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Introduction: Brexucabtagene autoleucel (brexu-cel) is an autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy approved for adults with relapsed or refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL). Blinatumomab is a CD19-directed bispecific T-cell engager that is also approved for r/r B-ALL, and often used as early salvage therapy. Data in the pediatric/AYA population suggest that patients who did not respond to blinatumomab may have inferior outcomes to CD19-directed CAR-T products compared to those who have achieved a response to blinatumomab or were blinatumomab-naïve (Myers et al. J Clin Oncol 2022). In this study, we evaluate the response to blinatumomab and subsequent response to brexu-cel in adults with r/r B-ALL. Methods: Retrospective data were collected from 25 centers across the U.S. as part of the real-world outcomes collaborative study of CAR-T in B-ALL (ROCCA). Consecutive patients treated with brexu-cel from 2021 to 2023 were categorized by blinatumomab exposure status. Those exposed were separated into “blinatumomab responders” (B-R), defined as patients achieving a CR/CRi in response to any number of cycles of blinatumomab, and “non-responders” (B-NR). Each cohort was compared for outcomes of interest. The primary outcome was CR/CRi rate at day 28 following brexu-cel administration. Secondary outcomes were duration of response (DOR), progression-free survival (PFS), and overall survival (OS). Survival outcomes were calculated from day of brexu-cel infusion and were not censored for allogeneic hematopoietic cell transplantation or maintenance therapy. All living patients were censored at data cutoff on June 30, 2023. Survival comparisons were made by log rank test. Results: Among 152 patients who received brexu-cel, the median follow-up time was 8.4 months. Eighty-eight (57%) of 152 r/r B-ALL brexu-cel recipients had received blinatumomab prior to apheresis. The median number of pre-apheresis blinatumomab cycles was 2 (range 1-12). The baseline characteristics of B-R, B-NR, and blinatumomab-naïve (B-NV) patients were similar, including pre-apheresis disease burden and receipt of maintenance therapy following brexu-cel infusion (Table 1). Seventy percent (N= 62) of the blinatumomab-exposed patients were B-R, while 30% (N=26) were B-NR. Rates of CR/CRi at day 28 following brexu-cel infusion were similar between B-R, B-NR, and B-NV patients (79% vs 84% vs 78%, respectively). Most of these remissions were negative for measurable residual disease (MRD), with similar MRD negativity rates in the three groups (table 2). 1-year DOR and PFS were significantly higher in the B-NV group compared to B-R or B-NR (77% vs 49% vs 50%, p<.0001; 60% vs 37% vs 30%, p<.0001). B-NV and B-R had better 1-year survival compared to B-NR (71% vs 65% vs 32%, p<.0001). There were more CD19-negative relapses following brexu-cel in B-NR (29%) and B-R (18%) compared to B-NV patients (8%), although this was not statistically significant. Conclusions: Brexu-cel induced deep responses in a majority of adults with r/r B-ALL, irrespective of prior exposure or response to blinatumomab. Similar to data published by the pediatric CAR-T cell groups, our data draw speculation that adult patients who did not respond to blinatumomab experience shorter overall survival following brexu-cel compared to those who responded to or did not receive blinatumomab. This should be confirmed in a larger, prospective clinical trial. Because this analysis could not account for patients who achieved durable remission after blinatumomab, these differences may not reflect superiority of sequencing brexu-cel before blinatumomab. The higher number of CD19-negative relapses in the blinatumomab-exposed cohort add to the interest in pursuing strategies to address antigen escape following CAR-T cell therapy directed against a previously targeted antigen.

