Citations

Abstract Background: A randomized multicenter trial (BMT CTN 1703) demonstrated that after reduced intensity conditioning HCT, PT-Cy-based GVHD prophylaxis led to significant reductions in acute and chronic GVHD, but was associated with significantly more Grade 2 (moderate) infections and similar overall survival vs Tac/MTX. A linked mechanistic study (BMT CTN 1801) found that PT-Cy led to pan-T cell depletion and reduced T cell receptor (TCR) repertoire diversity vs Tac/MTX. To discover the molecular mechanisms driving the association of PT-Cy with increased infections, we examined pathogen-specific T cell reconstitution in BMT CTN 1801 patients (n=165 PT-Cy, n=159 Tac/MTX). Methods: We performed deep TCR sequencing on 2,369 blood samples collected pre-HCT (recipient baseline) and on Days +7, 14, 28, 63, 100, 180, 270, 365, 730, and from the graft infusion product. We then applied a novel set of TCR classifiers (Adaptive Biotechnologies) capable of identifying pathogen-specific clones associated with CMV, EBV, SARS-CoV-2, HSV-1, HSV-2, parvovirus, RSV, influenza A, rhinovirus, adenovirus, HHV-6B, norovirus and Toxoplasma. Single-cell (sc) TCR/RNA-sequencing on a sample subset (n=26) was performed to determine the phenotype of pathogen-specific T cells. Results. By linking scRNA-seq with pathogen-specific TCR barcoding, we identified CD4 and CD8 memory T cells as their predominant T cell reservoir. We found that the total number of pathogen-specific singleton TCRs was significantly lower with PT-Cy, starting early post-HCT and persisting through 2 years. For example, at Day +14, PT-Cy patients had 7.8-fold fewer pathogen-specific singleton TCRs vs Tac/MTX (mean of 6.9 vs 54.1, p<0.001). Consistent differences between PT-Cy and Tac/MTX were observed for TCRs specific for each pathogen individually. Patients who developed Grade 3 (severe) viral infections had significantly fewer pathogen-specific singleton TCRs at Day +14 compared to those who had no viral infections (mean of 4.0 vs 32.5, p=0.03). Leveraging intrinsic TCR barcoding of the HCT infusion (“graft”) and of the patient's baseline samples (“recipient”), we could assign the graft/recipient origin of the pathogen-specific cells with high fidelity. This analysis revealed pronounced differences in the origin of pathogen-specific T cells with PT-Cy vs Tac/MTX, especially prior to Day +100. The absolute number of pathogen-specific TCRs originating from the graft was significantly higher with Tac/MTX vs PT-Cy. This difference was observed from day +7 through 6 months post-HCT, with up to 7.1-fold more graft-derived pathogen-specific TCRs in Tac/MTX vs PT-Cy (p<0.001 at each timepoint before day +100). Within patients who received Tac/MTX, the balance of graft vs recipient pathogen-specific clones significantly favored graft clones (for example, a mean of 14.9 graft vs 8.6 recipient pathogen-specific TCRs at Day+14, p=0.02). By contrast, with PT-Cy, in addition to having substantially fewer pathogen-specific TCRs overall, the proportion of these TCRs was not significantly different between graft and recipient clones (mean of 2.1 graft vs 3.3 recipient pathogen-specific TCRs at Day+14, p=0.42). These data uncover that, in addition to the reduction in pathogen-specific T cells with PT-Cy, there was a relative skewing of the anti-microbial T cell reservoir towards recipient cells that persisted after conditioning. Conclusions: PT-Cy led to in vivo T cell depletion across all T cell subsets, which prominently included clones tracked from the allograft itself into the HCT recipient, with a relative sparing of recipient T cell clones that survived transplant conditioning. While the mechanism for relative sparing of recipient cells has not yet been determined, these conditioning-exposed cells may be less proliferative than newly infused graft T cells. The depletion of graft T cells included CD4 and CD8 memory cells specific for infections, which may have contributed to relative deficits in protective immunity against infection in patients receiving PT-Cy. Importantly, these data suggest that with PT-Cy, persisting recipient TCRs may play a key role in preserving anti-infectious immunity. Taken together, these results provide a mechanistic basis for key post-transplant clinical outcomes of the landmark BMT CTN 1703 study. They also underscore the importance of recipient immune status with PT-Cy, creating the opportunity for targeted infection risk assessment in these patients.

