LOT (HR 3.25, 95% CI 1.06-9.97, p=.039) cohorts as compared to CAR-T. There were no significant differences in OS between CAR-T and BsAb. Median contact days were significantly higher for CAR-T vs BsAb in the 0-1 month interval: 19 vs 8 days in 2 LOT (p<.0001) and 18 vs 7 days in 3+ LOT (p<.0001) cohorts. There were no differences in contact days between CAR-T vs BsAb in subsequent time intervals. Over 1 year, CAR-T had significantly more time toxicity than BsAb: median 51 vs 36 contact days in 2 LOT (p<.0001) and 64 vs 38 days in 3L+ LOT (p<.0001) cohorts; these remained significant in the matched analysis. B symptoms (p=.04) and Grade ≥3 cytopenias (p=.007) were associated with higher contact days in 3+ LOT cohort in univariable analysis. Higher contact days were associated with inferior PFS (HR 1.01, 95% CI 1.00-1.02, p=.032) and OS (HR 1.01, 95% CI 1.00-1.02, p=.038) in 3+ LOT cohort regardless of treatment type. Discussion In this large real-world cohort of patients with R/R FL, CAR-T therapy resulted in better PFS but more time toxicity over the first year as compared to BsAb therapy. Excess time toxicity from CAR-T was driven by more contact days in the first month of treatment. This study provides benchmark data for counseling patients about expected time burden of CAR-T (51-64 days) and BsAb (36-38 days) over the first year of these therapies. Further, with superior PFS of CAR-T in this study and minimal impact of time toxicity on survival outcomes, these data can be used to better support shared decision-making in R/R FL by addressing patient preferences regarding both contact days as well as duration of disease control.

Abstract INTRODUCTION Outcomes for 1st relapse of pediatric B-lymphoblastic leukemia (B-ALL), especially high/intermediate-risk (HR/IR) relapse, remain unacceptably poor. Limited enrollment of this population on cooperative group clinical trials has impeded our ability to study potentially effective regimens. In the current era, patients can access innovative immunotherapies commercially. However, there is no mechanism to capture outcomes for these off-study patients and no comparative effectiveness data to guide treatment selection. METHODS We conducted a multicenter, retrospective study of patients <30 years who initiated 1st relapse therapy at a participating center from 2018-2022 (ReCALL-1 Study). Objectives were to define real-world survival outcomes, compare response rates of reinduction strategies, describe the post-reinduction treatment landscape, and, for patients with HR/IR relapse, assess the comparative effectiveness (CE) of blinatumomab to hematopoietic cell transplant (blina/HCT) v CD19 CAR T cells (CART). For the CE analysis, we emulated an open-label, randomized study of blina/HCT v CART who achieved an M1/M2 marrow at the end of an intensive reinduction (EoRI). Patients were classified by their intended treatment at EoRI. Cox regression models were used to adjust for unbalanced patient and disease features by arms. The primary outcome was overall survival (OS) from EoRI. RESULTS The full cohort included 479 patients from 33 centers (31 US, 2 international). Median time to relapse was 31 months (m); 77% had bone marrow (BM) involvement and 31% central nervous sytem involvement. With a median follow-up of 49m from relapse, 4 year (y) OS, event-free survival (EFS), and non-relapse mortality (NRM) were 64%, 43%, and 13%, respectively. Among patients with very early BM (<18m, n=79), early BM (18-35m, n=76), late BM (≥36m, n=162), and isolated CNS (n=85) relapses, 4y OS/EFS were 29%/20%, 57%/35%, 78%/49%, and 84%/61%, respectively. Only 19% received reinduction therapy on a clinical trial. Among patients with BM disease, R3 reinduction (n=179) and VXLD (n=61) had identical MRD-negative (<0.01%) CR rates of 38% (p=1.00) and equivalent treatment failure (TF; M3 or extramedullary disease) rates: R3, 8% v VXLD 7%, p=0.79. Blina (n=33) and inotuzumab-based (n=21) reinductions achieved MRD-negative CR rates of 39% and 52%, respectively, but higher TF rates of 39% and 24%. Reinduction mortality was 2%: R3, n=5; VXLD, n=3; 3-drug reinduction, n=1. Overall, as part of 1st relapse therapy, 36% received CART (78% commercial product), 44% HCT, 40% blina, and 11% inotuzumab. The emulated trial included 159 patients, 95 on blina/HCT and 64 on CART. Study arms were well matched by demographics, cytogenetics, and relapse sites, but CART patients were more likely to have relapsed <18m from diagnosis (34% v 24%) and have EoRI M2 marrows (31% v 11%), and less likely to have private insurance (36% v 51%). Unadjusted OS was comparable between arms (log rank p=0.18): CART, 60% at 4y; blina/HCT, 71%, as was NRM (10% v 13% at 4y). EFS was lower for CART (p=0.049): 4y EFS 35% v 49% for blina/HCT. After adjustment for unbalanced covariates, the hazard of death was equivalent for CART as compared to blina/HCT (aHR 1.1, 95% CI 0.6-2.1, p=0.67) and EFS became more comparable (aHR 1.3, 95% CI 0.8-2.1, p=0.22). 91% of blina/HCT and 97% of CART received their intended cell therapy; time from EoRI to cell therapy was shorter for CART (67 v 86 days, p<.001). In the CART arm, 34% underwent consolidative HCT; 1/3 were preplanned and 2/3 due to loss of B cell aplasia or NGS-MRD positivity. Of those with a 2nd relapse, CART patients were more likely to be CD19 negative (47% v 10%, p=0.003). CONCLUSION In this multicenter, real-world cohort of children treated for 1st relapse in the immunotherapy era, suboptimal outcomes for early BM relapse persisted, with particularly dismal 4y OS of 29% for relapses <18m after diagnosis. In contrast, survival for late BM and isolated CNS relapses compared favorably to historic data. Only 1 in 5 patients initiated relapse therapy on a clinical trial and although 1st relapse is not an approved indication for commercial CART in pediatrics, 36% received CART. In an emulated trial of post-reinduction blina/HCT v CART, adjusted EFS and OS were comparable, suggesting that CART may be a viable alternative to HCT for select patients. Post hoc analyses will identify whether specific subgroups may benefit more from one strategy.