High dose chemotherapy followed by autologous hematopoietic cell transplantation (auto HCT) is a standard therapy for patients with plasma cell disorders (PCD). A barrier to improving candidate selection for auto HCT is appraisal of risk for transplant related complications. Electrocardiography (ECG) is a standard pre-HCT test to evaluate the potential for arrhythmia and structural heart disease. We hypothesized that an artificial intelligence (AI) based interpretation of ECG waveform data (AI-ECG) could enhance risk prediction for cardiac-specific and other outcomes following auto HCT for patients with PCD. To test this hypothesis, we used several AI-ECG tools developed using a deep-learning based approach that were trained to predict comorbidity (Attia et al, Lancet 2019 & Grogan et al, Mayo Clin Proc 2021). Model outputs include a scaled prediction value indicating increasing risk for atrial fibrillation/flutter (AF), reduced ejection fraction (EF), or cardiac amyloidosis. We evaluated this tool in 9,225 ECGs obtained from 849 patients (median 6 ECGs/patient, inter-quartile range: 3-12) who underwent first or subsequent auto HCT at Memorial Sloan Kettering Cancer Center between 2016-2022 and who had a diagnosis of multiple myeloma (N = 810), amyloidosis (N = 37), or other PCD (N = 2). The endpoints were to determine whether baseline AI-ECG prediction of AF risk correlated with peri-transplant AF events, and to explore whether model outputs correlated with survival and other cardiac clinical outcomes. The mean age of patients was 61.0 years (range 23.7 - 81.2) and median follow up was 2.7 years post auto HCT. Contributing cardiovascular risk factors included a prior history of AF (N = 101, 11.9%), coronary or cerebrovascular disease (N = 95, 11.2%), and diabetes mellitus (N = 98, 11.5%). Reduced dose melphalan (< 200 mg/m 2) was administered in 26%. The HCT-comorbidity index (HCT-CI) was high risk (≥3) in 52.7%. The one-year overall survival and progression-free survival in the whole cohort was 94% (95% confidence interval (95% CI): 92 - 95%) and 86% (84 - 89%), respectively. Among patients not in AF at pre HCT evaluation, the 90-day cumulative incidence of AF was 5.6% (4.2 - 7.3%). In univariable competing risk regression, baseline pre HCT AI-ECG appraisal of AF risk was strongly correlated with incidence AF in patients who were in sinus rhythm before HCT (hazard ratio (HR): 25.1, 95% CI: 11.7 - 53.7, p < 0.001). In a multivariable model adjusting for patient age and HCT-CI, AI-ECG AF predicted risk remained associated with incidence of post HCT AF (HR: 13.4, 95% CI: 5.9 - 30.4, p < 0.001). Considering a decision threshold identified during original model training, AI-ECG predicted AF events with an accuracy of 75% (Mcnemar's p < 2 x 10 -16). The precision, recall, and F1-score were 0.94, 0.77, and 0.85, respectively. AI-ECG predicted age correlated highly with actual patient age (Spearman rho = 0.59, p < 2 x 10 -16). Amyloid risk scores were highly correlated with a known clinical history of amyloidosis (median 0.45 versus 0.05, Wilcoxon rank-sum p < 0.001). Patients with EF < 50% had greater prediction scores for cardiomyopathy compared to patients with normal EF (median 0.23 versus 0.01, Wilcoxon rank-sum p <0.001). In univariable analysis, increasing AI-ECG predicted age (HR 1.02, CI: 1.003 - 1.04, p = 0.02) and predicted AF risk score (HR: 3.2, CI: 1.4 - 7.2, p = 0.006) were associated with risk for death, whereas predicted amyloid score and predicted low EF were not associated with decreased survival. In multivariable analysis of all patients that considered patient age, hematopoietic comorbidity index, and remission status at HCT, increasing predicted AF score trended towards association with increased risk for death (HR: 2.3, 95%CI: 1.0 - 5.5, p = 0.059). Predicted AF score correlated highly with the HCT-CI and patient age. Finally, we examined whether risk prediction for low EF correlated with peri-HCT fluid overload (FO) defined by absolute weight gain. The incidence of ≥ 10% weight gain (grade 2 FO) and ≥ 20% weight gain (grade 3 FO) at 180 days post HCT was 7.4% (95% CI: 5.8%, 9.3%) and 1.0% (95% CI: 0.5%, 1.8%), respectively. Predicted low EF was not associated with development of either grade 2 or grade 3 FO in this population. In summary, AI-ECG predicts episodes of AF in patients undergoing auto HCT for PCD and may augment transplant risk appraisal when considered in conjunction with other measures of comorbidity.