Abstract Background: Infections account for over half of the non-relapse deaths among chimeric antigen receptor (CAR) T-cell recipients. Non-relapse mortality estimates are among the highest in patients with relapsed / refractory multiple myeloma (RRMM) receiving B-cell maturation antigen (BCMA)-directed CAR-T cell therapy. The current Center for International Blood and Marrow Transplantation Research (CIBMTR) study analyzed the burden, types, risk factors, and outcomes of infection and its impact on survival in 807 patients with RRMM receiving commercial idecabtagene vicleucel (ide-cel) CAR-T therapy from March 2021 to December 2023. Methods: The primary endpoint was infection density for overall infections and for organism type (bacterial, viral, or fungal) within 100 days post-CAR-T infusion. Infection density was estimated as the number of infections per 100 person days at risk, stratified into two distinct time intervals following CAR-T cell infusion: days 0-30 and days 31-100.Additional endpoints included the cumulative incidence of infections, infection-related mortality (IRM), and overall survival (OS). Multivariable Cox proportional hazards models were employed to identify factors associated with infectious complications within 100 days post-CAR-T cell infusion. Pre-specified risk factors were considered for the multivariable analysis (MVA) models. We further examined the impact of infections within 100 days of CAR-T on OS at any time beyond 100 days following CAR-T infusion. Results: Infections developed in 114 (14.1%) patients within 30 days and 226 (28%) patients within 100 days post-CAR-T infusion, resulting in an overall infection density of 0.49 per 100 patient-days and a 100-day cumulative incidence of 27.2%. Proportions of bacterial, viral, and fungal infections within 30 days of ide-cel infusion were 82 (10.2%), 50 (6.2%), and 5 (0.6%), respectively. Similarly, proportions of bacterial, viral, and fungal infections within 100 days of CAR T-cell infusion were 126 (15.6%), 125 (15.5%), and 8 (1%), respectively, with corresponding infection densities of 0.23, 0.22, and 0.012 per 100 patient-days. The 100-day cumulative incidence of bacterial, viral, and fungal infections were 14.1% (95% CI, 11.8-16.6%), 14.4% (95% CI, 12-16.9%), and 0.9% (95% CI, 0.3-1.6%) respectively. The 100-day IRM was 1.1% (95% CI, 0.5-2%). With a median follow-up of 11.6 months (1.1-26.7), 222 (27.5%) patients died, and infection was the primary cause of death in 17 cases (7.7%). In MVA, Karnofsky performance score ≤80 (p<0.001), infection prior to CAR-T cell infusion requiring with ongoing treatment after d+0 (p<0.001), cytokine release syndrome grade ³2 (p=0.002), and severe immune effector cell-associated neurotoxicity syndrome [ICANS] (grade ≥3) (p<0.001) were associated with an increased infection risk within 100 days post-infusion. Similarly, infection prior to CAR-T infusion requiring with continuing treatment after d+0 (p<0.001 for bacterial and p=0.003 for viral infections) and grade ≥3 ICANS (p<0.001 for bacterial and p=0.015 for viral infections) significantly conferred a heightened risk for bacterial and viral infections within 100 days of CAR-T infusion. Number of infections within 100 days (hazard ratio [HR], 2.36 for ≥2 vs. 0 infections; 95%CI, 1.48-3.77; p<0.001), extramedullary disease or plasma cell leukemia (HR, 1.8; 95%CI, 1.19-2.74; p=0.006), and prior BCMA-directed therapy (HR, 1.57; 95%CI, 1.06-2.33; p=0.025) were independent risk factors for inferior OS beyond day+100 after CAR-T therapy. Intravenous immunoglobulin (IVIG) replacement post-CAR-T therapy conferred a survival advantage (HR, 0.52; 95%CI, 0.38-0.72; p<0.001). Conclusion: In conclusion, study results demonstrate a significant incidence of infections for a prolonged duration (14.1% in the first 30 days and 28% in the first 100 days) in patients with RRMM undergoing ide-cel therapy. Notably, viral infections increased beyond d+30. Multiple infections (≥2 episodes) were associated with inferior OS. Results identify patients at an increased risk for infection and provide insights into risk-adapted interventions to mitigate infections and improve patient outcomes. Furthermore, continued surveillance for infection pre-emption and prevention beyond 3 months post-CAR T therapy may be necessary to reduce infection burden and IRM. Prophylactic strategies such as IVIG replacement could potentially modify infection risk in patients with RRMM receiving ide-cel.