Background Contact aspiration remains a frontline approach for mechanical thrombectomy (MT) in acute ischemic stroke (AIS). Early evidence correlates catheter size with procedural efficiency and clinical outcomes. Larger‐bore (LB) aspiration catheters may enhance clot ingestion, increase aspiration force, and facilitate faster and more complete recanalization. However, the transition from standard LB catheters (0.068‐0.072″) to super‐large‐bore (SLB, ≥0.080″) devices has raised questions regarding both safety and clinical benefit. Although the use of SLB catheters is increasing, comparative data on their performance versus LB catheters remain limited. This study aims to evaluate the safety and efficacy of SLB compared with LB catheters including data from a large multicenter international registry. Methods We retrospectively analyzed patients with AIS due to LVO treated at 46 international stroke centers between January 2013 and June 2025. Among eligible patients, propensity score matching (PSM) at a 5:1 ratio was used to balance baseline characteristics between those treated with standard LB catheters and those treated with SLB catheters. Safety endpoints included intraprocedural complications, symptomatic intracranial hemorrhage (sICH), distal embolization, and 90‐day mortality. Efficacy endpoints included functional independence at 90 days (modified Rankin Scale [mRS] 0‐2), successful recanalization (TICI ≥2b), first‐pass effect (TICI ≥2b on the first aspiration attempt), and procedural timing to TICI2b. Results A total of 3,100 patients were included (LB n=3,024; SLB n=67). After PSM (LB n=335; SLB n=67), safety outcomes were comparable between groups in terms of intraprocedural complications occurred (p=0.5), sICH (p>0.9), embolization to new territory (p=0.2), and 90‐day mortality (p>0.9). Efficacy outcomes were similarly consistent for functional independence (mRS 0‐2) (p>0.9), successful recanalization (p>0.9), first‐pass effect (p=0.5), and time to TICI ≥2b (27.6 vs. 24.5 minutes; p=0.9). These findings remained consistent in the subgroup with ICA and M1 occlusions, with no significant differences in safety (intraprocedural complications [p=0.4], sICH [p>0.9], embolization to new territory [p=0.6], or 90‐day mortality [p>0.9], nor in efficacy outcomes (functional independence at 90 days [p>0.9], successful recanalization [p=0.9], first‐pass effect [p=0.6], and time to TICI ≥2b [p=0.9]). Conclusion In this large multicenter analysis, the use of SLB aspiration catheters demonstrated comparable safety and efficacy to standard LB catheters for MT in AIS. Despite theoretical advantages in aspiration dynamics, SLB devices did not confer significant procedural or clinical benefit over LB catheters. These findings suggest that while SLB catheters are a feasible alternative, technical and clinical outcomes remain comparable to LB catheters. Further prospective studies are warranted to clarify potential clinical advantages. image