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

Background: Goals of patient-centered care for management of relapsed or refractory follicular lymphoma (R/R FL) are to improve clinical outcomes while maintaining or improving health-related quality of life (HRQoL). In ELM-2 (NCT03888105), a Phase 2, open-label, multicohort, multicenter study, odronextamab monotherapy demonstrated high and durable complete response rates and generally manageable safety in patients with R/R FL. We report here, for the first time, patient-reported outcome (PRO) results from ELM-2 in patients with R/R FL. Methods: Patients with R/R FL Grade 1-3a received odronextamab IV at 80 mg weekly in 21-day cycles in Cycles (C) 1-4. Optimization of the step-up regimen to mitigate cytokine release syndrome (CRS) was reported previously. Odronextamab was administered with steroid prophylaxis and step-up doses of 0.7/4/20 mg in C1, then 80 mg on Days 1, 8, and 15 of C2-4. After C4, odronextamab maintenance continued at 160 mg every 2 weeks until disease progression or unacceptable toxicity. Patients with durable complete response (≥9 months) switched to dosing every 4 weeks. Patients completed EORTC QLQ-C30, FACT-Lym, and EQ-5D-3L questionnaires at Weeks 1 (baseline), 2, 3, 4, and 10, then every 8 weeks for the remainder of the first year and every 12 weeks in the second year. Results here focus on six key PRO scales: EORTC QLQ-C30 Global Health Status/Quality of Life (GHS/QOL), physical functioning (PF), role functioning (RF), and fatigue; FACT-Lym lymphoma subscale (LymS); and EQ-5D-3L visual analog score (VAS). Longitudinal analyses using mixed models for repeated measures (MMRM) were conducted through Week 50 (the last visit with ≥10 patients with PRO data). Changes from baseline were considered statistically significant if the 95% confidence interval did not contain zero. No adjustment for multiplicity was performed, hence all statistical significance is nominal. Published ranges for minimum important difference (MID) to define clinically meaningful changes are: EORTC QLQ-C30 scales, 10 points; FACT-Lym LymS, 2.9-5.4 points; and EQ-5D-3L VAS, 7-12 points. For responder and time to definitive deterioration (TTDD) analyses, the upper end of these published MID ranges was used to define deterioration or improvement. Results: At the ELM-2 interim data cutoff on 31-Jan-2023, 140 patients with R/R FL Grade 1-3a had received at least 1 dose of odronextamab. Median age was 60.5 years (range: 22-84), with 38.6% ≥65 years, 52.9% male, 57.1% White, 32.1% Asian, 52.2% ECOG=0, and 47.1% ECOG=1. Median duration of follow-up was 26.6 months (range: 6.2-37.5). PRO completion rates for EORTC-QLQ-C30, FACT-Lym, and EQ-5D-3L were high at baseline and remained high for all assessments through Week 50. At baseline, moderate levels of general health (GHS/QoL) and high levels of functioning (PF and RF) were observed that were higher (better) than reference values for general cancer or non-Hodgkin's Lymphoma (NHL). Fatigue scores at baseline were lower (less symptoms) than reference values for general cancer or NHL. EORTC QLQ-C30 GHS/QOL, PF, RF, and fatigue scores were maintained from baseline through Week 50 (Table). For EQ-5D-3L VAS, the overall estimated mean changes from baseline improved statistically significantly but did not reach MID thresholds (Table). For FACT-Lym LymS, overall estimated mean change from baseline statistically significantly improved, and scores improved statistically significantly from Weeks 10 to 42 (except Week 34), with clinically meaningful improvements at Weeks 26 and 42 (Figure). The proportion of patients reporting meaningful improvement or stability across the six scales was higher than the proportion reporting meaningful worsening through Week 50 (Table). The median TTDD for EORTC-QLQ-C30 GHS/QoL was 22.41 (95% CI: 14.59 to not yet reached) months, corresponding to the median PFS. Median TTDD was not reached for EORTC QLQ-C30 PF, FACT-Lym LymS, and EQ-5D-3L VAS scales. Conclusions: For patients with R/R FL, patient-reported HRQoL results were favorable during odronextamab treatment until disease progression, with no detriments on patient-reported symptoms, functioning, and overall quality of life. These results complement encouraging clinical efficacy, durability of responses, and tolerability observed in this highly refractory patient population and support the future role of odronextamab in the management of patients with R/R FL.