Abstract Introduction: Among Non-Hodgkin lymphomas (NHL), DLBCL is the most prevalent subtype (~30% of diagnoses). First-line (1L) chemoimmunotherapy cures many patients (pts), but 30-40% will relapse. Prognostic and predictive biomarkers are needed to identify pts refractory to 1L therapy or at high risk of relapse, enabling timely intervention and improved outcomes. This study evaluated tumor-informed WGS-based longitudinal ctDNA monitoring in a real-world DLBCL cohort. Methods: We retrospectively analyzed ctDNA data from 49 pts with DLBCL. Plasma samples were collected before, during, and at the end of 1L therapy (EOT, defined as ± 21 days from the last infusion (preferred when available) or ± 14 days from post-treatment PET imaging) and during surveillance/subsequent treatments. A WGS-based tumor-informed assay (Signatera™ Genome, Natera, Inc.) was used for ctDNA detection and quantification. The association of ctDNA dynamics with event-free survival (EFS) was evaluated using Cox regression analysis, restricted to pts completing at least 5 cycles of 1L therapy. Results: The median age of the cohort was 62 years (range: 56-74), and median follow-up was 22 months (range: 14-30). Pre-treatment ctDNA-positivity rate was 100% (31/31). A total of 19 pts achieved ctDNA clearance during 1L therapy (early clearance within 3 cycles, n=5; late clearance between cycle 4 and EOT, n=14). Pts with no clearance or ctDNA-positivity at EOT (n=7) had significantly inferior EFS compared to those achieving ctDNA clearance (HR 8.04, 95%CI: 1.87-34.62, p=0051). On further stratifying the clearance group and comparing with no clearances, pts with early clearance had superior outcomes (HR 13.22, 95%CI: 1.48-1741.94, p=0.0166), relative to late clearances (HR 5.65, 95%CI 1.46–25.16, p=0.0129). Notably, all 5 pts with early ctDNA clearance remained serially negative and relapse-free. Of the 49 pts, 9 proceeded to chimeric antigen receptor T-cell therapy (CAR-T). Among 6 of these pts with available ctDNA results pre and post therapy, all 3 who stayed ctDNA-positive after CAR-T relapsed (1.3, 2, and 4.5 months post-infusion); 1 pt with pre- and post-CAR-T ctDNA-negativity and 2 pts with ctDNA clearance post-CAR-T remained relapse-free for 9.6, 15.9, and 22.4 months, respectively. Taken together, the PPV and NPV for a single ctDNA time point post CAR-T infusion were 100% for predicting long-term clinical outcomes. Conclusions: Our data support longitudinal ctDNA monitoring as a valuable prognostic and predictive biomarker in DLBCL. ctDNA clearance, particularly early clearance within the first 3 cycles of 1L therapy, is associated with improved pt outcomes. Longitudinal ctDNA monitoring and dynamics can enable identification of high-risk pts who do not clear ctDNA and may benefit from earlier referral for CAR-T. Furthermore, ctDNA monitoring pre- and post-CAR-T infusion is predictive of treatment response and can identify pts at high risk of relapse.