Abstract Despite concerns about the toxicity of allogeneic hematopoietic cell transplantation (alloHCT) in older patients, prospective data characterizing prevalence or risk stratification for geriatric morbidity such as disability or frailty are limited. We prospectively assessed the prognostic impact of the novel composite health assessment risk model (CHARM), a score established to predict 1-year nonrelapse mortality (NRM), among 1105 patients aged ≥60 years enrolled on the Bone Marrow Transplant Clinical Trials Network Study 1704. Secondary end points were assessed post-alloHCT at day 100 (D100), D180, and D365 in multivariable models adjusted with predetermined clinical variables. Among alloHCT survivors, the prevalence of disability by instrumental activities of daily living (IADL), frailty by the Physical Frailty Phenotype, and physical function impairment by Patient Reported Measurement Information System (PROMIS) was highest at D100 and lower on D180 and D365. Higher CHARM scores were independently associated with greater disability (coefficient, −0.64; 95% confidence interval [CI], −0.85 to −0.43; P< .001), increased frailty (coefficient, 0.19; CI, 0.081-0.31; P< .001), worse PROMIS physical function, greater PROMIS depression, increased serious organ toxicity by D100, more cognitive decline at D100, and higher mortality after acute graft-versus-host disease (GVHD) but not significantly associated with PROMIS anxiety or acute GVHD. Higher CHARM scores predicted worse disability-free survival (odds ratio [OR], 2.03; CI, 1.66-2.48; P< .001) and lower frailty-free survival (OR, 2.00; CI, 1.61-2.49). In summary, CHARM is an independent prognostic scoring system not only for NRM but also for geriatric morbidity and functional limitation–free survival through 1 year after alloHCT. Pre-alloHCT CHARM is a novel tool to aid shared decision-making for older patients. This trial was registered at www.clinicaltrials.gov as #NCT03992352.

Abstract Description In the tumor microenvironment of glioblastoma, myeloid cells act as a double-edged sword—they are a major cellular component suppressing the immune response while serving as a promising therapeutic target. Our study sheds light on the voltage-gated proton channel Hv1, predominantly expressed in myeloid cells, as a pivotal regulator of their physiological functions. Elevated Hv1 expression correlates strongly with poor prognosis in glioblastoma patients, underscoring its clinical significance. Using a glioma mouse model, we demonstrated that Hv1 depletion markedly extended survival. To overcome the limitations of existing tools, we engineered novel transgenic mouse lines optimized for Hv1 research. Our findings revealed tumor-induced Hv1 upregulation, with glioma-associated macrophages identified as the principal contributors. Crucially, we identified that Hv1 in infiltrating macrophages as the major driver of survival phenotype differences. Through a multi-faceted approach combining in vivo two-photon imaging, spectral flow cytometry, and spatial transcriptomic sequencing, we discovered that Hv1 depletion limits macrophage infiltration and enhances antigen presentation, ultimately fostering a stronger adaptive immune response. These findings establish the Hv1 channel as a crucial new immune regulator within the brain tumor milieu, offering a promising target for reprogramming macrophage function to combat glioblastoma. Funding Sources Supported by NIH R35NS132326 (LJW); Mayo Clinic Cancer Center and Mayo Clinic Center for Biomedical Discovery. Topic Categories Neuroimmunology (NEUR)

Abstract Description Follicular Lymphoma (FL) is a germinal center-derived malignancy representing approximately 20% of all non-Hodgkin’s lymphomas. Despite a relatively indolent disease course, FL is a biologically and clinically heterogeneous disease which poses significant clinical challenges due to its propensity for relapse and transformation into aggressive and untreatable forms of lymphoma. Here, we have leveraged computational techniques with WES, RNA-sequencing, and immune profiling data from FL tumors to gain further insight into the biologic basis for FL heterogeneity. We performed computational reconstruction of the B cell receptor repertoire on B cell sorted RNA-sequencing data from normal lymph nodes (n = 5) and FL tumors (n = 89). To gain a better understanding of FL B cell biology at the single cell level, we further investigated the clonal architecture of dominant malignant clonotypes in FL tumors using computational analysis of paired single cell V(D)J and 5’ GEX sequencing data from FL tumors (n = 21) and non-malignant lymph nodes (n = 3), allowing us to characterize the germinal center programs in malignant versus non-malignant B cells. Our data suggest that a subset of FL tumors consist of complex polyclonal B cell populations, some of which represent a pre-malignant FL precursor. Our data provide a deepened understanding of FL biology, including precursor cells, and contributes a refined transcriptomic characterization of malignant and non-malignant B cells in Follicular Lymphoma. Funding Sources This work was supported by the National Institutes of Health (R01 CA212162-01A1 to A.J.N and J.R.C., and P50 CA097274 to J.R.C., and A.J.N) Topic Categories Computational and Systems Immunology (COMP)