Background. The inclusion of gene mutations and chromosomal abnormalities in the 2022 WHO and ICC Classifications of MDS has enhanced diagnostic precision and is expected to improve clinical decision-making process. Although these two systems share similarities, clinically relevant discrepancies still exist and potentially cause inconsistency in their adoption in a clinical setting. In this study on behalf of the International Consortium for MDS (icMDS), we adopted a data-driven approach to provide a harmonization roadmap between the 2022 WHO and ICC classification for MDS. A modified Delphi Process consensus approach is currently ongoing among icMDS experts to finalize a harmonized MDS classification scheme. Methods. We analyzed retrospective international cohorts of patients with a diagnosis of MDS (n=7017) and AML (n=1002) according to WHO 2016 criteria. Hierarchical Dirichlet Processes were applied to define clusters capturing broad dependencies among all gene mutations and cytogenetic abnormalities. To investigate the features of importance and their impact on the clustering process, we employed the SHapley Additive exPlanations approach (SHAP). This allowed to define harmonized labels for each clinical entity. The clinical relevance of the unsupervised clustering was assessed through the analysis of phenotypic features and outcomes among each group. ( Blood 2022;140: 9828-9830) Results. Patients' characteristics are summarized in Table 1. We identified 9 clusters, defined by specific genomic features. The cluster of highest hierarchical importance was characterized by biallelic inactivation of TP53 (biTP53). According to SHAP analysis, bi TP53 was defined as 2 or more TP53 mutations, or 1 mutation with copy number loss or cnLOH. Most patients assigned to bi TP53 cluster had TP53 VAF>10% (77.9%) and complex karyotype (70.1%). Assignment to bi TP53 cluster was irrespective of blast count. Patients with monoallelic TP53 mutation segregated into other clusters. Hierarchically, the second cluster included patients with del(5q). SHAP analysis highlighted 5q deletion alone, or with one other chromosomal abnormality other than -7, and absence of bi TP53, as the most relevant features. Most of these patients had blast counts <5% (88.1%). The third distinct cluster included patients with SF3B1 mutations (in the absence of concurrent del(7q), abn3q26.2, complex karyotype or RUNX1 mutation). Most patients with MDS and SF3B1 mutation had <5% blasts (94.2%). Common co-mutated variants in the SF3B1 cluster included mutant DNMT3A (25.2%) and TET2 (38.3%). Morphologically defined MDS cases (i.e., not meeting criteria for bi TP53, del(5q) or SF3B1) were preferentially assigned to the following additional clusters: SF3B1 and concurrent higher-risk mutations (e.g., RUNX1 and ASXL1); SRSF2 and concomitant TET2 mutations; U2AF1 mutations with del(20q), del(7q) or -7; SRSF2 with TET2 mutations and co-mutational patterns including RUNX1 and ASXL1; and AML-like genomic signatures. Our analyses suggest that morphologically defined MDS is characterized by a large heterogeneity in terms of mutation profiles, not entirely captured by the presence of unilineage versus multilineage dysplasia, percentage of bone marrow blasts, and presence of hypocellularity and fibrosis. To better investigate the continuum between high risk MDS (i.e., patients with ≥10% blasts) and AML, an exploratory comparison was made using a cohort of AML (defined according to WHO 2016) patients analyzed using the same statistical methods. Only a partial overlap in genetic signatures was observed between MDS with ≥10% blasts and AML. However, similarities were observed between the AML-like MDS clusters (characterized by mutant NPM1, bZIP CEBPA, and Core Binding Factor abnormalities) and AML clusters defined by the same genetic signature, thus supporting the classification of these entities as AML, irrespective of blast count. Conclusion. Our study demonstrated the utility of a data-driven approach based on advanced statistical methods to generate a harmonized classification for MDS. Table 2 shows a provisional, hierarchical classification algorithm. Further refinement of entity labels and classification criteria is the subject of the ongoing modified Delphi Process consensus approach among icMDS experts.