Abstract Background: The coexistence of systemic mastocytosis (SM) and lymphoid neoplasms is rare and remains poorly defined. These cases are classified under SM with associated hematologic neoplasm (SM-AHN) in the WHO framework, though the ICC distinguishes SM with associated myeloid neoplasm (SM-AMN) as a separate entity. Emerging evidence points to SM with associated lymphoid neoplasms (SM-ALN) as a biologically distinct and clinically indolent subgroup (Aperna F et al, 2025). We performed a multisite retrospective study to characterize the clinico-molecular features and outcomes of SM-ALN. Methods: We conducted a retrospective analysis across Mayo Clinic sites, reviewing records from January 1980 to December 2024 to identify patients with SM-ALN. IRB approval was obtained. Of 22 cases identified, 4 were excluded due to co-occurring myeloid neoplasms. The final cohort included 18 patients. Variables analysed included age, sex, SM subtype, KIT mutation, symptoms, treatment, and survival outcomes. Results: Eighteen patients were included (median age: 61.5 years; range: 38–80; 11 female). Most had indolent SM (ISM, n=16); two had aggressive SM (ASM). SM preceded the lymphoid neoplasm in 4 cases (22%), followed it in 6 (33%), and was concurrent in 8 (44%). Low-grade lymphomas (n=12, 67%) included follicular lymphoma (n=2), CLL (, n=2), marginal zone (n=1), lymphoplasmacytic (n=1), and mantle cell (n=1). High-grade lymphomas (n=6, 33%) included diffuse large B-cell lymphoma (DLBCL, n=3), Hodgkin lymphoma (n=2), and T-cell acute lymphoblastic leukemia (n=1). SM-related symptoms were present in 16 of 18 patients (89%). The most common manifestations included dermatologic symptoms (rash/pruritus, 56%), systemic complaints (fatigue/weight loss, 39%), GI symptoms (17%), and anaphylaxis (6%). KIT D816V testing mutation was positive in 10 of 16 patients tested (63%). Tryptase was elevated (>20 ng/mL) in 15 of 18 (83%). NGS data was available for 9 patients: among the two ASM cases, both harbored SRSF2 mutation; one also had JAK2, DNMT3A, RUNX1, TET2, and TP53, while the other carried DNMT3A and IDH1. Mutations observed in ISM cases included CCND3, CXCR4, NOTCH2, SF3B1, MYD88 L265P, ASXL1, and TET2. SM management was divided into two categories: (1) Conservative approach, including observation alone in 4 patients (22%) and symptomatic therapies such as antihistamines or leukotriene inhibitors in 7 (39%); and (2) Cytoreductive treatments, comprising avapritinib in 5 patients (28%), cladribine in 1 (6%), and imatinib in 1 (6%). Management of lymphoid neoplasms included intensive regimens such as R-CHOP and hyper-CVAD for high-grade subtypes (e.g., DLBCL and T-ALL), while indolent forms (e.g., CLL and follicular lymphoma) were treated with bendamustine-rituximab or observation depending on disease burden. Overall, 13 patients (72%) received systemic therapy. At a median follow-up of 81 months (6.7 years), 17 of 18 patients (94%) were alive and progression-free. Median OS and PFS were not reached. The sole death occurred in a patient with ASM, while all ISM cases remained alive. ASM was associated with a higher (though nonsignificant) risk of death (OR 33.0; 95% CI, 0.89–1220.9; p = 0.111). Among patients with high-grade lymphomas (n=5), 80% were alive at follow-up, compared to 100% with indolent lymphomas (n=13). Discussion: Our findings support SM-ALN as a clinically indolent and biologically distinct subset within SM-AHN. Most patients had ISM and low-grade lymphoid neoplasms, with favorable outcomes regardless of lymphoma subtype or diagnostic sequence. High-risk mutations were confined to ASM cases, reinforcing underlying biologic differences. These findings align with prior Mayo Clinic data showing longer survival in SM-ALN compared to SM-AMN (median OS 8.1 vs 2.0 years; p<0.01). Treatment was primarily directed by the lymphoid malignancy, with limited need for cytoreduction in ISM. Larger, prospective studies are needed to confirm these observations and optimize management strategies. Limitations include the study's retrospective, single-center design and limited racial diversity. Multi-institutional studies are warranted to validate these findings and guide optimal management. Conclusion: SM-ALN is a rare but distinct SM subtype characterized by indolent behavior, favorable treatment responses, and prolonged survival. Recognition of this subset is critical to avoid over-treatment and to guide risk-adapted management strategies.