Introduction: Brexucabtagene autoleucel (brexu-cel) is an autologous anti-CD19 chimeric antigen receptor (CAR) T cell therapy approved for adults with relapsed/refractory B-cell acute lymphoblastic leukemia (R/R B-ALL). Bridging therapy, defined as anti-leukemia therapy given between apheresis and lymphodepleting chemotherapy, was permitted on the pivotal ZUMA-3 trial. The optimal bridging therapy is unknown in this setting. Here we report patient and disease characteristics in those receiving bridging therapies prior to brexu-cel and the impact of bridging on clinical outcomes in a large multicenter cohort. Methods and Results: ROCCA includes 25 US institutions contributing retrospective data from 152 B-ALL patients treated with standard of care brexu-cel between 2021-2023. Ninety-nine patients (65%) received bridging therapy, while 53 patients (35%) received no bridging therapy. Bridging therapy consisted of cytotoxic chemotherapy ( n=65, 66%), immunotherapy ( n=26, 26%; 23 inotuzumab, 3 blinatumomab), tyrosine kinase inhibitors (TKI) ( n=20, 20%; 16 ponatinib), steroids only ( n=10, 10%), and intrathecal chemotherapy ( n=22, 22%). The median age of the cohort was 46 (IQR 32-61). Patients were heavily pre-treated with a median of 4 prior lines of therapy. The median days from apheresis to infusion was 33 (IQR 26-42). 119 patients had known pre-apheresis blast counts; the bridging group had higher pre-apheresis blast burden, with 21 of 76 patients (28%) having ≥ 50% blasts compared to only 5 of 43 patients (12%) in the no bridging group ( p=0.02). In addition, more patients who received bridging had pre-apheresis extramedullary disease (32% vs. 15%, p=0.02). All other baseline characteristics were similar between the two groups (Table 1). Fifty-four (54%) patients had response assessment after bridging therapy and prior to brexu-cel infusion. In patients who received inotuzumab for pre-apheresis active disease, defined as ≥ 5% blasts, 6 of 13 (46%) who had post-bridging assessment achieved a complete response (CR; 5 measurable residual disease (MRD)+, 1 MRD-), with a mean proportional reduction in blast burden of 46% from baseline. In contrast, after chemotherapy bridging, only 2 of 16 patients (13%) with pre-apheresis active disease had a CR. Patients receiving chemotherapy bridging had a mean proportional increase in blast burden of 4.4%. In recipients of TKI bridging, 2 of 4 patients (50%) with pre-apheresis active disease had a CR. Compared to no bridging, patients in the bridging group had similar rates of grade 3 or 4 CRS (9% bridging vs. 8% no bridging, p=0.73) and grade 3 or 4 ICANS (34% vs. 26%, p=0.32). In univariate analysis, there was no statistically significant difference in day 28 response with 63 patients (72%) achieving MRD- complete response in the bridging group as compared to 36 patients (78%) in the no bridging group ( p=0.60). Non-relapse mortality was similar between the two groups (17% bridging vs. 9% no bridging, p=0.20). Overall survival (OS) and progression-free survival (PFS) were superior in the no bridging group: 1-year OS 74.7% vs 56.8% (log-rank p=0.04), and 1-year PFS 57.3% vs 41.7% (log-rank p=0.04). In a multivariate analysis stratified by bridging and pre-apheresis disease burden, patients with pre-apheresis blasts ≥ 5% and bridging had worse survival than ≥ 5% blasts and no bridging: 1-year OS 45.3% vs. 87.5% and 1-year PFS 27.7% vs. 64.3% (Figure 1). However, patients with < 5% blasts had similar survival regardless of bridging. Conclusions: In our real-world analysis, adults with R/R B-ALL receiving bridging therapy had a higher disease burden at baseline. Despite greater baseline disease, there were no significant differences in toxicity and day 28 response in those receiving bridging therapy vs. not. While survival was inferior in patients with pre-apheresis active disease who received bridging, this may be confounded by the degree of tumor burden. In patients with < 5% blasts pre-apheresis, bridging did not impact survival. Furthermore, inotuzumab bridging demonstrated the most significant disease debulking. However, the comparisons in this study are limited by the variability in practice for post-bridging disease reassessment and the small proportion of patients with active disease who did not receive bridging. A more uniform approach to peri-CAR disease assessment would enable more robust study of optimal bridging strategies.

Background: BMT CTN 1703 was a Phase 3 trial comparing Tac/MTX (n = 217) to post-transplant cyclophosphamide (PT-Cy)/Tac/MMF (n = 214) GVHD prophylaxis after reduced intensity conditioning unrelated donor hematopoietic cell transplant (HCT). PT-Cy significantly improved GVHD-free Relapse-Free Survival (Bolanos-Meade et al NEJM 2023). However overall survival was not significantly different and the # of Grade 2 infections was higher with PT-Cy. To investigate its biologic underpinnings 1703 was linked to a mechanistic study, BMT CTN 1801, which co-enrolled 324 pts (159 CNI/MTX 165 PT-Cy). The resulting dataset enabled an analysis of post-HCT T cell reconstitution at an unprecedented level of detail. Methods: Samples were collected from the HCT infusion and on D+7, 14, 28, 63, 98, 180, 270, 1- and 2-yr. We extracted DNA (2,225 samples) and performed Adaptive Biotech β-strand T Cell Receptor (TCR) Immunosequencing (TCR-Seq). We profiled 44,077 (median) TCRs/sample resulting in 215,155,719 T cells analyzed. We evaluated multiple TCR diversity measures longitudinally and before/after cGVHD and infections. Each measure evaluates a specific aspect of TCR diversity, including Simpsons Clonality (focuses on the most expanded clones) Diversity Slope (mid-range clones) Richness (both mid-range and less-expanded clones) and Singletons (the TCR-Seq equivalent of naïve T cells). This analysis was robust to the full range (1000-50,000) of down-sampled TCRs sequenced. Results: We identified major differences in TCR reconstitution in Tac/MTX vs PT-Cy that begin early and persist through 2 yr post-HCT. These resulted in a significantly less diverse TCR repertoire with PT-Cy with substantial implications for its efficacy and toxicity. The most salient differences are: (1) PT-Cy caused significant in-vivo T cell depletion early post-HCT (% T cells/total WBC at D+28: 8.2% (Tac/MTX) vs 2.2% (PT-Cy) p=2.2x10 -23). (2) The remaining donor T cells in PT-Cy undergo substantial clonal expansion ( Fig 1) resulting in significantly constrained TCR diversity measured by Clonality, Slope, Richness, Singletons (not shown) and Singletons/Richness ( Fig 2) which began early (D+14) and persisted for 2 yr. (3) Linked T cell depletion and clonal expansion resulted in a TCR diversity bottleneck after PT-Cy ( Fig 1). Due to the bottleneck, while the fraction of T cells originating from the transplant infusion at =/> 1 yr was similar between arms (18% vs 24%, p=0.7) there were significantly fewer Singleton TCRs in PT-Cy, suggesting a reduction in naïve T cells ( Fig 2), an outcome that has critical consequences for both cGVHD and infection. Thus while cGVHD onset with Tac/MTX was linked to a significant drop in TCR diversity due to singleton clonal expansion (median log-2 fold change in singletons with Tac/MTX = -0.25 p = 0.01) this drop was not observed with PT-Cy (log-2 fold change = -0.05, p = 0.1). Along with the significantly decreased # singletons at all time-points in PT-Cy ( Fig 2) this suggests that while cGVHD after Tac/MTX is linked to substantial naïve T cell expansion, the same is not true with PT-Cy, identifying a