Abstract Background The expansion of hematopoietic stem and progenitor cells (HSPCs) in the bone marrow is universally associated with adverse outcomes and disease progression in all chronic myeloid neoplasms, to include chronic myelomonocytic leukemia (CMML). However, HSPCs are a heterogeneous cellular compartment and the impact of its composition on clinical outcomes remains poorly defined. Single cell RNA-sequencing (scRNA-seq) represents an optimal strategy to annotate cellular composition but no large clinically annotated scRNA-seq datasets are currently available. To address this, we have embarked to generate a clinically annotated 500 patient CMML scRNA-seq atlas from CD34+ enriched BMNCs to establish among the largest clinically and genetically annotated single cell references for any chronic myeloid malignancy. Here we report the interim analysis of 113 clinically annotated cases that demonstrates massive reshaping of HSPC composition that is independently a predictor of overall survival. Methods Single-cell RNA expression profiling was performed on 113 CD34-enriched CMML BMNC samples using 10x Genomics GEM-X Universal 3' Gene Expression v4 (4-plex) chemistry. Libraries were sequenced on NovaSeq S4 flow cells in two runs, and data were processed using Cell Ranger to generate gene expression matrices. A total of 502,659 single cells from 113 samples were processed using Seurat. The upper threshold for gene count was defined as the mean number of detected genes plus two standard deviations data normalization was performed using the log-normalization method. Batch correction and integration were conducted with Harmony to mitigate technical variation across pools. Descriptive statistics were used to tabulate clinical and genetic parameters. KM curves, log-rank test, and cox regression were used to calculate survival, test for statistical differences, and perform multivariate analysis, respectively. Results To derive high resolution cell annotations, we employed the SingleR algorithm using a large hematopoietic reference of over 300,000 single cells (Zhang, X. Nature Immunology, 2024). Using this approach a diverse set of cell types were identified that included HSCs, 23 myeloid progenitors, 18 erythroid progenitors, and 18 lymphoid progenitors. This diverse cellular repertoire displayed massive reshaping relative to the normal CD34 enriched reference including a >53x expansion of multilineage GMPs and a >100x depletion of B-cell progenitors consistent with the known myeloid skewing seen in this disease. To understand whether expansion of specific progenitors was associated with outcomes we iteratively evaluated key progenitor populations and observed that expansions of HSC (HR 0.468 p<0.005) and MEP (HR 0.485, p<0.005) were associated with improved survival while GMP (HR 1.729, p=0.029) expansions were associated with inferior survival when using a cut point derived with a maximally selected ranks statistics approach. To achieve a more comprehensive metric of HSPC composition we explored GMP ratios to include GMP/HSC ratios and GMP/MEP ratios and observed that both were associated with inferior survival in univariate and multivariate when considering clinical and genetic features such as the CPSS-molecular prognostic score and FAB classification. When considering both GMP/HSC and GMP/MEP ratios in a multivariate model only GMP/MEP ratios and CPSS molecular remained independently prognostic. As an orthogonal approach, pseudotime projections were carried out using a reference map from Setty et al., 2019 to calculate differentiation potential and branch probabilities. This approach enabled both cell identity assignment and placement of cells along the hematopoietic differentiation trajectory. Samples were classified as monocyte-biased, MEP-biased, or normal-like, as previously described (Ferrall-Fairbanks et al. 2022) and demonstrated that increased GMP ratios are associated with a monocytic biased trajectory and that this trajectory is also associated with overall survival. Conclusion This study represents an interim analysis of among the largest scRNA-seq cohorts generated in chronic myeloid malignancies. This enabled us, for the first time, to demonstrate that HSPC composition is independently prognostic even when considering modern CMML prognostic models. As this cohort continues to increase, validation of these findings and examining the impact of therapy on HPSC composition in serial samples will be prioritized.