novel mechanism for cGVHD control with PT-Cy. The substantially fewer singletons in PT-Cy vs Tac/MTX may also increase the risk of Grade 2+ infections. T cell responses to new infections rely on antigen recognition/effector maturation of naïve (singleton TCR) T cells. After infection, the TCR repertoire became less diverse for both Tac/MTX and PT-Cy (log-2-fold singleton change -0.17 and -1.2 p = 0.0006 and 0.01) indicating that singletons in both cohorts were capable of expanding to pathogens. However the markedly decreased # singletons in PT-Cy at all timepoints was associated with significantly fewer singletons prior to infection (mean 3979 at 5K read-depth for Tac/MTX vs 2820 for PT-Cy p<0.001). This singleton deficit would place PT-Cy patients at higher risk of missing the critical mass of TCRs required to respond effectively to infections, consistent with their increased rate of Gr 2 infections. Conclusions: We performed longitudinal TCR-Seq on >200 million T cells from 324 HCT patients, representing the largest post-HCT TCR-Seq analysis in the history of the field, and enabling novel insights into TCR dynamics. These data identify a previously unappreciated global TCR diversity bottleneck with PT-Cy that simultaneously protects patients from cGVHD and places them at higher risk of infectious complications.

Background Pancreatic ductal adenocarcinoma (PDAC) is a challenging target for immunotherapy because it has an immunosuppressive tumor microenvironment. Neoadjuvant chemoradiotherapy can increase tumor-infiltrating lymphocyte (TIL) density, which may predict overall survival (OS). We hypothesized that adding programmed cell death protein 1 (PD-1) blockade to chemoradiotherapy would be well tolerated and increase TILs among patients with localized PDAC. Methods Patients were randomized 2:1 to Arm A (receiving pembrolizumab plus chemoradiotherapy (capecitabine and external beam radiation)) or Arm B (receiving chemoradiotherapy alone) before anticipated pancreatectomy. Primary endpoints were (1) incidence and severity of adverse events during neoadjuvant therapy and (2) density of TILs in resected tumor specimens. TIL density was assessed using multiplexed immunofluorescence histologic examination. Results Thirty-seven patients were randomized to Arms A (n=24) and B (n=13). Grade ≥3 adverse events related to neoadjuvant treatment were experienced by 9 (38%) and 4 (31%) patients in Arms A and B, respectively, with one patient experiencing dose-limiting toxicity in Arm A. Seventeen (71%) and 7 (54%) patients in Arms A and B, respectively, underwent pancreatectomy. Median CD8+ T-cell densities in Arms A and B were 67.4 (IQR: 39.2–141.8) and 37.9 (IQR: 22.9–173.4) cells/mm2, respectively. Arms showed no noticeable differences in density of CD8+Ki67+, CD4+, or CD4+FOXP3+ regulatory T cells; M1-like and M2-like macrophages; or granulocytes. Median OS durations were 27.8 (95% CI: 17.1 to NR) and 24.3 (95% CI: 12.6 to NR) months for Arms A and B, respectively. Conclusions Adding pembrolizumab to neoadjuvant chemoradiotherapy was safe. However, no convincing effect on CD8+ TILs was observed.