Abstract Introduction: Graft Failure (GF) is a rare but devastating outcome of HCT. Primary GF (PGF), defined as a failure of neutrophil recovery by Day+28, is straightforward to diagnose. Diagnosing secondary GF (SGF) is more challenging, with its broad time-range, multiple confounding diagnoses, and lack of predictive biomarkers. In BMT CTN1703/1801, we analyzed patients receiving RIC HCT for heme malignancies with either Tac/MTX (n=159) or PT-Cy (n=165) GVHD prophylaxis. SGF was defined as donor chimerism <5% after initial donor engraftment. With Tac/MTX, there were 3 PGF and 1 SGF diagnoses. With PT-Cy, there were 4 PGF and 6 SGF. Median SGF diagnosis was Day +64 (range: Day+28-215). There were too few Tac/MTX patients to analyze SGF, but sufficient events with PT-Cy. To identify PT-Cy SGF predictors, we leveraged lymphocyte, T, B, and NK cell reconstitution analysis. In SGF we found an early, profound deficit in the reconstitution of all major lymphocyte populations, including total lymphocytes, T, B, and NK cells, as early as Day+28. This enabled the modeling of a SGF risk classifier based on the Absolute Lymphocyte Count (ALC). Methods: Clinical ALC measurements were performed on all SGF patients (n=6) and on non-GF controls with ALCs available (146 of 155 non-GF patients). Flow cytometry was performed on all PT-Cy SGF patients (n = 6) and from a subset of non-GF controls (n = 18: controls were chosen as patients without relapse or severe GVHD, to reduce confounders introduced by immunologic interventions, and for whom all samples, including from the graft infusion, were available). T, B, and NK counts, as well as T cell subsets, were compared (using Welch's T test) on Days 7, 14, 21, 28, 42, 63, 98, 180, 270, 365, 730, with SGF patients censored on the day of GF diagnosis. To interrogate the optimal ALC cutoff, the cumulative incidence of SGF was computed at Days +28 and +42, with death without GF as a competing risk. Results: We have previously demonstrated that, compared to Tac/MTX, PT-Cy patients exhibited an early decrease in reconstitution of all T cell populations (with normal NK and B cell reconstitution). Here we focused specifically on PT-Cy patients with or without SGF. Graft CD34 counts/kg were not different between SGF patients and non-GF patients (mean CD34/kg = 1.38 x10e6 (SGF) vs 0.67 x10e6 (non-GF, p = 0.61) However, even amidst the overarching early suppression in T cell reconstitution with PT-Cy, SGF patients could be easily distinguished from the larger PT-Cy cohort, based on more profound deficits in ALC, T, B and NK cells reconstitution, measured using 2 strategies: (1) SGF patients demonstrated significant early (Day +28) quantitative defects in the reconstitution of the ALC (mean +/- SEM 262+/-32 cells/µL (non-GF) vs 60 +/- 25 (SGF, p<0.0001), CD4 T cells (62 +/- 12 cells/µL vs 19+/-15, p=0.048), CD8 T cells (15 +/-3 cells/µL vs 3.5 +/-1 p=0.0009), all CD8 T cell subpopulations, as well as NK cells (116+/-31 cells/µL vs 2.9+/-1.4 cells/µL, p= 0.002) and B cells (3.5 +/-1.4 cells/µL vs 0.16+/-0.07 p =0.03). (2) In SGF, there was a significant deficit in the rate of rise of all major lymphocyte populations between Days 28-42-60 vs non-GF, including CD4 T cells (p<0.0001), CD8 T cells (p = 0.0002), B cells (p<0.0001), and NK cells (p =0.048). These discoveries suggested that a classifier could be identified to risk-stratify patients for SGF. We explored an ALC cutpoint, amenable to standard clinical lab analysis. A statistically significant threshold was identified at both Days+28 and +42, with Day+42 being most predictive: A threshold of 120 cells/µL was identified as optimal, with landmark analysis documenting a SGF rate of 34.7% below the cutpoint, and SGF of 1% above it (HR = 45.9, 95% CI 5.7 - 366). Conclusions: Despite the small number of events, PT-Cy patients with SGF demonstrated a distinctive reconstitution trajectory that encompassed an early, substantial, and sustained deficit in all lymphocyte counts, as well as a lack of their longitudinal expansion. This enabled the discovery of a candidate ALC biomarker cutpoint at Day+42 that could distinguish patients who were more likely to develop SGF. If confirmed, these data could generate a predictive biomarker for SGF, which would enable the design of trials evaluating early interventions (e.g. CD34+ boosts, DLI, modification of immunosuppression) to improve outcomes for these patients.

Abstract Background: Despite the promising efficacy of CAR-T for patients with relapsed or refractory (R/R) large B-cell lymphomas (LBCL), more than 60% of patients will relapse, the majority of which occur in the first 6 months. Approximately 30% of patients with LBCL treated with CAR-T achieve a partial response (PR) on day 30 (D30) PET-CT assessment. Of patients in a D30 PR, 70% will eventually progress, yet the standard of care remains close observation. Early consolidative treatment strategies utilizing therapies with a different mechanism of action may improve outcomes, but there are currently no reliable biomarkers. Epcoritamab (Epco), a bispecific antibody directed against CD20 and CD3, has been approved by the FDA for LBCL patients who relapse after at least 2 lines of therapy. By treating prior to overt relapse, Epco has the potential to salvage inadequate responses post CAR-T. This study is a trial-in-progress that will evaluate the efficacy of epco compared to observation for patients with LBCLs achieving a PR on D30 post CAR-T PET-CT assessment. Methods This is an investigator-initiated, randomized, phase II, multicenter, open-label study (NCT06238648) evaluating epco monotherapy for a fixed duration of 12 cycles compared to observation for LBCL patients with D30 PR after standard of care CAR-T. A maximum of 120 patients will be randomized 1:1 to epco or observation across 10 academic centers. Stratification factors include line of CAR-T (second vs third line) and costimulatory domain (CD28 vs 4-1BB). Key inclusion criteria include PET evidence of a D30 PR. non-bulky disease ( <7.5cm), ANC of >1000, hemoglobin >7 g/dL if asymptomatic or >8 if symptomatic, platelet count >50,000. G-CSF, pRBCs and platelet transfusions are allowed. Key exclusion criteria include ongoing or uncontrolled CRS or ICANS, and active or symptomatic CNS disease. This study is available to all eligible patients, regardless of race, gender, or ethnic origin. To adapt to current practices, prior bispecific antibody exposure is allowed if used as holding or bridging therapy without disease progression. Epco is administered subcutaneously at a dose of 0.16mg on day 1, 0.8mg on day 8, prior to full dose of 48mg on day 15. Epco is administered weekly in 28 day cycles (C) for C1-3, on day 1 and 15 of C4-9 and on day 1 of C10-12. PET-CT response is assessed by the 2014 Lugano criteria after 2 cycles, and then every 3 months during active treatment. The primary objective is efficacy, measured as conversion from D30 PR to CR. The secondary endpoints include frequency and severity of treatment emergent adverse events, ORR, duration of response, duration of complete response, progression free survival, event free survival, and overall survival. Peripheral blood samples will be collected pre-treatment and during treatment to assess for biomarkers of response and resistance and CAR-T persistence. The study was activated in January 2024 and recruitment is ongoing.

Abstract Introduction: Circulating tumor DNA (ctDNA) has emerged as a promising biomarker for treatment response monitoring, risk stratification, and early recurrence detection for patients with lymphoma. Tumor-informed ctDNA testing for detecting molecular residual disease (MRD) is seeing early adoption in this setting, demonstrating technical feasibility and clinical need for personalized monitoring tools. However, the prognostic utility of ctDNA across indolent and aggressive subtypes of lymphoma remains poorly understood. Here, we present real-world data on ctDNA detection and clearance dynamics in patients with various lymphoma subtypes, including patients who are newly diagnosed and those in the relapsed/refractory setting receiving chimeric antigen receptor (CAR)-T therapy. Methods: We performed a retrospective, real-world analysis of ctDNA testing in 148 patients with either B-cell (n=129) or T-cell lymphoma (n=19). Among the 129 patients with B-cell lymphoma, 113 patients had aggressive subtypes (n=84 with DLBCL; n=29 with other), and 16 had indolent lymphoma subtypes. ctDNA was analyzed using a tumor-informed 16-plex mPCR-NGS assay (SignateraTM, Natera, Inc.) from September 2020 - May 2025. Plasma samples (n=1,122; median: 7 per patient, range: 1-31) were collected at baseline, during therapy, at end-of-treatment (EOT), and during follow-up per physician's discretion. ctDNA status at baseline and EOT, and clearance kinetics