Abstract Monoclonal gammopathy of undetermined significance (MGUS) is the most common plasma cell dyscrasia, present in ~3% of the population over 50yo. MGUS carries a 1% per year risk of malignant transformation for the rest of the affected individual’s life; long-term followup is recommended for all patients with MGUS. Different risk stratification models exist to evaluate potential for progression to malignancy. The Mayo risk model, published in 2005, uses the presence of 3 risk factors (abnormal free light chain (FLC) kappa/lambda ratio (KLr), M-spike ≥1.5 g/dL, non-IgG isotype) to confer a 3% per year risk of progression instead of the average 1%. For many years, the only FDA-approved measurement of FLC was the FreeLite assay (Binding Site), which uses polyclonal sheep antibodies. Recently, other FLC assays have become available in the US, including the Sebia FLC ELISA, which employs rabbit polyclonal antibodies. The assays have similar reference intervals (RI), however differences in analytical performance between the FreeLite and Sebia were previously reported. The objective of this study was to determine the performance of the Sebia FLC assay in the Mayo risk stratification model of MGUS patients for progression in comparison to FreeLite. Cryopreserved serum samples from a cohort of 923 MGUS patients with available long-term clinical followup (median follow-up time: 7.7years, range: 0.0 to 46.9) was used to measure FLC using Sebia ELISA on a DS2 automated platform (Dynex) and FreeLite on a Siemens BNII nephelometer. Passing-Bablok (P-B) regression and Spearman correlation were used to compare the KLr between assays. Cox proportional hazards models for progression to multiple myeloma or a related plasma cell malignancy were used to estimate the prognostic effect and ability to discriminate low and high risk of abnormal KLr for each assay. Analyses were carried out in R software. Correlation between Sebia and FreeLite KLr had a Spearman r = 0.796; P-B fit: Sebia KLr = 0.825*(FreeLite KLr) – 0.048, 95% CI of slope: 0.810-0.839). With FreeLite, 32.9% of patients had a KLr outside RI for the method. For Sebia, 48.0% of patients had a KLr outside the method specific RI. Despite the individual samples analytical disagreement, both assays showed similar clinical performance for risk stratification: Sebia abnormal KLr was associated with a hazard ratio (HR) of 2.77 (95%CI: 1.79-4.28 c-statistic=0.6505) for progression, while FreeLite abnormal KLr was associated with a HR of 3.31 (95%CI: 2.20-5.00, c-statistic=0.6529), and the difference in c-statistics was not statistically significant (p=0.93). The risk assessment is performed only once per patient, at the initial diagnosis of MGUS. The similarity in clinical performance between FreeLite and Sebia assays support the use of either method as a predictor for risk of progression for MGUS patients.

In pathologies of the heart, blood vessels, and airways, and in cancer as well, the ultimate therapeutic target is often modulation of cellular contractile force. For discovering new therapies, drug screening technologies typically use biochemical or structural surrogates for contractile force rather than contractile force itself. Because such approaches are indirect, some hits are false while other potential hits could be missed. To fill this gap, we developed a new high‐throughput method that utilizes cellular contractile force directly as the reporter ‐‐called contractile force screening (CFS)‐‐ and established feasibility of CFS in the context of drug discovery in asthma. During an acute asthma attack, contractile forces generated by airway smooth muscle cells act to constrict the airway and thus obstruct airflow. To dilate constricted airways, asthma patients use bronchodilators to reduce these contractile forces and thus allow the airway to open more fully, but currently available bronchodilator medications often fail to relax that muscle sufficiently, especially in severe asthma. To address this unmet need for more effective bronchodilator medications, we implemented CFS to evaluate 10,000 small molecule compounds selected randomly from the Chembridge DIVERset® library. Acrylamide gels were made in 96‐well plates and fluorescent markers and collagen were coated onto gel surfaces. Upon each gel we cultured primary human airway smooth muscle (HASM) cells to near confluence. Drug effects were quantified as the ‘force response ratio’, namely, the ratio of the contractile forces before and after drug addition. By screening mixtures of 8 compounds simultaneously, we were able to evaluate 2000 compounds per week in quadruplicate. After retesting individual compounds from initially positives, we identified 2 individual compounds that relaxed HASM cells in a dose‐dependent and a non‐toxic manner. The mechanism of action is still under investigation but we found that these compounds work independent of cAMP. CFS provides a convenient, rapid, and inexpensive platform for drug discovery based upon a physiological endpoint, namely, cell contractile force. Furthermore, CFS technology has the potential to become a new high‐content assay for drug discovery in any disease process in which cellular contractile force plays a central role. Support or Funding Information NIH P50HL107171 (CADET phase I), R01EY019696 (Eye BRP), NRF GRN (NRF‐2013S1A2A2035518)