during first-line (1L) induction therapy were correlated with clinical outcomes. Results: The median patient age was 61 years (range: 18.3–84), and median follow-up was 18.7 months (range: 0.6–54.4 months). Disease stage at diagnosis was available for 139 patients: stage I (n=15, 11%), stage II (n=31, 22%), stage III (n=16, 12%), and stage IV (n=77, 55%). Stage was unknown in 9 patients. Overall, ctDNA detection at baseline was 95.7% (90/94), including 100% in patients with indolent B-cell (11/11), and T-cell lymphomas (6/6), and 94.8% (73/77) in patients with aggressive B-cell lymphomas. Across all subtypes, EOT ctDNA status was strongly prognostic for event-free survival (EFS). Patients with ctDNA-positivity at EOT had significantly worse EFS (HR: 7.33, 95%CI: 2.8-19.18, p<0.0001). In aggressive lymphomas, particularly in DLBCL, ctDNA positivity at EOT was associated with a markedly worse prognosis (Aggressive: HR: 7.69, 95%CI: 2.62-22.56, p=0.0002; DLBCL only: HR: 5.74, 95%CI: 1.71-19.23, p<0.01). Among patients with evaluable ctDNA time points relative to 1L therapy (N=60), ctDNA clearance at any time point during treatment correlated with improved EFS. (HR: 18.55, 95%CI: 4.82-71.32, p<0.0001). All patients who did not clear ctDNA relapsed, yielding a positive predictive value of 100% (11/11); the negative predictive value for those who did clear was 88% (43/49). The remaining six patients turned positive during surveillance prior to relapse. Of 15 patients treated with CAR-T cell therapy, 11 had pre- and post-infusion timepoints for ctDNA analysis. Of these, 82% (9/11) were ctDNA-positive prior to CAR-T, and 55% (5/9) achieved post-infusion ctDNA clearance and a complete clinical response, though one became ctDNA-positive and relapsed (13.3 months post-CAR-T), and another suffered non-disease mortality (22.3 months post-CAR-T). In contrast, all 4 patients remaining ctDNA-positive post-CAR-T relapsed or died within a median of 3.3 months (range: 1.3–6.4 months). Two patients persistently ctDNA-negative remain disease-free. Taken together, the PPV and NPV for 12-month EFS following CAR-T therapy using a single ctDNA timepoint were both 100%. Conclusions: This is the first report of the largest, real-world study evaluating the utility of ctDNA across a broad spectrum of heterogeneous lymphoma subtypes in patients receiving various standard of care therapies. ctDNA status at EOT and on-treatment clearance were strong predictors of clinical outcomes across multiple histological subtypes of lymphoma treated with standard-of-care agents including CAR-T cell therapy. The robustness of these findings across biologically distinct subgroups highlight the broad applicability of ctDNA testing for risk stratification and recurrence monitoring for both aggressive and indolent disease. Further prospective studies are needed to validate these findings.

Abstract Description Measles is a highly contagious virus that presents as fever, cough, and a rash that spreads from the face to the rest of the body. Other serious complications, such as pneumonia, deafness, and encephalitis, can occur in immunocompromised and unvaccinated populations. Although there is an effective vaccine, there are currently no FDA-approved antivirals for measles. Moreover, there has been an increased incidence of measles outbreaks in the United States. Two main targets for measles virus antiviral therapies include its surface glycoproteins, hemagglutinin (H) and fusion (F), which mediate attachment and fusion of the viral and cellular membranes, respectively. After binding of the H-protein to SLAM or nectin-4 on the host cell surface, the F-protein undergoes a conformational change to initiate a fusion event. Using a hybridoma-based approach, we isolated a panel of human monoclonal antibodies from the peripheral blood B cells of vaccinated or naturally infected measles donors that bind either the H or F proteins. These antibodies potently neutralize against a pseudotyped vesicular stomatitis virus expressing measles H and F proteins in vitro by inhibiting viral attachment or fusion. Structural studies will identify critical contact residues between these antibodies and their respective antigens and inform mutational escape assays for likely sites for immune evasion. The protective efficacy of these antibodies will also be assessed using a cotton rat in vivo model. Topic Categories Vaccines and Immunotherapy (VAC)